MOBILE COMMUNICATIONS THEORY AND PRACTICAL DDI UNO eINPAU CeMOBILE COMMUNICATIONS PREFACE Today, mobile communications play a central role in the voice/data network arena, With the deployment of mass scale 3G just around the corner, new directions are already being researched. In this paper we address about the theoretical and practical scenarios of mobile communications. This document is presented on the industrial training acquired at Dialog Telekom Lid at North Western Region, from 6th of Augusts 2013 till the 06th February 2013. Also it should be mentioned here that Dialog Telekom Ltd is provided us a 3 month training program and I am under trained at Network Planning and Operational division, The sections covered in this document has been divided into six main chapters, starting with an Introduction to Dialog Telekom, proceeds with Network Architecture and ends with a abbreviations, The first chapter Dialog Telekom presents some historical background of the company, the services provided, and the present performance of the Dialog Telekom Networks (Pvt) Ltd. I dedicated that chapter for Dialog Telekom for show my gratitude to that organization. Next the report precedes under four sections Network Planning & Network Operations, Microwave Transmission Planning & Microwave Transmission Planning and BSS Operations. section the details of the training we have done, areas of exposure during our training period, information on plant, equipment and machinery encountered during training have been presented This book is intended to be used as a supplement to all textbooks on signals and systems or for self study. It may also be used as a textbook in its own right. Each topic is described very well. NDGD SENARATH Page 2 of 125MOBILE COMMUNICATIONS ACKNOLEDGEMENT This is my third report as a student of Sir John Kotelawale Defence University. I thought I am. very lucky to having golden opportunity to training in a leading telecommunication company like DIALOG GSM. Also this is my first training in mobile communication side. So having, this golden opportunity extremely I got good knowledge in mobile communication side. Sometimes I felt little bit difficulties to understand some points, but the internal staff all are help me to overcome such difficulties. of al I like to thanks to the Vice Chancellor of KDU Major General MP Peiries, Commanding Officer, Cornel HMU Herath, Divisional Officer, Major HRAJKK Basnayake and all the Troop Commanders in Intake 27. And also I like to thanks the Chief Executive Officer Doctor Hans Wijesuriya to be kindly for giving this opportunity to me. I wish to extend my sincere thanks to Mr. Koshala Chandralal (Manager North Wester Region) Mr. Shiron Cader (Engineer transmission Planning & Development), Mr. Chandana Bandara (Engineer), Mr. Mahinda Panampitiya (Engineer), Mr. Duminda Pathiraja (Engineer), Mr. Viraj Senanayake (Engineer), Mr. Sajith Anuradha (Engineer), Mr. Sriyantha Malawaarachehi (Engineer), Mr. Manjula Rathnayake (Engineer) & Mr. Buddhika Many thanks go to Other Specialists, Engineers and all other staff of the relevant divisions for their support, guidance and assistance. My special thanks to Human Recourse Division of DTL for coordinating training activities & given help to successful my training. Tam grateful to my mother and father for their support, guidance and assistance throughout the life. Lt NGDGD SENARATH Bsc gdilmika@gmail.com NDGD SENARATH Page 3 of 125MOBILE COMMUNICATIONS CONTENTS 1. TRAINING ORGANIZATION(DIALOG TELEKOM LTD. 1.1. Introduction .. 12. History of Dialog 13. Vision and Mission 1.3.1. Dialog Vision 1.3.2. Dialog Mission.. 1.3.3. Corporate Value: 1.4, Dialog Service 1.4.1. Dialog GSM. 1.4.2. Dialog Internet .. 1.4.3. Dialog W@P 1.4.4. Dialog Packet Data Services..... 1.4.5. Dialog SAT....... 1.4.6. Dialog 3G Network. 1.5. Organizational Structure ...... 1.5.1. The Board of Directors... 1.6. Key Milestones of Dialog Telekom INTRODUCTION TO MOBILE COMMUNICATIONS 2.1. History of Global System for Mobile Communication 2.2 GSM Radio Network 2.3 GSM Network... 2.3.1 Base Station System (BSS)... 2.3.2 Network Sub System (NSS) . 2.3.3. Transmission Network... 2.4 UMTS Services . 2.4.1 UMTS Architecture. 2.4.2 General Packet Radio System 2.5 UMTS Interfaces sce pee eee els 2.6 UMTS Terrestrial Radio Access Network. 2.6.1 Radio Network Controller 2.62 Node B.. N NDGD SENARATH Page 4 of 125MOBILE COMMUNICATIONS 2.6.3 UMTS User Equipment... 2.7 GSM and UMTS Core Network. 2.8 Hierarchical Structure of UM interface. 2.9 Voice Signal Processing .... 2.10 Analog Digital Conversion .. 2.11 Speech Coding. 2.12 Chanel coding. 2.13. Interleaving.. 2.14 Burst... 2.14.1 Normal Burst. 2.14.2 Access burst . 2.14.3 Frequency Correction Burs 2.14.4 Synchoronous burst. 2.14.5 Dummy Burst. 2.15 Hierarchy of Frames. 2.16 Channel Concept... 2.17 Logical Channel Type: 2.17.1 Common Chanel (CCH)... 2.17.2 Dedicated Chanel (DCH)... 2.18 Cell global identity(CGI-MCC+MNC+LAC+CI 2.19 Base station identity code (BSIC)... NETWORK PLANNING AND OPTIMIZATION 3.1. Radio Network Planning. » 3.2. Improving the Coverage... 3.3. CELL Planning process. 3.4. Traffic and coverage analy: 3.5. Nominal cell planning... 3.6. Strategic Network Planning .. 3.7. Wireless Network Design. 3.8. Mentum Planet... 3.8.1. Network Planning with Mentum Planet 5.4 3.9. Surveys [and radio measurements] . 3.10. System designed [final cell plan] NDGD SENARATH Page 5 of 125MOBILE COMMUNICATIONS 3.11. Site acquisition... 3.12. Implementation... 3.13. System tuning. 3.14. Frequency reus 3.15. Frequency allocation for Dialog. 3.16. Cellular Frequency Planning 3.16.1. Frequency Hopping Base Band Hopping..... Radio Frequency Hopping. MAIO - Mobile Allocated Index Offset FHS - Frequency Hopping Sequenc HSN - Hopping Sequence Number . 3.17. Equipment Plannin; 3.17.1. Mechanical Down Tilt (MDT). 3.17.2. Electrical Down Tile (EDT)... 3.17.3. Comparison of Mechanical and Electrical Downtilt .. 3.18. Improving the Capacity. 3.19, Radio Network Optimization & Performance Monitoring..... 3.19.1, Nemo Outdoor . 3.20. Repeater Systems ... TRANSMISSION PLANNING AND OPERATIONS .... 4.1. Introduction. s 4.2. Transmission Technologie: 4.2.1. Plesiochronous Transmission (Plesiochronous Digital Hierarchy — PDH) 55 4.2.2. Synchronous Digital Hierarchy (SDH)... 43. Transmission Planning... 4.4. Microwave Transmission . 4.4.1. Designing and Development of Transmission Infrastructure .....57 4.4.2. Path Design 4.4.3. Map Surve 4.4.4. FIELD SURVEY. 4.4.5, Visual tests for LOS clearance. NDGD SENARATH Page 6 of 125MOBILE COMMUNICATIONS 4.4.6. Instruments of Path survey . 4.5. Path Profiles .. 4.5.1. Path Profiles - Manually .. 4.5.2. Path Loss 4.0 Software 4.5.3. Altitude.. 4.5.4. Azimuth. 4.5.5. Antenna Height... 4.5.6. Fresnel Zone. 4.5.7. Earth Bulge. 4.5.8. Equivalent Earth curvature . 4,6. Frequency Considerations... 4.6.1. High Band &Low Band.. 47. Radio Surveys ... 4.7.1. Path Survey. 4.7.2. Site Surveys 4.8. Main factors that affect Microwave Propagation. 4.8.1. Diffraction... 4.8.2. Refraction. 4.8.3. Reflection. 4.9, Interference Analysis of Microwave Links 4.9.1. Unintended Radiation .. 4.9.2. Information Bandwidth... 4.9.3. External Interference.. 4.9.4. Intra System Interference. 4.9.5. Overreach interference. 4.9.6. Adjacent section interference. 4.9.7. Junction interference. 4.9.8. Frequency Interference .... 4.9.9. Co-Channel Interference. 4.9.10. Adjacent Channel Interferene: 4.9.11. C/I ratio objectiv 4.9.12. Solutions for Interference 4.10. Losses in microwave transmission... NDGD SENARATH Page 7 of 125MOBILE COMMUNICATIONS 4.10.1. Free Space Losses... 4.10.2. Atmospheric Losses... 4.10.3. Other Losses 4.10.4, Path Unavailability 4.10.5. Basic Radio Link Equation (Link Budget Calculation): .. 4.11. Protection Methods of Links 4.11.1. Hot-standby Branching. 4.11.2. Frequency Diversity Branching... 4.11.3. — Space Diversity Branching 4.12. Transmission Operations Divisior 4.12.1. Main Components of the Microwave system. 4.12.2, Antenna Unit 5. BSS PLANNING AND OPERATIONS .. 5.1. Introduction to Network Operation. 5.2. Base Station Subsystem ... 5.2.1. Transcoder. 5.2.2. Base Station Controle 5.2.3. Base Transceiver Station... 5.3. What is a Base Station 5.3.1. Frequency rang: 5.3.2. Features of DBS3900. 5.3.3. DBS3900 Hardware Components. 5.3.4. Functions of the BBU3900: .. 5.3.5. Hardware Components of BBU3900.. 5.3.6. GTMU Board 5.3.7. WMPT Boards 5.3.8. WBBP Boards.. 5.3.9. UPEU Boards. 5.3.10. UEIU Boards. 5.3.11. UELP Boards 5.3.12. UFLP Boards 5.3.13. UTRP Boards 5.3.14. UBFA Boards. NDGD SENARATH Page 8 of 125MOBILE COMMUNICATIONS 5.3.15. BBU 3900 Cable Connection... 5.3.16. BBU3900 Cable List... 5.4. RRU (Remote Radio Unit)... 5.4.1, The functions of the RRU 3908 5.4.2. Logical Structure of the RRU3908... 5.4.3. RRU3908 Board. 5.4.4. RRU3908 Cable Connection 5.4.5. RRU3908 Cable List... 6. ABBREVIATIONS..... List of Figures NDGD SENARATH Page 9 of 125MOBILE COMMUNICATIONS Figure 2-2: Basie GSM and UMTS Network Structure. Figure 2-3: UMTS Architect Figure 2-4: UTRAN Architectur Figure 2-5: Basic GSM and UMTS Network Structure... Figure 2-6: Hierarchical structure of UM interface .. Figure 2-7: Step of voice signal processing... Figure 2-8: Analog digital conversion... Figure 2-9: Normal burst. Figure 2-10: Access burst Figure 2-11: Frequency correction burst... Figure 2-12: Synchoronous burst Figure 2-13: Dummy burs Figure 2-14: Hierarchy of frames ....... Figure 2-15: Channel Concept... Figure 2-16: Logical channels ...........ssscssssssssssssssssssssssseessseeessseeeesseeeeesees - - 28 Figure 3-1: Cell planning process 35 Figure 3-2: Wireless and network designing on Mentum Planet. 38 Figure 3-3: Basie site acquisition procedure. Figure 3-4: 900MHz Frequency Channels Figure 3. : 1800MHz Frequency Channels. Figure 3-6: Frequency re use Figure 3-7: Base Bands Hopping... Figure 3-8: Radio Frequencies Hopping... Figure 3-9: Mechanical down tilt coverage . 46 Figure 3-10: Electrical downtilt mechanism..... wT Figure 3-11: Comparison of mechanical and electrical downtilt. 48 Figure 3-12: Test Mobile Systems. Figure 3-13: Nemo drive test data on Google Earth Figure 3-14: Screenshots of Nemo software. Figure 3-15: PICO repeater system. Figure 3-16: Outdoor repeater system ... Figure 4-1: Excel work sheet analysis... Figure 4-2: Azimuth.. NDGD SENARATH Page 10 of 125MOBILE COMMUNICATIONS Figure 4-3: Fresnel Zone... Figure 4-4: Earth curvature Figure 4-5: ITU Organizational Structure. Figure 4-6: Frequency band Selection Figure 4-7: Fading. ... Error! Bookmark not defined. 7 oa72) 12 Figure 4-8: Ducting... Figure 4-9: Overreach interference. Figure 4-10: Adjacent section interference Figure 4-11: Junction interference Figure 4-12: Co-Channel Interference. Figure 4-13: Adjacent Channel Interference.. Figure 4-14: C/I ratio objective Figure 4-15: Block Diagram for Radio Equipment. Figure 4-16: Hot-standby Branching... Figure 4-17: Frequency Diversity Branching ......scseeeeee : eres) Figure 4-18: Space Diversity Branching... 79 Figure 4-19: Main Components of the Microwave system 80 Figure 5-1: Schematic diagram of the base station DBS 3900. 84 Figure 5-2: DBS 3900. Figure 5-3: Logical Structure of the BBU3900 .. Figure 5-4: BBU3900 Figure 5-5: Slots of the BBU3900..... Figure 5-6: BBU 3900 boards.. Figure 5-7: GIMU board. 91 Figure 5-8: WMPT board. on Figure 5-9: WBBP boards 97 Figure 5-10: UPEU boards. 98 Figure 5-11: UEIU board. Figure 5-12: UELP boards Figure 5-13: UFLP board. Figure 5-14; UTRP boards... woe OL Figure 5-15: UBFA board... ou 102 Figure 5-16; BBU 3900 cable connection 103 NDGD SENARATH Page 11 of 125MOBILE COMMUNICATIONS Figure 5-17: Logical structure of the RRU3908 ..ssssssssttntnentstatnsesentnenses Figure 5-18: RRU boards... Figure 5-19; RRU3908 cable connectior NDGD SENARATH Page 12 of 125MOBILE COMMUNICATIONS CHAPTER 01 1. TRAINING ORGANIZATION(DIALOG TELEKOM LTD.) NDGD SENARATH Page 1 of 125MOBILE COMMUNICATIONS 1.1, Introduction Dialog Telekom Limited is the leading mobile communication supplier in Sri Lanka. That is fair to recognize Dialog as the leader since its widest coverage across the country and largest customer base over 3 million subscribers. While Dialog GSM (Global System for Mobile communication) network pursuit its recognition as the leading service provider of the country, the company extended its business scope in to many streams providing last mile information and communication solutions to Sri Lanka, 1.2. History of Dialog Dialog was incorporated as a private limited liability company on 27 August 1993 and converted to a public limited liability company on 26 May 2005. From 1993 it developed its GSM network centered in Colombo city and start commercial operation at 1995. At that time Dialog was known as the MTN Networks and its GSM subscriptions were branded as the “Dialog-GSM”. From its begging it had an attractive and meaningful tagline “The Future. Today” As an initial network Dialog GSM only covered the crowded and industrialized areas like Colombo city. As a result of its customer centric services and modem marketing strategies, it starts recording profits at 1998. Then Dialog started to expand its network all over the country and keep its Quality of Service (QoS) at a very higher level than other service providers. As a result at 2000 it became the leading mobile telecommunication service supplier in the country. As the leader in mobile communication, Dialog started to extend its business scope to provide more last mile solutions to Sri Lankan individuals and corporate bodies. At 2001, it launched the “Dialog Internet”, and started to be recognized as an Internet Service Provider (ISP) other than its core business. Consequently “Dialog SAT” and “Dialog Global” were launched at 2002 and 2003. Today, proving there tagline “The Future. Today” Dialog has pursuit various Value Added Services (VAS) and latest technologies of telecommunication in the country and willfully seeking for more and more future technologies. 1.3. Vision and Mission 3.1. Dialog Vision To be the undisputed leader in the provision of multi-sensory connectivity resulting always, in the empowerment and enrichment of Sri Lankan Lives and Enterprises. NDGD SENARATH Page 2 of 125MOBILE COMMUNICATIONS 1.3.2. Dialog Mission To lead in the provision of technology enabled connectivity touching multiple human sensors and faculties, through committed adherence to customer driven, responsive and flexible business processes, and through the delivery of quality service and leading edge technology unparalleled by any other, spurred by an empowered set of dedicated individuals who are driven by an irrepressible desire to work as one towards a common goal in the truest sense of team spirit. 1.3.3. Corporate Values Total Commitment to our Customers v — Dynamic & Human Centered Leadership Commitment to task & Team work v ~ Uncompromising integrity v Professionalism and accountability > Foremost concem for respect & care 1.4. Dialog Services 1.4.1. Dialog GSM As the core business Dialog provides “Dialog GSM”, a GSM mobile communication network both working on GSM-900 and GSM-1800 bands. Initially it was only in GSM-900 and while growing of the network and subscribers GSM-1800 was introduced, Now Dialog GSM is the GSM network with widest coverage with 676 base stations island wide and best QoS in the country. It provides all GSM based value added services to its customers including SMS, MMS, WAP, ete. Dialog GSM started only with post paid subscribers and it introduce the pre paid subseriber services recently after that, Now Dialog GSM is the mobile communication supplier for over 3.5 billion Sri Lankan. 1.4.2. Dialog Internet Dialog start operating as an ISP in Sri Lanka launching Dialog Internet at 2001. It provides last mile international data services to corporate bodies and individuals of Sri Lanka. Now Dialog Internet has populated as a prepaid ISP provider to domestic users. Dialog uses common international data services and its own satellite services to provide Dialog Internet. NDGD SENARATH Page 3 of 125MOBILE COMMUNICATIONS 1.4.3. Dialog W@P Dialog W@P is a service introduce to provide WAP (Wireless Application Protocol) services to Dialog GSM subscribers. WAP is a technology used to access internet through mobile phones. A WAP enabled phone can used to surf internet via the Dialog W@P service. 1.4.4, Dialog Packet Data Services As GSM based packet data services Dialog launched the GPRS (Global Packet Radio Services) data service and EDGE (Enhanced Data Rates for GSM Evolution) data services firs in Sri Lanka, These services provide an efficient and low tariff based data services to GSM subscribers. 1.4.5. Dialog SAT Dialog SAT is a satellite mobile telephony service which can use to fulfill the communication needs of remote locations and special situations like disasters where typical GSM coverage is inaccessible, For an example in Northern and Eastern province of Sri Lanka is at a war situation and Dialog SAT can be used to cater the communication needs of those areas, Dialog SAT is based on the “THURAYA” satellite phone solutions, THURAYA provides mobile equipment which can communicate in both GSM and Satellite networks, and it provides GPS (Global Positioning System) solutions too, 1.4.6. Dialog 3G Network Dialog is the first operator to introduce 3G (Third Generation) mobile communication the south Asian region, 3G is W-CDMA (Wideband — Code solutic ision Multiple Access) based technology to provide high data rates in air interface allowing High quality speeches, video streaming, high speed data services and many more. Dialog launched its non commercial 3G trial version at 2004 and launches the commercial version in near future, It will make Sri Lanka and United States are equal countries in mobile telecommunication technologies. 1.5. Organizational Structure The company’s organization structure is regularly adjusted to facilitate the realization of the company’s strategic objectives, on the backdrop of the financial position of the Company. and the volume of business activities transacted by the human resources of the company. Dialog Telecom objective in organization designing is to provide for the sound management of sustainable growth, ensure organizational effectiveness and the creation and retention of future leaders. NDGD SENARATH Page 4 of 125MOBILE COMMUNICATIONS 1.5.1. The Board of Directors The Company's business and operations are managed under the supervision of the Board of Directors comprising of five e non executive directors and one executive director. Dr. Hansa Wijayasuriya is the current Chief Executive of the company. The Board consists of the following 6 directors. > > vvv v Tan Sri Dato’ Ir. Muhammad Radzi bin Haji Mansor— Chairman Dr. Shridhir Sariputta Hansa Wijayasuriya — Chief Executive Ir Prabahar s/o Nagalingam Kirupalasingam Mr. Moksevi Ras igh Prelis Mr. Yusof Annuar bin Yaacob Dato’ Mohammed Shazalli bin Ramly A sample employee structure of an engineering division of Dialog Telekom is shown below, General Manager Manger Manager Manager ‘Asst Manager Engineer ‘Asst Engineer Technical ‘Technician NDGD SENARATH Page 5 of 125MOBILE COMMUNICATIONS 1.6. Key Milestones of Dialog Telekom, > Dialog Telekom was incorporated in Sri Lanka under the name of MTN Networks (Private) Limited on 27th August 1993 > Dialog commenced operations in 1995. The company’s postpaid mobile service was initiated in March 1995 under the “Dialog” brand name. > In 1997, introduction of automatic International Roaming > Short Messaging Service (SMS) was introduced in June 1998, > Introduction of prepaid services in 1999 under the band name “KIT” > Launch of GPRS (General Packet Radio Service), support High Speed Packet Based Mobile Data Services in 2001 > The launch of Satellite Mobile Telephony Services under the brand name of Dialog SAT in 2002. > Introduction of Multi-Media Messaging (MMS) in 2002 placing itself among the first 35 networks in the world to support this break through mobile telecommunications technology > The introduction of the Dual Band usage of 900MHz and 1800MHz channels in 2003 optimized the spectrum efficiency as well as the Quality of Service. > In 2003 launch Dialog Global, a forerunner in the International Services market. > In 2004, becomes the first operator in South Asia launch a test run in 3G network > In 2006, becomes the first operator in South Asia launch a commercial 3G network NDGD SENARATH Page 6 of 125MOBILE COMMUNICATIONS CHAPTER 02 2. INTRODUCTION TO MOBILE COMMUNICATIONS NDGD SENARATH Page 7 of 125MOBILE COMMUNICATIONS 2.1 History of Global System for Mobile Communication The term GSM was first introduced in 1982 in Europe, meaning Group Spéciale Mobile Objective of the GSM is to define a new international standard for mobile communication in 900MHz frequency band using digital technology. GSM differs significantly from its predecessors in that both signaling and speech channels are digital, which means that itis seen as a second generation (2G) mobile phone system. At 1991, the first GSM system was ready to use and also the meaning of GSM was changed to Global System for Mobile Communications from Group Spéciale Mobile. The first derivative of GSM was defined as Digital Cellular Systems 1800 (DCS 1800, working on frequency of 1800MHz), and United States, the DCS. 1800 was adapted to make Personal Communications Systems (PCS 1900, working on the 1900MHz frequency band). The Global System for Mobile Communications (GSM) is the most popular standard for mobile phones in the world. GSM phones are used by over a billion people across more than 200 countries. 2.2 GSM Radio Network In radio interface GSM uses both Frequency Division Multiple Access (FDMA) and Time Division Multiple Access (TDMA) to access the radio network and Frequency Division Duplex (FDD) as the duplexing technique. Altogether its radio interface can be expressed as a FDMA/TDMA‘FDD interface. While making a voice or data call there should be two data channels allocated to a single mobile station (MS) in order to provide the full duplex. These two channels are called Up Link (UL, from MS to Network) and Down Link (DL, from network to MS). As the GSM standards specify, each FDMA channel should have 200 kHz band width and they are subdivided in to 8 data channels through TDMA. Band UL(MHz) DL(MHz) No. of | Duplex Carriers Frequeney GSM—900 [890-915 935960 124 4 MHz DCS— 1800 | 1710— 1785 1805 — 1880 374 95 MHz The GSM bandwidth is only 25MHz and for DCS it is 75MEz, thus only 124 channels available in GSM and 374 channels in DCS. Considering these frequency bands, the main problem arise is how cater thousands of subscribers with these limited resources. As a solution to this problem cellular frequency reuse patterns are introduced. Cellular frequency reuse divides the coverage NDGD SENARATH Page 8 of 125MOBILE COMMUNICATIONS area into small cells each has a set of carriers so that neighboring cells may not have the same frequencies. Number of carriers in a single cell should be able to cater the subscribers in that particular cell area. This is the foundation of the GSM cellular concept. Fig2.1: Frequency Resse in GSM The advanced functions of radio network such as signaling, handovers, call setup procedures, ete, are discussed at the latter part of this report. All these functionalities, controllers and Entities are collectively called the Base Station System (BSS) of the GSM network. 2.3. GSM Network Switching of voice and data calls, keeping subscriber information, Billing, VAS, etc. are provide by the core network. This is technically called the Network Sub System (NSS) of the GSM network. Describing NSS in brief is bit of tricky without having a proper understanding over GSM funetionalities. Thus NSS is lately described under the appropriate divisions. Eee Sess seoceneet a con Figure 2-1: Basic GSM and UMTS Network Structure NDGD SENARATH Page 9 of 125MOBILE COMMUNICATIONS GSM network can be divided in to three major parts. + Base Station System (BSS) + Network Sub System (NSS) + Transmission Network 2.3.1 Base Station System (BSS) Base Station System implement and control the GSM’s wireless communication (Radio) network, This is the system which directly interacts with the subscribers’ mobile phone, what is technically called the Mobile Station (MS). BSS implements the way of transmitting, receiving, multiplexing, duplexing and other radio based functionalities such as way of frequency reuse, handovers, ete. As shown in above figure the BSS has two major components. Those are Base Transceiver Station (BTS) and Base Station Controller (BSC). BTS is the last end equipment of GSM network, which is responsible of providing transmit and receiving of radio signals thus called the transceiver, BTS do less intelligent operations but it gives the physical connectivity of MS to the network. A BTS may serve single or multiple cells and transmit and receive number of carrier frequencies depending on its hardware configuration, OMC-R (Operation and Maintenance Centre ~ Radio) is a user interface of the BSS. Generally these are computer terminals, through them user are able to connect to the BSC and do changes and observe its configuration 2.3.2. Network Sub System (NSS) NSS has a very complicated structure as shown in the above Figure and there are many different divisions involved to planning and operations of it. Figure only shows the switching system components. But NSS involves switching system, VAS, Intelligent Network (IN), etc. Each of these fields is discussed in detail at the section corresponding to the respective divisions. For the instant I just mentioned the divisions which are involved in NSS transactions. First the Switch Planning and Switch Operations divisions are working on the switching system. Same as the radio network, planning is done by the Switch Planning division and operations by Switch Operations division. Basic entity in mobile switching is Mobile service Switching Centre (MSC). MSC is integrated with a Visitor Location Register (VLR), a database server to hold subscriber information. Home Location Register (HLR) is the main subscriber database. IN is operations and planning are handle by the same division. Then Technology and VAS planning and Technology and VAS operations divisions take care of the Dialogs value added NDGD SENARATH Page 10 of 125MOBILE COMMUNICATIONS services. Planning division plans and implements the VAS applications related to the GSM network and corresponding operation division maintains the smooth operation of such services. In Dialog SMS (Short Message Service) is also handle by the VAS divisions. 2.3.3 Transmission Network Transmission network interconnects all network elements to complete the GSM network. There are different ways and technologies in transmission, And also there types of transmission and different capacities. To complete the local transmission needs of Dialog, as the most suitable way to the country, Dialog has chose microwave links. There are other solutions used in the network, but the widely used way is microwave, Transmission planning and transmission operations divisions are working on local transmission network. Additionally Transmission Operations division takes care of the Dialog’s international satellite links too. There are two special divisions in Dialog to do the International Network Planning and operations. They are responsible of planning and operations of international links for IDD voice traffic and signaling, Dialog uses Vo-IP (Voice over IP) to transmission of international traffic. 2.4 UMTS Services The UMTS provides support for both voice and data services. The following data rates are targets for UMTS: * 144 kbps—Satellite and rural outdoor © 384 kbps—Urban outdoor * 2048 kbp—Indoor and low range outdoor Data services provide different quality-of-service (QoS) parameters for data transfer. UMTS network services accommodate QoS classes for four types of traffic: * Conversational class—Voice, video telephony, video gaming :—Multimedia, video on demand, webcast Streaming cla * Interactive class—Web browsing, network gaming, database access * Background class—E-mail, short message service (SMS), file downloading The UMTS supports the following service categories and applications: * Internet access—Messaging, video/musie download, voice/video over IP, mobile commerce (e.g., banking, trading), travel and information services. NDGD SENARATH Page 11 of 125MOBILE COMMUNICATIONS 24.1 Intranet/extranet access—Enterprise application such as e-mail/messaging, travel assistance, mobile sales, technical services, corporate database access, fleet/warehouse management, conferencing and video telephony. Customized information/entertainment—Information (photo/video/music download), travel assistance, distance education, mobile messaging, gaming, voice portal services. Multimedia messaging—SMS extensions for images, video, and music; unified messaging; document transfer. based services—Yellow pages, mobile commerce, navigational service, UMTS Architecture The public land mobile network (PLMN) described in UMTS Rel. '99 incorporates three major categories of network elements: The UMTS core network GSM phase 1/2 core network elements—Mobile services switching center (MSC), visitor location register (VLR), home location register (HILR), authentication center (AuC), and equipment identity register (EIR). GPRS network elements—Serving GPRS support node (SGSN) and gateway GPRS support node (GGSN). UMTS-specific network elements—User equipment (UE) and UMTS terrestrial radio access network (UTRAN) elements. based on the GSM/GPRS network topology. It provides the switching, routing, transport, and database functions for user traffic. The core network contains, circuit-switched elements such as the MSC, VLR, and gateway MSC (GMSC). It also contains the packet-switched elements SGSN and GGSN. The EIR, HLR, and AuC support both cireuit- and packet-switched data. The Asynchronous Transfer Mode (ATM) is the data transmission method used within the UMTS core network. ATM Adaptation Layer type 2 (AAL2) handles circuit-switched connections. Packet connection protocol AALS is used for data delivery. NDGD SENARATH Page 12 of 125MOBILE COMMUNICATIONS Games ‘Gore networ| C sg.eeret, Figure 2-2: UMTS Architecture 2.4.2 General Packet Radio System The General Packet Radio System (GPRS) facilitates the transition from phasel/2 GSM networks to 3G UMTS networks. The GPRS supplements GSM networks by enabling packet switching and allowing direct access to external packet data networks (PDNs). Data transmission rates above the 64 kbps limit of integrated services digital network (ISDN) are a requirement for the enhanced services supported by UMTS networks. The GPRS optimizes the core network for the transition to the introduction of the UMTS. 2.5 UMTS Interfaces The UMTS defines four new open interfaces (see Figure 2.3): igher data rates. Therefore, the GPRS is a prerequisite for . Uu interface—User equipment to Node B (the UMTS WCDMA air interface) . Iu interface—RNC to GSM/GPRS (MSC/VLR or SGSN) ° Ju-CS—Interface for circuit-switched data © Iu-PS—Interface for packet-switched data . ub interface—RNC to Node B interface . Tur interface—RNC to RNC interface (no equivalent in GSM) The Iu, Jub, and Iur interfaces are based on the transmission pri mode (ATM). les of aynchronous transfer NDGD SENARATH Page 13 of 125MOBILE COMMUNICATIONS 2.6 UMTS Terrestrial Radio Access Network The major difference between GSM/GPRS networks and UMTS networks is in the air interface transmission. Time division multiple access (TDMA) and fregency division multiple access (FDMA) are used in GSM/GPRS networks. The air interface access method for UMTS networks is wide-band code division multiple access (WCDMA), which has two basic modes of operation: frequency division duplex (FDD) and time division duplex (TDD). This new air interface access method requires a new radio access network (RAN) called the UTMS terrestrial RAN (UTRAN). The core network requires minor modifications to accommodate the UTRAN Two new network elements are introduced in the UTRAN: the radio network controller (RNC) and Node B. The UTRAN contains multiple radio network systems (RNSs), and each RNS is controlled by an RNC. The RNC connects to one or more Node B elements. Each Node B can provide service to multiple cells. The RN functions in GSM/GPRS networks. Node B in UMTS networks is equivalent to the base transceiver station (BTS) in GSM/GPRS networks. In this way, the UMTS extends existing in UMTS networks provides functions equivalent to the base station controller (BSC) GSM and GPRS networks, protecting the investment of mobile wireless operators. It enables new services over existing interfaces such as A, Gb, and Abis, and new interfaces that include the UTRAN interface between Node B and the RNC (Iub) and the UTRAN interface between two RNCS (Iur). The network elements of the UTRAN are shown in Figure 2.4. Core network ANC E a Msc ome aa — = sasn a lub 7 E ANG Node & Figure 2-3: UTRAN Architecture 2.6.1 Radio Network Controller The radio network controller (RNC) performs functions that are equivalent to the base station controller (BSC) functions in GSM/GPRS networks. The RNC provides centralized control of the Node B elements in its covering area. It handles protocol exchanges between UTRAN NDGD SENARATH Page 14 of 125MOBILE COMMUNICATIONS interfaces (Iu, Iur, and Tub). Because the interfaces are ATM-based, the RNC performs switching of ATM cells between the interfaces. Circuit-switched and packet-switched data from the lu-CS and Iu-PS interfaces are multiplexed together for transmission over the Tur, lub, and Uu interfaces to and from the user equipment (UE). The RNC provides centralized operation and maintenance of the radio network system (RNS) including access to an operations support system (OSS). The RNC uses the Tur interface. There is no equivalent to manage radio resources in GSM/GPRS networks. In GSM/GPRS networks, radio resource management is performed in the core network. In UMTS networks, this function is distributed to the RNC, freeing the core network for other functions. A single serving RNC manages serving control functions such as connection to the UE, congestion control, and handover procedures. The functions of the RNC include: * Radio resource control Admission control Channel allocation © Power control settings * Handover control © Macro diversity © Ciphering © Segmentation and reassembly Broadcast signalling © Open loop power control 2.6.2. Node B Node B is the radio transmission/reception unit for communication between radio cells. Each Node B unit can provide service for one or more cells. A Node B unit can be physically located with an existing GSM base transceiver station (BTS) to reduce costs of UMTS implementation. Node B connects to the user equipment (UE) over the Uu radio interface using wide-band code division multiple access (WCDMA). A single Node B unit can support both frequency division duplex (FDD) and time division duplex (TDD) modes. The Iub interface provides the connection between Node B and the RNC using asynchronous transfer mode (ATM). Node B is the ATM termination point. NDGD SENARATH Page 15 of 125MOBILE COMMUNICATIONS The main function of Node B is conversion of data on the Uu radio interface. This function includes error correction and rate adaptation on the air interface. Node B monitors the quality and strength of the connection and calculates the frame error rate, transmitting this information to the RNC for processing. The functions of Node B include: * Air interface transmission and reception © Modulation and demodulation © CDMA physical channel coding * Micro diversity © Error handling * Closed loop power control Node B also enables the UE to adjust its power using a technique called downlink transmission power control, Predefined values for power control are derived from RNC power control parameters. 2.6.3. UMTS User Equipment The UMTS user equipment (UE) is the combination of the subscriber's mobile equipment and the UMTS subscriber identity module (USIM). Similar to the SIM in GSM/GPRS networks, the USIM is a card that inserts into the mobile equipment and identifies the subseriber to the core network. The USIM card has the same physical characteristics as the GSM/GPRS SIM card and provides the following functions: ‘* Supports multiple user profiles on the USIM © Updates USIM information over the air © Provides security functions © Provides user authentication * Supports inclusion of payment methods ‘+ Supports secure downloading of new applications The UMTS standard places no restrictions on the functions that the UE can provide. Many of the identity types for UE devices are taken directly from GSM specifications. These identity types include: © International Mobile Subscriber Identity (IMSI) * Temporary Mobile Subscriber Identity (TMSI) * Packet Temporary Mobile Subscriber Identity (P-TMSI) NDGD SENARATH Page 16 of 125MOBILE COMMUNICATIONS Temporary Logical Link Identity (TLLI, * Mobile station ISDN (MSISDN) © International Mobile Station Equipment Identity (IMEI) * International Mobile Station Equipment Identity and Software Number (IMEISV) © The UMTS UE can operate in one of three modes of operation: * PS/CS mode—The UE is attached to both the packet-switched (PS) and circuit switched (CS) domain, and the UE can simultaneously use PS and CS services. * PS mode—The MS is attached to the PS domain and uses only PS services (but allows CS-like services such as voice over IP [VoIP). * CS mode—The MS is attached to the CS domain and uses only CS services. 2.7. GSM and UMTS Core Network. Now GSM network operators have introduced a rule also UMTS and access to the network elements and the network architecture of the GSM network, as well as GPRS and EDGE back. UMTS and GSM usually have a common core network for the transmission of voice and data. For this reason, both network elements of the GSM and UMTS is contained in the following illustration and description. can) Figure 2-4: Basic GSM and UMTS Network Strueture The combined UMTS-GSM network architecture is divided into an access network with the mobile and base stations and the core network to the existing network architecture of GSM and DCS. Within the access network, there are similar components as in GSM to UMTS. Due to new features you have chosen another name. Each wireless network has its own transmission and reception area, which is referred to as Radio Access Network (RAN). It used different frequencies and transmission methods. In the UMTS network, this area is called UMTS NDGD SENARATH Page 17 of 125MOBILE COMMUNICATIONS Terrestrial RAN (UTRAN) in the GSM network as GSM / EDGE RAN (GERAN), respectively. The GERAN is composed of the base station (BTS) and the controller (BSC). In UTRAN, the base station is the Node-B. B stands for base or base station. Several of them are controlled by a Radio Network Controller (RNC). In UTRAN, the controller (RNC) are interconnected as opposed to GERAN. Among other things, the so-called soft handover is possible. Two Node B must provide a terminal. The mobile phones are referred to as user equipment (UE). The instrument itself as a Mobile Equipment (ME), the SIM card as UMTS. Subscriber Identity Mobule (USIM).In the core network circuit-oriented connections are managed by the MSCs. There is a home location Home Location Register (HLR), the subscriber records in the temporary files Visitors Visitor Location Register (VLR) are stored the exchanges. The GMSC, the gateway switching center, is responsible for the transition to networks, The packet-based data traffic is handled by the SGSN (Serving GPRS Support Node). The routing to the Internet takes over the GGSN and from landline and other mot (Gateway GPRS Support Node). This network architecture allows quick changeover between UMTS and GSM / GPRS, if the terminal used to support dual-mode. Then available for customers in non-UMTS UMTS-GSM-served areas. Problems are few applications that do not work with GSM. For example, video telephony. In order to achieve the high transmission rate in UMTS networks, the core network has to be adapted. Once UMTS is established and the GSM us .¢ is reduced, the conversion of the core networks is expected to start. This is to be converted from the SS7 based signaling to a pure IP network. Since most traffic based on IP, the language will be changed out. The traditional circuit switching will disappear in favor of packet switching, At least then voice-over-IP (VoIP) in the mobile reality. NDGD SENARATH Page 18 of 125MOBILE COMMUNICATIONS 2.8 Hierarchical Structure of UM interface ‘Communcston management (CM) Networkapplicationayer(L3) obit and secrty manager ) Rao resowcesmanagomont(FR) Datainklayr(.2) grated managenent RACH CCH AOCHPCH SOCCH SACCH TCH Prysialinktayer(t) TOHOTOHITCH2, . SACOH. « TOHZSIDL Murirame Figure 25: Hierarchical structure of UM interfice The first layer is the physical layer, which is marked as LI and is the lowest layer. This layer provides the radio link needed in transmission of bit stream. It defines the radio access capability of the GSM system and provides the most fundamental radio channel (logical channel) for the information transmission of higher-layer , including the traffic channel and control channel. The second layer, marked as L2, is the data link layers and it is the middle layer. It applies the LAPDm protocol. This layer includes various types of data transmission structures. It controls the data transmission so as to ensure the reliable dedicated data links which are set up between the mobile station and base station. The LAPDm protocol is based on the D channel link access protocol (LAPD) in ISDN. For LAPDm, the radio transmission and control characteristics are suitable to the signal transmission at the Um interfa The third layer is the network application layer, which is marked as L3 and is the top layer. It includes various types of messages and programs for control and management of the services. That is to say, in this layer, specific messages of the mobile station and the system control processes are packed into different protocols and mapped to logical channels. L3 includes three sub-layers: the Radio Resources management (RR), Mobility Management (MM) and Communication Management (CM). These are the major contents of the messages transmitted via the Um interface. The CM sub-layer includes three major parts: © CC (call control service), NDGD SENARATH Page 19 of 125MOBILE COMMUNICATIONS SS (supplementary service) and * SMS (short message service). 2.9 Voice Signal Processing obits Iteteing txypion —— Bustlomatinn —— Netin —— janrssin Figure 2-6: Sep of voice signal processing How Voice Signal Processing in GSM The radio channel is quite different from the wired channel. First, the radio channel has a distinct time-change characteristic. The radio channel is exposed to the air, so it is vulnerable to the interferences in the aii The signal is influenced by various interferences, multi-path fading and shadow fading, so the error bit ratio is rather high. To solve the problems mentioned above,we use a technique for the voice, to pass an analog-to-digital converter is actually a sampling process in the rate of SKHz, after quantification each 125s contains 13bit of code stream; then speech coding is performed with every 20n as a segment and the code transmission rate is reduced to 13Kbit/s, which becomes 22.8Kbits after the channel coding; then the voice becomes a code stream at 33.8kbit/s after code interleaving, encryption and burst, formatting and is transmitted finally. The processing at the terminal is just the reverse of the above procedures. NDGD SENARATH Page 20 of 125MOBILE COMMUNICATIONS 2.10 Analog Digital Conversion i ‘CHANNEL ‘CHANNEL CODING DECODING. INTERLEAVING |DEINTERLEAVING| ‘Transmission Figure 2-7: Analog digital conversion 2.11 Speech Coding GSM is a digital system, so speech which is inherently analog, has to be digitized. The method employed by current telephone systems for multiplexing voice lines over high speed trunks and is pulse coded modulation (PCM). The output stream from PCM is 64 kbps, too high a rate to be feasible over a radio link. 2.12 Chanel coding Channel coding adds redundancy bits to the original information in order to detect and correct, if possible, errors ocurred during the transmission. The channel coding is performed using two codes: a block code and a convolutional code. The block code receives an input block of 240 bits and adds four zero tail bits at the end of the input block. The output of the block code is consequently a block of 244 bits. A convolutional code adds redundaney bits in order to protect, the information. A convolutional encoder contains memory. This property differentiates a convolutional code from a block code. A convolutional code can be defined by three variables :n, kand K. The value n corresponds to the number of bits at the output of the encoder, k to the number of bits at the input of the block and K.to the memory of the encoder. The ratio, R, of the code is defined as R= k/n, Example- Let's consider a convolutional code with the following values: k is equal to 1, n to 2 and K to 5. This convolutional code uses then a rate of R = 1/2 and a delay of K = 5, which means that it will add a redundant bit for each input bit. The convolutional code uses 5 NDGD SENARATH Page 21 of 125MOBILE COMMUNICATIONS consecutive bits in order to compute the redundancy bit. As the convolutional code is a 1/2 rate convolutional code, a block of 488 bits is generated. These 488 bits are punctured in order to produce a block of 456 bits. Thirty two bits, obtained as follows, are not transmitted : C1 +15) forj=0, 1, ... 31 1 bit input 2 bit input The block of 456 bits produced by the convolutional code is then passed to the interleaver. 2.13. Interleaving An interleaving rearranges a group of bits in a particular way. It is used in combination with FEC codes( Forward Error Correction Codes ) in order to improve the performance of the error correction mechanisms. The interleaving decreases the possibility of losing whole bursts during the transmission, by dispersing the errors. As the errors are less concentrated, it is then easier to correct them, 2.14 Burst 2.14.1 Normal Burst FRAME 1(4.615ms) mAb Guafd Tail Flag Training Flag Tail Guard Data Period Bits Bit sequence Bit 2 Bits Period Figure 2-8: Normal burst Carries traffic channel and control channels BCCH, PCH, AGCH, SDCCH, SACCH and FACCH. ‘© Data - Two blocks of 57 bits each. Carries speech, data or control info. © Tail bits - Used to indicate the start and end of each burst. Three bit always 000. NDGD SENARATH Page 22 of 125MOBILE COMMUNICATIONS © Guard period - 8.25 bits long. The receiver can only receive and decode if the burst is received within the timeslot designated for itSince the MS are moving. Exact synchronization of burst is not possible practically. Hence 8.2Sbits corresponding to about 30us is available as guard period for a small margin of error. © Flag bits - This bit is used to indicate if the 57 bits data block is used as FACCH. © Training Sequence - This is a set sequence of bits known by both the transmitter and the receiver( BCC of BSIC). When a burst of information is received the equaliser searches for the training sequence code. The receiver measures and then mimics the distortion which the signal has been subjected to. The receiver then compares the received data with the distorted possible transmitted sequence and chooses the most likely one. 2.14.2 Access burst Tail Synchronisation Encrypted Tail Guard Bits Sequence Bits Bits Period Figure 29: Access burst © Carries RACH. * Has a bigger guard period since it is used during initial access and the MS does not know how far it is actually from the BTS. NDGD SENARATH Page 23 of 125MOBILE COMMUNICATIONS 2.14.3 Frequency Correction Burst Guaid Tail Tail Guard Period Bits oe Bits Period Figure 2-10: Frequeney correction bust Carries FCCH channel. Made up of 142 consecutive zeros. ¢ Enables MS to correct its local oscillator locking it to that of the BTS. 2.14.4Synchoronous burst Guafd Tail Encrypted Synchronisation Encrypted Tail Guard Period Bits Bits Sequence Bits Bits Period Figure 2-11: Synchoronous burst Caries SCH channel. * Enables MS to synchronise its timings with the BTS, © Contains BSIC and TDMA Frame number. NDGD SENARATH Page 24 of 125MOBILE COMMUNICATIONS 2.14.5Dummy Burst Guafd Tail Flag Training Flag ,,, Tail Guard Period Bits Bit sequence Bit ee Bits Period Figure 2-12: Dummy burst © Transmitted on the unused timeslots of the BCCH carrier in the downlink. NDGD SENARATH Page 25 of 125MOBILE COMMUNICATIONS 2.15 Hierarchy of Frames 1 HYPER FRAME = 2048 SUPERFRAMES = 2 715 648 TDMA FRAMES (3 H 28 MIN 538 760 MS ) O }1 ]2 }3 [4 75) 6 ' ' 2043 | 2044 | 2045) 2046|2047| AFFIC CHANNELS 1 SUPER FRAME = 1326 TDMA FRAMES (6.128) LEFT (OR) RIGHT 1 SUPER FRAME = 51 MULTI FRAMES | | 48) 49] so SIGNALLING CHANNELS ofp fs ial il 1 SUPER FRAME = 26 MULTI FRAME: 1 MULTIFRAME = 26 TDMA FRAM ib iL [ad O fl (243) 4]5] 6} 7] 0} 1) 2 (4.615ms) TDMA FRAM ——) oH 1 TIME SLOT = 13625 BITS (0877 ~<— [oft [2]s]4]s]o]7]o] i] 2] 3] q fd 70 > (4.615 ms) 2. 15511: — 4 — 1 1 bit =36.9 micro sec Figure 2-13: Hierarchy of frames, NDGD SENARATH Page 26 of 125MOBILE COMMUNICATIONS 2.16 Channel Concept Downlink Uplink Figure 2-14: Channel Concept > Physical channel - Each timeslot on a carrier is referred to as a physical channel. Per carrier there are 8 physical channels. > Logical channel - Variety of information is transmitted between the MS and BTS. There are different logical channels depending on the information sent. The logical channels are of two types, + Traffic channel * Control channel NDGD SENARATH Page 27 of 125MOBILE COMMUNICATIONS 2.17 Logical Channel Types LOGICAL CHANNELS TRAFFIC SIGNALLING FULL RATE, HALF RATE, Bm 22.8 Kb/S|_— [Lm 11.4 Kb/s BROADCAST | |COMMON CONTROL] | DEDICATED CONTROL = & = = FCCH -- FREQUENCY CORRECTION CHANNEL, SCH — SYNCHRONISATION CHANNEL BCCH ~ BROADCAST CONTROL CHANNEL, PCH -- PAGING CHANNEL RACH --RANDOM ACCESS CHANNEL AGCH ACCESS GRANTED CHANNEL SDCCH ~ STAND ALONE DEDICATED CONTROL CHANNEL (DOWN LINK ONLY SACCH ~ SLOW ASSOCIATED CONTROL CHANNEL OTH UP & FACCH—FAST ASSOCIATED CONTROL CHANNEL << >UPLINK ONLY DOWNLINKS Figure 2-15: Logical channels 2.17.1 Common Chanel (CCH) I. Broadcast Control Channel (BCH) ca BCCH( Broadcast Control Channel ) Broadcast control channel (BCCH) is a base to mobile channel which provides general information about the network, the cell in which the mobile is currently located and the adjacent cells * Downlink only * Broadcasts general information of the serving cell called System Information * BCCH is transmitted on timeslot zero of BCCH carrier © Read only by idle mobile at least once every 30 secs. NDGD SENARATH Page 28 of 125MOBILE COMMUNICATIONS > FCCH( Frequency Correction Channel ) Frequency correction channel (FCCH) is a base to mobile channel which provides information for carrier synchronization, * Downlink only. © Enables MS to synchronise to the frequency. > SCH( Synchroni ‘Synchronization channel (SCH) is a base to mobile channel which carries information for frame n Channel ) synchronization and identification of the base station transceiver © Downlink only © Carries information for frame synchronisation. Contains TDMA frame number and BSIC. I, Common Control Chanel (CCCH) > PCH Paging channel (PCH) is a base to mobile channel used to alert a mobile to a call originating from the network © Downlink only. * Used by the Network to contact the MS. > AGCH Access grant channel (AGCH) is a base to mobile which is used to assign dedicated resources (SDCCH or TCH) © Downlink only * Used by the network to assign a signalling channel upon successfull decoding of access bursts. > — RACH Random access channel (RACH) is a mobile to base channel used to request for dedicated resources, © Uplink only ‘© Used by the MS to access the Network. NDGD SENARATH Page 29 of 125MOBILE COMMUNICATIONS 2.17.2 Dedicated Chanel (DCH) Control Channel > — spccH Stand-alone dedicated control channel (SDCCH) is a bi-directional channel allocated to a specific mobile for exchange of location update information and call set up information © Call setup * Location update © Sms ¢ Imsi attach and de attach > SACCH Slow associated control channel (SACCH) is a bi irectional channel used for exchanging control information between base and a mobile during the progress of a call set up procedure. The SACCH is associated with a particular traffic channel or stand alone dedicated control channel = Used on Uplink and Downlink only in dedicated mode. = Uplink SACCH messages - Measurement reports. = Downlink SACCH messages - control info, > FACCH Fast associated control channel (FACCH) is a bi-directional channel which is used for exchange of time critical information between mobile and base station during the progress of a call, The FACCH transmits control information by stealing capacity from the associated TCH © Uplink and Downlink. © Associated with TCH only. © Isused to send fast messages like handover messages. © Works by stealing traffic bursts. * Voice Channel 2.18 Cell global identity(CGI-MCC+MNC+LAC+CI) Network identity parameters mainly include cell global identity (CGI) and base station identity code (BSIC). CGIFMCC+MNC#LAC#CI NDGD SENARATH Page 30 of 125MOBILE COMMUNICATIONS Once MS receives SYS INFO, it decodes the CGI information, and decides whether it can stay in the cell according to the MCC and MNC indicated by CGI. At the same time, it judges whether the current location area is changed, so as to decide whether to execute location update. During the location update process, MS will report the new LAI to the network, so that the network can know the LA in which MS is currently located. As a global cellular mobile communication system, GSM conducts strict coding for each GSM network in every country, and even every location area, BTS, and cell, so as to ensure that each cell corresponds to a unique number all over the world. The adoption of this coding scheme can achieve the following objectives: 1, Ensure that MS can correctly identify the current network, so that MS can accurately select the network expected by subscribers and operators. 2. Ensure that the network can know the real position of MS, so that the network can connect various service requests to the MS. 3. Ensure that the MS can report correct neighbor cells’ information to the network during conversation, so that network can perform handover when necessary to keep continuous conversation for the mobile subscribers. © Mobile Country Code (MCC) : MCC consists of 3 decimal numbers. It indicates the home country of the mobile subscriber. MCC is composed of 3 decimal numbers. The coding range is decimal 000-999, * Mobile Network Code (MNC) : MNC is used to uniquely identify a specific GSM PLMN network in a certain country (decided by MCC).MNC is composed of two decimal numbers. The coding range is decimal 00-99. MCC & MNC is usec * international mobile subscriber identity (IMSI) © location area identity (LAN. 1. LAL. Itis periodically transmitted in system information of each cell. MCC indicates the home country of GSM PLMN.And MNC indicates the network number of GSM PLMN.MS uses the received information as the important basis for network selection, 2. IMSI of MS. MS’s IMSI also contains MCC . It shows the resident country of the mobile subscriber. When MS logs on the network or applies for a certain service, it must report its IMSI to the network (When TMSI is unavailable.). The network uses the MCC in IMSI to judge whether this subscriber is an international roaming subscriber. NDGD SENARATH Page 31 of 125MOBILE COMMUNICATIONS IMSI also contains MNC. It shows the home GSM PLMN network of the subscriber. When MS logs on the network or applies for a certain service, it must report IMST to the network (When TMSI is unavailable.). The network judges whether this subscriber is a roaming subscriber according to the MNC in IMSI, and uses it as one of the important parameters for addressing to subscriber HLR. As the unique country identity standard, MCCs are allocated and managed by the International Telecommunication Union (ITU). ITU Recommendation E.212 (blue book) stipulated the MCC number for every country. Due to the special meaning of MCC and MNC modification of it is prohibited once it has been set in the network. If a country has more than one GSM PLMN, different networks must have different MNC. MNC is allocated by relevant telecommunication management department of the country. Location Area Code (LAC): To locate the location of MS, the whole area covered by each GSM PLMN is divided into different location areas. LAC is used to identify different location areas. Cell identity (C1) :To uniquely identify each cell in the GSM PLMN, the network operator needs to allocate one code for each cell, which is the cell identity (C1). Cell identity, together with LAI, is used for identity of each cell in the world. 2.19 Base station identity code (BSIC) In GSM system, each BTS is allocated with a color code, which is called BSIC. MS can identify two cells with the same BCCH by the help of BSI . In network planning, effort should be made to make sure that BCCH of neighbor cells are different from the serving cell’s BCCH to reduce the interference. > Network colour code (NCC) ‘Network Colour Code NCC for GSM NCC is a part of BSIC. MS uses it to distinguish adjacent BTS that belong to different GSM PLMN. NCC is composed of 3 bits, with the range of 0 to 7. NCC and BCC together form the base station identity code (BSIC), transmitted on synchronous channel of each cell. > BTS colour code(BCC) BTS Colour Code BTS for GSM BCC is a part of BSIC. MS uses it to distinguish adjacent BTS that belong to different GSM PLMN. BCC is also composed of 3 bits, with the range of NDGD SENARATH Page 32 of 125MOBILE COMMUNICATIONS 0 to 7. NCC and BCC together form the base station identity code (BSIC), transmitted on synchronous channel of each cell. NDGD SENARATH Page 33 of 125MOBILE COMMUNICATIONS CHAPTER 03 3. NETWORK PLANNING AND OPTIMIZATION NDGD SENARATH Page 34 of 125MOBILE COMMUNICATIONS 3.1. Radio Network Planning This section is responsible for designing the radio network architecture with the objective of improving the Coverage and the Capacity of the network. One of the main obstacles in doing this is the limited number of frequency channels available. 3.2. Improving the Coverage The main objective of any mobile operator is to provide an island wide coverage which will increase its subscriber bank and will also help to give its subscribers an uninterrupted coverage at any part of the country trough establishing new Base Stations in previously uncovered areas. Also the GSM coverage of the network should be improved with the growth of the number of subscribers in an area. In some places between two cells there are coverage holes, which are areas with low Receive Level, which is not strong enough to make a call. This coverage hole should be filled with acceptable receive signal level. One of the solutions to this is a new site installation, 3.3. CELL Planning process. The cell planning process can be shown as follows, Traffic and coverage analysis Nominal cell The cell planning process starts with a traffic and coverage analysis. The analysis should System tuning Figure 3-1: Cell planning process 3.4. Traffic and coverage analysis. produce information about the geographical area and the expected capacity need. The types of NDGD SENARATH Page 35 of 125MOBILE COMMUNICATIONS data collected are, + Cost. + Capacity. + Coverage. + Grade of service [GOS] + Available frequencies. + Speech quality index. + System growth capacity. The traffic demand [that is how many subscribers will join the system and how much traffic will be generated] provides the basis of cellular network engineering. The geographical distribution of the traffic demand can be estimated by using demographic data, such as + Population distribution. + Car usage distribution, + Income level distribution. * Land usage data. + Telephone usage statistics. + Other factors such as subscription charges, call charges, and price of mobile stations, 3.5. Nominal cell planning Upon completion of the data received from traffic and coverage analysis a nominal cell plan is produced. The nominal cell plan is a graphical representation of the network, which simply looks like a cell pattern on a map. However there is a lot of work behind it. Nominal cell plans are the first cell plans that are produced and they from the basis of the further planning. Quit often a nominal cell plan together with one or two examples of coverage predictions is included tenders. At this stage, coverage and interface predictions are usually initiated, Such planning needs computer aided analysis tools for radio propagation studies for example ERICSSON planning tools TEMS cell planner. 3.6. Strategic Network Planning The strategic planning phase focuses on establishing a cost/benefit ratio for all of the various scenarios that can be considered in order to fulfill a speci bility to deal with scenarios and its unmatched post-processing analysis of any simulations, Mentum Planet is perfectly suited to handle the requirements of the strategic network planner. Key requirements NDGD SENARATH Page 36 of 125MOBILE COMMUNICATIONS + Scenario management + Batch processing + Analysis comparison + Statistical analyses and reporting + Accurate deterministic propagation modeling + Advanced traffic modeling + Automatic site placement & selection 3.7. Wireless Network Design When performing the detailed design of a network, the engineer is faced with constraints all the time, Finding the right sites and optimizing the radio configuration is something that requires accuracy in all aspect of the work, as well as easy-to-use software solutions. When. doing a detailed design, the key is to being able to quickly analyse various design options (i.e., candidate sites, antenna configurations) either interactively or using automatic tools. Access to good quality geographical information, such as up-to-date satellite imagery, is a significant cost saving factor as it reduces site visits. With the inclusion of MapInfo Professional GIS as well as the support for detailed modeling of all radio-access standards, Mentum Planet is the world’s, most trusted tool when it comes to the design of a wireless network. Key requirements: © Automated model tuning * Accurate propagation modeling © Easy access to antenna models * Automatic planning capabilities © Accurate network modeling & simulations © Advanced GIS with available satellite imagery NDGD SENARATH Page 37 of 125MOBILE COMMUNICATIONS olneany Figure 3-2: Wireless and network designing on Mentum Plant 3.8. Mentum Planet This is a software delivers the most advanced and easy-to-use planning and optimization product on the market. Dialogue use its 5.4 version and its network structure contain License Server, Database maneger and Workstations. Those a situated in a same place but Network Planning and optimization team at every region can remotely login to the workstation. The licen server provide the access to use the softweare. Because we need a license to use the sofiweare, The Database Manager store all the data, Nobody can modify the data except a qualified engineer who has good experience with that. If anybody need to modify or add data he or she had to send data to that person and he will decide and do whatever the necessary things. This database contain each and every detail of any site such as type of equipment, ant directions, Rx power Tx power ete. 3.8.1. Network Planning with Mentum Planet 5.4 First of all we need to load height layer (geographical height from the sea level. This is need to make the 3D maps) and site file layer(contain all the detail of sites) . load required sites. We can filter 3G, DCS, GSM and LTE. This will help to minimize the complexity of the project. We can predict the coverage area of the neighboring site of the no coverage area, Then we can guess what is the best location to place the BTS. To the accuracy of the prediction first we had NDGD SENARATH Page 38 of 125MOBILE COMMUNICATIONS to use the best tuned model. Because the coverage distribution is different from place to place. Radio frequency can effect so many things. So we had to use different models for different areas. Then we add a new site with the relevant equipment and predict the coverage. We can assign frequencies for BSCH and Hop set using this software but as a practice we done it manually. 3.9. Surveys [and radio measurements] The nominal cell has been produced. Next radio measurements are performed in order to verify the coverage and interference predictions. The sites where the radio equipments will be placed are visited. When planning a cellular network, it is necessary to access the real environment to determine whether it is a suitable site location, We use Global Mapper software and GPS(Global Possioning System) with a Mobile phone to get a brief idea how will be the caverage distribution and what should be the antenna height. Not only that for Install a BTS we need a Transmission link so we had to plan a Microwave link with line of sight. That also we done by the Global mapper with the available location, 3.10. System designed [final cell plan] Once we have optimized and can trust the predictions generated by the planning tool, the dimensioning of the BTS equipment, BSC. And MSC is performed. The final cell plan is then produced. As the name implies, the plan is later used during system installation. 3.11. Site acquisition This division carries out searching and acquiring lands to build new sites with the advice of the Radio Network Planning and Optamization team. The objective this is to improve coverage or capacity or both, Site acquisition is a lengthy process which involves getting approvals from various authorities and institutions such as, TRC - Telecommunications Regulatory Commission CEA ~ Central Environmental Association UDA - Urban Development Authority MOI ~ Ministry Of Interior CAA — Civil Aviation Authority LA ~ Local Authority NDGD SENARATH Page 39 of 125MOBILE COMMUNICATIONS Basie site acquisition procedure is given below, Network Planning Division Site Acquisition Radio Network Planning Checking about customer Proposal seeds potential areas of high service capacity and ‘Search Area Description future business plans. + Geographical Bariers Coverage + ‘Area Plan Selection of x number of locations Acouiring Deeds ob Legal veifcation (by Legal Division) + Joint Feasibility Study With oS Project Division & Microwave Planning Division & Legal Division Order by Dialog Site Acquisition —> Management to start construction Sends the approvals through Approval by LA ‘TRC after the Joint Chairman Inspection Approval eg Inspection by LA Technical Officer Copy to the Ministry of Health Inspection by PHI Upon approval, ‘Submitting to the Local Authority. Obtained Approval Copies of Building Plan + Drawings Figure 33: Basie site acquisition procedure NDGD SENARATH Page 40 of 125MOBILE COMMUNICATIONS 3.12. Implementation. System installation, commissioning, and testing are performed following final cell planning and system design, 3.13. System tuning. After the system has bee3n installed, itis continually evaluated to determine how well it meets the demand. This is called system tuning. It involves, Checking that the final cell has been successfully implemented. * Evaluating customer complaints, © Checking that the network performance is acceptable. Changing parameters and taking other measures. The system needs constant retuning, due to the fact that the traffic and number of subscribers continuously increase, Eventually the system reaches a point where it must be expanded so that it can manage the increasing load and new traffic. At this point, a traffic and coverage analysis is performed and the cell planning process cycle begins again. 3.14. Frequency reuse. The frequency reuse is implemented because only a small number of radio channel frequencies were available for mobile systems. The concept of frequency reuse is based on assigning to each cell a group of radio channels used within a small geographic area. Cells are assigned a group of channels that is completely different from neighboring cells. The coverage area of cells is called the footprint. This footprint is limited by a boundary so that the same group of channels can be used in different cells that are far enough away from each other so that their frequencies do not interfere. 3.15. Frequency allocation for Dialog In Sri Lanka the Telecommunication Regulatory Commission [TRC] carries out the monitoring of the frequency spectrum, It allocates a frequency band for every telecommunication operator who is allowed to carry out their services to the public. There are two frequency band allocate for the Dialog. NDGD SENARATH Page 41 of 125MOBILE COMMUNICATIONS > GSM 900MHz band The Dialog is reserved a 7.5MHz bandwidth of the 900MHz GSM spectrum by the TRC which consists of 36 frequency carriers from frequency channel 88 to 124. Frequency Band Frequency Range Channels Used GSM 900MHz (GSM) UL 890-915 88-124 DL 935 ~960 GSM 1800MHz (DCS) UL 1710-1785 312 — 885 DL 1805 - 1880 20 MHz duplex gap. cHo cues cH124 cHo cuss cH 124 = = 2 g # 3 E 3 a f a s 8 3 & § g — ——___ ‘UP LINK DOWN LINK Figure 3-4: 900MHlz Frequency Channels > GSM 1800MHz band (DCS) The Dialog is reserved a 6.5MHz bandwidth of the 1800MHz DCS frequency band by the TRC which consists of 33 frequency carriers from frequency channel 549 to 581 Frequency Band Frequency Range Channels Used GSM 900MHz (GSM) UL890—915 88-124 DL 935 ~960 GSM 1800MHz (DCS) UL 1710-1785 312 — 885 DL 1805 - 1880 In GSM-900 band Dialog uses channel number 88 to 124. Each of these channels has 200 kHz NDGD SENARATH Page 42 of 125MOBILE COMMUNICATIONS bandwidth and 20 MHz duplex gap. In GSM-1800, also called DCS (Digital Cellular System) Dialog uses channel number 549 to 581. Using one carrier frequency, 8 channels can be formed using TDMA (Time Division Multiple Access). To accommodate the requirement of channels using limited number of physical channels different frequency techniques are used. 20MEz duplex gap zs HO. 6rS HO. 18s HO $88 HO. zs HO. ers HO. 18s HO 88 HO. ZHI SO8l + f 7H OLLI 7H BLL SSS UP LINK, DOWNLINK Figure 3-5: IS00MHIz Frequeney Channels 3.16. Cellular Frequency Planning Frequency planning in a cellular network is a very important since the available frequency band for a specific service provider is a limited resource. The word ‘Cellular’ is used in GSM communication since the frequencies are planed in cellular wise. There are different set 0 frequencies used in GSM communication, Cellular architecture is built in such a manner that the set of frequencies allocated to a service provider is divided in to set of small frequency groups and re used them using a repeating pattern, Here neighboring cells can’t have same frequency since it will make interference. Figure 3.6; Frequency re wse Frequency planning is one of the major tasks of Radio Network Planning and Optamization section. The division use special software tool running in Solaris platform to do the frequency planning. Itis called the ‘Planet tool’. This tool can be used to analyze the affect of interference, NDGD SENARATH Page 43 of 125MOBILE COMMUNICATIONS obstructions, ete. and to visualize the covering area of a cell. Planet is an advance tool which stores the data about all network configurations and can be used to analyze even technologies like frequency hopping. There are two type of hopping * Frequency Hopping * Base Band Hopping 3.16.1, Frequency Hopping When conventional frequency concepts are not capable to cater the capacity and quality requirements newer techniques like Frequency Hopping (FH) are introduced. FH is changing the frequency channel in a pseudo random pattern to minimize the effect of interference and improve the frequency utilization. In this context only the BCCH (Broadcast Control Channel) will have a fixed frequency. 3.16.2. Base Band Hopping In this type of hopping, only frequencies used by the TRXs can be allocated to the FHS (Frequency Hopping Sequence). The BCCH supporting Time Slot cannot hop’s 0 of the BCCH TRX is always transmitting on the BCCH frequency. Other timeslots can use other frequencies unless the BCCH frequency is transmitted by any other TRX at the same time. TRX | bol ATATATATATATA| TRX3 SET n gT rex 4([V[TVIVIVIVIVIVIV] Figure 37; Base Bands Hopping The major advantage of the BBH is the time TS | to TS 7 of the BCCH frequency containing TRX is allowed to perform hopping. But Frequency Hopping performs best with at least 4 hopping frequencies. So cells need at least 4 TRXs and it is the disadvantage of this system. 3.16.3. Radio Frequency Hopping mex! RT TT TTT.) rex? (CIOIOIOIOIGICIG) x3 CVOIOIGIOIRION€S] rRxt EWMOOIMOIOIOIC| Figure 3-8: Radio Frequencies Hopping NDGD SENARATH Page 44 of 125MOBILE COMMUNICATIONS In RFH system each Frame unit is connected to one carrier unit. Hopping is performed by changing the carrier frequency within the carrier unit by a synthesizer. So it is also known as Synthesized Frequency Hopping (SFH). In this system, a FHS can contain up to 64 frequencies. The TRX supporting the BCCH (e.g. TRX | of the following figure) cannot hop. We can get good capacity after applying the RFH (or SFH) for a site. There are three main external parameters considered for Frequency Hopping, which can be modified by the operator, + MAIO + FHS + HSN 3.16.4. MAIO - Mobile Allocated Index Offset The Mobile Allocated Index Offset allows determining the correct line in the Mobile Allocation look up table to find the corresponding ARFCN .The MAIO is selectable for each timeslot and each TRX separately. It is constant on the TRX but it changes between the frame units, Range is 0 to 63. BSIC Channels are to identify each station and sub stations. It can be represented in 2 codes. * NCC ( Network Color Code ) — represented in 3 bit binary form, Therefore it the numbers are from 0 to 7. And DIALOG TELEKOM has been given from 4 to7. * BCC (Base station Color Code ) — it’s also in 3 bit form. But they have give the permission for DIALOG to use all the numbers. So the BSIC values for DIALOG are 40 ~ 47 & 70 ~ 77. The 1* digit represents the NCC value & the 2" represents the BCC value. 3.16.5. PHS - Frequency Hopping Sequence FHS is the set of frequencies (maximum 63) to be used in the frequency-hopping group. It is given by the operator and can be different for each Timeslot and each TRX of each cell. 3.16.6. HSN - Hopping Sequence Number The HSN is one of 4 input parameters to the GSM hopping sequence generator algorithm. Range of HSN is 0 to 63. HSN = 0 means the hopping is in cyclic mode. NDGD SENARATH Page 45 of 125MOBILE COMMUNICATIONS 3.17. Equipment Planning Choosing the correct equipments to implement a BTS (Base Transceiver Station) is very important since those are the things which actually define the behavior of the BTS. Specially choosing the correct antenna will very important, When choosing an antenna, there are deferent factors to consider. They are radiation pattern, Gain of the antenna, Size and weight of the antenna and price. There are two important types of antennas. The efficiency of a cellular network depends of its correct configuration and adjustment of radiant systems: their transmit and receive antennas. And one of the more important system optimizations task is based on correct adjusting tilts, or the inclination of the antenna in relation to an axis, With the tilt, we direct radiation further down (or higher), concentrating the energy in the new desired direction, When the antenna is tilted down, we call it ‘downtilt,, which is the most common use, If the inclination is up (very rare and extreme cases), we call ‘uptilt. 3.17.1. Mechanical Down Tilt (MDT) These antennas are comparatively low cost but side lobs effect is higher and tilting of these antennas is done mechanically so that back lobe effect may higher. MECHANICAL DOWNTILT. Figure 39: Mechanical down tlt coverage NDGD SENARATH Page 46 of 125MOBILE COMMUNICATIONS Mechanical + The downtilt angle varies over the horizontal beamwidth, Patterns measured +90° from the center of the beam have decreasing tilt angle until there is no tilt 90° from the main beam, + The horizontal half-power beam width increases with greater downtilt angle, + The resulting gain reduction depends on azimuth direction Electrical 3.17.2. Electrical Down Tile (EDT) EDT are down tilt using a face difference provided to each dipole of the antenna and hence back lobe and side lob effects are lesser. But these are expensive than the MDTs. Addition to the antennas there are deferent equipments used in BTS to complete its functionality. Some these may need to be carefully designed since otherwise it may lead to alter the required performance of the site. For an example lets say a combiner unit (ANCG, ANY, etc.). These combiners reduce the transmit power by 3dBm, So these kinds of equipments should be carefully design. ~=0 o @=70 o = 140 o = 210 o @ = 280 o Figure 3-0: Electrical downit mechanism + There is uniform downtilt over the whole azimuth range. + The horizontal half-power beamwidth is independent of the downtilt angle. + There is identical gain reduction in all azimuth directions. NDGD SENARATH Page 47 of 125MOBILE COMMUNICATIONS 3.17.3. Comparison of Mechanical and Electrical Downtilt HORIZONTAL RADIATION PATTERN IN THE HORIZONTAL PLANE MECHANICAL ELECTRICAL {Down angle vanes over the azzmuth range 1 Constant downtit angle over he whole azmmut range set dountit angle only in main directon (0°), No downtit in tit axis direction (+-90" trom main beam), 11 Horizontal hal-power beam wih increases with 11 Horizontal halt: power beam independent ot ‘ising downtit ange. doantit ange 1 Resuting gain reduction depends on azmth drection 1 Identical gain reduction forall azimuth directions, (can rarely be considered in network planning). Figure 3-11: Comparison of mechanicel and eletial downslt 3.18. Improving the Capacity Capacity Improving is another of the major tasks of Radio Network Planning and Optamization section, With the increasing number of subscribers the capacity of the network will have to be increased inevitably. Also when there is a large scale event like an international sports festival or an exhibition where a large number of subscribers are expected to gather the capacity at that particular place should be increased to accommodate the increase in traffic. There are many approaches to this, © Implementing additional sites. The advantage of this approach is that the frequency reuse can remain the same. But additional costs will have to be incurred for site acquisition and payment of rentals, Also redesign of old cells will be necessary. NDGD SENARATH Page 48 of 125MOBILE COMMUNICATIONS * Increasing the number of TRX in the cell. For a single BTS the number of TRX can be increased up to 12.With this approach there is no need to search and acquire new sites. This will improve the capacity but tighter reuse of frequencies will be necessary. ‘* Implementation of concentric cells. This refers to the implementation of an inner zone layer with smaller cell size to co exist with the outer zone layer with the normal cell size. This is normally done by power reduction or using dual band technique. Due to the smaller cell area of th iner zone smaller reuse will be possible which increases the capacity. Also ad ional TRXs can be implemented in the inner cell. This technique is heavily used in the Dialog GSM network © Installing new micro cells. Micro cells are a lower cell layer which is overlaid by an umbrella cell, New micro cells can be installed to handle the excess traffic and this will increase the capacity of that cell area. In this approach the reuse pattem for micro cells will be smaller and spectrum efficiency is higher, But new sites have to be acquired for this and the initial cost is higher. It is clear that a smaller cell size increases the traffic capacity. However a smaller cell size means more sites and a higher cost for the infrastructure. What is needed is in fact a method that matches cell sizes to the capacity requirements. The system is started using a large cell size and when the system capacity needs to be expanded, the cell size is decreased in order to meet the new requirements. This method uses different cell sizes in different areas and is called cell splitting. 3.19. Radio Network Optimization & Performance Monitoring Quality of the live network is monitored and maintain by the Radia network planning and operation section. There are deferent software tools to obtained and analyze network statistics. These are specific to the vendor of the network equipment (Alcatel, Ericsson, Huwawi, ete.) Addition to network statistics network quality can be monitored using drive tests. Drive test is, done u ing software called NEMO and by connecting a supported mobile phone to NEMO, network behavior can be monitored. 3.19.1, Nemo Outdoor ‘Nemo Outdoor is a laptop-based drive test tool which supports over 200 terminals and scanning receivers from various vendors and all major network technologies. NDGD SENARATH Page 49 of 125MOBILE COMMUNICATIONS A single software platform plus modularity means easy tailorability, enabling you to tailor the product precisely to your needs. Nemo Outdoor’s powerful software platform works for all technologies and for different protocol and application testing options, giving a consistent look and feel. It’s also the only portable measurement solution that offers multiple simultaneous data connection measurements, and runs on a single laptop. Nemo Outdoor produces measurement files in the open ASCII Nemo File Format, enabling quick and easy troubleshooting and analysis, using Nemo Analyze or third-party post-processing tools. Equipment arrangements for Drive Test Lazptop . Figure 3-12: Test Mobile Systems Figure 3-13; Nemo drive test data on Google Earth NDGD SENARATH Page 50 of 125MOBILE COMMUNICATIONS (rere nse su sas ae STS am Figure 3-14: Sereenshots of Nemo software When considering Receiving levels greater than -75 or -80dBm (Green color) is good. Rx quality measures 0 to 7 and Rx quality 0 is good. SQI varies -20 to 30 and values that are closed to 30 gives good quality. C/I (Carrier to Interference ratio) worst varies 0 to 17 & 12-17 are very good values. On Neighbors presentation shows the Rx levels, BCCH & BSIC of neighbors of the current cell. By analyzing it, we can say the cell, which the next handover occurs. Hopping channel window displays the Rx level and the C/I ratio of all Hopping channels. 3.20. Repeater Systems A repeater is a bidirectional RF power amplifier. It is used to cover the coverage holes in an economical way. The RF repeaters are not similar to repeaters used in digital transmission lines, which regenerate the signal. RF repeater only amplify both the signal and the noise, hence cannot improve the SNR. There can be several reasons which lead to coverage holes even in a thoroughly designed NDGD SENARATH Page 51 of 125MOBILE COMMUNICATIONS network. They are, + Unfavorable terrain (mountains, narrow valleys) + Less than optimum BTS sites. (In areas where the traffic intensity is low, it is not cost efficient to install a base station.) + Tunnels and underground stations. © Sport arenas. + Indoors with metal or conerete walls. To be able to receive and transmit signals in both directions, the repeater is connected to a ected towards the base station and to a service antenna directed towards the donor antenna area to be covered. The signal captured by the donor antenna is amplified by the repeater and served to the hole either by the service antenna or for a tunnel using a leaky feeder. For the uplink direction the signal generated by the mobile station is picked up by the antenna or leaky feeder, amplified and send to the BTS of the donor cell. There are two kind of repeaters > PICO indoor repeater ( : sip Donar antenna \ PARTS INCLUDED + BiDirecoonal Amplifor Figure 3-15: PICO repeater system We use for small factories those don’t having then indoor coverage. When we install a PICO repeater we had to consider about the cable loss so we use the minimum cable lengths. We can split the coverage by using the splitter from one repeater and two antennas, We can get the GSM and 3G traffic from one dual repeater. NDGD SENARATH Page 52 of 125MOBILE COMMUNICATIONS > Outdoor repeaters Workin; co pamee Link Server Norking Antenna Donar yy))))) om : ))) ines 1, hey Repeater unit BTS Coverage Repeater Coverage Figure 3-16: Outdoor repeater system Those type repeaters install for large factories. This having much more transmitting power. When installing repeater systems the following factors should be considered, © Install the repeater system with minimum distance or path loss to the donor BTS. If line of sight is possible, most suitabl order to achieve a good SNR and power budget © The receiving antenna’s beam width should be narrow as possible. * Isolation of two antennas should be considerably high. (About 75dB). © Mini zing the overlapping areas. (especially outdoor repeaters having those © Operating the repeater amplifiers in linear range © Minimizing the cable loss. NDGD SENARATH Page 53 of 125MOBILE COMMUNICATIONS CHAPTER 04 4. TRANSMISSION PLANNING AND OPERATIONS NDGD SENARATH Page 54 of 125MOBILE COMMUNICATIONS 4.1. Introduction Transmission network is the way of interconnecting each entity in the GSM network. Under this section Dialog’s transmission network is described and two divisions Transmission Planning and Operations are involved in planning and operations of transmission respectively. Before going to the practical information, a brief description on theories is added. 4.2. Transmission Technologies Transmission is delivering high capacities of data through an appropriate medium to interconnect two entities. In the context of Dialog Telekom transmission is used to interconnect different and distance telecommunication entities. For an example a BTS should connect to a BSC to its operation. These transmission links can convey voice calls, data traffic or signaling information. Transmission medium doesn’t worry about what it transmit but the way of transmit and the capacity. There are world standards to accommodate digital data transmission, Some of them are discussed bellow. 4.2.1. Plesiochronous Transmission (Plesiochronous Digital Hierarchy - PDH) Dialog uses PDH as its main transmission hierarchy. PDH defines a transmission link, which is consist of PCM (Pulse Code Modulation) channels of 2.048 Mbps each consist of 32 time slots of each 64 kbps. These channels are standardized as El channels. Network equipments mapped the data into E1 channels and these channels are interconnected by the transmission network. For an example A-bis links in BTS is an El link, which can direetly connected to transmission equipment which is working in E1 level. Dialog uses microwave transmission as its major transmission method. In a microwave link there can be more than one El. There are link equipments with 2, 4, 8, 16, ete. PCMs. But with the growth of the network need of the high capacity transmission links were raised. There are two choices. To move into a different technology or getting higher speeds through the same technology. To fulfill these requirements Dialog chose Super PDH (SPDH) as the solution, SPDH links provide higher number of PCM links. For an example an Eclipse microwave link can cater 75 El channels. 2.2. Synchronous Digital Hierarchy (SDH) SDH came with the solutions to limitations of PDH. It defines a digital transmission hierarchy which supports very higher data rates than PDH. As Els in PDH, SDH has STM levels of data NDGD SENARATH Page 55 of 125MOBILE COMMUNICATIONS transmission. For an example STM-1 link is capable of catering 155.52 Mbps. A very higher bandwidth compared to PDH. SDH links are commonly used over fiber optic transmission. Another big advantage of SDH is its cross connecting capability. In SDH, data from multiple tributary are byte iterleaved and allows efficient cross connect without complete multiplex or demultiplex. That means one can insert an El channel to a STM-I channel through multiplexing and get it out some other place without complete demultiplex of channel. 4.3. Transmission Planning The transmission of signal in the microwave spectrum is predominantly via the space wave which in the simplest form occurs on a path having adequate clearance over the intervening. terrain and is composed of direct and indirect or reflected components, Broadband radio relay system uses this mode of propagation over line of sight paths between successive relay stations to provide long distance communication circuits. The transmission Planning section concerns about: > Planning Microwave paths & Optical fiber paths. > Installing > Updating microwave links > Connecting remote sites For this the suitable path should be found and the parameters of the link should be checked for required levels. This is done using different analyzing methods and instruments. 4.4. Microwave Transmission Microwave is the most widely used large-scale data and voice transmission medium in telecommunication and radio/Television broadcasting industry today. There are some other Medias as Infra Red, Optical fiber, cables...etc. Microwave has many advantages over other Medias such as: v Travels a long distance compared to IR or cables Low cost vv Simple to maintain v Installation is easier High data rates are possible But we have to face following problems when using microwave links. > Seriously effected and by rain, Fading of the link increases with the rain and the link may totally loss if rain exceeds a maximum value. > Line of site is strictly required NDGD SENARATH Page 56 of 125MOBILE COMMUNICATIONS > Difficult to use within areas where climate is rapidly changing. > The link may loss due to ducting. > Length of the link is limited. > Cannot be used for communication between countries...etc 4.4.1, Designing and Development of Transmission Infrastructure Proper Designing and development of microwave links shows the path full fill the future demands of capacity particularly in backbone connections. When designing the Microwave network Designing team always trying to make connections in mesh form so it can have no of independent paths connecting critical two points. This is applicable to all backbone connection between major points in the network. Another important factor is cost effectiveness and Flexibility of the network. When designing. the network cost per El is concerned, at the same ti ¢ the reliability of the network is another key factor of designing. Dialog Telekom Transmission Infrastructure consists of more than 630 microwave links interconnecting all nodes to make as a single Telecommunication Network. This has been a most widest and strong Transmission network in Sri Lanka, 4.4.2. Path Design Path Design is a field study on Radio link line-of-sight clearance and feasibility. It consists of collecting all required information and processing it for an optimum MW link design. To fulfill this requirement LOS surveys are done. There are two steps in LOS surveys. 1, Map Survey 2. Field Survey 4.4.3. Map Survey Maps are the principal sources of data for office study that usually precedes field survey and for the field survey itself. A preliminary study of the map is required for planning of one or more routes which might appear to be possible between the terminal points given, based on available data and the plotting of profiles which are necessary preliminary, for all of the indicated paths and alternates. Initial Map-work Mainly there are two types of maps Topographical Maps and Digital Terrain Maps. Transmission planning division at Dialog use the 1:50,000 scale topographical maps obtained from the Survey Department of Sri Lanka. In these maps the contour lines are 20m apart and they show mountain ranges, rivers and lakes. They also show major highways, airports and rail tracks. NDGD SENARATH Page 57 of 125MOBILE COMMUNICATIONS Route Map When planning a microwave link various route options should be investigated. As site acquisition is a crucial element in the planning process and also because of the environment considerations it is preferable to keep the options as open as possible. So here a recommended route and a number of alternative routes are selected. 4.4.4, FIELD SURVEY It consists of following steps: v Identification of the site position (using GPS) ~; Calculate link Azimuth and identify the link direction v Check Obstructions in the link direction y Near obstructions (trees, buildings etc.) v Far obstructions (hill peaks, trees over mountains etc.) There are most important things are available to note during the field survey to avoid interferences, reflections and also achieve needed clearance and regulations. They are: > Site near high power radars > Link over water paths > Near obstructions in LOS which may reflect/diffract energy > Crossing of other system routes of similar frequencies > Building regulations of the city > Landmark location 4.5. Visual tests for LOS clearance > Anchored balloons Mirror Flashing > > Flags v ‘Smoke/ Flares 4.4.6. Instruments of Path survey > GPS Satellite Receiver > Binoculars > Compass NDGD SENARATH Page 58 of 125MOBILE COMMUNICATIONS Altimeter vv Theodolite v Inclinometer v Camera Handheld radio v > Flashing mirrors v Topographical Maps 4.5. Path Profiles The major requirement of a microwave link is that satisfaction of line of sight condition between two sites. Therefore, when planning of transmission links, verification of line of sight condition becomes a primary necessity, The Path Profiles are necessary to determine site locations and antenna heights. Care must be taken to assure free sight between the sites and avoid reflections. The line of sight verification (Path profile) can be carried out two ways. > Fully manual work > By using a software tool. 4.5.1. Path Profiles - Manually The manual line of sight verification is commonly known as ‘Constructing a Path Profile” among the staff members. The first thing in construeting a path profile is to get the exact positions of the two locations of the proposed link by longitudes and latitudes. Next in the 1:50000 map, the locations are marked as accurate as possible, Conneeting the two locations by a solid line would be the next step. Sometimes, the two locations would be in two map sections, and to line up more than two maps would be required, In such a situation, a care should be taken to arrange the maps accordingly and accurately, because this can cause substantial errors in our construction. The constructed line should then be divided into one- centimeter parts and the whole length will be noted. The next step is the most important step and the one that should be performed very carefully. The heights of the two locations should be read from the map. The maximum height for each centimeter should be read and noted in front of each centimeter. A table is created to enter the obtained data as follows. NDGD SENARATH Page 59 of 125MOBILE COMMUNICATIONS No. Height 1 750-40 2 720120 3 600 In the first box, the height of the location should be included with the proposed antenna height in meters. For the heights of the ground, there should be 20m added if the land is covered with tress, or 2m added if the land is covered with shrubs or smaller tress. Addition of both the figures is considered as the height of the ground, After that, the obtained data will be entered to an Excel worksheet. The columns of the worksheet should be defined as follows. Distance in ascending order ance in descending order Earth bulge > Elevation > True height (Earth bulge + Elevation) > Line of Sight (Straight line obtained from y = mx + ¢) » Fresnel Zone > LLofF » Clearance from LOS (LOS — True height) > Clearance from LL of Fl (LL of Fl ~ True height) aie Test ane 1 Test si t Site 2 (11,.5Km 180 160 | fatal 140 120 | 400 80 60 40 20 ° 4 Height [rm] 2.3 4 5 6 7 8 9 1011 12 13 14 15 16 17 18 19 20 21 22 23 24 Scaled Distance [em], Figure 41: Excel work sheet analysis NDGD SENARATH Page 60 of 125MOBILE COMMUNICATIONS 4.5.2. Path Loss 4.0 Software The other method used to create a path profile is the Path Loss 4.0 software. Though the whole profile generating process can be done with this software the division uses it only after finding a link with LOS from the Excel sheet based software to ascertain the effect of geo climatic conditions on the link and to find out the suitable radio unit and the antenna with the suitable diameter also considering the equipments available in stocks. The effect of Refraction, Reflection, Diffraction, Various losses and Fading effects can also be included and analyzed using this software. Terrain Data This refers to the data about surface variations plus the effects of the obstacles such as trees and buildings. The GPS coordinates is used for the calculations of the terrain data using the geographical details available. Inputting the closest reference point is also important to improve the accuracy of the resulting path profile, Geo Climatic Data Various standards such as Vigants and Barnett’s method divide the environment in to various climatic zones with unique climatic conditi s. Sri Lanka belongs to the N region in the Vigants and Barnett’s method. The effect of the climatic factors to the link can be added through the software by selecting the region to which the region belongs to, Also inputting the correct value of the rainfall is essential to plan a link accurately. Link Frequency Here the exact link frequencies (both Tx.and Rx.) should be inputted considering the distance between the sites and the frequency bands approved by the TRC, After drawing the path profile the link frequencies might have to be changed if desired value of receive strength is not achieved. Antenna and Radio Unit details The diameter of the Antenna is an important parameter which affects the reliability of the link and depends on the expected capacity of the link. Dialog network normally uses Andrew brand of antennas. Though the Antenna is able to handle a wide frequency band the Radio Unit is designed to handle only a limited frequency band which is specified in the equipment. Dialog NDGD SENARATH Page 61 of 125MOBILE COMMUNICATIONS uses many brands of Radio Units such as Harris, Eriesson, and Siemens ete. The brands and the specifications of the available equipments are obtained from the stock keepers and are entered into the software taking the capacity and reliability issues into considerations. Also When a transmission tower of another operator is shared the antenna diameters allowed by them will have to be used. (Large antennas might not be allowed due to tower strength limitations.) 4.5.3. Altitude The altitude is the vertical displacement above the sea level. It can be measured by using a properly calibrated Altimeter, Also it can be calculated on the map by using contour lines if the Geographical Coordinates of the site is known, 4.5.4, Azimuth The azimuth is the Horizontal angle estimated clockwise from the North to the direction under consideration. A compass is used to measure azimuth which is essential for antenna alignments. Station A NG Azimuth from station A to station B Azimuth from station B to station A Zap Za Station B Figure 42: Azimuth Zpa 4.5.5. Antenna Height Decidi 1g the position at which the antenna should be mounted is one of the major outcomes of the Path Profile analysis. In calculating the antenna height all present obstructions should be cleared and a sufficient margin for future obstructions such as high rise buildings still under construction, tree growth should be taken in to account. At Dialog 15m is added to the elevations of the intervening terrain between the end sites to accommodate for those obstructions. NDGD SENARATH Page 62 of 125MOBILE COMMUNICATIONS 4.5.6, Fresnel Zone Path clearance is described in terms of Fresnel zones. Fresnel zones are families of ellipsoidal boundaries described by points at which a reflected radio wave would travel an integer multiple of half wavelengths further than by a direct route between the transmitter and receiver. Reflections from odd-numbered Fresnel zones will add in-phase at the receiver. Even- numbered Fresnel zone clearance is undesirable because reflections from even-numbered Fresnel zones will be anti-phase at the receiver and will cancel the primary signal. The radius of the Fresnel ellipsoid is related to the wavelength by: Indirect Ray - Direct Ray =n (wavelength); where n= no. of the Fresnel zone 2 The Fresnel ellipsoid gives the estimate of the space volume involved in the propagation phenomena from Tx. antenna to Rx. Antenna, 18 Fresnal Zone First Fresnel Zone radius (in m) Distance from Tx. to the interested point (in Km) Hop length of the path (in Km) D-d = Frequency (in GHz) n Fresnel Zone F,=F. Jn mo>p0e7 Figure 43: Fresnel Zone 4.5.7, Earth Bulge The earth itself has a curvature of its surface and the effect of that also should be included in the path profile calculations. For long hops in flat terrains we get a large value for earth bulge (50-60m) which can affect the calculations greatly. NDGD SENARATH Page 63 of 125MOBILE COMMUNICATIONS 4.5.8, Equivalent Earth curvature Considering the joint effect of the radio ray bending and of the earth curvature, earth radius R is multiplied by a factor K, in order that the radio path is straight. The K factor is a measure of the ray bending effect and depends on the atmospheric structure at a given time, K factor = Equivalent Earth Curvature True Earth Curvature Figure 4-4: Earth curvature 4.6. Frequency Considerations The frequency allocation within Sri Lanka is carried out by the TRC (Telecommunication Regularity Commission) according rules and regulations laid out by its main body the ITU (Intemational Telecommunication Union). The ITU is an international standard body set up by the United Nations which has the internal structure given below. mu International Telecommunication Union ITU-R (formerly CCIR) nu: ITU-TD (formesty CCIT) Radio-communicstion Telecommunication Standardizing Telecommunicaton “Agency ‘Agency Development Agency Cary out the task of| Coordinating radio fraquencies ‘ + WARC RD fry FRB) Ward Administ Rao Conseco Radio eps Boe ‘Responsible for allocating specific tequeney ‘hands to present and future services. ‘© Defines the intemtional rules for frequency assignments within the bands set by WARC Figure 4-5: ITU Organizational Structure NDGD SENARATH Page 64 of 125MOBILE COMMUNICATIONS the microwave frequency planning is handled by the TRC itself. For any specific link the operating frequency should be obtained by the TRC by providing the necessary details. Some of the typical transmission frequencies allocated for microwave links is given below. Frequency Frequency TxJRX. Hop Band (GHz) Range (GHz) Spacing (MHz) _| Length (Km) 7 T1=T9 161 > 15 1B 12.75 — 13.25 266 9-15 15 144 —15.35 490 5.9 18 17.7=19.7 1010 2.5-5 23 21.2-23.6 1232 1522.5 26 24.5 — 26.5 1008 1s > Microwave Frequency Allocations 4.6.1. High Band &Low Band For each frequency band the frequency range is divided as Low Band [LB] & High Band [HB]. Each link will contain a frequency from the LB and the corresponding frequency from the HB. The corresponding frequency means the frequency, which is derived, when the lower band frequency is added to the T/R spacing of the frequency band. For a single site the transmission planning division tries to maintain either all Low band frequencies or High band frequencies of a certain frequency band in order to make optimum use of the available frequencies. A AA A Txt Txn] | |Rxt Rxn| <—____ >. Low Band High Band Figure 4-6: Frequeney band Selection The Low Band & High Band structure for some of the frequency bands as used at Dialog Telekom is given below. Frequeney Range (GHz) High Band (Rx) (MHz) Low Band (Tx) (MHz) 13 13017 MHz to 13115 MHz | 12751 MHz to 12849 15 14893 MHz to 15012 MHz | 14403 MHz to 14522 18 18901 MHz to 19261 MHz | 17919 MHz to 18279 23 22752 MHz to 23280 MHz | 21520 MHz to 22048 26 26008 MHz to 26508 MHz | 25000 MHz to 25500 NDGD SENARATH Page 65 of 125MOBILE COMMUNICATIONS 4.7. Radio Surveys It is vital when planning a radio route that once the map work is completed a physical survey is conducted. This is important to check line of site. Obstructions that are not shown on the map such as trees, buildings can block LOS and be a showstopper for the planned route. The site coordinates should also be carefully checked. Generally the surveying process can be divided into two parts the Path Survey and the Site Survey. 4.7.1, Path Survey The traditional method to check LOS is to flash the path. This involves reflecting the sun’s rays off mirror and checking for the flash at the distant end. One needs to be careful when checking fora flash that one is looking at the flash from the mirror and not incidental reflections off glass in buildings and car windows for example. It is essential to be in telephone contact with the person doing the flashing to get them alternatively start and stop flashing and ensure that you are observing the correct flash of light. If flashing does not get through then one must investigate the cause of the obstruction. Once the obstruction has been located its height and distance can be measured using a theodolite. For planning in urban areas a good telescope is often quite adequate 4.7.2. Site Surveys To plan a microwave installation properly it is essential to carry out not only a path survey but also a site survey. The purpose of the site visit is to ascertain the accuracy of the assumptions made on site readiness and to draw up a scope of work. On this visit the following aspects should also be considered, > Site Coordinates and Altitude Nowadays handheld GPS systems are used to check site coordinates. The site coordinates used for the path profiles should be carefully checked as a detailed analysis of path profile is meaningless if the site coordinates are inaccurate. On paths where a dominant obstruction exist the site elevation is also a key element to check. > Existing Tower Details The tower height should be measured to check the existing records and to ensure that there is sufficient space on the tower for the new antennas. One should also check where the antenna support struts can be secured. These struts must be secured to strong and rigid portions of the tower structure, Some tower members have tensile strength only and not suitable for antenna support. The tower itself may need to be assessed by a civil engineer for structural strength especially for larger dimensional antennas. Local obstructions to the LOS such as other towers: NDGD SENARATH Page 66 of 125MOBILE COMMUNICATIONS and buildings or trees should also be checked. > Earthing Existing earthing arrangements on the tower should be checked in order to assess where the Earth Straps from any new feeders should be connected. > Other general aspects While on site survey one should identify space on site to offload antennas and equipments. Also the primary power and battery supply adequacy should be verified and equipment locations in the building should be planned. These must be planned in advance or it could lead to delays during radio equipment installations. Also the positioning of the air conditioning unit should also be checked. Details of site access should also be carefully considered along with site directions which should be clearly specified for equipment deliveries and installation crews. 4.8. Main factors that affect Microwave Propagation Geographical factors and climatic conditions affect microwave propagation to a great extent Hilly terrains may cause it difficult to implement a link with LOS. Planer surfaces and mainly paths with large pools of water will cause problems due to reflections off it. Large amount of rainfalls may cause the link to fade and may even duet it result in link unavailability. Dialog transmission links are planned intending to mai availability over 99.99% to count propagation failures. 4.8.1, Diffraction Diffra nis the apparent bending and spreading of waves when they meet an obstruction, It is one particular type of wave interference caused by the partial obstruction or lateral restriction of a wave. Diffraction effects become weaker and ultimately undetectable as the size of obstruction is made larger and larger compared to the wavelength, Its importance lies in the fact that obstacles in close proximity to microwave beam can cause additional losses during propagation, 4.8.2. Refraction Bending of a wave when it passes from one medium to another is called refraction. It is the effect of different speeds of wave propagation in two substances that have different densities. For example when light passes from the less dense medium air into the more dense medium glass it slows down (from 300 million to 200 million meters per second) and is refracted. The same thing happens to the microwaves when the travel across layers of the atmosphere with different densities. The amount of refraction depends on the densities of the media, the angle NDGD SENARATH Page 67 of 125MOBILE COMMUNICATIONS at which the wave strikes the surface of the second medium and the amount of bending and change of velocity corresponding to the frequency of the link, The effect of refraction is significant when the antenna height difference of the two end sites differ greatly because it will cause the link to travel across many layers. 4.8.3. Reflection The signal radiated by a typical microwave antenna has a half power beam width of +7 1. In the general case the geometry of a line of sight path will be such that the signal incident at a line of sight path will be such that the signal incident at a reflection point power would approximate the power in the direct signal. If the reflection point was perfect the reflected ray would have the same magnitude as the direct, ray and the veetor sum of the two at receiving antenna would give an interference pattern having a maximum 6dB above free space level and a minimum approaching unfitted loss, Fading A microwave radio link suffers various signal fluctuations in time for a number of reasons. These signal variations around the nominal receive level are commonly known as fading. There are various fading effects such as diffraction fading, beam spreading or defocusing, multipath fading, ducting or blackout fading and refractive fading. Another major cause of fading is the rain attenuation in hi; below. frequency systems. Some of these fading mechanisms are discussed Fade margin Fade margin is the amount by which a received signal level may be reduced without causing system performance to fall below a specified threshold value. The following figure shows the receive level as a function of time during a fading event, As the figure shows, larger fade margin the smaller possibility for the signal to drop below the receiver threshold level. Consequently the system performance is improved by increased fading margin. This is achieved by higher transmit level, larger antennas, lower threshold level, reduced path length, ete. Receive Level ‘Nominal Atmospherical Transmit Level Disturbances Receiver Threshold Outage Figure 4-7: Fading Time NDGD SENARATH Page 68 of 125MOBILE COMMUNICATIONS Rain fading Rain attenuation is the single most controlling factor for path availability above 11GHz.The main elements in the atmosphere that absorb electromagnetic energy is water vapor and oxygen. This includes the amount of rain, size of the raindrops, density of the rainfall and moisture on tree foliage. As the rain rate increases the instantaneous amount of water in the path also increases resulting in very high attenuation, The higher the frequency the higher the water absorption will be. So high frequency bands such as 23GHz and 38GHz are only useful for short hops. Possible ways to overcome rain fade are site diversity, uplink power control, variable rate encoding and receiving antennas larger than the requested size for normal weather conditions. The world is divided in to number of Rain climate zones from A to Q according to rainfall of the region. Sri Lanka is fall into N-region according to this classification. From this table designers can calculate the effects in each zone and consider that in path designing. This figure is also an input parameter to the Path Loss 4.0 software used by Dialog. Multipath Fading Fading due to layering of the atmosphere is the dominating factor of degradation of microwave links. Meteorological conditions in the space separating the transmitter and the receiver may some times cause detrimental effects to the received signal. Rays that normally would have been lost in the atmosphere may be refracted into the receiving antenna where they are added to the wanted signal. The phase and amplitude relationship between signals determines the resulting input signal at the receiver. This affects the transmission in two ways. Sometimes all components of the useful signal spectrum will be equally reduced. This is called non-selective or flat fading. On some occasions only some of the spectral components will be reduced causing the spectrum to be distorted. This is called frequency selective fading. The total effect of due to multipath fading is the sum of the flat fading and the frequency selective fading. Ducting Duct fading is caused by atmospheric inversion developing in the vicinity of a path and trapping the radiated signal, If both antennas are in the duct a low loss path exists and signal rise above normal levels. Ifone antenna is outside the duct or the duct is formed between the antennas the received signal can be very weak for long period until the duct disperses. The height or thickness of a duct has a bearing on the frequency that it can propagate. However, in the NDGD SENARATH Page 69 of 125MOBILE COMMUNICATIONS microwave region the dimensions are usually sufficient to affect all frequencies similarly, DUCT Reflected 4.9, Interference Analysis of Microwave Links Microwave links may be interfered due to various reasons. They can be classified as follows. 4.9.1. Unintended Radiation The primary function of a transmitter is to generate RF power containing information (modulation over a specified bandwidth). Other unintentional emissions are also may be produced during this procedure. Spurious emissions: any radiation that is not required for transmitting the desired information (and not harmonically related to fundamental frequency). Harmonies: frequencies that are harmonically related to the fundamental frequency of transmission. These Spurious emissions and Harmonies may cause interferences. The limits of the allowable spurious and harmonies are defined in the Radio Regulations. 4.9.2. Information Bandwidth The type of modulation techniques determines the required RF bandwidth of a microwave radio channel. As examples # For 16x2 Mbps capacity, QPSK radio, RF channel spacing is 28 MHz. + For 16x2 Mbps capacity, 16QAM radio, RF channel spacing is 14 MHz © For 8x2 Mbps capacity, QPSK radio, RF channel spacing is 14 MHz. * For 8x2 Mbps capacity, 16QAM radio, RF channel spacing is 7 MHz. These variations of the bandwidth of the channel may cause interferences on other links. NDGD SENARATH Page 70 of 125MOBILE COMMUNICATIONS 4.9.3, External Interference Interferences from other systems, those using the same medium, cause external interference for the system considered, These external interferences may occur due to * Possible sources include radio, radar and other devices * Coupling between wave-guides + Bad grounding and shielding 4.9.4, Intra System Interference Interference within the system itself is called inter system interference This can be classified into © Overreach interference ‘* Adjacent section interference Spur or junction interference 4.9.5. Overreach interference A part of microwave link pointed to a tower may overreach to a tower which is a near in line with the pointed tower. This overreach link may cause interference to the link pointed to that overreach tower. This is called overreach interference. B F2 D Figure 48: Overreach interference Countermeasures to avoid Overreach Interference * A longer overreach path AD as compared to the direct path CD. © Better antenna tion at A and D. Earth blocking in the overreach path, NDGD SENARATH Page 71 of 125MOBILE COMMUNICATIONS 4.9.6. Adjacent section interference Microwave radiation patterns from antennas usually have side lobes in addition to main beam, When same frequencies are used in same tower for different sections the effect of adjacent section cause interference on the next channel. = (=) ( Figure 4-9: Adjacent sceton interference Countermeasures to avoid Adjacent Section Interference # Better front to back ratio for the antenna. * Use the same frequeney on alternate sections. 4.9.7. Junction interference When the angle between two antennas is reduced the beam of one link may cause interference on other and this is called junction interference. (4) Figure 4-10: Junetion interference Countermeasures to avoid Junction Interference * Better antenna discrimination. * Cross polarization 4.9.8. Frequency Interference Interference caused because of the frequencies selected and due to the pattern they are organized is called frequency interference. Generally two types frequency interferences can be identified. They are, 1. Ce 2. Adjacent Channel Interference Channel Interference NDGD SENARATH Page 72 of 125MOBILE COMMUNICATIONS 4.9.9, Co-Channel Interference When the interfering signal is at the same frequency as the carrier (desired) the interference is called “Co-Channel” Interference. This cause a huge damage to the signal quality and the accuracy of the data transmitted in the link. Rx! FL REO, Figure 4-11: Co-Channel Interference 4.9.10. Adjacent Channel Interference When the interfering signal is one channel away (T-T) from the carrier (desired) the interference is called “Adjacent Channel” Interference. The effect of adjacent channel interference is lesser than theyco-channel interference but should be avoided. Rx F Figure 4-12: Adjacent Channel Interference Fig. 4.15: Adjacent Channel Interference 4.9.11. C'I ratio objective The C/l objective is used to determine how much RF interference one receiver can tolerate in the presence of other radio systems that operate in the same frequency band (co-channel, adjacent and semi-adjacent channel). VANTED CARRIER (©) INTERFERENCE (1) RX! Figure 4-13: C/L ratio objective NDGD SENARATH Page 73 of 125MOBILE COMMUNICATIONS The radio-frequency (RF) carrier-to-interference (C/I) ratio at the vietim receiver’s input is required to be greater than or equal to the C/I objective, to achieve the threshold-to-interference (Tit) objective in a digital radio receiver. A lower C/I objective indicates a higher tolerance of the receiver for a given interference source. A di 1 microwave link will perform essentially error-free with its receive signal level about 10 dB above a critical T/I ratio, that C/I ratio at the digital radio's 10-6 BER “static” threshold (T) point. 4.9.12. Solutions for Interference The primary interference consideration for digital victim systems is threshold degradation because performance is not significantly affected when the desired signal level is more than about 10 dB above its outage (10-3 BER) threshold. Most digital systems employ data stream regeneration at each hop to prevent an accumulation of interference and spectrum distortion effects. Therefore, itis possible to consider the effects of interference separately for each digital hop regardless of whether it is part of a long haul or short haul system. There are several solutions to the interference those can be used in different conditions. Antenna Radiation Pattern The antenna radiation pattern gives the antenna radiation in all directions on both the principal planes (V and H) relative to the main beam. This is available from the antenna manufacturer and can be used for interference analysis. So when an antenna is installed the radiation patterns of those antennas should be checked and the antennas should be installed such that the radiation patterns don’t overlap Antenna Side and Back lobe Levels This parameter is specified in the radiation envelope patterns. The front-to-back ratio gives an indication of the backlobe levels at angles larger than typically 90 degrees. Typically, the front- to-back ratio increases with increasing frequency and with increasing antenna diameter. High Performance antennas can provide front-to-back ratios in the order of 65 dB, sufficient in many cases, to allow back-to-back transmission of the same frequency in both directions. So when antennas are installed this ratio should be considered in order to prevent the interference between links. NDGD SENARATH Page 74 of 125MOBILE COMMUNICATIONS Antenna Alignment The purpose of this procedure is to ensure that maximum signal strength is present at both of the link. This is achieved by aiming the signal from each antenna directly at the centre of the opposite antenna, To perform the antenna alignment procedure we must have person at each antenna, It is also advisable to have some sort of communication between the two sites. Antenna alignment involves adjusting the direction of each antenna until the received signal strength reaches its highest level at each end of the link. There are two steps to the alignment procedure. Rough Visual Alignment - in which each antenna is pointed such that it radiates in the approximate direction of the other antenna. + Fine Alignment - using the azimuth (horizontal angle) and elevation (vertical angle) adjustment hardware built into each antenna mount. This is performed while monitoring the RSSI voltage on the ODU, this voltage is measured using a voltmeter. Cross Polarization Another important parameter in frequency planning is the discrimination of cross-polar signals in the antenna, With a good cross-polarization antenna, the full frequency band can be utilized by using both the vertical and horizontal polarization planes. Largest discrimination is always in the main lobe direction. So the interference can also be minimized using cross polarization, Typical values: 30 dB for Standard antennas 40 dB for cross-polar antennas HifLo frequency Assignment HI/LO system is a frequency assigning system that is used in assigning TX and RX frequencies for a site such that interference will not occur. A radio’s transmitter may be transmitting in the higher region of the frequency band with its duplex receiver “looking” for a signal in the lower region of the band. The site will be labeled HI/LO if we take the convention of TX/RX. The next site must be reversed and labeled LO/HI. So two sites will transmit in two frequencies (one from Hi band and one from Low band) and they will not interfere with each other. A HU/LO convention should be established in the system such that a site does not interfere with itself. NDGD SENARATH Page 75 of 125MOBILE COMMUNICATIONS 4.10. Losses in microwave transmission 4.10.1. Free Space Losses This is the loss due to the attenuation of the radio signal as it travels through space and it is a function of Path Length and transmis FSL = 92.4 + 20 log1o D + 20 logio F FSL = Free Space Loss D = Path Lengt! jon frequency. kilometers F = Radio Frequeney in Gig hertz, 4.10.2. Atmospheric Losses This lose is due to signal attenuation resulting from absorption of oxygen molecules and water vapor in the atmosphere. The attenuation is a function of frequency and atmospheric composition. This lose does not include losses due to rain or fog. 4.10.3. Other Losses # Jumper! Wave guide Losses are derived from manufacturer's specification. These losses represent the total loss from the RF Unit Wave-guide Flange to the Antenna Feed point. * Pad Losses refer to intentional signal attenuation caused by resistive circuits (Pads) wl are inserted between the antenna feed p and the RF unit flange, + Safety Factor) Miscellaneous Losses are used for a measure of conservatism. A.0.5 dB Safety Margin per site is usually included in a typical path calculation, 4.10.4. Path Unavailability The reliability of the microwave link is commonly expressed in terms of “percent availability”. The percent of time that the system is expected to operate without an outage, Path Reliability may also be expressed in terms of “Percent Unavailability”, or expected outage time. This is calculated by subtracting the availability % from 100. Mostly the figure of 99.995% minimum path availability is used. The unavailability of the system at 0.005% can be expressed in minutes per year as follows: (365.25 days/yr) X (24 hrs/day) X (60 min/hr) X (0.005/100) = 26.3 min/yr Reasons for path unavailability: + Propagation Failure (greater than 10 sec outage) + Multi path (usually Non - diversity) * Rain Attenuation NDGD SENARATH Page 76 of 125MOBILE COMMUNICATIONS + Atmospherie Duet Entrapment + Equipment failure in an unprotected system + Power Failure * Poor Maintenance + Antenna feeder system Failure Ete... Tx ‘ ! Rx Rx| ‘| Tx Figure 4-4: Block Diagram for Radio Equipment Fig. 4.17; Block Diagram for Radio Equipment 4.10.5. Basic Radio Link Equation (Link Budget Calculation): Pr=Pr+Gr+Gr-FSL-A crx- A crs- Amr -A-FM Pr = Transmitted Power (dBm) A crx = Loss in Tx feeder (4B) Pr = Received Power (dBm) A crx = Loss in Rx feeder (dB) Gr = Tx antenna gain (dB) ‘Aga = Loss in RF branching system (dB) Ge = Rx antenna gain (4B) A = Other attenuations FSL_ = Free space loss (4B) FM =Field Margin (dB) NDGD SENARATH Page 77 of 125MOBILE COMMUNICATIONS 4.11, Protection Methods of Links Space and Frequency diversity branching can be implemented to either eliminate or to reduce fading. Diversity reception decreases the chance that a signal will be lost by combining signals from two or more antennas (space diversity) o by transmitting the same signal on two or more frequency channels (frequency diversity). Space and frequency diversity use redundant hardware but also decouple the paths used by microwave transmissions. Frequency diversity is not normally used in the Dialog network because spectrum is scarce. Space diversity and Hotstandby methods are usually used in important backbone links. By adding path diversity schemes to a radio design, you can increase path availability, which improves overall system reliabi ry and availability 4.11.1. Hot-standby Branching The Hot-standby configuration is often used to give equipment protection for microwave links. This configuration gives no improvement of system performance but reduces the system breakdown possibility due to equipment failures. The transmitters and receivers operate at the same frequency. A transmit switch is used to one or the other transmit signal. Though both transmitters actually transmit the signal only one is switched on to the antenna, In the receive direction the signals is split in to two paths and the best signal is selected rx I] Rx pe ee sit 4 Tx J Rx eee ee 4.11.2. Frequency Diversity Branching In frequency diversity both transmitters transmit simultaneously each signal is fed to its respective receiver without a transmit switch or a receiver hybrid. re Plo a fi re PLP T fe Figure 4-16; Frequeney Diversity Branching NDGD SENARATH Page 78 of 125MOBILE COMMUNICATIONS 4.113. Space Diversity Branching With space diversity only one frequency pair is used. Normally in the Dialog GSM network one antenna is used for receiving alone and another antenna is used for both transmit and receive funetions to implement space diversity. The branching unit filters the signals and combines the two signals onto the antenna when the same antenna is used for both transmit and receive frequencies. The system performance may be significantly improved by use of space diversity. Identical information is transmitted over separate paths. Whenever space diversity is used, angle diversity should also be employed by tilting the antennas at different upward angles. Ry Ry Figure 4-17: Space Diversity Branching 4.12. Transmission Operations Division Transmission of data streams can be done through wires, optical fibers or through air interface. In MTN data transmission through wires and through the air interface is used. For the transmission through the air interface the microwave frequency range is used. Ina GSM network microwave links can be used to provide, Interconnection between BTS Gateway point interconnection between other telecom operators 4.12.1. Main Components of the Microwave system > Antenna Unit. » Outdoor Unit (ODU) Indoor Unit (IDU) v - Rectified power source (-48V) ODU to IDU cabling (IF cable) yi v Termination Blocks to connect the tributary cable NDGD SENARATH Page 79 of 125MOBILE COMMUNICATIONS = = ne TopoRTT —__or POWER borane TRODORINT 4.12.2. Antenna Unit Antenna unit maintains the gqnpestign 4p,tbs, qtheh end iaia.sRictQMane Signal path, provided that the line of sight condition is satisfied. The area which the microwave signal intends to travel is known as the fresnel zone. In order to have an uninterrupted communication, the two antennas should be placed face to face, without any obstruction between, > An antenna consists of four major parts, namely > Feeder > Shielded Reflector > Radome > Offset Tower Mount or Boom Bracket. In Dialog Telekom links we use 3 types of solid dish antennas. 0.3 m diameter Antenna 0.6 m diameter Antenna 1.8 m diameter Antenna NDGD SENARATH Page 80 of 125MOBILE COMMUNICATIONS CHAPTER 05, 5. BSS PLANNING AND OPERATIONS Sector Antenna Battery Bank | Le Dise Antenna = Dise Antenna MW Link (To BTS) <@Vt0BTS | Jumper Cable i (2m, 31m, Se) j s 3g a | Bock Frame | wm 5 BTS Tertinal B Modem (Mfonitoring) x or ‘lanes LED's eS NDGD SENARATH Page 81 of 125MOBILE COMMUNICATIONS 5.1. Introduction to Network Operation The Network Operations Division is responsible of maintaining and upgrading of the Base Station Subsystem (BSS).Commissioning new sites Network Operations Division has to define the PCM path (Abis path) and configure it. The s also a responsibility of the division. The Network Operations Division also does routine visits to the sites for examine the PCM paths, BTS equipments and alarms for the proper operation and report them, 5.2. Base Station Subsystem The Base Station Subsystem is composed of 3 parts, © Transcoder (TC) which handles multiplexing of channels. The Transcoder is situated between the BSC and the MSC. * Base Station Controller (BSC) which communicate across the standardized Abis interface. © Base Transceiver Station (BTS) 5.2.1. Transcoder The Transcoder is located between the BSC and the MSC. The MSC identifies only 64Kbps channels, therefore the Transcoder converts the 16Kbps A-ter mux interface in to the 64 Kbps an interface. 5.2.2. Base Station Controller The Base Stat n Controller provides resource and equipment management facilities for the BSS. It allocates resources to manage the flow of information between the BSS and the NSS acting as a switching unit by establishing a path between them. Some of the main functions of aBSC are, * Provision of signaling links to the MSC. © Signaling control of the BTSs and hence the Mobile Stations. . Database and Resource management. © Signaling control of links with the MES. * Switching of traffic between the MSC and the BTSs. © Routing of traffic between the MFS and the BTSs. © Provision of Operation and Maintenance facilities. NDGD SENARATH Page 82 of 125MOBILE COMMUNICATIONS 5.2.3. Base Transceiver Station The area covered by a BSS is divided in to cells and each cell is managed by a Base Transceiver Station, The BTS houses the radio transceivers and antennas that define a cell and handles the radio-link protocols with the Mobile Station. Its transmitting power defines the size of a cell Ina large urban area like the Colombo city area there will be a large number of BTSs deployed. So the requirements for a BTS include ruggedness, reliability, portability, and minimum cost. Some of the main functions of a BSC are, * Providing radio transmission, control and base band functions for a cell. © Supporting the transmission and receive functions through the Air interface with the MSs. © Supporting antenna diversity and frequency hopping. © Performing Radio channel measurements and Radio frequency testing. © Providing transmission and multiplexing facilities at the A-bis interface. In Dialog GSM there are mainly 3 types of BTS provided by different vendors. © Aleatel BTS * Ericsson RBS © Huawei BTS 5.3. What is a Base Station Communication through the mobile devices essentially we need BTS. So to archive this the Dialog regianol office at Kurunegala region use Huawei equipment. So some equipment they use can be categorized as follwes, GSM & DCS 3G BTS 3012 BTS 3812E BTS 3900 DBS 3800 DBS 3900 DBS 3900 Today mobile communications giant is developing rapidly. Operators overtaking competitors offer many different services. In the construction of 2G and 3G invested a lot of money. Naturally, the mobile operators want these costs, such as to optimize and reduce, because these networks are heterogeneous and construction is carried out in both directions, Huawei offered a solution to the problem, have developed a base station controller NDGD SENARATH Page 83 of 125MOBILE COMMUNICATIONS BSC6900 , it operates simultaneously in two modes such as GSM and UMTS. They also developed a Base Station Huawei DBS3900, wi also supports dual mode operation. It tums out, that's enough to buy one controller and base stations DBS3900 and they will serve the GSM network and UMTS (3G). Reducing costs significantly, even during installation. Thus it is again provided the impetus to the development of Huawei equipment. This base station supports over IP transport, which is a very important characteristic. Just DBS3900 support a smooth transition to a four-generation networks, LTE. In this report we discussed about the 1DBS3900 because it support both GSM and the UMTS. Here you can see the Schematic diagram of the base station DBS 3900.i « DBS3900 components: 2 BBU3900 T — antenna 2 RRU3908, RRU3804,RRU3008 — russ ca— mH —— RF jumper Grounding cable — Feeder MBSC Power cable a = ea CPRI cable ‘BBU3900 |= Grounding cable Trunk cable Power cable Figure 5-1: Schematic diagram of the base station DBS 3900 The DBS3900 base station basically consists of three parts: 1. BBU-this is the main part of the BS (processes information) 2. RRU-transmitters is TRx. 3. Antenna (Sector cell) Sectors connected with RRU coaxial cables, the so-called jumpers. RRU blocks placed on top of the mast near the sectors. This is very convenient because used on older transmitters located in a container on the ground, and to run the coaxial cable sectors of large cross section, which is not very good. Blocks RRU and BBU connected to the optical cable. BBU is placed in a container on the ground on a ground and BBU-RRU losses are reduced to zero as connected NDGD SENARATH Page 84 of 125MOBILE COMMUNICATIONS on optics. BBU connected to any transport equipment (Multiplexer releyka) and further to the base station controller BSC6900 (E1 through an ATM or IP). 5.3.1, Frequency range. BRU Frequency band RX bang (ante) TX bana (maniz) (99010915 93510960 28010908 92510950 350 NRE easi0 848 26910894 1800 Mie 1.880% 1.890 133010 1.870 1900 mez Band | (2100 Mes) 1.920% 1,980 2.110%02.170 Beng 11 (1800 n=) 780010 1.910 183010 1.990 RRUS80s Bana iv AWS) 1.710% 1.755 2.11010 2.155 Banaviviesomms) | s2ato8s9 269to 894 5.3.2. Features of DBS3900 . Advanced Platform-Based Architecture Based on the unified hardware platform, the DBS3900 supports three working modes: GSMmode, GSM+UMTS dual mode, and UMTS mode through configuration of different software.In addition, the DBS3900 supports smooth evolution to the Long-Term Evolution (LTE). The RF module integrates the duplexer and the Transceiver Unit (TRU), thus enhancing integrity of RF parts and meeting future requirements for a compact, high-efficiency, and low- cost base station. Support 900MPGSMand 850M. Support High 40M band and low 40M band of 1900M. . Transmission Sharing, Share the CPRI port. The CPRI data of the GSM and UMTS networks can be multiplexed on then same optical cable, which reduces the quantity of CPRI ports. Share transmission resources between the Abis and the lub interfaces. NDGD SENARATH Page 85 of 125MOBILE COMMUNICATIONS . High Capacity When the DBS3900 works in GSM mode, a BBU3900 supports the maximum cell configuration of $24/24/24, and RRU3908 supports a maximum of six GSM carriers. When the DBS3900 works in GSM+UMTS dual mode, a BBU3900 supports the maximum cell configuration of GSM $24/24/24 or UMTS $8/8/8, Capacity of the RRU3908 can be expanded through cascading of RRU3908s, and three cascaded RRU3908s can supportthe cell configuration of GSM S4/4/4 + UMTS S2/2/2 or GSM S5/5/5 + UMTS S1/1/1.When the DBS3900 works in UMTS mode, a BBU3900 supports 24 cells, the maximum configuration of 3 x 8, 1,536 CEs in the uplink, 1,536 CEs in the downlink. In addition, theBBU3900 supports the HSDPA and HSUPA. An RRU3908 supports a maximum of four UMTS carriers. . Low Power Consumption The DBS3900 can control the power-on/off of boards through software, disabling of RF channels through software, voltage adjustment of PA power supply, and the rotation speed of the fan, This enable adjustment of power requirements based on the actual trafic load, thus reducing power consumption, . Coverage The transmission distance of a single-mode optical cable at one level (that is, from the BBU to anRRU or from one RRU to another RRU) is 40 km. The RRU supports a maximum of three levelsof cascading, which enables the longest distance between RRUs and a BBU to be 100 km, When the DBS3900 works in UMTS mode, one RRU3908 can support open loops in both Space Time Transmit Diversity (STTD) and Time Switched Transmit Diversity (TSTD) modes and closed loops in TX diversity mode, which enhances the performance in DL coverage and capacity. ‘The DBS3900 supports the 2-way RX diversity and 4-way RX diversity, which enhances the performance in UL demodulation and receiver sensitivity. . Networking Capability The DBS3900 supports multiple network topologies, such as star, tree, chain, and ring topologies. The DBS3900 supports Flex Abis networking. The DBS3900 supports co- ig in UMTS mode, the DBS3900 supports ATM and IP dual stack to protectoperators' early investment in ATM transport. The jon between the GSM and the UMTS. When worl transt 1DBS3900 supports optimized transmission on the Abis interface. NDGD SENARATH Page 86 of 125MOBILE COMMUNICATIONS . Flexible Clock Synchronization Modes When the GSM network uses E1/T1 transport and UMTS uses IP transport, the clock of the UMTS can be directly extracted from the GSM, thus implementing clock resource sharing without additional investment in the Global Positioning System (GPS) or clock server. Synchronization with the IP clock, a highly cost-effective clock solution, which can be obtained through software upgrade without additional hardware, The dynamic transmission bandwidth sharing is supported in GSM+UMTS dual-mode IP networking. Clock phase lock, tracing, and memory functions and free-run synchronization mode. When the clock operates in free-run mode, the system can keep operational for at least 90 days at normal temperature. 5.3.3. DBS3900 Hardware Components The DBS3900 consists of the BBU3900 and the RRU3908 which are connected with fiber. The BBU3900 is an indoor baseband unit. It provides physical interfaces for connection with the BSC/RNC and RRU. It performs centralized management (OM and signaling processing) of the entire base station system and provides reference clock for the system. The RRU3908 is an outdoor remote RF unit, It processes baseband signals and RF signals. The Local Maintenance Terminal (LMT) and Site Maintenance Terminal System (SMT) can implement the maintenance of the DBS3900 through the BBU3900. RRUSOOS —RRUIBDS —_-RRUZBOS ‘853900 ; oe Figure 5-2: DBS 3900 The BBU3900 is a baseband processing unit. It provides physical ports for connection to the BSC/RNC and the RRU3908, performs centralized management of the entire DBS3900 system in terms of Operation and Maintenance (OM) and signaling processing, and provides the system clock. 5.3.4, Functions of the BBU3900: * Provides ports between the BBU3900 and the BSC/RNC for data communication. © Provides the CPRI ports for communication with the RRU. NDGD SENARATH Page 87 of 125