INTRODUCTION TO WIRELESS MOBILE COMMUNICATIONS

History and evolution of mobile radio systems Types of mobile wireless services/systems Cellular WLL Paging Satellite systems Standard Future trends in personal wireless systems.

INDEX
1

UNIT I
INTRODUCTION TO WIRELESS MOBILE COMMUNICATIONS

Question number 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35

Question What is the footprint area of the satellite? What are geostationary satellites? What is sidereal time? What is sidereal day? What is direct orbit? What is retrograde orbit? What is equatorial orbit? What is polar orbit? What are classification orbit depend on attitude? What are the benefits of Paging? Write in short about the Worlds first Cellular System. What are the principles of Cellular Architecture? What are the advantages of Digital techniques in cellular Systems? What are the characteristics of PCS? What is the Technology used by PCS? What are the advantages of cellular systems with small cells? What are the limitations of conventional mobile telephone system? What are the disadvantages of cellular systems with small cells? Define BCA. What is breathe? Why 800 MHz frequency is selected for mobiles? What is the Marketing name of narrowband IS-95 CDMA network? What are the three segments of paging? Write in short about ERMES What are the advantages of APOC standard? What is CPP? What are the advantages of Data Paging Signage System? What are the different types of Hand over? What is the necessity of Standards? What are the applications of a satellite system? Give the benefits of paging systems? What is a page? What are the channels used in mobile communication systems? What are the basic units of a Cellular system? What are the classifications of Wireless technologies and systems?

Page no 5 5 5 5 5 5 5 5 6 6 6 6 6 6 7 7 7 7 7 7 7 8 8 8 8 8 8 8 8 9 9 9 9 9 9 Page number

2

Question number

DESCRIPTIVE ANSWERS

1 2 3 4 5 6 7 8 9 10

Explain the development history of mobile radio systems. Describe in detail about the history of development of Paging and the future trends of paging systems. Explain in detail about the Standards adopted for Paging Systems. Discuss in detail about the Recent Developments in Paging Systems. Explain in detail about the Mobile radio standards around the world. Discuss in detail about the Future trends of Personal Wireless Systems. Describe in detail about the Wireless Local loop and LMDS. Explain about the basic cellular system. Discuss in detail about the satellite mobile systems. Discuss in detail about the general satellite systems.

10 11 13 15 16 18 20 22 24 25

UNIT I
3

INTRODUCTION TO WIRELESS MOBILE COMMUNICATIONS

SHORT ANSWERS
1. What is the footprint area of the satellite? The satellite antenna transmit signal towards the earth in a particular Patten called its foot print. The signal is stronger at the center and decrease to father level towards outer edge of the footprint.

2. What are geostationary satellites?

The satellites that rotate the same speed of the earth are called geostationary satellites.

3. What is sidereal time?

The sidereal time is measured relative to the fixed stars. One complete rotation of the earth relative to the fixed stars is not a complete rotation relative to the sun the reason for this is because the earth moves in its orbit around the sun.

4. What is sidereal day?

The sidereal day can be defined as one complete rotation of the earth relative to the fixed stars. One sidereal day has 23 hours, 4.1 sec, 56 min. At an attitude of 35,786 the orbital period becomes 23 hours, 4.1 sec, 56 min, which the time the earth to rotate 360 around the axis this period is called a sidereal day.

5. What is direct orbit?

An orbit in which a satellite moves in same direction as the earth is called direct orbit.

6. What is retrograde orbit?

An orbit in which a satellite moves in opposite direction as the earth is called retrograde orbit.

7. What is equatorial orbit?

An orbit with an inclination is 0 the satellite is said to be equatorial orbit.

8. What is polar orbit?

An orbit with an inclination is 90 the satellite is said to be polar orbit.

9. What are classification orbit depend on attitude?

1. Low Earth Orbit 2. Medium Earth Orbit 3. Intermediate Circular Orbit 4

4. Geostationary Orbit

10. What are the benefits of Paging?

1. 2. 3. 4. 5. 6. 7. Low cost message delivery Extended battery life Strong in-building penetration Reliable and expanded coverage Efficient messaging Controlled accessibility Broadcasting capability

11. Write in short about the Worlds first Cellular System.

The worlds first cellular system was implemented by the Nippon Telephone and Telegraph Company (NTT) in Japan. The system deployed in 1979, uses 6FM Duplex channels (25 KHz for each one way link) in the 800 MHz band.

12. What are the principles of Cellular Architecture?

Low power Transmitters and Coverage Zones. Frequency Reuse. Cell splitting to increase Capacity. Hand off and Central Control.

13. What are the advantages of Digital techniques in cellular Systems?

Improved Spectral Utilization. Lower Bit rate Voice Coding Reduction of Overhead for Signaling. Robust Source and Channel Coding Techniques. More Robust Interference. Flexible Bandwidth. Inclusion of New services Improved Efficiency.

14. What are the characteristics of PCS?

Mass market applications Can be customized by individual users Coverage: in-building, outdoor stationary and outdoor on-the-move Additional services include: universal access ID, less in weight, longer battery life, etc

15. What is the Technology used by PCS?

PCS is not based on any single technology but uses a number of standards including:

GSM900/1800/1900 (European and North American GSM standards) 5

DECT (Digital Enhanced Cordless Telephony) PHS (Personal Handyphone System) IS-95 CDMA (Code Division Multiple Access) IS-136 TDMA (Time Division Multiple Access)

16. What are the advantages of cellular systems with small cells?
Higher capacity Less transmission power Local interference only Robustness

17. What are the limitations of conventional mobile telephone system?

Limited service capability Poor service performance Inefficient frequency spectrum utilization

18. What are the disadvantages of cellular systems with small cells?
Requires complex infrastructure Requires frequent hand-over Involves complicated frequency planning

19. Define BCA.

Borrowing Channel Allocation is a method by which more frequencies are allotted dynamically for high traffic cells.

20. What is breathe?

The cells in which the frequency allocation is based on CDMA technique are called as breathe.

21. Why 800 MHz frequency is selected for mobiles?

Fixed Station Services 30 MHz to 100 MHz Television Broadcasting 41 MHz to 960 MHz FM Broadcasting 100 MHz Air to Ground system 118 MHz to 136 MHz Maritime mobile services 160 MHz Military Aircraft use 225 MHz to 400 MHz Frequency bands between 30 MHz to 400 MHz is crowded with large number of services and above 10 GHz is not used due to propagation path loss, multipath fading and improper medium due to rain activity. So 800 MHz is chosen for mobile communication.

22. What is the Marketing name of narrowband IS-95 CDMA network?

The Marketing name of narrowband IS-95 CDMA networks is cdmaOne.

23. What are the three segments of paging?

One-way paging Two-way paging Telemetry paging services.

24. Write in short about ERMES.

ERMES (Enhanced Radio Messaging System) was developed in the late 1980's by a group of paging manufacturers and European Paging Operators. It was designed to provide a high speed PanEuropean system for standard tone, numeric and alphanumeric messages in a multi-network environment, enabling users to roam throughout any region in which an ERMES operates.

25. What are the advantages of APOC standard?

Greater subscriber capacity and longer messages per radio channel Minimum service costs per subscriber Minimum upgrading and network investment costs Improved completed-call performance Competitive pager design with smaller and longer life batteries More user facilities Compatibility with POCSAG pagers and networks

26. What is CPP?

In Caller Pays Paging (CPP) systems there are no ongoing fees or contractual obligations for subscribers. The owner only pays for the initial purchase of a paging device.

27. What are the advantages of Data Paging Signage System?

The flexibility of this paging facility enables remote management of a wide-range of systems, such as those used by travel agents, water irrigation and power controllers, etc.

28. What are the different types of Hand over?

Intra-satellite hand over Inter-satellite hand over Gateway hand over Inter-system hand over

29. What is the necessity of Standards?

Standards help to ensure or promote the following; Wide variety of products and services to customers Interoperability between products and services made by different vendors. Easier introduction of PCS products into the national market. Healthy competitiveness among vendors, which in turn may lead to reduced cost and improved product quality. 7

Development and innovation according to common guidelines. More accessible services to customers

30. What are the applications of a satellite system?

Weather forecasting. Radio and TV broadcast satellites. Military services. Navigation.

31. Give the benefits of paging systems?

Wide spread coverage Long battery life Small light weight sets Economical

32. What is a page?

It is a brief message which is broadcast over the entire service area, usually in a simulcast fashion by many base stations at the same time.

33. What are the channels used in mobile communication systems?

1. 2. 3. 4. Forward voice channels (FVC) Reverse voice channels (RVC) Forward control channels (FCC) Reverse Control channels (RCC)

34. What are the basic units of a Cellular system?

Mobile stations Base stations Mobile Switching Center (MSC) or Mobile Telephone Switching Office (MTSO).

35. What are the classifications of Wireless technologies and systems?

Cellular mobile radio systems Cordless telephones Wide-area wireless data systems High-speed WLANs Paging/messaging systems Satellite-based mobile systems

DESCRIPTIVE ANSWERS
8

1.

Explain the development history of mobile radio systems.

1921 - Detroit Michigan Police Dept. made the earliest significant use of Mobile radio in a vehicle in the United States. The system operated at a frequency close to 2 MHz. The channels soon became overcrowded. 1940 - New frequencies between 30 and 40 MHz were made available. Increasing the available channels encouraged a substantial buildup of police systems. Shortly thereafter other users found a need for this form of communication. Private individuals, companies, and public agencies purchased and operated their own mobile units. 1945 - First public mobile telephone system in the U.S. was inaugurated in St. Louis, Missouri with three channels at 150 MHz. Six channels spaced 60 kHz apart were allocated for this service by the FCC, but the mobile equipment was not sophisticated enough to prevent interference. 1947 - A Public mobile system using frequencies in the 35 to 44 MHz band began operations along the highway between New York and Boston. These frequencies were thought to carry greater distances however a problem with skip-distance propagation carried interfering conversations for long distances. These early mobile telephone systems used push-to-talk operation. 1949 - FCC authorized separate radio channels to common carrier entities known as "Radio Common Carriers" (ROC). These companies do not provide public telephone service, but interconnect to the public telephone network to provide mobile telephone services equivalent to the wire line common carriers. 1955 - Number of wire line channels available at 150 MHz was expanded from 5 to 11 by the creation of new channels between the old ones (channel spacing of 30 kHz). 1956 - 12 wire line channels were added near 450 MHz. All systems operated in a manual mode, with each call to or from a mobile unit being handled by a special mobile telephone operator. 1964 - A new system (150 MHz) was developed providing automatic channel selection for each call, eliminated the need to push-to-talk operation, and allowed customers to do their own dialing. 1969 - Automatic capability was extended to the 450 MHz band and the so called "Improved Mobile Telephone System" (IMTS) became the standard for mobile telephone service in the U.S.

Advanced Systems (Cellular Concept)

As early as 1947, it was realized that small cells with frequency reuse could increase traffic capacity substantially and the basic cellular concept was developed. However, the technology did not exist. 1953 - AT&T proposed to the FCC a broadband mobile telephone system to operate in the 800 MHz region.

1970 - FCC announced a tentative allocation of 75 MHz in the 800 MHz region and invited industry to submit proposals for achieving communication objectives and demonstrating feasibility. 1971 - AT&T responds with a technical report asserting feasibility by detailing how a "cellular system" might be composed. No other proposed systems were submitted to the FCC. 1974 - FCC makes a firm allocation of 40 MHz for mobile telephone service and solicited applications for developmental Systems to prove the feasibility of so-called "Cellular Systems" but because of the beginnings of Bell Systems divestiture proceedings, ruled that Western Electric could not manufacture cellular terminal equipment. This was because Western Electric makes the network equipment and the restriction from selling both terminal and network products were to prevent further monopolization. 1975 - AT&T applied for authorization to operate a developmental cellular system in Chicago. 1977 - License granted in March of 1977. Illinois Bell Telephone constructs and operates a developmental cellular system. 1978 - Mid 1978 the Equipment Test phase commenced. The Service Test-phase started in late 1978. Twenty-one hundred mobile sets were procured from three suppliers for the test and the system served over 2000 trial customers. 1981 - FCC issues standard rules and due to the direction already taken, In the Bell System divestiture proceedings, now rules that Western Electric is permitted to manufacture cellular terminals as well as the network equipment. In the years between 1974 and 1981, AT&T Bell Labs worked with all other cellular terminal vendors to develop their cellular phones so that consumers would have quality products available to use on the cellular network.

10