WIRELESS COMMUNICATION (18EC71)- VII SEM ECE

(UNIT - 2)

By

B S SUDHA
Associate Professor
Dept. of ECE
Dr.AIT
Bangalore
 UNIT – 2
Common Cellular System Components

 Common cellular network components

 Hardware and software views of cellular network
 3G cellular systems components.
 Cellular component identification,
 Call establishments
 This chapter takes:-
 A Look at the various hardware network elements that are used to create a wireless
cellular network.
 The structure and operation of 2G & 2.5G network hardware elements.
 Recommended identification systems used by wireless networks etc.,

The network elements may be divided into 3 basic groups-

(1) The mobile or Subscriber device – provides users link to wireless network
(2) Base station system – provides wireless systems link to subscriber over air interface
(3) Wireless switching system – provides the interfaces to the PSTN and PDN
- Correct information and connections to locate the subscriber and the
data bases needed to support system operations.

Common Cellular Network Components:-

A Typical (1G) wireless cellular telecommunication system is shown in fig.1
It consists of several sub systems or network elements
1. Mobile Station(MS)
2. Base Station System(BSS)
3. Network Switching System(NSS)
FIG.1:-Typical wireless cellular system components
 Subscriber Devices(Mobile Tranceiver)
 Subscriber Device(SD)- Link between the customer and the
wireless network.
 Must be able to provide a means for the subscriber to control
and input information to the phone and display its operational
status.
 SD – must be able to sample, digitize and process audio and
other multimedia signals.
 Transmit and receive RF signals
 Process system control messages etc.,
The basic sections of SD are:-
(1) Man – Machine interface
(2) RF transceiver section
(3) Signal processing section
(4) A system control processor
(5) Power supply / management section
Subscriber Devices
Base Station System (BSS)Components
Base Station System (BSS)Components
 Handles all radio interface-related functions for the
wireless network.
BSS consists of-
(1) Many radio base stations(RBS’s) – includes
- Antennas, transmission lines
- power couplers
- RF power amplifiers
- tower mounted preamplifiers
- other associated hardware
(2) Base Station Controller(BSC)-Supervises the operation
no. of RBS’s
(3)Trans-coder Controller(TRC) – performs rate
adaptation- VOCODER
 Radio Base Station(RBS)
 Consists of all radio and transmission interface equipment needed to
establish a radio link with the MS.
 2 types
(1) TDMA RBS
(2) CDMA RBS
 TDMA RBS- Consists of
- Distribution switch
- Multiple transceiver units
- RF combining and distribution units
- Energy control unit
- Power supply components
 CDMA RBS – Consists of
- same as that of TDMA RBS
- Timing and frequency module
- Channel cards
 Base Station Controller(BSC)

(Typical block diagram of CDMA BSC)

Base Station Controller(BSC)
 System description and Interface
 Operation and Protocol
Transcoder Controller
 Consists of subsystems that perform
transcoding and rate adaptation
 TRC can be either a standalone unit or
combined with BSC to yield an integrated BSC /
TRC
 Switching System Components(NSS)
 Visitor Location Register(VLR)
 Mobile Switching Center(MSC)
 Home Location Register(HLR)
 Interworking Location Register(ILR)
 Gateway MSC
 Authentication center(AUC)
 Equipment Identity Register(EIR)
 Interworking Units(IWU)
Visitor Location Register(VLR)
 Data base that temporarily stores information
about any MS that attaches to a RBS in the area
serviced by a particular MSC
 In a typical wireless network, the VLR is
integrated with MSC to form an MSC/VLR, thus
reducing amount of SS7 n/w signaling necessary
to perform n/w operations
Mobile Switching Center(MSC)
Basic functions performed by MSC:-
• Setting up & control of voice calls
• Providing voice path-handoff process
• Call routing to a subscriber etc.,

Components / sub systems-

 Central processor & associated processor
 Group switch
 Traffic interface
 Timing & Synchronization module
 S/W to provide operations & maintenance
( O&M)functions
 Main functions of MSC:-
 Interface functions
 Switching functions
 Signaling functions
 MSC Data base functions
 Description of Data bases
Home location Register(HLR)
 HLR is a data base that stores information about every user that has a cellular service
contract with a specific wireless service provider.
 Stores permanent data about-
- the n/w’s subscribers,
- information about subscribers contracted tele services /supplementary services.
- Dynamic data about the subscribers present location
HLR implementation HLR – stand alone network
HLR sub systems:-
• Storage
• Central processors
• I/O systems
• Statistics & traffic measurement data collector
• SS7 signaling links
HLR subscription profile:-
 Services types
- Teleservices
- Bearer services
- Supplementary services
 Interworking Location Register(ILR)
 Used to provide inter system roaming
 Allows a subscriber to roam in several different systems

Authentication Center(AUC)
 Provides HLR with triplet ie.,(Cipher key, a random no., & a
signed response)for a particular MS,on request from VLR.

Equipment Identity Register(EIR)

 A data base used to validate the status of the mobile equipment
Data bases in EIR – 3
- White list
- Black list
- Grey list
Gateway MSC(GMSC)-
 Interfaces the wireless mobile n/w to other telecommunication
networks
 Charging & Accounting functions are implemented in GMSC

Interworking Unit(IWU)-
 Required to provide an interface to various data n/w’s
Data Transmission IWU(DIWU)-
SMS Gateways & IWU’s-
 To provide SMS operations
2 n/w elements are required
- SMS-GMSC
- SMS-IWMSC
Network Management System(NMS)
 Performs n/ w surveillance & support O&M of entire n/w
 Perform 5 management
- fault management
- performance management
- Trouble management
-configuration management
- Security management

Other Nodes
- SMS or Service center(SC)
- Billing gateway(BGW)
- Service order gateway(SOG)
Hardware and Software views of the cellular
network:-
Hardware view of the cellular network
Software view of the cellular network:-

CGI=Cell global identity

 3G Cellular system components
 For 3G cellular systems, the n/w elements have
transformed to reflect the transition of the system
towards an all IP or packet n/w.
 This system has resulted in the transformation of BSC
function to that of a Radio Network Controller(RNC).

 3G Basic components are:-

- Core Network(CN)
-Radio Access Network(RAN)
- Radio Network Controller(RNC)
- Radio Base Station (RBS)
Cellular component identification:-
 To switch a voice call from PSTN to a mobile subscriber
the correct cellular n/w elements must be involved in the
operation.
 So it is necessary to address these elements correctly.
Types of Cellular component identification:-
 Subscriber device identification - 3
- Mobile station ISDN identification no.(MSISDN)
- International mobile subscriber identity(IMSI)
- International mobile equipment identity(IMEI)
Cellular system component Addressing
For cellular system addressing following addressing
schemes are used:-
 Local area identification(LAI)
 Cell global Identity(CGI)
 Radio Base Station identity code
 Location Numbering &
 Addressing cellular network switching nodes.
Addressing cellular network switching nodes
 Messages between both PSTN & PLMN network elements
are sent over the SS7 network
 To facilitate this operation , signaling point addresses or
point codes are assigned to the n/w switching elements &
processing nodes.
 SS7 network numbering for the n/w signaling points (SP’s)
consists of 3-byte(24 bits) addresses that specify the
telecommunication service provider (N=0-255),the n/w
cluster no.(C=0-255) & the member no.(M=0-255)in the
format,
SPC(Signaling point code) = N-C-M
Global title and Global title translation
 Global Title (GT) is an address of a fixed n/w element.
 GT does not contain the information needed to perform
routing in a SS7 system
 Correct routing information is performed by the
SCCP(Signaling Connection Control Part) translation
function
Call Establishment
 Introduced in first chapter
 3 Main operations in call establishment are:-
- Mobile terminated call
- Mobile originated call
- Call release
Mobile terminated call
Mobile originated call
Call release operation
THANK YOU