WIRELESS LOCAL LOOP

Presentation Outline

What is WLL?WLL SETUP.WLL ARCHITECTURE.WLL CONNECTION SETUP.Differences with mobile cellular system.ADVANTAGES.COST CONSIDERATION

DefinitionWhat is WLL?

- WLL is a system that connects subscribers to the local telephone station wirelessly.

Systems WLL is based on:CellularSatellite (specific and adjunct)Microcellular

A WLL system replaces the copper loop with radio frequency loop,maintaining the existing services of a basic telephone system.

Local loop:cicuit between the subscriber equipment and the local exchange.

WLL:-•Due to drastic changes in internet,these services use the broadband local loop systems.•To deal this deal in the short term ,the digital subscriber line(DSL) technologies,including HDSL,ADSL and very high bit rate DSL(VDSL) is need to be developed.

•In WLL system,entire coverage area is divided into a number of hexagonal sub-areas called cells.but we get services in only one cell.•Eg BSNL is providing one cell area.

•But if the WLL is based on CDMA then user can use all services of cellular system.eg in India, Reliance,Tata Indicom.

A general WLL setup

WLL setup:

•WLL is a kind of radio system.•Most of the WLL systems are developed according to the standards for mobile systems.•In terms of multiple access(FDMA),the time division multiple access(TDMA) and code division multiple access(CDMA).•WLL provide a variety of data services and multimedia services as well as voice.

telephone

BSC

FSU

BTS 1

BTS 2

BTS3

BTS4

WLL switch

PSTN switchPC FAX

FSU

AIR INTERFACE

WLL SYSTEM ARCHITECTURE

WLL ARCHITECTURE:

In a WLL architecture, BSC(base station controller) is the heart of a WLL system.It interfaces with the PSTN,BTS and a operation maintenance centre(OMC) to perform call processing,voice coding etc.

BTS(base transceiver system) interface between the BSC and subscriber stations.one BTS has an antenna power control functions,which may be omnidirectional or directional.

It placed at the centre of the hexagonal cell and serves subscriber within the cell.

FSU(fixed subscriber unit) is an interface between subscriber wired devices and WLL network.The wired devices can be telephone and fascimile as well as computers.

FSU PERFORMS: channel encoding/decoding,modulation/demodulation and transmission/reception of a signal .

WLL should provide…Toll-quality serviceExpand from a central office to about 5

milesLow license costSubscriber costs equivalent or better than

copper

Advantages:

The advantages of WLL system includes:

Rapid installation. Flexible Planning. less fault liabilities. cost effectiveness. copper saving. suitable for congested area.

Cost Considerations

• Wireless cost is constant over distance for WLL• Wireline depends on distance AND terrain

Connection Setup

PSTNSwitch function

WLLController

AMHLR

Transceiver WASU

TrunkAir Interface

UWLL

TWLL

Wireless Access Network Unit(WANU)– Interface between underlying

telephone network and wireless link– consists of

• Base Station Transceivers (BTS)• Radio Controller(RPCU)• Access Manager(AM)• Home Location Register(HLR)

WANU

Wireless Access Subscriber Wireless Access Subscriber Unit(WASU)Unit(WASU)– located at the subscriberlocated at the subscriber– translates wireless link into a translates wireless link into a

traditional traditional telephone telephone connectionconnection