It is about CDMA AND GSM SIM TECHNOLOGY

1. WLL-WIRELESS IN LOCAL LOOP_FIXED WIRELESS
SERVICE TO PROVIDE PRIMARY ACCESS TO THE
TELEPHONE NETWORK . THIS SYSYTEM
REPLACES THE COPPER LOOP WITH RADIO
FREQUENCY LOOP.MAITAINING THER EXISTING
SERVICES OF A TELEPHONE.
ACCESSING THE WLL SYSTEM
CDMA _THE MOST POPULAR WAY OF
ACCESSSING THE WLL SYSTEM
CODE DIVISION MULTIPLE ACCESS DEVELOPED
BY Q1UALCOMM US USES THE SPREAD
SPECTRUM TECHNOLOGY IN WHICH ALL USERS
COMMUNICATE SIMULTANEOUSLY THROUGH
THE SAME RADIO CHANNEL OCCUPYING THE
ENTIRE CHANNEL BANDWIDTH THE DISTINCTION
B/W USERS IS MADE BY ASSIGNING A UNIQUE
DIGITAL CODE. THE FREQUENCY BANDS
ALLOCATED FOR THE CDMA-BASE WLL SYSTEM
IS 824-849 Mhz(UPLINK)& 869-894Mhz ( downlink).
THE ENTIRE COVERAGE AREA IS DIVIDE INTO A
NUMBER OF SU-AREAS CALLED CELLS.THYE
CELLS ARE OF TWO TYPES
MACRO HAVING A RADIUS OF 10 TO 30 KM.
MICRO HAVING RADIUS OF 50 TO 200 METERS.
CDMA USES MACRO CELL ARCHITECTURE.
THE BASIC SUBUNITS OF A WLL SYSTEM ARE
1)BSC-BASE STATION CONTROLLER
2)BTS-BASE TRANSRECEIVER SUB-SYSTEM
3)OPERATION AND MAINTAINANCE CENTRE
4)MOBILE SET
5)FIXED WIRELESS TERMINAL

2. THE BSC IS THE HEART OF A WLL SYSTEM. IT
INTERFACES THE PSTN,BTS AND OMC.
THE BTS IS THE INTERFACE B/W THE BSC AND
SUBSCRIBER STATIONS.THE BTS HAS AN
ANTENNA SYSTEM,WHICH MAY BE
OMNIDIRECTINAL OR UNIDIRECTIONAL.IT LISES
AT THE CENTRE OF THE HEXAGONAL CELLS
THE USER IS PROVIDED WITH A MOBILE
HANDSET.THE FIXED WIRELESS
TERMINALCONSISTS OF A TELEPHONE
INSTRUMENT AND A RADIO TERMINAL.THERE IS
A PROVISION TO CONNECT A FAX MACHINE&A PC
TO A TELEPHONE INSTRUMENT. THE OMC IS
MEANT FOR MAN MACHINE COMMUNICATION OF
BTHE WLL SYSTEM. IT IS A PC CONNECTED
THROUGH A SERIAL DATA LINK TO THE BSC. THE
OMC DIRECTLY INTERACTS WITH THE BSC FOR
ALL ACTIVITIES LIKE ADDITION OF
SUBSCRIBERS,PROVISION OF VARIOUS
FACILITIES,SYSTEM
CONFIGURATIONMANAGEMENT,EXTRATING
BILLING INFORMATION, SYSTEM STATUS STUDY.