GSM VS CDMA TECHNOLOGYBY TARUSH RASTOGI

DEFINATION GSMo GLOBAL SYSTEM FOR MOBILE COMMUNICATION o SET OF RULES DEVELOPED BY EUROPEAN TELECOMMUNICATIONS STANDARD INSTITUTE (ETSI) IN 1989. AND OFFICIALLY LAUNCHED IN 1992

CDMA

o CODE DIVISION MULTIPLEACCESS o CDMA HAS ITS ROOT IN PRE-WORLD WAR II IN AMERICA.IN 1995 CDMA WAS ,FOR THE FIRST TIME USED FOR MOBILE COMMUNICATION IN U.S.A.

TECHNOLOGY USED GSMo GSM IS THE COMBINATION OF FDMA & TDMA o IN FDMA THE SPECTRUM ARE DIVIDED IN FREQUENCY SLOTS.EACH USER GET ONE SLOT THAT IS USED AT WILL o IN TDMA THE FREQUENCY BAND IS NOT PATITIONED BUT USER ARE ALLOWED TO USE IT FOR A PRE DEFINED TIME AT ONE TIME

CDMAo CODE DIVISION MULTIPLEX ACCESS o CODE DIVISION MEANS THE VOICE ANALOG SIGNAL IS CONVERTED INTO ITS CORRESPONDING DGITAL SIGNAL BUT THIS DIGITAL SIGNAL IS ACCORDINGLY A UNIQUE CODE ASSIGNED TO THAT USER

TECHNOLOGY USED GSM CDMATime Power Time Power

Frequency

FDMA & TDMA

Frequency

CDMA

ARCHITECTURE OF GSM

ARCHITECTURE OF CDMA

FREQUENCY PATTERNo DUE TO THE LIMITED SPECTRUM ALLOCATION & TO FULLFILL THE DEMANDS THE FREQUENCY IS RE-USED IN GSM THIS PHENONENON IS CALLED FREQUENCY RE-USE PATTERN.BUT THE CELL USING THE SAME FREQUENCY MUST BE SAPERATED BY AN APPROPRRIATE DISTANCE. o WHILE IN CDMA IT WORKS ON THE SPREAD SPECTRUM TECHNIQUE WHICH MEANS THAT IT SPREAD THE INFORMATION CONTAINED IN A PARTICULAR SIGNAL OF INTEREST OVER A MUCH GREATER BANDWIDTH THAN THE ORIGINAL SIGNAL.

CELL STRUCTURE & FREQUENCY ALLOCATION GSM CDMA

HAND OVER/ HAND OFFo HAND OVER IS A PROCESS OF TRANSFERRING A CALL FROM ONE CELL TO ANOTHER CELL. THIS IS NECESSARY TO CONTINUE A CALL WHILE THE USER IS MOVING.

o THIS IS NEEDED BECAUSE AS THE USER IS MOVING HE MAY GET MUCH FAR FROM THE BTS TO WHICH IT IS CONNECTED AND THE SIGNAL STRENGHT MAY BE GET WEEK ENOUGH THAT CALL MAY DROP. SO HANDOVER IS DONE TO AVOID CALL DROP, AND THE USER GET CONNECTED TO NEW BTS WHICH PROVIDE STRONG SIGNAL TO CONTINUE A CALL.

HAND OVER / HAND OFF GSMo GSM USES A HARD HANDOFF WHEN THE MOBILE MOVES FROM ONE CELL SITE TO ANOTHER.A HARD HANDOFF CAN INCREASE THE CHANCES OF THE CALL DROP.A HARD HANDOFF REQUIRES THE MOBILE TO BREAK THE CONNECTION WITH THE OLD BTS PRIOR TO MAKE THE CONNECTION WITH THE NEW ONE. HARD HANDOFF ARE ALSO CALLED BREAK BEFORE MAKE

CDMAo CDMA USES A SOFT HANDOFF WHEN THE MOBILE MOVE FROM ONE CELL SITE TO ANOTHER.A SOFT HANDOFF HAS A LESS CHANCES OF THE CALL DROP DUE TO ITS MAKE BEFORE BREAK PROCCESS.A SOFT HANDOFF REQUIRES THE MOBILE TO MAKE THE CONNECTION TO NEW BTS BEFORE BREAKING THE CONNECTION WITH THE OLD BTS. SOFT HANDOFF IS ALSO CALLED MAKE BEFORE BREAK

HANDOVER/ HANDOFF GSM CDMA

SIGNAL RECEPTION GSMo WHEN THE SIGNALS TRAVEL TO A MOBILE THROUGH DIFFERENT PATH, IT WILL PICK THE 1ST SIGNAL REACHED TO IT, NO MATTER HOW WEAK THAT SIGNAL IS.THUS LEAD TO CALL DISTURBANCE, LOW SPEECH, AND SOME TIME ECHO.

CDMAo IN CDMA A RAKE RECEIVER IS USED. IT IS A MULTIPLE SIGNAL RECEIVER.THE RAKE RECEIVER IDENTIFIES THE THREE STRONGEST MULTI-PATH SIGNAL AND COMBINE THEM TO PRODUCE ONE VERY STRONG SIGNAL. BOTH MOBILE AND CELL SITE USE A RAKE RECEIVER.

SIGNAL RECEPTION GSM CDMA

POWER ADJUSMENT GSMo IN GSM SYSTEM MOBILE TRANSMITS THE SIGNAL STRENGTH AS PER THE DISTANCE OF THE MOBILE FROM THE BTS. MOBILE NEAR TO THE BTS TRANSMIT A STRONG SIGNAL WHILE THE MOBILE FAR FROM THE BTS TRANSMIS A WEAK SIGNAL. THIS WOULD INCREASE THE CAPACITY OF THE SYSTEM.

CDMAo IN CDMA THE POWER CONTROL FEATURE IS ENABLE. THIS ENSURE THAT THE BTS RECEIVE ALL SIGNALS AT THE APPROPRIATE POWER. o BOTH FORWARD AND REVERSE LINKS USE POWER CONTROL TECHNIQUES

POWER ADJUSMENT GSM CDMA

ADVANTAGES &DISADVANTAGES OF GSM ADVANTAGE:o GSM IS ALREADY USED WORLDWIDE WITH OVER 1 BILLION SUBSCRIBER. o INTERNATIONAL ROAMING PERMITS SUBSCRIBERS TO USE ONE PHONE. o GSM IS MATURE,MATURITY MEANS A MORE STABLE NETWORK. o THE AVAILIBILITY OF SIM PROVIDE SECURE DATA ENCRYPTION.

DISADVANTAGES:o LESS SECURE NETWORK. o EXTREAMLY LARGE NETWORK CREATE MORE COMPLEX FOR FREQUENCY PLANNING.

ADVANTAGES & DISADVANTAGES OF CDMA ADVANTAGES:o o o o o INCREASED CELLULAR COMMUNICATIONS SECURITY. SIMULTANEOUS CONVERSATION. INCREASED EFFICIENCY. SMALLER PHONE. EXTREMDED REACH- BENIFICIAL TO RURAL USERS SITUATED FAR FROM THE CELL.

DISADVANTAGES:o CDMA IS RELATIVELY NEW, AND THE NETWORK IS NOT ASMATURE AS GSM. o CDMA CANNOT OFFER INTERNATIONAL ROAMING.

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