Code division multiple access (CDMA) allows all terminals to send signals simultaneously over the same frequency by assigning each terminal a unique spreading code. The receiver can isolate a particular sender's signal by correlating the received signal with the known spreading code. CDMA offers advantages like higher capacity and integration of encryption due to the use of spreading codes, though receivers are more complex.

3. CDMA on signal level I data A key A signal A data  key key sequence A Real systems use much longer keys resulting in a larger distance between single code words in code space. 1 0 1 1 0 0 1 0 0 1 0 0 0 1 0 1 1 0 0 1 1 0 1 1 0 1 1 1 0 0 0 1 0 0 0 1 1 0 0 A d A k A s

4. CDMA on signal level II signal A data B key B key sequence B signal B A s + B s data  key 1 0 0 0 0 0 1 1 0 1 0 1 0 0 0 0 1 0 1 1 1 1 1 1 0 0 1 1 0 1 0 0 0 0 1 0 1 1 1 B d B k B s A s

5. CDMA on signal level III A k (A s + B s ) * A k integrator output comparator output A s + B s data A 1 0 1 1 0 1 A d

6. CDMA on signal level IV integrator output comparator output B k (A s + B s ) * B k A s + B s data B 1 0 0 1 0 0 B d

7. CDMA on signal level V comparator output wrong key K integrator output (A s + B s ) * K A s + B s (0) (0) ?

10. Comparison SDMA/TDMA/FDMA/CDMA

11. Telecommunications Systems year Subscribers [million] 0 200 400 600 800 1000 1200 1400 1600 1996 1997 1998 1999 2000 2001 2002 2003 2004 approx. 1.7 bn GSM total TDMA total CDMA total PDC total Analogue total W-CDMA Total wireless Prediction (1998) Mobile Phone Subscribers world-wide

12. Development of mobile telecommunication systems 1G 2G 3G 2.5G IS-95 cdmaOne IS-136 TDMA D-AMPS GSM PDC GPRS IMT-DS UTRA FDD / W-CDMA EDGE IMT-TC UTRA TDD / TD-CDMA cdma2000 1X 1X EV-DV (3X) AMPS NMT IMT-SC IS-136HS UWC-136 IMT-TC TD-SCDMA CT0/1 CT2 IMT-FT DECT CDMA TDMA FDMA IMT-MC cdma2000 1X EV-DO HSDPA

25. GSM: overview fixed network BSC BSC MSC MSC GMSC OMC, EIR, AUC VLR HLR NSS with OSS RSS VLR

27. GSM: elements and interfaces NSS MS MS BTS BSC GMSC IWF OMC BTS BSC MSC MSC A bis U m EIR HLR VLR VLR A BSS PDN ISDN, PSTN RSS radio cell radio cell MS AUC OSS signaling O

28. GSM: system architecture U m A bis A BSS radio subsystem MS MS BTS BSC BTS BTS BSC BTS network and switching subsystem MSC MSC fixed partner networks IWF ISDN PSTN PSPDN CSPDN SS7 EIR HLR VLR ISDN PSTN

29. System architecture: radio subsystem U m A bis A BSS radio subsystem network and switching subsystem MS MS BTS BSC MSC BTS BTS BSC BTS MSC