==Evolution of Cellular Systems==
[[Image:cdma1.jpg|500 px|center]]
==Multiple Access Methods==There are predominantly three types of multiple access methods.<br>'''=== Frequency Division Multiple Access:''' ===In this system , each user is alloted allotted a different set of frequency frequencies to operate upon. The uplink(mobile to base station) frequency is different from downlink frequency(base station to mobile).[[Image:cdma6.jpg]]<br>|[Refhttp://www.ai.u-hyogo.ac.jp/~thai-proj/presen/20051222-Ishikawa.pptCDMA]]]
'''Time Division Multiple Access:'''In this system each user is allocated a different time slot.Forward link frequency and reverse link frequency is the same. A synchronous switch is responsible to do the time switching.
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