=== Frequency Division Multiple Access ===
In this system, each user is allotted a different set of frequencies to operate upon. The uplink(mobile to base station) frequency is different from downlink frequency(base station to mobile).
[[Image:cdma6.jpg|thumb|700px|center|[http://www.ai.u-hyogo.ac.jp/~thai-proj/presen/20051222-Ishikawa.ppt CDMAFDMA]]]'''=== 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 for the time switching.[[Image:cdma10.jpg|thumb|center|TDMA]]'''=== Code Division Multiple Access:'''===There is no restriction on time and frequency in this scheme. All the users can transmit at all times and at all frequencies. Because users are isolated by code, they can share the same carrier frequency, eliminating the frequency reuse problem encountered in other technologies.<br>[[Image:cdma11.jpg|600 px|centre|CDMA]]<br> A comparative study between the above three access technologies with respect to time and frequency is as shown below<br>.[[Image:cdma12.jpg|600 px|centre|Comparison of cellular access schemes]]
==Code Division Multiple Access==