Code Division Multiple Access


The Full form of CDMA is Code Division Multiple Access. CDMA is a digital cellular technology which displays a network of multiple accesses. The various radio communication technologies use this technique as channel access method. It is generally used for the communication of mobiles. Multiple access means that over a channel of single communication, several transmitters can transmit information simultaneously.


In this system, different users are assigned different CDMA codes and for the entire duration, the user can access the whole bandwidth. It does not limit the user’s frequency range, as it sends over the complete range of frequency and it also optimizes the use of bandwidth which is available. Therefore, CDMA enables various users to share a band of frequencies between users. It is used as an access technique on many levels of mobile phones. During World War II, CDMA technology was developed to protect the wireless transmissions from jamming by English allies.


Qualcomm patented this technology after the war and made it commercially available. The first CDMA system was launched in Hong Kong by Hutchison Telephone Co in September 1995. CDMA technology is used in GPS (Global Positioning System) and by several mobile phone companies (e.g. Qualcomm standard IS-2000 also known as CDMA 2000. W-CDMA is also used in UTMS 3G mobile phone standard.