Seminar on Code Division Multiple Access

Now a day’s mobile communication is growing at a faster rate day by day the users for cell phone is growing very much. In CDMA we can have multiple users transmitting over one channel. CDMA is a new digital wireless transmission technology form of spread spectrum and it was launched in early nineties. CDMA works by converting speech voice into digital wave and then transmit it as radio wave. The frequency for the CDMA is not defined and many times a lots of user has to use the same frequency without interference and the receiving device is design to use the data out of received signal.

History: – The first cell phone were introduced in 1980’s and has the AMPS (Advanced Mobile Phone System). In coming years the demand for cell phone starts increasing and CDMA came into existence in 1994.CDMA uses digital modulation and processing technique. A phone is called cellular because it divided the area into small cells and each cell is assigned a frequency.

CDMA has a bigger capacity over GSM mobile and uses less interference and lower radiation and it more secure than GSM. CDMA uses pseudo- random code sequence. GSM is an extended version of time division multiple access.

Basis of CDMA: – CDMA uses spread spectrum technology which means transmission in which the data sequence occupies a bandwidth in excess of the minimum bandwidth to send information. In it a multiple user can share a common channel without any external interference.

Advantages and Disadvantages: – It is best for building system and it reduces average transmitted power. It improves the telephone traffic capacity. It also improves voice quality and eliminate external interference. Also provides reliable transport mechanism for data communication. It does not support multi part fading and also does not support multi user interference.

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