What is CDMA?

CDMA which stands for Code Division Multiple Access is a cellular digital technology that is used for both voice and data communications on mobile devices. CDMA is the foundation on which various access methods such as cdmaOne, CDMA2000, and the latest WCDMA are built on. CDMA cellular systems are considered to be far superior to TDMA and FDMA, which is the reason why CDMA plays a very important role in developing practical, robust, and more secure radio communication systems.

CDMA is an example of the Multiple Access, where various transmitters can transmit information concurrently over a single channel of communication. This allows lots of users to share the same band of frequencies. To allow this without undue hindrance between the users, CDMA makes use of the Spread Spectrum technology and a special programming scheme in where each transmitter is assigned a code.

Each user in a CDMA system makes use of different codes to regulate their signals. Determining the codes to be used to modulate the signals is very important in the performance of CDMA systems. The best performance with CDMA happens when there is a good division between the signal of the desired user and the signals of other users in it. The division of these signals is made possible by comparing the received signal with the locally generated code of the desired user. If the received signal matches the desired user's code, then the correlation function will be high and the system can then extract that signal. If the desired user's generated code has nothing in common with the signal, the correlation should be as close to zero as possible thereby discarding the signal, and this is referred to as cross-correlation.

Features of CDMA

There are lots of features of CDMA and some of them are:

1. In CDMA, every channel makes use of the full spectrum that is available.

2. Individual conversations in CDMA are primarily encoded with a pseudo-random digital sequence, after that, they would be transmitted using a wide frequency range.

3. CDMA unfailingly presents better capacity for both voice and data communications, by allowing more subscribers to connect at any given time.

4. CDMA is the primary platform on which 3G technologies are built on. For 3G, CDMA makes use of 1x EV-DO and EV-DV.

Benefits and Advantages of CDMA

The following are the benefits or advantages of CDMA:

1. In CDMA, the signal to be transmitted is spread across the wide bandwidth due to spreading. Therefore CDMA is more robust against fading and noisy environments.

2. As the transmitted information is lesser than the noise floor, it is very difficult to interfere with the CDMA spectrum. Besides, it is very difficult for hackers to crack the CDMA code used over the traffic channels. Therefore CDMA is a more secure system.

3. CDMA allows for the use of the entire bandwidth at the same time and consequently there is no limit on a number of users per cell, unlike the FDMA and TDMA access schemes. This depends on a number of codes that are supported by the CDMA compliant base station. Besides, it is easier to add users.

4. During the switching between the cells, due to the soft handoff feature, the initial connection is being set up with a new cell and therefore, it minimizes chances of call drop or call disconnection.

5. CDMA networks can easily work across other cellular networks such as GSM and LTE. Therefore nationwide roaming is possible without any issues.


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