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Advantages of CDMA | Disadvantages of CDMA

This page covers advantages and disadvantages of CDMA technique. It mentions CDMA advantages or benefits and CDMA disadvantages or drawbacks. It provides links on various topics on CDMA (Code Division Multiple Access) basics.

What is CDMA?

Introduction:
The term CDMA stands for Code Division Multiple Access. It is cellular technology in which there are two main systems viz. Base Station (BS) and mobile subscribers or users. The unique codes are assigned to the users for communication with BS or NodeB. CDMA allows multiple transmitters to transmit information over single channel simultaneously. This makes it possible to share same bandwidth by multiple users.

CDMA

In CDMA entire bandwidth is being used by users all the time and each have their unique codes (e.g. PN codes) to recover the data. The system works based on spread spectrum concept.
Refer CDMA tutorial>> , What is CDMA>> and CDMA versus OFDM>> for more information.

Benefits or advantages of CDMA

Following are the benefits or advantages of CDMA:
➨In CDMA, signal to be transmitted spread across the wide bandwidth due to spreading. Hence CDMA is robust against fading and noisy environment.
➨As the transmitted information is below the noise floor, it is difficult to intrude the CDMA spectrum. Moreover it is difficult for hackers to decipher the CDMA code used over traffic channel. Hence CDMA is more secure system.
➨CDMA allows use of entire bandwidth simultaneously and hence there is no limit on number of subscribers per cell unlike TDMA and FDMA access schemes. This depends on number of codes supported by the CDMA compliant base station. Moreover it is easy to add users.
➨During the handover between the cells, due to soft handoff feature initially connection is being established with new cell and hence it minimizes chances of call drop or disconnection.
➨CDMA networks can interoperate with other cellular networks such as GSM/LTE. Hence nationwide roaming is possible without any issues.

Drawbacks or disadvantages of CDMA

Following are the disadvantages of CDMA:
➨In CDMA, orthogonal codes are used by mobile subscribers. Orthogonality between the codes need to be maintained in order to recover the data. The subscribers which are farthest from BS will incur more attenuation and hence will lose the orthogonality and hence it will be difficult to recover the data.
➨CDMA uses soft handoff. In this type of handoff, mobile needs to establish connection with the new target cell before disconnecting itself from serving cell. This procedure it more complex compare to the hard handoff type.
➨Precision code synchronization is needed to recover the original baseband signal.
➨Increase in number of users will decrease the overall QoS.
➨Near far problem is encountered in CDMA system. This requires close control of transmit powers of CDMA handsets. This helps farthest CDMA Phone to transmit at higher power compare to CDMA phone which is closer in order to maintain good SNR at BS (Base station).
➨Self Jamming is observed in CDMA system due to loss of orthogonality of PN codes or spreading sequences of different subscribers.



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