Advantages And Disadvantages Of Code-Division Multiple Access (CDMA)

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Code-division multiple access (CDMA)
Discussion of CDMA
Code-division multiple access (CDMA) is a multiple access method used by different types of radio communication technologies. Direct-sequence spread spectrum signals uses CDMA which allow more than one user to share a channel. CDMA is a form of multiplexing which allows many signals to occupy a transmission channel and optimizing the use of available bandwidth. Therefore, the receiver separates the signals from the users by cross correlation of the received signal with each of the user unique code sequences. If the code sequence is designed to have a small cross correlation, it can minimize the crosstalk inherent. There is a spreading signal in code-division multiple access (CDMA) systems
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CDMA normally operates on bands of frequency of 800MHz and 1900 MHz. In CDMA, the voice signal is first digitized and then it spread out the resultant data over the entire frequency bandwidth. The data is sent in a unique code for use at any time in the specific range. Below is the list of advantages and disadvantages of CDMA:
Advantages :
1. Efficient utilization of specific frequency spectrum.
2. Flexible distribution of resources.
3. Large signal bandwidth reduces the multipath fading.
4. Addition of users is easy and no limit for the number of users.
5. Highly secured from hackers.
6. Better signal quality.
7. No sense of handoff when changing cells.

Disadvantages :
1. The overall quality of service decreases when the number of users increases.
2. Self-jamming.
3. Near far problem occurs.

Noise effect on CDMA
1. Near Far
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In order to get a good design, the bandwidth of modulation need to be minimized for transmission. A transmission bandwidth that has a greater magnitude than the bandwidth required for the minimum signal is used by the spread spectrum. The advantage of spread spectrum is that it can be many users use the same bandwidth at the same time without interfering with each other. However, this is not good for a few number of users because it is not economic. Spread spectrum is a form of wireless communications. The frequency of the transmitted signal is varied purposely to get a higher bandwidth. Spread spectrum uses demodulate, wideband, intercept and some signal that is hard to detect which is noise-like signal. Other than that, spread spectrum signals are harder to interfere with other signal than the narrow band signals. Spread spectrum is a wide signals, they transmit lower spectral power density than the narrow band transmitters. There are two types of spread spectrum techniques which are Direct Sequence Spread Spectrum and Frequency Hoping Spread

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