Which one of the following statements is not correct regarding the features of CDMA?

Question

Question

This question was previously asked in

UPSC ESE Electronics & Communication 2022 Official Paper

Multipath fading may be substantially increased because the signal is spread over a large spectrum.
Channel data rates are very high in CDMA systems.
The near-far problem occurs at a CDMA receiver if an undesired user has a high detected power as compared to the desired user.
Many users of a CDMA system share the same frequency.

Answer 1

Key Points

In code division multiple access (CDMA) systems, the narrowband message signal is multiplied by a very large bandwidth signal called the spreading signal.
The spreading signal is a pseudo-noise code sequence that has a chip rate which is orders of magnitudes greater than the data rate of the message.
- Channel data rates are very high in CDMA systems. Consequently, the symbol (chip) duration is very short and usually much less than the channel delay spread
All users in a CDMA system, as seen from Figure use the same carrier frequency and may transmit simultaneously.

F2 Savita Engineering 14-11-22 D49

The power of multiple users at a receiver determines the noise floor after de-correlation.
- If the power of each user within a cell is not controlled such that they do not appear equal at the base station receiver, then the near-far problem occurs.
- The near-far problem occurs when many mobile users share the same channel. In general, the strongest received mobile signal will capture the demodulator at a base station.
Multipath fading may be substantially reduced because the signal is spread over a large spectrum.
- If the spread spectrum bandwidth is greater than the coherence bandwidth of the channel, the inherent frequency diversity will mitigate the effects of small-scale fading.