Question

In a Rayleigh fading channel, determine the gain (expressed in dB ) in average signal-tonoise ratio obtained in a system that uses a 3-order combining scheme over the system with no diversity combining, if the receiver uses

(i) maximal ratio combining
(ii) equal gain combining
(iii) selection combining.

Answer 1

In a Rayleigh fading channel, the gain in average signal-to-noise ratio obtained in a system with a 3-order combining scheme depends on the diversity combining technique used. Maximal Ratio Combining and Equal Gain Combining provide an average SNR gain of 3 dB, while Selection Combining does not provide any gain.

Step-by-step explanation:

In a Rayleigh fading channel, the gain in average signal-to-noise ratio obtained in a system with a 3-order combining scheme can be determined for different diversity combining techniques. Let's consider the three cases:

1. Maximal Ratio Combining (MRC): In MRC, the combining scheme takes the ratio of the powers of the received signals from multiple antennas. This results in an average SNR gain of 3 dB, as the combining gain is proportional to the square root of the number of antennas used.
2. Equal Gain Combining (EGC): In EGC, the combining scheme applies equal weight to the received signals from multiple antennas. This also results in an average SNR gain of 3 dB, similar to MRC.
3. Selection Combining: In selection combining, the receiver chooses the best signal among the received signals from multiple antennas. In this case, the average SNR gain is 0 dB, as the combining scheme only uses the best signal and discards the rest.