Optimum threshold switching to spatial diversity systems

In selection antenna diversity the rules to choose the signal to demodulate from the set of received ones, is critical. We present a choice algorithm for a two antennas diversity based on the ratio ρ between the power of the sum of the signals received from both the two antennas, P_AB, and that received from one antenna, P_A . We show that with average equal power received from the two antennas, the threshold value ρ which minimizes the probability of choosing the least power signal (Pes) turns out to be equal to 1.75, and the corresponding Pes is about 10% with an error margin of ±1 dB on the measured powers