Diversity technique for DAPSK signal over the frequency-selective fading channel

In this paper, a maximal ratio combining (MRC) and weighted maximal ratio combining (WMRC) diversity receiver are proposed. The MRC receiver makes a decision at each branch based on the minimum distance criterion. The performance of the MRC receiver is analyzed on the frequency-selective Rayleigh and Rician fading channels, in terms of the union bound for bit error probability. In addition, the WMRC receiver, which assigns weighting factors to the decision variable at each branch, based on the optimum decision boundaries, is proposed. The performance of the WMRC is investigated through the computer simulation and compared with those of MRC and equal gain combining (EGC). From the results, it is found that the performances of the WMRC and MRC are better than those of EGC on both the frequency-selective Rayleigh and Rician fading channels and performance improvements over the EGC are noticeable when the number of diversity branches is large as long as the root mean square (rms) delay is smaller than or equal to 10% of the symbol period.