Algorithms for coherent diversity combining of M-ary orthogonal signals

This paper discusses the use of coherent demodulation for antenna array receivers employing direct sequence spread spectrum techniques and M-ary orthogonal modulation. Three different approaches are discussed. The first is a conventional receiver using training sequences and decision feedback for channel estimation. The other two techniques employ decisions from a simple non-coherent combining receiver to circumvent the need for training sequences. Simulation results are used to compare their performance in different scenarios