Selective diversity with discrete power loading over rayleigh fading channels

This paper revisits a selective diversity system with optimum continuous power loading which was originally proposed by Skinner and Cavers in [1] and which yields minimum average probability of error when the diversity paths are orthogonal. In a first part, the paper offers an alternative look at the system considered in [1] and provides some slightly modified results. In a second part, the paper considers a practical implementation of this system by proposing an optimum discrete power loading scheme. The problem in its discrete fashion is to minimize the average bit error rate for a given total energy constraint resulting in an optimum discrete power loading as a function of the channel status. This discrete implementation of the scheme makes the system more robust against imperfect and/or outdated channel estimates. In addition in this case only the index of the adaptation region (rather than the instantaneous channel status) has to be sent back to the transmitter.