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 in Skinner and Cavers (February 1973) 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 T. A. Skinner and J. K. Cavers (February 1973) 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 This discrete implementation of the scheme makes the system more robust against imperfect and/or outdated channel estimates.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 he sent back to the transmitter.