Diversity combining with discrete power loading over fading channels

This paper studies a system with diversity reception combining and adaptive discrete power of transmission based on an idea presented by J. F. Haves (February 1968) wherein he showed that feedback information improves the performance significantly in a Rayleigh multipath medium. We first have an alternative look at the system considered by J. F. Haves (February 1968) by providing slightly modified and compact results. We then consider the 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 channel status. This discrete scheme also makes the system more robust against imperfect and/or outdated channel estimates and does not need to feedback the instantaneous channel status but instead the index of the adaptation region.