Algorithm for reducing the peak to average power ratio in a multicarrier communications system

One of the main implementation disadvantages of a multicarrier communication system is the possibly high peak to average power ratio of the transmitted signals. One proposed solution is given by Jones and Wilkinson. It is based on applying a specific phase shift (not dependent on the codeword) to each dimension of the transmitted codewords. These phase shifts are known both to the transmitter and the receiver. Thus the phase shifts can be compensated for in the receiver without changing the distance properties of the code. Therefore, neither the rate nor the code performance is sacrificed. The phases need only once be computed off-line and the complexity of the system does not increase. Our combination is to provide an algorithm to compute the phases that minimize the maximum peak to average power ratio taken over all possible transmitted signals. The new algorithm enables us to apply the Jones-Wilkinson method to various medium length as well as long codes of practical interest, a computational task for which no solution was known before. We apply our algorithm to some of the codes adapted for use in the physical layer of future wireless local area networks by the ETSI BRAN Hiperlan-II standardization committee. We report the computed reductions in peak to average power ratio.

Duke Scholars

Author Vahid Tarokh Electrical and Computer Engineering