Increasing diversity with non-standard signal sets in wireless OFDM systems

When operating in a wireless transmission environment with available diversity greater than the minimum Hamming distance of its error control code, orthogonal frequency division multiplexing (OFDM) systems can suffer a diversity loss relative to their single-carrier counterparts when both systems are employing identical error control codes. A method of trading complexity for increased diversity in wireless OFDM systems is considered. The method employs a multidimensional signal set, where each signal point in the set is a linear transform of a signal point drawn from a multidimensional signal set that is the product of standard two-dimensional signal sets, each rotated about the origin. The peak-to-mean envelope power ratio (PMEPR) of the proposed system is considered, and it is shown that the PMEPR can be reduced further at the sample points, albeit moderately, by a modification of the proposed signal sets on certain subsets of the subcarriers. Finally, performance curves for the proposed system are given for environments with a varying amount of frequency diversity available in the channel