A balancing method for PMEPR reduction in OFDM signals

A relation is established between the strength of a binary code over the alphabet {+ 1, - 1}, and its ability to reduce peak-to-mean envelope power ratio (PMEPR) in n-subcarrier (OFDM) signals. Based on this relation, a method is proposed to deterministically bound PMEPR of such signals using coordinate-wise multiplication by a balancing vector (BV) chosen from a code of given strength. A practical probabilistic scheme considering a small number of candidate codewords is devised. For this scheme, estimates on the PMEPR reduction achievable with arbitrary high probability are derived. In particular, the scheme provides for large n. PMEPR of ln n. + 2.01 ln ln n with (ln 2) - (log(2) n)(2) + 1 bits of redundancy, the failure probability at most e(-n), and testing n/(ln ln n) candidate BVs. Finally, several practical settings are considered. For example, for quaternary phase-shift keying, n = 128, the scheme with 36 bits of redundancy (18 redundant subcarriers), by testing only 4 BVs provides over 2 dB PMEPR reduction, for any failure rate below 10(-2.5).