Dynamic Allocation of Reserved Tones for PAR Reduction

The high Peak-to-Average-Power ratio (PAR) of Orthogonal Frequency Division Multiplexing (OFDM) transmission systems has become a significant issue in the design of modern multicarrier systems. One of the earliest and most popular techniques is tone reservation [1], where a set of unused tones (or specially reserved-tones) are exploited to generate time-domain signals to reduce the signal peaks. The reserved-tones are usually allocated in advance and are unused for data transmission. In this work, choosing the reserved-tones dynamically based on the actual signal realization via an l1-norm constraint is proposed and shown to significantly improve the PAR performance of tone reservation. With the reserved-tones being chosen dynamically and no side information about the reserved-tone set at the receiver, additional processing is needed. Methods to help the receiver reliably estimate the reservedtone set are also explored. For an N = 64 16-QAM OFDM system, dynamically choosing the reservedtones reduces the PAR by 1.2 dB at 10 symbol clip probability compared to a fixed reserved-tone set.