Ordered phase sequence testing in SLM for improved blind detection

Selected mapping (SLM) is a promising technique to reduce the high peak-to-average power ratio (PAR) of orthogonal frequency division multiplexing (OFDM) signals. In this paper we present an altered form of SLM that tests phase sequences in an ordered manner and ceases testing when the PAR is below a threshold. Aside from having a reduced computational complexity compared to traditional SLM, our modification allows for maximum a posteriori (MAP) blind detection of SLM phase mappings in the receiver. MAP detection is possible because, by testing the phase sequences in an ordered way, different phase mappings have different probabilities of occurrence. We derive the MAP metric as well as a lower-complexity approximation to the MAP metric.