Design of orthogonal subsets for M-ary spread spectrum communications with OFDM modulation

Based on the sampling-concatenating operation with any integer interval, a large number of orthogonal subsets are designed for M-ary spread spectrum (MSS) communications with orthogonal frequency division multiplexing (OFDM) modulation. Any two sequences in the designed subset are orthogonal to each other, that is, the in-phase cross-correlation (IPCC) between them is equal to zero. Compared with the previous researches, the designed multiple subsets may possess more sequences at the cost of the peak-to-mean envelope power ratio (PMEPR) and inter-subset IPCC, which will be suitable for MSS-OFDM communications where the larger number of sequences means higher data rate. We provide a simple example to show how the designed algorithm works, and the corresponding performance of PMEPR and IPCC is analyzed.