Soft Demodulators Based on Deterministic SMC for Single-Carrier GSM in Broadband Channels

To enjoy advantages of both the single-carrier (SC) transmission and the generalized spatial modulation (GSM), a hybrid architecture of SC-GSM has been developed in the literature. However, low-complexity demodulation for SC-GSM signals with near-optimal performance is challenging, especially in soft decision making. To this end, based on the deterministic sequential Monte Carlo (SMC) principle, we propose two low-complexity demodulators for the SC-GSM system with zero-padding (ZP) in broadband channels. By exploiting the natural triangular structure of the multi-path channel to apply SMC sampling, a vector-level SMC demodulator without the need of the sequential construction process is proposed, significantly saving the computational burden. To lower the required computation during the sampling and weight updating processes of the vector-level SMC demodulator, a symbol-level SMC demodulator is further proposed, which takes samples from the expanded constellation including the origin. In particular, an efficient online legality check scheme, which eliminates illegal samples during each sampling step, is integrated into the symbol-level SMC demodulator to avoid error propagation and save the computational burden dramatically. Both proposed demodulators produce soft outputs, which can be used for soft demodulation in coded systems, especially for turbo receivers. The simulation results verify the near-optimal performance of the two proposed demodulators in the uncoded and coded SC-GSM system with ZP, respectively.