Soft Decoding Assisted Interference Cancellation in a Non-Binary LDPC Coded Fast Frequency Hopping Multiuser System Using Product Combining

In this contribution, soft-input-soft-output (SISO) decoding aided successive interference cancellation (SIC) is considered in fast frequency hopping (FFH), M-ary frequency shift keying (MFSK) using product combining (PC), when operating in multiple access (MA) Nakagami-m channels. All users´ M-ary source symbols are encoded using non-binary LDPC codes and the encoded symbols are transmitted using FFH-MFSK modulation. A sub-optimum soft metric is proposed which is based on self-normalization of the diversity combiner outputs. In the context of the proposed SIC scheme, the receiver exploits the soft information fed back by the LDPC decoder to the demodulator in order to cancel the interference imposed by the reliably detected symbols. Our simulation results show that the proposed scheme is capable of combatting the effects of multiuser interference and outperforms conventional iterative decoding by about 1 dB.