Reverse stripping soft decision decoding for general Gaussian fading broadcast channel

Recently, Tse and Yates have shown that for a general fading Gaussian broadcast channel with channel states known by the receivers only, binary expansion superposition (BES) signaling with hard decision decoding (HDD) comes within a constant gap to the channel capacity. In this work, we extend the achievability strategy of Tse and Yates by considering the use of soft-decision decoding (SDD) for the BES constellation. Multi-stage reverse stripping at each receiver permits partial cancelation of the less-significant-bit(LSB) interference and facilitates a decomposition of the fading channel into parallel effective channels between the binary input and its log likelihood ratio (LLR) at the receiver, which simplifies the design for capacity-approaching codes suitable for iterative decoding. We observe that for the degraded AWGN broadcast channel and for the non-degraded intermittent AWGN channel, the inner bound achievable by BES signaling with SDD can come within one bit of the capacity boundary for moderate to high SNR levels.