Low-Complexity Near-Optimal Decoding for Analog Joint Source Channel Coding Using Space-Filling Curves

Abstract

Analog Joint Source-Channel Coding (JSCC) is a communication strategy that does not follow the separation principle of conventional digital systems but approaches the optimal distortion-cost tradeoff over AWGN channels. Conventional Maximum Likelihood (ML) analog JSCC decoding schemes suffer performance degradation at low Channel Signal to Noise Ratio (CSNR) values, while Minimum Mean Square Error (MMSE) decoding presents high complexity. In this letter we propose an alternative two step decoding approach which achieves the near-optimal performance of MMSE decoding at all CSNR values while maintaining a low complexity comparable to that of ML decoding. An additional advantage of the proposed analog JSCC decoding approach is that it can also be used in Multiple Input Multiple Output (MIMO) fading channels.

Analog joint source-channel coding over MIMO channels

“…Rather than directly decoding the source samples x from the received symbol y, as in standard ML and MMSE decoding methods, it is possible to use an alternative twostage decoding approach in which we first calculate an estimate of the transmitted channel symbolsŝ and then decode the source samples from this symbol estimate [17]. In the case of AWGN channels, the linear MMSE estimate of the channel symbols s is given bŷ…”

“…Under this assumption, the spatially causal component of the interference in (17) can be successively removed with the FB filter L − I n T without altering the noise statistics at the decoder inputs. An advantage of analog JSCC is that there is no delay in the encoding and re-encoding steps which significantly simplifies the implementation of DF MIMO receivers.…”

Analog joint source-channel coding for MIMO Multiple Access Channels

“…Since the analytical optimization of these parameters is extremely difficult when α = 2 [8], the optimum values of δ i and α i is obtained for different SNRs using off-line computer simulations [10]. When the CSI is not available at the encoders, the values for δ and α corresponding to the expected average SNR can be used.…”

Bandwidth expansion analog joint source-channel coding with channel inversion and multiple receive antennas

“…However, capacity approaching practical systems based on separation require high complexity and delay. Analog joint source-channel coding (JSCC) is an alternative to traditional digital systems with separated encoders, and can achieve near optimal performance with much lower complexity and delay [2]- [7].…”

“…However, it is usual to have constraints on channel bandwidth. Many recent works [2]- [7] have presented near optimal analog schemes with bandwidth compression or expansion, focusing mainly on AWGN channels [2]- [4]. Flat Rayleigh fading channels have been recently analyzed, for instance, in [5]- [7], but only with bandwidth compression.…”