Analog Transmission of Correlated Sources over fading SIMO Multiple Access Channels

Abstract

Joint Source-Channel Coding for discrete-time analog sources is an appealing transmission approach because of its extremely low delay and complexity. When the users access the channel orthogonally, analog transmission of correlated information over fading Multiple Access Channels (MACs) using modulo-like mappings provides better performance than uncoded transmission. In this work, we propose a simplified decoder for modulo mappings in possibly non-orthogonal MAC scenarios with single-antenna users and a multiple-antenna receiver. Sphere decoding is investigated to reduce the computational complexity when the number of users is large. In addition, affordable strategies are proposed to optimize the mapping parameters according to the channel conditions and the source correlation. The obtained results show that the use of modulo mappings is suitable when the number of antennas at the receiver is larger than the number of users and for high correlation between user data.

Existing System

Shannon-Kotel’nikov Mapping, Optimal Decoding.

Proposed System

In this work, we have addressed the use of modulo mappings for the transmission of multivariate Gaussian sources over fading MACs. We have investigated a MAP decoding strategy to estimate the user symbols. In addition, the use of a sphere decoder makes the implementation of the MAP estimation practical for a large number of users. Simulation results have shown that MAP decoding practically achieves the same performance as MMSE decoding, but with lower complexity, while it clearly outperforms ML decoding, specially for non-orthogonal access. Thereby, the proposed analog JSCC scheme, together with MAP estimation and sphere decoding, is a truly zero-delay low-complexity solution to reliably transmit correlated information over fading MACs, specially for scenarios with high correlation and where the number of receive antennas is larger than the number of users. An appropriate optimization of the mapping parameters also ensures that the analog JSCC system achieves equal or better performance than the uncoded scheme for all SNR regimes.

Architecture

BLOCK DIAGRAM