General Achievable Rate Region Research Articles

Effects of relay and side information at one encoder on the coverage regions in Gaussian multiple‐access channel

AbstractThe two‐user multiple‐access relay channel (MARC) is investigated in the presence of side information (SI) available only at the informed transmitter in the present article. First, for the discrete alphabet and memoryless MARC with common and private messages, partial decode and forward strategy at the relay and fixed locations of the nodes, a general achievable rate region is obtained. The SI effect is seen and can be analyzed. Second, we extend the discrete result to a practical communications model: Gaussian multiple‐access relay channel (GMARC), showing previous works as its special cases. Third, the effect of (perfect and nonperfect) SI on the maximum coverage region of GMARC for a fixed rate of the transmitters and a fixed distance between relay and destination is analyzed. It is shown that the SI increases the coverage region of encoders, and consequently, it can improve communication energy efficiency. Finally, mathematical findings are validated numerically by using Matlab.

A general achievable rate region and two certain capacity regions for Slepian–Wolf multiple‐access relay channel with non‐causal side information at one encoder

A general achievable rate region and two certain capacity regions for Slepian–Wolf multiple‐access relay channel with non‐causal side information at one encoder

Impact of the relay on the coverage region of multiple‐access channels

From practical and theoretical viewpoints, performance analysis of communication systems by using information-theoretic results is important. In this study, first, the authors obtain a general achievable rate region for three-user discrete memoryless multiple-access relay channel (MARC) via partial decode and forward strategy and regular block Markov encoding/backward decoding. Also by extending the discrete alphabet results to the continuous alphabet channel, an inner bound for three-user Gaussian MARC (GMARC) is achieved. Next, based on the inner bound of three-user GMARC, they analyse the impact of a relay on the coverage region of MARC, as a basic model for uplink communications between a base station and users with the help of a relay. This analysis includes the coverage region for the multiple-access channel and two-user GMARC as special cases. Considering rate regions for the GMARC and fading GMARC, it is proved that in a fixed transmission rate, the relay extends coverage region of the MARC. Numerical illustrations confirm their theoretical results.

On multiple‐access relay channel with common message

AbstractIn this paper, we obtain a general achievable rate region for discrete memoryless multiple‐access relay channel (DM‐MARC) with common message via partial decode and forward strategy and regular block Markov encoding/backward decoding. This general achievable rate region, as an extension of the achievability part of the relay channel via partial decode and forward strategy to the MARC, subsumes the previous known achievable rate regions for multiple‐access channel with common message and MARC. Also, by applying Fano's inequality, we derive an outer bound for DM‐MARC with common message. By extending the discrete alphabet results to the continuous alphabet, an inner bound for Gaussian MARC (GMARC) is achieved. As expected, our results for the Gaussian MARC includes the previous results for the Gaussian multiple‐access channel with and without common message and the Gaussian relay channel as special cases. Finally, by considering a specific topology for MARC, performance of GMARC with common message versus the position of the relay is investigated numerically. Also, it is shown that our achievable rate region is larger than the previous rate region of GMARC with common message with irregular encoding/successive decoding. Copyright © 2014 John Wiley & Sons, Ltd.

On the Role of Estimate-and-Forward With Time Sharing in Cooperative Communication

In this paper, we focus on the general relay channel. We investigate the application of the estimate-and-forward (EAF) relaying scheme to different scenarios. Specifically, we study assignments of the auxiliary random variable that always satisfy the feasibility constraints. We then consider the Gaussian relay channel with coded modulation, where we show that a three-level quantization outperforms the Gaussian quantization commonly used to evaluate the achievable EAF rates in this scenario. Last, we consider the cooperative general broadcast scenario with a multistep conference between the receivers. We first apply EAF to obtain a general achievable rate region with a multistep conference. We then use an explicit assignment for the auxiliary random variables to obtain an explicit rate expression for the single common message case with a two-step conference.