In 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.

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