Recently, due to the importance of green communications and power‐limited systems, energy efficiency in vehicular technologies has become a hot research topic. In this paper, we analyze energy‐efficient coding schemes in multiple access relay channels. First, the coding scheme in the multiple access relay channel is introduced. At the desired source rates, 3 optimal sets of resource allocation (the total power consumption, the relay power consumption, and the source power consumption) are given in the closed form. The analysis shows that the proposed energy‐efficient schemes achieve higher data rates and significantly outperform especially by reducing the relay energy consumption, which is useful for the shared relays. Moreover, the results allow a comprehensive description of the power consumption systems and give a detailed understanding of the desired message coding and the resource dedication for every desired sum rate.

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