Efficient use of joint source-destination cooperation in the Gaussian multiple access channel

We consider the impact of destination cooperation on improving the achievable rate region in a multiple access channel with joint source-destination cooperation (MAC-SDC). Such cooperation may be appealing in systems with a more powerful destination than the sources, such as the uplink of cellular networks. We propose a coding scheme in which each source employs superposition block Markov encoding and partial decode-forward relaying, while the destination employs quantize-forward relaying and backward decoding. The sources partially exchange their messages using not only the direct links between them as in source cooperation, but also the feedback links from the destination, hence they are able to exchange more information at the same power by utilizing the destination as a relay. We analyze the condition on channel and power parameters such that involving destination cooperation is strictly better than just having source cooperation. Results for Gaussian channels show improvement especially when the inter-source link qualities are close to source-destination link qualities. These results provide guideline for practical systems such as cellular networks in determining when it is beneficial for the base station to cooperate with mobile users in the uplink communication.