On the Design of Energy Efficient Transmission in Cooperative Networks with Bidirectional Asymmetric Traffic

Energy efficient transmission has become increasingly important in future green communications. We focus on cooperative networks with multiple Amplify-and-Forward relays deployed in this paper. A joint relay selection and power allocation transmission scheme applicable to both one-way and two-way relay networks is proposed for minimizing the weighted energy consumed per bit transmitted. Close-form analytical results of power allocation are first developed at each relay. Then the relay consuming the least energy or the direct transmission mode is chosen by the sources. Based on the proposed scheme, we characterize the energy consumption for training and power allocation information exchanging between nodes. Besides, the energy efficient cooperating regions are discussed in one-way and two-way relay networks. It is indicated that the shape of the region depends on both the path loss exponent and the asymmetry traffic in the one-way relay network while only lies on the path loss exponent in the two-way relay network. Simulation results demonstrate that the proposed scheme yields considerable reduced energy consumption compared to that of the best worse relay selection scheme when proper number of relays is deployed. It is also shown that the two-way relaying can achieve higher energy efficiency than the one-way relaying.