Study On The Power Allocation Of Cooperative Communication And Relay Selection

Cooperative communication is an efficient way to improve the network performance without changing the backbone networks apparently. This is because cooperative communication can form the virtual array to gain the space diversity by making nodes share their antenna. Thus, cooperative communication would overcome the deep fading and only assemble one antenna in real networks.Relay protocol design, power allocation and relay selection are the hot problems in cooperative communication. In this paper, we consider these problems respectively. Firstly, this paper investigates the relay selection problems. We propose one novel relay selection scheme based on choosing the maximum harmonic mean for two-way amplify-and-forward (AF) relay networks. We also show that the sum rate of the relay network is the function of the weighted harmonic mean of the channel conditions. Moreover, we derive that this relay selection scheme would achieve the full diversity order by analyzing the average symbol error probability.Secondly, this paper investigates the power allocation problems for two-way relay networks. We propose one unified power allocation scheme for two-way AF relay networks. Only by exploiting the statistical channel conditions, this scheme could optimize the network performance in high signal-to-noise ratio (SNR) regions under three criteria, i.e., average sum rate, average symbol error probability and average outage probability at the same time. Applying convex optimization techniques, we obtain the close-form solution, and finally we testify the performance gain of this power allocation scheme by the computer simulations.Lastly, this paper investigates the joint power allocation and relay selection optimization problems. We propose different joint optimization schemes for one-way and two-way relay networks. One scheme is to minimize the total power under certain quality of service (QoS), and another is to optimize QoS given some power budget. By our analysis, these optimization problems can be formulated as convex optimization problems, and separated as two procedures, i.e., firstly selecting relay and then allocating power among the nodes. Also, these problems can obtain the close-form solutions.