Relays Meet Cooperative Transmission In Wireless Networks

With the rapid development of communication technology, the huge and fast expantion of the traffic has become the most outstanding issue in the future wireless networks. Relay, with the advantage of its good performance and conve-nience in deployment, has become a part of this mobile networks. In this thesis, we choose three typical scenarios-WiMAX Networks、Data Center Networks and Cellular Networks to study the performance of relays.In WiMAX, we propose DPRP (Dual-Path Relay Placement) to improve the efficiency of relay station placement. DPRP can achieve efficient spatial reuse by two independent parallel transmission paths. For a given attenuation coefficient, DPRP needs less RSs than Single-Path Relay Placement (SPRP) when the SS’s Spectrum Efficiency exceeds a certain threshold. The analysis proves that the higher the Spectrum Efficiency is, the greater the difference is between the relay’s number of two models. If the new model is integrated with the SPRP model, the total number of RSs required per cell will decrease a lot.Data Center Networks (DCNs) suffer from the complex wiring issues, which has motivated us to consider a wireless solution. Researchers have made great achievements in wireless DCNs. But so far, no research has focused on the power allocation for wireless DCNs. In this paper, we consider dynamic power allocation for wireless DCNs. An optimal power allocation procedure with low complexity is derived to maximize the total throughput of all live wireless transmissions. To demonstrate the effectiveness of our strategy, extensive simulation study is carried out and the results show that our proposed allocation scheme significantly outperforms the existing equal power allocation scheme.Following fast growth of cellular networks, increasingly users have drawn attention on the contradiction between dynamic user traffic and fixed data plans. So in this paper, we build a new data plan sharing system, which is based on the scenario that some smartphone users have surplus data traffic and are willing to help others download data. To realize this system, we first propose a LT-code based UDP protocol. It is robust to transmission errors and encourages more concurrent transmissions. It also can be implemented easily with low cost. Then we design a real environment experiment and the results show that users in our system not only can manage their surplus data plan more efficiently, but also achieve a higher speed download rate.