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Research On Multi-Relay To Multi-User Transmission In Single Cell

Posted on:2012-04-24Degree:MasterType:Thesis
Country:ChinaCandidate:Y ChenFull Text:PDF
GTID:2178330338991932Subject:Communication and Information System
Abstract/Summary:PDF Full Text Request
The development of wireless communication technology is more and more rapid recently, promoted by human's growing demand to communication more freely anytime and anywhere. The next generation wireless broadband communication system is characterized by wider coverage and higher-speed transmission rate. In recent years, wireless relay technology is attracting more and more attention, as a key method to solve the coverage problem at cell edge. Wireless relay can improve the signal quality at cell edge and increase cell throughput but have no significant influence to the backbone structure. Relay also has the advantages of low cost and convenient site selection. Multi-antenna technology (MIMO) is the most effective technology to increase channel capacity and improve system reliability, which is also considered as one of the most promising means in the next-generation wireless systems. It is promising to combine relay technology with MIMO technology. More than one Multi-antenna relay can be deployed in one cell (or sector) to provide seamless coverage. It is a very valuable topic that how to efficiently use the multiple multi-antenna relays to achieve better transmission performance.Firstly, a scenario that two relays send downlink data to two users in single cell is considered in this paper. Both relays work at decoding and forward mode. Multi-user SDMA scheme is used in the first hop and the relays transmit to the users using the same time-frequency resources in the second hop. Because the matching degree of the throughputs of two-hop relay transmission affects the system performance significantly, we study and solve the time allocation optimization problem of the two hops. Then we consider the power allocation scheme at the base station. Because it is difficult to solve the power allocation optimization problem directly, a suboptimal power allocation method is obtained to match the capacities of the two"BS-Relay-User"links, which can be realized by numerical iteration. Simulation results show that the proposed time and power allocation methods effectively enhance the system throughput.Secondly, there may be more than two relays and more users in single cell. In this case the multiuser diversity gain can be obtained by user selection, if the user amount is more than relays. User selection methods are firstly designed at two-relay case, which jointly consider channel gains, interference avoidance and capacity matching. In addition, too many relays sharing the same time-frequency resources will produce severe interference. So we further consider using relay selection to reduce the number of the relay working simultaneously, which can also make time allocation, power allocation optimization method and the user selection method available at the multi-user and multi-relay scenario. Relay and user selection method can make good tradeoff between space multiplexing gain and interference avoidance. Simulation results show that the multi-user and multi-relay system can achieve higher system throughput using the relay and user selection method.
Keywords/Search Tags:Multi-relay, MIMO, Time allocation optimization, Power allocation optimization, User Selection
PDF Full Text Request
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