Research On Key Virtual MIMO Technologies In LTE Uplink

LTE, which is the unique standard of 3G wireless network evolution, introduces MIMO technology to increase the data rate and the system capacity. MIMO can exploit the spatial multiplexing gain to improve the channel capacity and meanwhile get spatial diversity to improve reliability of signal, reduce error rate by eliminate the multi-path effects and fading effects of wireless channel. However, in the uplink of LTE system, it is very difficulty to install multi-antenna in the user side because of the size and cost problem in terminal. In order to deal with it, LTE adopts the virtual MIMO which can bind the user with only one antenna and make virtual MIMO channels. However, problems have emerged, such as who will be selected to be bound and how to communicate with the base station after pairing process. In this paper we sum up these two as one pairing algorithm problem and one distributed space-time code problem.To solve the pairing algorithm problem, we have carefully studied some traditional pairing algorithms and improved algorithms. Then we find that few of them take user's QoS into consideration though it is very important. We propose a pairing algorithm considering QoS to put the data rate and delay of service into pairing processing. The simulation results show that the algorithm we proposed can get a good performance both in system throughout and user fairness. Moreover, it can distinguish packet of different service to guarantee qualified service.To solve the distributed space-time code problem, we improve Alamouti space-time code through bringing in the conception of cooperation and then propose a distributed Alamouti space-time code scheme based on DF method. In this paper we analyze distributed Alamouti space-time code based on DF method and probability of error by comparing it with centralized Alamouti space-time code and direct send model. The simulation results show that the distributed Alamouti space-time code based on DF method can improve the system bit error rate performance through getting cooperative diversity gain and spatial diversity gain simultaneously. In addition, if the decode process is correct, the performance of this method is very close to the centralized Alamouti space-time code.