Research On MIMO Soft Information Forwarding Techniques In Wireless Communications

MIMO system enables wireless communication quality greatly improved without increasing the bandwidth, and has become the basic architecture of 3G and 4G system. However, future wireless communication needs to offer more multimedia services in farther distance.Large scale MIMO system can greatly increase the channel capacity and cooperative communication technology can extend the communication distance, which make them popular candidates. In this paper, we research soft information forwardingcooperation in MIMO systems, propose estimate-and-forward(EF) and mutual information-based forwarding(MIF) with and without direct link between the source node and the destination node, and analyze the performances of the proposed schemes with generalized signal-to-noise ratio(GSNR). Specifically speaking, the main research work of this paper is as follows.1) We propose EF scheme for MIMO and large scale MIMO system forwarding scheme.In MIMO system with and without direct link between the source node and the destination node, we respectively construct EF function by employing the conditional expectation of the received signal at the relay node, acquire the forwarding factor, and derive the expression of received signal at the destination in order to get detection method in the two conditions. Furthermore, we modify thisEF algorithm and make it suit for large scale MIMO system.2) We propose MIF scheme for MIMO and large scale MIMO system forwarding scheme.In MIMO system with and without direct link between the source node and the destination node, we respectively construct MIF function by employing the mutual information between the transmitted signal at the source node and the received signal at the relay node as the metric for hard decision, acquire the forwarding factor, and derive the expression of received signal at the destination in order to get detection method in the two conditions. Furthermore, we modify this MIF algorithm and make it suit for large scale MIMO system.3) We propose GSNR calculation method for the proposed cooperation framework in this paper. In multi-relay transmission systems employing soft information forwarding, there exists obvious non-linear relationship between the received signal at the destination node and the transmitted signal at the source node, which makes it hard to get the expression of error rate for the whole system. With GSNR, we can further analyze the reliability of each scheme besides the error rate.The research results show that the proposed two soft information forwarding schemes including EF and MIF in MIMO system with and without direct link between the source node and destination node can effectively increase the reliability of wireless communication system. Specifically, the schemes without direct link can extend the communication distance. In all the schemes, MIF shows the best reliability.