Research On MIMO Multi-way Relay Transmission Scheme

With the rapid development of wireless communication technology,the number of wireless communication users and user demands have also grown exponentially,which puts higher requirements on wireless communication systems.The Multi-Input Multi-Output(MIMO)technology has attracted people's attention because of its ability to provide users with higher data transmission rates;As a new type of multiple access,Signal Space Alignment(SSA)technology can reduce the space dimensions occupied bysignals through the multiple antennas at nodes,thereby enhancing the use of space resources.In recent years,there have been many researches on the application of SSA technology in multi-user MIMO relay systems.However,these studies mainly focus on the derivation of system degrees of freedom.There is little research on system reliability,so this article focuses on the reliability of MIMO multi-way relay systems.First,for MIMO-Y symmetric transmission(MIMO-Y)systems,this paper proposes a transmission scheme based on signal space reconstruction.In this scheme,we first increase the flexibility of the user precoding vector selection by increasing the user antenna redundancy,and then select the user precoding matrix according to the principle of the alignment signal vector two-by-two orthogonality.When the signal space is reconstructed,the aligned signal vectors are orthogonal to each other.comparing the conventional scheme,the angle between signal vectors increases in this scheme,so the minimum distance between the symbols increases,and the average BER of the system improves.On this basis,an optimal search algorithm is also designed to maximize the channel gain in the orthogonal direction and maximize the minimum distance between symbols,thereby improving the relay decoding performance.In order to further improve the system performance of bit error rate,the relay adopts maximum likelihood(ML).but the complexity of ML decoding is very high.Therefore,this paper proposes a simplified ML decoding scheme based on vector orthogonality of alignment signals.Then the research channel is extended to a Multiple Input Multiple Output Relay Asymmetrical(MIMO MWR)channel,and the antenna constraints and performance at this time are analyzed.Secondly,aiming at the MIMO multi-way relay interference channel,this paper proposes a MIMO relay amplification forwarding(AF)transmission scheme based on the maximum SINR criterion.In the multi-access phase(MAC),the user performs signal preencoding and sends the signal to the relay.The pre-encoded interactive signals are aligned in the trunk.During the broadcast phase(BC),the relay amplifies and forwards the received signal.After receiving the signal,the user performs SINR interference suppression and zeroforcing decoding,and then the desired received signal can be obtained.This scheme simplifies the relaying strategy from decoding to AF,and the relay does not need to do complex processing,which greatly simplifies the complexity of the system and increases the transmission rate.At the same time,the SINR scheme is used instead of the zero-forcing interference suppression scheme to improve the system's capacity when the signal-to-noise ratio is low.