Research On Interference Alignment And Compressive Sensing In Two-way Relay Network

Wireless relay can efficiently expand the cell coverage area on the premise of no increase in thenumber of base stations. Two-way relay protocal can achieve higher spectrum efficiency thanone-way relay protocal through network coding (NC). Considering the lower complexity and highertransmission efficient of amplify and forward relay protocal, the research is based on the Amplifyand Forward-Two Way Relay Network (AF-TWRN). In order to pursue higher channel capacity ofAF-TWRN, it is necessary to reduce and even eliminate the interference between users. Interferencealignment (IA), as a new direction of interference management, can effectively reduce theinterference between users and improve the system performance. To realize IA, each node needs toknow the channel state information, which can be achieved by channel estimation. Sparse multipathchannel estimation based on compressive sensing (CS) can greatly improve the utilization rate ofsystem resources because it makes full use of the sparse structure of two-way relay channel. Themain contents are listed as follows:First, apply CS to estimate AF-TWRC. We convert the problem to point to point channelestimation firstly. Then use orthogonal matching pursuit algorithm to estimate the cascadeconvolution channel formed after convertion. The proposed method, compared with tranditionalchannel estimation method, needs much shorter training sequence.Second, aiming at the cellular network interference problem, under the improved tri-sectorantennas model, we design a novel interference alignment algorithm to remove the inter-cellinterference (ICI) and eliminate inter-user interference (IUI) separately. Meanwhile dynamic powerallocation is introduced to improve the system transmission performance. The proposed algorithmcan efficiently cancel interference and reduce bit error rate (BER).Third, combine IA and NC to eliminate the multi-user interference of AF-TWRN. By designingproper beamforming vector, we align the transmit signal of each pair of communication nodes in themultiple access channel phase and align the received signal of them in the broadcast channel phase.Furthermore, we optimize the forward matrix at the relay with the goal of achieving maximal sumrate of the system. The proposed scheme needs much less antennas at the relay and improves theachievable sum rate of the system compared with traditional methods.