Research And Simulation Of The Integration Mechanism Of MIMO And PNC In Wireless Multi-hop Networks

The lack of spectrum resources restricts the development of the wireless communication. Therefore, the objective of most of the study of communication technologies is to improve spectrum efficiency. Multiple-Input Multiple-Output (MIMO) technique is able to achieve diversity gains and spatial multiplexing gains due to the multiple antennas at the transmitting and receiving terminals, which improves both reliability and system capacity. Meanwhile, physical layer network coding (PNC) can encode the transmitted signals by making use of the propagation property of electromagnetic wave, therefore, the signals can be transmitted in two-way relaying channel. Compared with the traditional relaying techniques, two-way relaying technique can improve the throughput and the spectrum efficiency. When MIMO is combined with PNC, both the spectrum efficiency and the throughput of the network can be further increased.This thesis focuses on developing an integration mechanism of MIMO and PNC in wireless multi-hop networks. More explicitly, it focuses on developing a scheme of signal space alignment (SA) which supports PNC, a precoding design for eliminating the interference between different users and a scheme of integrating the relay antenna selection, and a precoding vector selection scheme for the over-constrained problem when solving the SA problem.This thesis is an extension of existing research. Firstly, we generalize the traditional two-way relaying channel which is usually used in the study of PNC to the multi-way relaying channel with multiple user nodes and a single relay node. Secondly, the multi-way relaying channel is fully studied. The main works and contributions of the dissertation are listed as follows:1) The multi-way relaying channel system model is established, and the two-timeslot transmission scheme without interferences between different users and supporting PNC is proposed. Assume that the perfect channel state information is well known by each node, the precoding of user nodes can be designed to align the signal space. With the help of detection at the relay node, the superposition signal which supports PNC can be achieved. After that, the precoding of the relay and the detection of the users can be designed jointly to eliminate the interferences. 2) The precoding for the purpose of SA in the proposed scheme is studied, and the constraint conditions of SA and the existing degrees of precoding vector selection freedom are researched. Meanwhile, the system symbol-error rate performance is analyzed, the diversity gains of end-to-end data stream and the existing degree of freedom of the whole system are obtained consequently. The simulation results verify our theoretical analysis.3) A joint relay antenna and precoding vector selection scheme is proposed for the scenario that the relay antenna number dissatisfy the constraint conditions of SA. Since the precoding vector and relay antennas are closely related, separate optimization may decrease the system performance. The scheme proposed in this thesis, not only reduce the complexity of precoding optimization, but also guarantees the reliability of the transmission.