Dempster-shafer Theory Based Techniques For Two-way Multiple-antennas Relay

Two-way relay as a key technique of 4G system can enhance communication coverage, reduce the energy consumption and ensure the reliability of communication. Two-way relay system combining the Multiple-Input Multiple-Output(MIMO) and Network Coding(NC) can ensure the information transmission and exchange for multiple users. Furthermore, full-duplex(FD) communication is an important technique of 5G system. FD relay system simultaneous transmit and receive signal can enhance the spectral efficiency. However, due to the effect of channel fading and self-interference(SI), the performance of system is affected when the relay cannot explicitly obtain the information of the users. Therefore, it is important to study the reception scheme and SI suppression scheme with high performance for two-way half-duplex(HD) MIMO relay and two-way FD MIMO relay.Dempster-Shafer(D-S) evidence theory draws more attention and has been proved to achieve a good performance in many fields such as artificial intelligence research, cooperative communication and so on. The channel fading, noise and SI can be accurately characterized by D-S evidence theory which can combine different evidence. Therefore, it can obtain reliable decision result. This paper focuses on the reception scheme and SI suppression scheme based on D-S evidence theory in the two-way HD MIMO relay and two-way FD MIMO relay respectively. The main contents are described as follow.(1)The MIMO-DS NC scheme is proposed in the multiple access phase(MAP) of two-way HD MIMO relay system, which adopts D-S evidence theory to detect the signals of each source node before mapping them into network-coded signal. Moreover, the further scheme called MIMO-DS PNC is proposed which comes from the vector space perspective and combines physical-layer network code(PNC) mapping with D-S theory to obtain network-coded signal without estimating each source node signal. Meanwhile, we study end-ot-end average bit error rate(BER) performance based on the space-time coding(STC) and antenna selection(AS) schemes exploited in the broadcast phase(BCP). Simulation results reveal that the proposed MIMO-DS NC/PNC schemes obtain better BER performance and throughputs compared with traditional schemes with a little complexity increasing and no matter which schemes are adopted in the BC phase, MIMO-DS PNC always achieves full end-to-end diversity gain as MIMO-ML NC.(2)The Dempster-Shafer network coding(DS-NC) scheme is proposed in the MA phase of two-way FD MIMO relay system, which adopts D-S evidence theory to detect the signal of each source node with SI suppression considered in the basic probability assignment(BPA) computation. Furthermore, the proposed DS-Sum and Difference(SAD)-PNC scheme adopts D-S evidence theory to detect the sum and difference signal for two source nodes considering the SI cancellation in obtaining basic probability assignment(BPA) function. In order to reduce the complexity, the further proposed Dempster-Shafer physical-layer networkcoding(DS-PNC) scheme considers SI suppression from vector space perspective and combines physical-layer network coding(PNC) mapping with D-S theory to obtain network-coded signal without estimating each source node signal. Finally, the proposed DS-PNC scheme is studied with the SI signal model which considers analog radio frequency(RF) cancellation, the effects of I/Q modulator imbalances, and power amplifier(PA) nonlinearity of the transmitter. Simulation results reveal that the proposed schemes outperform the traditional spatial-domain suppression schemes and DS-PNC achieves the same diversity gains as the ideal cancellation. Furthermore, considering the SI signal model with nonlinear distortion and radio frequency cancellation, the DS-PNC scheme is also superior to the traditional schemes.