Multi-Way Relaying System:Transceiver Design And Performance Analysis

As the emerging applications, such as video conference, multi-player gaming as well as disaster and emergence relief, grow so sharply, the multi-way communication is draw-ing more and more attentions in both academia and industry societies. In such wireless networks, each user transmits its messages to all the other users, and on the other hand, it also receives the messages from all the others. Without all the direct links between distributed users, the technique of multi-way relaying (MWR) has become the key to fa-cilitate the information exchange among multiple users. Therefore, under the half-duplex constraint, designing the efficient MWR protocols and its corresponding transceivers acts a significant role in realizing the MWR system in practise.In order to simultaneously study the characteristics of shadowing effect and small-scale fading within wireless channels on relay transmission, this work first presents the composite channel model, i.e., the Generalized-K channel model. Afterwards, this work investigates the performance of multi-hop communication operating in decode-and-forward (DF) fashion, such as error probability, outage probability, level cross rate and average outage duration. Simulations illustrate that it is beneficial to deploy as many hops as possible, when the channel condition is good; on the contrary, it is advantageous to use as less hops as possible, when the channel falls severely.To implement the multi-way communication, this work applies the technique of space division multiple access (SDMA) to built the MWR system, and divides the multi-way relaying into two consecutive parts, i.e., the multiple access (MAC) phase and broad-cast (BC) phase. The relay requires enough antennas to separate and to forward the signals from and to multiple users. Due to the asymmetry property between the MAC phase and the BC phase, there exists plenty of space-time resources within the BC phase. Hence, how to efficiently exploit such resources becomes the essential point of this work.For the non-regenerative and regenerative MWR system, this work establishes the equivalent base-band space-time channel model. Afterwards, by using the criteria of total minimum mean square error (MMSE), this work jointly designs the transmitter and receivers at the relay and the users, under the relay transmit power constraint. Al-though the jointly designed transceivers are twisted as functions of each other, the itera- tive algorithms with quick convergence rate is proposed for computing such transceivers. Simulations unveil that the jointly designed linear transceivers outperforms other linear transceivers within unicast scheme in the context of systematic performance.On the other hand, assuming the single-antenna users are involved, there is still de-gree of freedom (DoM) in time domain which can be harvested by each user. The signal transmitted by the relay in each time-slot of BC phase contains the strong multiuser in-terference. However, in the perspective of the entire BC phase, the signal cross all BC phase can thus be regarded as diversity signals only containing self-interference (SI). Therefore, this work derives three performance metrics indicating the detection reliabil-ity for amplify-and-forward (AF), estimate-and-forward (EF) and decode-and-forward (DF) MWR system. According to those metrics, the minimum mean square error and successive interference cancellation (MMSE-SIC) receivers can then be implemented. Simulations demonstrate that the maximum likelihood (ML) based receiver outperforms the others.Finally, for the sake of reducing the burden caused by estimating the channel state information (CSI) and its corresponding feedbacks, this work proposes the non-coherent MWR system with the aid of fast frequency hopping/M-ray frequency shift keying (FFH/MFSK). To exchange information reliably, the work initially proposes the ML-based non-coherent multiuser receivers. Afterwards, the majority vote-based single-user receiver is given in order to reduce the detection complexity. Finally, the sub-optimal ML multiuser receiver is provided to balance the detection reliability and complexity. The advantage of the proposed non-coherent MWR system lies in that it can harvest the diversity gains in frequency domain while requires no CSI at all.