The Physical Layer Network Coding In Wireless Cooperative Communication System Theory And Key Technology Research

As a major breakthrough in information theory, Network Coding has found its applications in wireless communication systems, and the most rep-resentative application scenario is the Physical-layer Network Coding (PNC) aided cooperative wireless two-way relay network. Compared to the tradition-al one-way relay transmission scheme, PNC aided wireless two-way relay can effectively reduce the exchange time of bidirectional information flows in the wireless relay network, thus improving network throughput. Recently, PNC has attracted widespread attention from both academics and industry practitioner-s. The dissertation mainly focuses on the wireless two-way relay model and the relevant advanced transmission schemes which combine PNC and Multiple Input Multiple Output (MIMO) technology. Moreover, the dissertation extend-s the study to the more complicated MIMO-Y channel, and proposes several practical schemes to improve the transmission reliability. Finally, armed with the theoretical insights, the dissertation considers the application of PNC in UWB (Ultra-Wideband) network. The major work and contributions are sum-marized as follows.To begin with, the dissertation studies the basic MIMO transmission schemes for PNC. For two-way relay network consisting of two single-antenna source nodes and one multi-antenna relay node, the dissertation first points out the defects of some existing virtual-MIMO based schemes. Then a Maximal Ratio Combining like (MRC-L) relay receiver is proposed, which is tailored for binary PNC and achieves near optimal performance with low implementa-tion complexity. The MRC-L receiver also has a clear physical interpretation; the receiver makes decision according to three correlations, the correlations be-tween the received signal and the sum and difference of two channel responses, respectively, and the correlation between the channel responses. Analysis and simulation show that the proposed MRC-L receiver achieves full diversity ad-vantage in the multiple access (MA) phase of PNC transmission. Based on this receiver design, the dissertation further clarifies the idea of two-phase diversity transmission scheme for PNC, in which MRC-L receiver is used for MA phase and Space Time Coding (STC) or Relay Antenna Selection (RAS) is used for broadcasting (BC) phase. Analysis and simulation show that an end-to-end di-versity advantage is achieved with the two-phase diversity designs. In addition, for MIMO two-way relay network where two source nodes and one relay n-ode are all equip with the same number of antenna, a simple Zero Forcing (ZF) based MIMO-PNC transmission scheme is proposed. To be specific, the source nodes use ZF pre-coding and detection in MA and BC phases, respectively, to decouple the MIMO two-way relay channel into multiple Single Input Single Output (SISO) two-way relay channels in which the proposed MRC-L receiver is used at the relay. Therefore, the proposed ZF based MIMO-PNC scheme achieves spatial multiplexing gains at relatively low cost.Second, the dissertation studies the RAS methods in MIMO two-way relay network. For network consisting of two single-antenna source nodes and one multi-antenna relay node, we propose a simple common relay antenna selection (C-RAS) scheme for binary PNC. Unlike other two-phase diversity transmis-sion schemes, the proposed C-RAS scheme requires only one Radio Frequency (RF) unit at the relay, and chooses only one common antenna for both MA and BC transmissions. Therefore, the proposed C-RAS scheme also achieves end-to-end diversity advantage at low-cost. In addition, for MIMO two-way relay network where the two sources nodes are equipped with the same number of antenna which is less than that of the relay node, we propose two practically RAS schemes, namely, the Respective Relay Antenna Selection (R-RAS) and C-RAS, to bypass the size constraints of ZF based MIMO-PNC while gaining end-to-end diversity advantage. Moreover, the end-to-end diversity orders of the proposed schemes are carefully analyzed while explicit results are present-ed. Simulation results validate the theoretical analysis and show the advantage of the proposed schemes.Third, this dissertation studies user selection and RAS of MMO-Y chan-nel. The existing spatial diversity-oriented scheme for MIMO-Y channel may require additional antennas at the source nodes, which is a limitation for prac-tical application. On the other hand, the number of source nodes and the an-tenna of a dedicated relay node are relatively easy to increase. Based on the observations, two alternative spatial diversity-oriented schemes are proposed for MIMO Y channel, namely, user selection and RAS. In particular, a new application scenario for MIMO-Y channel is proposed where three groups ex-change information with the help of a relay while only one group representa-tive is selected to carry out communication. By judiciously selecting the group representative, the system performance of MIMO-Y channel is improved. Fur-thermore, following the similar line of C-RAS scheme in MIMO two-way relay channel, a practical C-RAS scheme is proposed for MIMO-Y channel, which not only bypasses the size constraints of ZF based transmission scheme for MIMO-Y channel but also improves the end-to-end diversity advantages. Ex-tensive simulation results are presented to show the advantages of the proposed scheme while some interesting observations will inspire future work.Fourth, this dissertation extends the previous theoretical study to UW-B network and focuses on the low-complexity transmission that is robust in the presence inter-symbol interference (ISI). The insights obtained from this scheme are the foundation of the design for UWB PNC transmission. By not-ing that the ISI-robust transmission is the key to improve UWB network’s throughput, a novel code optimization based ISI pre-mitigation scheme is pro-posed for the Codeword Matching and Signal Aggregation (CMSA) noncoher-ent UWB system. In particular, an interesting orthogonal block code is con-structed which enjoys two special properties, namely Shifted-Orthogonality and Shifted-Repetition, that distinguishes the proposed block code from the ordinary orthogonal block code. It is observed that, when the optimal code occurs, the leaked signal energy or the interference can be partially used to enhance the detection performance of CMS A in the presence of IFI/ISI. There-fore, the system performance is greatly improved. Moreover, the optimized transmit signal structure and receiver design in the presence of ISI for high data-rate all inspire the later design for UWB PNC transmission, since PNC itself emphasizes effective management of ISI in the MA phase.Finally, the dissertation studies the application of PNC in the cooperative UWB two-way relay network. By noting the equivalent relation between SIMO (Single Input Multiple Output, SIMO) channel and UWB multipath channel, the dissertation starts from the basic detection principle and proposes a unified UWB receiver structure that is specific to binary PNC. Under the framework, several practical relay receivers are developed to facilitate UWB-PNC trans-mission, including the Rake-based UWB PNC coherent receivers, such as All Rake (ARake), Selective Rake (SRake) and Partial Rake (PRake) receivers. Moreover, a Transmit Reference (TR) based non-coherent UWB PNC schemes is proposed to address the low-complexity and practical design for UWB net-work, where the complicated channel estimation overhead is bypassed at the receiver. To be specific, the signal structures of the two end nodes are careful-ly designed while a novel noncoherent UWB-PNC detector is developed with the simple Auto-correlation Receiver (AcR) structure. The combination of the signal structure and receiver designs achieves a low-complexity transmission scheme for UWB PNC. Furthermore, we analyse the key influencing factors for the proposed schemes. Based on the analytical results, the power allocation between source nodes under the sum power constraint and the relay placement are also discussed. Simulation results show the effectiveness and advantages of the proposed UWB PNC schemes.