Research On High Spectral Efficient Broad-Sense Cooperative Communication Techniques For Wireless Networks

Today, wireless communication techniques develop at very fast speed. Compared with wire communication, wireless communication is better in the periods and costs of lines of communication deployment, area coverage, restriction of geographical surroundings and maintenance of lines. And it has been the fast developing and widely-applied fundamental technique in present information communication field. The spectral efficiency and energy efficiency of wireless network is low because of wireless fading, node power, communication ranges and network topology. Meanwhile the requirements on the applications of wireless communication increase continuously. So meeting the demand of communication using the resource in existence has been a hot topic which comes to the attention of experts mostly.Considering that broad-sense cooperative communication techniques have the main characteristics that obeying certain protocol or mechanism, coming to communication by multiple relaying nodes, and improving the holistic performance of wireless network using cooperative transmission among multiple nodes. So broad-sense cooperative communication techniques, including cooperative relaying, cooperative diversity, cooperative multiplexing, opportunistic communication, network coding and their integrated techniques, can resolve the above hot topic. Broad-sense cooperative communication techniques take the system's joint optimization into account from the aspects of multiple nodes and the entire network. And the research and application of these techniques indicate that wireless communication will definitely come into a brand-new seedtime.In this dissertation, it is focused on the distributed wireless networks. On the basis of analyzing in-depth the characteristics and advantages of the fundamental techniques in broad-sense cooperative communication, it is mainly discussed that high spectral efficient broad-sense cooperative communication techniques for wireless networks from three aspects, i.e., researching the strategies of cooperative networks; discussing the characteristics of the cooperative strategies and analyzing the performance of the cooperative strategies. The main work of this dissertation can be summarized as follows:1. For bidirectional relaying channels, multi-hop communication, the time-division-duplex mode of bidirectional communication and the half-duplex mode of nodes are the dominant factors leading to lower spectral efficiency. To improve the resource efficiency of bidirectional relay, a bidirectional successive relaying scheme (BSR) is proposed. The inter-relay interference in BSR leads to performance loss and for the moderate inter-relay interference, the performance fall down badly. To compensate loss caused by the inter-relay interference, two reformative schemes that utilize physical network coding and dirty paper coding respectively are proposed. Focusing on the two-hop chain network, the bidirectional achievable rates of three relaying schemes, BSR, bidirectional successive relaying based on physical network coding (PNC-BSR) and bidirectional successive relaying based on dirty paper coding (DPC-BSR), are analyzed. The characteristics of PNC-BSR and DPC-BSR are discussed and the results show that for the moderate inter-relay interference, both of the reformative schemes can improve achievable rate of the bidirectional relay network. And PNC-BSR offers a superior performance when the power of the inter-relay interference is bigger than the one of the needful signals. Furthermore, taking PNC-BSR into account, the normalized throughput performance of the conventional hop-by-hop relaying, AF BAT-relaying and PNC-BSR over a two-hop network are analyzed and the results confirm that PNC-BSR is valid to improve the resource efficiency of bidirectional relay. And then the idea of extension application for PNC-BSR and DPC-BSR in multi-hop network is presented.2. To improve transmission reliability of PNC-BSR over wireless fading channels, a bidirectional successive relaying based on network path selection (NPS-BSR) is proposed. Based on the research of PNC-BSR, NPS-BSR first selects the"best"relay from multiple available relays based on instantaneous channel conditions in wireless fading environments and then uses this"best"relay for cooperative forwarding between transmitter and receiver. Focusing on the information exchange in two-hop network, outage probability and average capacity of four relaying schemes for the quasi-static Rayleigh fading environment are developed. The results show that in contrast to the conventional hop-by-hop relaying, the opportunistic relaying and PNC-BSR, NPS-BSR combats wireless fading more effectively with the identical resource efficiency of PNC-BSR. With the number of relays for cooperation increasing, a superior diversity gain is obtained. And then the mechanism of extension application for NPS-BSR in multi-hop network is presented.3. To effectively reduce the average number of retransmissions and improve resource efficiency for wireless broadcast channels, a cooperative network coding scheme based on selective transmission (ST-CNC) is proposed. Space-time cooperative transmission and network coding are simultaneously applied to wireless broadcast scheme. According to the feedbacks from receivers, source node and assistant node combine different lost packets from different receivers and broadcast the combined packets in manner of Alamouti cooperative transmission. Focusing on the network with one source, single relay and two destination nodes, outage performance and network coding gain of four broadcast schemes, traditional broadcast scheme, the broadcast scheme using network coding, the broadcast scheme using Alamouti cooperative transmission and ST-CNC scheme, are analyzed. The results show that in contrast to the other broadcast schemes, ST-CNC offers simultaneity diversity gain and network coding gain.4. To improve the performance of multiple-relay cooperative communication system and reduce the complexity of cooperative schemes, a multi-relay hybrid-forwarding cooperative transmission scheme (MRHF-CTS) is proposed, which selects the mode of forwarding according to the result of decoding at relay nodes. Expressions for outage probabilities are derived at high SNR regimes for the quasi-static Rayleigh fading environments when two relays are involved and AF, DF and MRHF-CTS are assumed respectively. The results show that with lower complexity, MRHF-CTS achieves the required quality of the receiving signals at destination node using lesser forwarding time and the resource efficiency of multiple-relay cooperative communication system is improved as a consequence. Furthermore, a selective cooperative technique with mutual relaying (MR-SCT) is proposed for multi-relay DF cooperative communication system. Expressions for theoretical BER performance of the MR-SCT schemes are derived. The results show that for the inferior quality of the wireless path between source and relay, for each relay, the number of nodes involved in cooperation is increased by using the interaction among relays to achieve the requirement of communication without additional conditions.