Cooperation In The Wireless Communication Network Diversity

Transmissions over wireless channels suffer from multipath fading and cochannel interference. Diversity has been accepted as an effective technique to combat these deleterious effects. Space, or multiple-antenna, diversity combined with other diversity, e.g., time and frequency diversity, leads to a transmission technique that gives dramatic performance gains without incurring the expenditure of transmission time or bandwidth. A new form of single-user space diversity for the cellular environment has been proposed, called "cooperative diversity" or "user cooperation diversity". Distributed antennas belonging to multiple users in the wireless network are collected, each with their own information to transmit, so that the users form a "virtual antenna array" (VAA). This type of structure could be viewed as a distributed or extended multiple-input multiple-output (MIMO) system.Several efficient cooperative diversity protocols, including amplify-and-forward (AF), decode-and-forward (DF), selection DF, and incremental AF, are now widely used. By the analyses of their outage probability, we made comparisons among the diversity orders under these protocols, and found that geometry structures have profound effects on the system performances. But all these results are based on repetition codes. Later, Nicholas Laneman proposed space-time based cooperative diversity, which can achieve full spatial diversity in the number of cooperating terminals, and proves to have higher spectral efficiency than repetition-based schemes. The specific implementations of the distributed space-time cooperative (DSTC) systems, in the AF mode and the DF mode, are respectively proposed. Note that, in the two-relay DSTC systems, introduced by Paul Anghel, the two relay terminals are always selected to implement the Alamouti scheme. Actually, the source could also possibly be utilized to cooperate with the relay terminals. Therefore, the conventional two-relay DSTC systems are not the optimum. Further, an increasingly large number of people began to focus on the large-scale wireless relay networks. By the calculation of the upper bound of the network capacity, researches seek to find applicable relaying architectures, with which the lower bound of the network capacity can get close to the theoretical upper bound when the number of the relay terminals approaches the infinite. Note that, with the relaying architectures, the antennas belonging to the destination terminals should independently decode the information received.In this dissertation, by examining the relaying protocols and conventional one-relay and two-relay DSTC systems, we proposed the two relay DSTC systems with feedback information in both the AF mode and the DF mode. The proposed system could achieve less transmission error rate and higher diversity order. Due to the advantage of the LDPC-STBC over the STBC in the traditionalMIMO systems, we extended the LDPC-STBC scheme to the distributed MIMO systems, and introduced the LDPC-DSTC systems with one or two non-regenerative relays. Because of the robustness of the LDPC, the LDPC-DSTC systems with regenerative relays can be considered as MIMO systems. Finally, by making investigations into two relaying architectures, we introduced two dirty paper coding based relaying architectures, and give out their implementation methods.In all the schemes in this dissertation, the relay terminals are only utilized to assist the transmission from the source to the destination, but do not have their own information to transmit. Actually, users in the network could play the role not only of the source terminal but also of the relay terminal. The future research of the cooperation communications, with the consideration of this point, is undoubtedly very promising; the distributed source coding and the joint distributed source/channel coding would be a great help to the improvement of the system performance.