Collaborative Communication Key Technologies

Multihop wireless network (MHWN) (including wireless Ad-hoc network and wireless sensor net-work) is a research hotspot in present information technology field. For its differences from traditional network in node capacities (limited energy, processor and memory), network characters (random de-ployment, dynamic topology, large dimension, multi-hop), and traffic patterns, there exist many spe-cial requirements for the design of MHWN's physical layer and network protocols. MHWN's essential communication manner is multi-hop; and the basic characteristic is that there has no fixed infrastruc-ture or central control system is equipped in it. Compared with the traditional networks with fixed infrastructure, MHWNs are more flexible, and have important application value in intelligent family, environment surveillance and automatic production and so on. Multi-hop wireless networks have get great attention of some government, military department, industry and academe.The traditional methods which are used to improve the communication performance are to make use of corresponding physical layer technologies of links between source and destination, such as ex-ploiting new coding, modulation, signal processing techniques to approach channel capacity. Coopera-tive communication takes the system's joint optimization into account from the aspects of multi-nodes and the entire network. And it drives the development of wireless communication. Multi-nodes can combat fading of wireless network efficiently via cooperation, and can be used to extract the communi-cation capability adequately by sharing their resource. Consequently, the cooperative communication technique is very suitable for the wireless multi-hop network environment. For the system based on cooperative communication, how much promoting of system performance and the changing of com-munication protocols are two problems which come to people's attention mostly. For the design of cooperative communication system's physical layer, the two essential problems are:1,How to cooper-ate?(The problem of designing and choosing cooperative strategies.) 2,Cooperate with whom?(The problem of how to choose the proper cooperative nodes.)In this paper, we mainly discuss cooperative communication from three aspects, analyzing the performance of cooperative networks; researching the changing of traditional communication model and protocol concepts; and analyzing the cooperative network coding. The main work of this paper can be summarized as follows:1. For the purpose of solving the trouble of analyzing BER performance of complex AF cooperative diversity network, a method of estimating the BER performance is proposed.2. A new type of space time block code (STBC) is expanded and utilized in cooperative diversity networks. The character of this code and the performance of cooperative networks is evaluated. The tradeoff between performance of cooperative networks and the number of cooperative nodes is investigated.3. Taking into account of full use of system resources, and integrating the information of physi-cal layer resources and high level resources, a cooperative communication technique based on geographic position information is studied.4. Thinking of the influence of basic concepts of link after importing cooperative communication technique, a finer model of describing the cover range of virtual node is proposed.5. According the characteristic of network coding and cooperative communication, the research of cooperative network coding technique on the interconnection and combination of network coding technique with cooperative communication is carried out.