The Research Of Rate-embedded Differential Space-Time Coding Based On Cooperative Communication

With use of mutual cooperation among multiple nodes sharing transmission path in a wireless network, cooperative communication system has become the hot spot of the communication field in recent years.Cooperatitive communication system does not require an additional multi-antenna configurations and can be obtained similar to the MIMO (Multiple-Input Multiple-Out-put) system spatial diversity, thereby improving the link performance.On the basis of the theoretical study of the cooperative communication technologies, a large number of studies for a deeper level of cooperative communication technology has emerged in recent years. With the combining of space-time coding techniques and cooperative communications technology in cooperative relay networks, multiple relay nodes antenna is equivalent to a distributed "virtual antenna array", and the design of space-time coding to be able to tap the spatial diversity gain and improve anti-interference ability among the intensively and reduce the energy consumption of the nodes in the network and its research has become the focus of the researchers.For most the current works on cooperation communications are based on the assumption of the availability of perfect channel state information(CSI) at the receiver, requiring for reliable multi-channel estimates, which will increase the frequent channel estimation burden, and increase the number of the channel parameters which the receiver needs to estimate. Therefore, it is necessary to study cooperative communication of differential transmission systems which not require the receiver knowing perfect channel state information.In this thesis,we first introduce the basic theory of wireless communications, MIMO models and theories of space-time coding, make inquiries-depth analysis of several typical space-time coding techniques and briefly introduced the concept of distributed space-time code, cooperative communication model and protocol.We investigate differential space-time coding (DSTC)scheme based on the single-relay and two-hop cooperative model of cooperative communication.For the problem that information symbols must be unitary matrix to meet the requirements of the differential transmission which have redundant information, resulting in lower data transfer rate. In the rates-embedded differential space-time coding scheme of this thesis, based on two-hop single-relay cooperative model, the full-rate space-time codes and the traditional low-rate space-time codes alternately be used in cooperative differential transmission at the appropriate slots, and the two different types of information symbols matrix, break through the limit that the information symbol of the differential transmission matrix must meet the restrictions of the unitary characteristics and the cooperative differential data transmission rate can be achieved. Simulation results show that compared to the scheme using unitary matrix as the information symbol matrix in the two-hop single-relay cooperative differential space time coding system, in this improved scheme, the data rate of the system can beimproved significantly under the premise of guaranteeing the error performance On the other hand, with the same transfer rate, the error performance of the rate-embedded cooperative differential space-time coding scheme is significantly better than using the unitary matrix as the information symbols matrix in the cooperative differential space-time coding scheme.