| Multiple-Input Multiple-Output system (MIMO) can increase system's channel capacity and spectrum efficiency significantly in the premise of not sacrificing the extra bandwidth. The technology of Space-time coding can obtain the diversity gain through the MIMO channel, thereby improving the reliability of wireless communication systems. However, based on the design features of MIMO systems, we need to place multiple antennas at the mobile terminal, so that many aspects of the actual communication will be limited. As an effective space diversity way, the cooperative diversity technology can form virtual MIMO through mutual cooperation among single antenna users, which not only overcomes the limitations of MIMO systems, but also obtains similar performance with MIMO system, which has better application prospects.In this paper, we focus on the applications of space-time block codes in the cooperative diversity technology. Based on the coding features of orthogonal space-time block codes, we can improve the transfer rate by changing the transfer mode. However, according to the channel state information, we can allocate different power for sending the code word, which could further improve the system performance. We can not only get the diversity gain but also reduce the decoding complexity, and improve the system spectrum efficiency effectively by the combination of the space-time block codes and cooperative diversity technology.In this paper, the main work is as follows:1) space-time coding techniques are introduced, the system model and design criteria of the space-time coding are discussed, including encoding and decoding method and the orthogonal design principle, to further improve system performance, the space-time block coding technology with some feedback is introduced.2) several typical diversity technologies are introduced, and cooperative diversity technology is highlighted, including collaborative system model, relay cooperation protocol and the consolidation strategy of the receiver.3) the space-time block coding technology is used to the relay coordination model, in order to overcome the shortcomings of taking too time in the traditional collaboration solutions, the way of two-user collaboration is used to change it according to the orthogonal property of the space-time block codes, so it can reduce the transmission time effectively and improve the system's spectrum efficiency.4) In order to further improve system performance, the DF protocol is as an example to discuss the optimal power allocation scheme. According to the channel status information between users, different power factors are allocated between the source and the relay. According to the simulation of the equal power and optimization power allocation program, it can be seen that compared to the equal power allocation program, the optimization power allocation program can improve the system performance more effectively by using the channel state information. |
