Combining Schemes For DF Cooperative Relay Systems

As the development of wireless communications technology, people's requirement of wireless data services is also growing. The loss of wireless channel is one of the main obstructions for increasing channel capacity and improving service quality. And multi-antenna diversity technology is an effective measure to deal with the channel loss. However, the multi-antenna diversity requires that the communications equipment has multiple antennas, which is difficult to achieve in nodes of many systems because of the limits of size and power. Cooperative diversity technology appeared in this context.Diversity technology is on the same signal at the receiving end multiple copies to merge, compared with time diversity and frequency diversity, spatial diversity can improve the system of transmission reliability, without any increase in transmission time and bandwidth conditions. Cooperative diversity is an emerging technique which makes a user with single transmitter can realize space diversity in distributed communication network. It collects the nodes in the wireless networks to form a virtual multi-antenna array. As a result, the system exploits the cooperation among all the node to obtain diversity gain.There are decode-and-forward (DF) and amplify-and-forward (AF) for cooperation relay communication typical relay agreement, my paper mainly study combining mode of DF cooperation, and the main contents are as follows:Firstly, the paper introduces the history of the wireless communication, simple summarizes cooperation communication, and analyzes the significant of the researching subject.Secondly, the paper studied diversity combining technique deeply. Diversity technique includes space diversity, frequency diversity, time diversity, etc. MRC,SC and EGC and are three common ways of combining. When the diversity is in different, I simulation the three combining mode, and compares PER of the three ways.Thirdly, the paper introduces the cooperation system model and two combining mode:DF and AF,it mainly studies the relays threshold selection strategy based on DF mode, when receiver use MRC,EGC,SC and compares PER of the different ways.Finally, This paper mainly studies the dual-diversity technology:it is the traditional antenna technology and cooperative diversity receiving diversity in the combination with traditional technology, on the basis of traditional the MRC system research cooperation MRC system (C-MRC system), and is applied to the traditional dual-diversity technology.