The Research Of Opportunistic Relay Cooperation Systems With Link Adaptation

Cooperative diversity as a efficient technology to against themultipath fading which exploit diversity via a virtual distributed antennaarray where each antenna belongs to a different node. Opportunistic relay(OPR) cooperation systems that invite a best relay to forward messagebecome the hot spot in cooperation diversity technology, since it can notonly save system power consumption and lower costs, but also achievesthe same diversity-multiplexing tradeoff as achieved by more complexdistributed space–time coding. Link adaptive technology can improve thedata transfer rate in the premise of reliable transmission. In order to fightagainst the challenge of multi-hop wireless transmission and oftime-varying, This paper studies the opportunistic relay (OPR)cooperation systems based on link adaptive technology, in order tomaximize spectral efficiency, the main work is as follows:1. To modeling analysis for the wireless channels, and theperformances analysis of single relay cooperation system while use different relay protocol.2. While the adaptive modulation technology is applied in thephysical layer, evaluate an opportunistic relay cooperation system whichusing adaptive decoding and forwarding in relays, the system performanceindicators such as average spectral efficiency, outage probability andaverage bit error ratio are analyzed in detail. Finally, the theoreticalcalculation and simulation results show that the system performance issuperior to the Amplify and forwarding (AF) opportunistic cooperationsystem.3. As the traditional layering design only use a fixed communicationmode, and the design in every level is considered in the worst channelcondition of communication, so it can’t very well used in mobilecommunication. So we here import the cross-layer design ideas to the OPRcooperation systems, joint data link layer and physical layer of theadaptive decoding OPR (DF-OPR) cooperation systems with optimizationdesign. The protocol of cooperative hybrid automatic repeat request withopportunistic relay (C-HARQ-OPR) is proposed in the purpose to improve the system spectral efficiency. Firstly, the truncated hybrid automaticrepeat request (HARQ) packet and frame structure are designed in the datalink layer; Then, according to the quality of service (QoS) requirements,we obtain the parameters of several AMC send modes by the method ofcurve fitting; At last, according to the relationship between the averagespectral efficiency and average lost package rate, the optimizationalgorithm is designed to solve the system optimal spectral efficiency indynamic.