The Delay Analysis At Transmitting End Of Cooperative SR-ARQ Protocols With Network Coding

Cooperative diversity is a technology which is widely put attention in wireless communication systems recently. As a important breakthrough in the field of information, network coding has become a new research direction in wireless networks. Considering the common communication features of cooperative diversity and network coding, this paper mainly studied the transmitting end delay performance of Selective Repeat Automatic Retransmission Request (SR-ARQ) in network-coded cooperative network. Cooperative diversity is one of the most powerful techniques to mitigate the effects of fading through the establishment of virtual multiply antenna array. Network coding technology can effectively improve the system throughput, but it also can increase the packet error rate to some extent. As the significant error-control technologies, SR-ARQ protocol has an important role in ensuring the quality of the transmission. However, when the retransmission cycle increase gradually, the network’s delay will increase while the throughput will decrease. Adaptive modulation and coding (AMC) scheme at the physical layer is applied in order to increase the spectrum efficiency, which is able to adaptively change the modulation and coding scheme and the transmission rate according to the real condition of the wireless channel.The paper first analyzed the transmitting end delay performance of traditional cooperative diversity system, link adaptation technique is allowed at the physical layer and the wireless channel of single relay cooperative diversity system is modeled. The channel feature is captured by a Finite State Markov Chain (FSMC) while maximal-ratio combining policy for signals is used at the destination. Based on the queuing theory, the queuing analysis model for SR-ARQ protocol under cooperative diversity network is established. On the basis of previous research, network coding is employed at the relay, then we analyzed the average queuing delay of packets from the source at relay under network-coded cooperative system and non-NC cooperative system respectively, explained the influence on the feedback delay. A FSMC model of the network-coded cooperative system is developed just like the non-NC cooperative one. The transmitting end delay statistics are obtained by using the matrix-geometric methods.Because the data size is very large in the process of numerical calculation, the feedback delay value is set to a fixed value and take a small value. Also in this paper, simulation results verified the accuracy of the transmitting end delay calculation model and the related results is demonstrated in this paper. Meanwhile we analyze the impact on transmitting end delay in different system parameters. The calculating results for the transmitting end delay fully concerns the random time-varying feedback delay. The exact probability distribution of transmission delay help the transmitter control the packet flow and improve the network performance of communication system.