Performance analysis of random linear network coding in cooperative communication

Abstract

A performance of random linear network coding using relay selection based on outdated channel state information has been analyzed in two-hop relay network. Relay selection and random linear network coding have been studied widely because these techniques can improve an efficiency and a performance of wireless network systems. Relays provide high data rates and larger coverage of wireless communication system by reducing the distance between a source and a destination. The relay selection in a cooperative communication is a technique in which well-selected relay nodes are used to transfer a data after receiving feedback of channel state information from the source or the destination. Since a diversity gain can be deployed by the relay selection, it can achieve more performance gain of wireless systems which have dynamically varying channel environments. Random linear network coding is an enhanced technique of network coding that is presented as an alternative to traditional routing scheme. It is efficient to transmit data in the networks with dynamically varying connections. According to traditional routing schemes, nodes just perform receiving and forwarding data packets. However, the nodes of networks using network coding allow combining data packets by encoding. These facts lead to solve the problems that nodes of network in conventional routing cannot share links. Thus, the network coding brings about reliable communications and efficient data transmissions compared with simple routing system. However, in practical cases it is important to consider that channel state information quickly becomes outdated due to issues of mobility, propagation delay and transmission delay. The estimated channel state information can be different from the actual channel state information. If the outdated channel state information is used in transmission, the optimal relay cannot be selected properly and the error also can occur frequently. Moreover, the error can be propagated rapidly to whole networks through a lot of relays. Consequently, the destination node cannot decode successfully and it causes a significant performance degradation. From the facts described above, it is needed to investigate the performance analysis of random linear network coding using outdated channel state information. We consider two relay selection schemes to examine performance for random linear network coding using outdated channel state information in relay network. First, the outage probability using the single relay selection scheme based on perfect and outdated channel state information is analyzed mathematically. Moreover, various channel correlation coefficient and various number of relays are considered in the analysis. Second, the multiple relay selection scheme is considered to compare the performance of single relay selection scheme. Here, the multiple relay selection scheme based on perfect channel state information is investigated in the analysis. It is found that the proposed system causes performance improvement as the correlation coefficient or the number of relays increases.