CARD-BS: Consider of Back-off Suspension in CARD for WLAN

Wireless multi-media service and real-time applications are becoming increasingly popular in our daily life. These services put forward more requirements for quality of service (QoS). Cooperative technology, which takes more advantage of wireless channel resource, can improve the quality of communications. Among the cooperative technologies CARD (Cooperative Access with Relay´s Data) is one of the most excellent algorithms, which is characterized by encouragement mechanism and inherited back-off. However these characteristics and channel busy/idle state are not exhaustively considered in the analysis of back-off process. In order to make a more accurate estimation of CARD performance, Back-off Suspension State (BSS) and Channel State Markov Sub-Chain (CSMSC) model are introduced to the analysis model. Based on the modified model CARD-BS focused on Back-off Suspension is proposed, BSS and CSMSC are used to analyze the influence of above characteristics and channel busy/idle state on back-off process respectively. The numerical results of CARD-BS show that the performance of CARD is underestimated, especially in the terms of collision probability and average service delay. Under CARD-BS, the collision probability and average service delay are both improved.