QoS Control Method Based on Adaptive Cooperation between Network Coding and IEEE 802.11e EDCA

概要

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Recently, network coding (NC) has been popularly applied to wireless networks in order to improve scarce wireless capacity. In wireless LANs, NC can be applied to packet retransmission in which multiple packets can be simultaneously transmitted by a single transmission trial at a base station (BS). In this paper, we assume wireless LANs with QoS functionality and propose adaptive cooperation between NC and IEEE 802.11e EDCA. In EDCA, when network load is high, QoS is significantly degraded even for high priority class. To solve this, existing methods improve backoff control, and decrease packet loss caused by collision. However, this cannot prevent packet loss caused by channel fading. In the proposed cooperation between NC and EDCA, QoS of all priority classes is improved from the aspect of efficient loss recovery. Unlike NC method with no QoS control, we encounter transmission scheduling problem among an NC packet, a single lost packet and a new packet. Moreover, in the constitution of packets encoded into NC packet, packet's intrinsic priority should be considered. Therefore, we propose how to schedule the packets to be transmitted in BS, and how to constitute NC packets to be encoded. Finally, we show the effectiveness of the proposed method by extensive computer simulations.