IEEE802.11e とDCF の混在無線LAN環境への受信機会制御適用による動的QoS保証

摘要

IEEE 802.lie Enhanced Distributed Channel Access (EDCA) is a MAC protocol for WLAN to realize Quality of Service (QoS) control. EDCA offers the possibility of denning four different classes of service at the MAC layer so that QoS requirements can be supported. Service between classes is differentiated by different sets of channel contention parameters. However, it is difficult to guarantee QoS of the high-priority stations in EDCA where both EDCA stations and Distributed Coordination Function (DCF) stations are connected to an access point (AP), because QoS control is not considered in DCF. This paper proposes a novel scheme to guarantee the QoS requirement of the high-priority stations in EDCA in such a mixed environment. In this scheme, Receiving-Opportunity Control in MAC Frame (ROC) proposed by the authors is employed. ROC probabilistically refuses data frames from low-priority stations. This paper analyzes the appropriate probability which satisfies the requirement of high-priority stations in EDCA. The effectiveness of the proposed scheme is validated through simulation.%IEEE802.11e EDCA（Enhanced Distributed Channel Access）では，フレームに4つの優先度を設けることで，通信品質を要求されるデータを優先的に送信するQoS（Qualityof Service）制御を実現している.しかし，EDCAで構成されるネットワーク内にDCF（Distributed Coordination Function）で動作する端末が混在すると，EDCAのQoS制御機能の低下する問題がある.本稿では，DCFで動作する端末に対してAP（Access Point）の機能変更のみで導入が可能なQoS制御方式ROC（Receiving-Opportunity Controlin MAC Ftame）を用いることで，EDCAのQoS 制御機能低下を防止する方式を提案する.さらに，任意の混在環境において，フロー数，パケット長，データレート等のパラメータを基に解析的に適切なROC制御を行う方法を示し，EDCAだけでは満たすことのできないQoS要求にも対応できる方式を提案する.シミュレーションにより提案方式の有効性を示す.