This paper describes a QoS control scheme for a wide area ubiquitous wireless network which is designed to accommodate many wireless terminals (WTs), such as sensors and actuators, in a large cell area. The purpose of this paper is to establish a QoS control scheme in a media access control (MAC) layer that can hold the transmission delay time of high priority (HP) class traffic within a predefined value regardless of how much low priority (LP) class traffic there is. Several QoS control schemes for wireless communication use have been proposed. However, in the wide area ubiquitous wireless network, an access point (AP) accommodates many WTs and the AP traffic volume often drastically changes. Therefore, conventional schemes sometimes cannot control the QoS of HP traffic. To solve this problem, we propose a QoS control scheme that calculates a suitable initial back-off window size (IWS) of random access (RA) for each QoS class by using equations derived from a Markov chain behavior model. The proposed scheme adjusts the window size so as to prevent increased transmission delay of HP traffic. The scheme's performance is clarified by computer simulation.
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