FHCF: a simple and efficient scheduling scheme for IEEE 802.11e wireless LAN
Mobile Networks and Applications
Analysis of IEEE 802.11e for QoS support in wireless LANs
IEEE Wireless Communications
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HCCA has been standardized to provide real-time services with reservation based QoS support using the polling mechanism. To decide whether the service is admitted, the ACU is presented in the specification. The reference scheduler is also specified to allocate wireless resources according to the admission result. However, it is not specified how to collect the QoS information for the service. Furthermore, these mechanisms may operate inefficiently when VBR traffic is generated because these are designed by considering only CBR characteristic. It may cause to degrade the QoS of real-time services generated by VBR. In this paper, we propose three mechanisms to guarantee the QoS of realtime services in the polling based WLAN system. The QoS information for the service is collected using the proposed TS establishment procedure. Then, the effective bandwidth based admission control mechanism decides whether to admit the service according to effective bandwidth. Effective bandwidth is calculated using the collected QoS information. Finally, the token bucket based scheduling mechanism assigns wireless resources depending on the token stored in the bucket. The token bucket size and the token arrival rate are calculated by effective bandwidth. The simulation results show that the proposed mechanisms efficiently transmit the admitted TSs within the delay bound regardless of traffic characteristics. Therefore, the proposed mechanisms can contribute to guarantee the QoS of the real-time services in WLAN.