Wireless LAN access points as links with adaptive bandwidth: throughput and feedback control

The throughput of a wireless LAN access point is an important parameter for QoS over wireless LANs. This paper builds on previous results in order to model wireless LAN access points as data communication links and parameterize the throughput of the access point. The previous work models wireless LAN access points of IEEE 802.11b as FIFO queuing systems, whose service time is a function of payload. This paper shows that a wireless LAN access point functions as a data communication link with variable bandwidth. It is possible to parameterize the performance of the access point as if it were a link with adaptive-bandwidth, bounded by two limits: the lower and upper adaptive-bandwidth bounds. Performance of different access point brands can be compared using the adaptive-bandwidth characteristic. Adaptive-bandwidth was analyzed and shown to be a strictly increasing linear fractional transformation of payload. The adaptive-bandwidth of the access-point link-model is used to calculate the throughput of the access point. The throughput of access points is studied in terms of a feedback control system, whose ratio of output to input gives the throughput in terms of access point parameters and offered load.