A Generalized TCP Fairness Control Method for Multiple-Host Concurrent Communications in Elastic WLAN System Using Raspberry Pi Access Point

The IEEE802.11n wireless local-area network (WLAN) has been widely adopted due to the flexible coverage and lower installation cost. However, the TCP throughput unfairness was detected when multiple hosts concurrently communicate with a single access-point (AP). Previously, the authors proposed the TCP fairness control method for only two hosts in the elastic WLAN system using Raspberry Pi AP, which dynamically adapts the topology according to the traffic demand. The delay is introduced in the packet transmission to the faster host from the AP, which is optimized by the PI feedback control such that the measured throughput becomes equal between the hosts. In this paper, the authors proposed a generalization of this method for any number of hosts by newly introducing the target throughput as the equal goal among the hosts. It is dynamically updated using the measured throughputs. The effectiveness of the proposal is verified through experiments using the elastic WLAN system testbed with one AP and up to four hosts.