A proposal of TCP fairness control method for two-host concurrent communications in elastic WLAN system using raspberry pi access-point

The IEEE802.11n based Wireless Local Area Networks (WLANs) have been extensively deployed due to the flexible coverage, the easy installation, and the lower cost. To reduce the energy consumption while increasing the performance, the elastic WLAN system has been studied, such that it can dynamically change the network configuration according to traffic demands. As well, the test-bed has been implemented and for the access point (AP), Raspberry Pi is used as a portable, energy conservation, and powerful computing device. Our test-bed measurements with a single AP of two concurrently communicating hosts found the unfairness throughput results, due to the TCP windows size became different among them. To overcome this drawback, in this paper, we propose the TCP fairness control method for two concurrently communicating hosts in the elastic WLAN system. By controlling the delay at the packet transmission, the slower host will obtain more transmission opportunities than a faster host. The delay is firstly calculated by the received signal strength (RSS) from every host. After that, the delay is controlled by the PI controller to balance the both throughputs. For evaluations, we execute the proposal in the elastic WLAN system test-bed and carry out extensive measurements, where the TCP throughput fairness is achieved.