Cross-layer performance evaluation of random AIFSN scheme in densely deployed WLANs

In densely deployed wireless local area networks (WLANs), the throughput performance of WLANs significantly deteriorates as the number of neighboring WLANs increases due to an increase in frame collision probability. To improve throughput performance, we have studied the random arbitration interframe space number (AIFSN) scheme, which is an extension of the carrier sense multiple access with collision avoidance (CSMA/CA). The use of AIFS, the length of which is determined randomly, virtually divides nodes into contending and non-contending groups and maintains a small number of contending nodes. Our previous studies only focused on the performance of the media access control (MAC) layer. This paper investigates the transport and application performance of the random AIFSN scheme through a simulation by using the QualNet network simulator. We evaluate the transport layer throughput and the session delay, which is a metric for evaluating the quality of experience (QoE), in simulation scenarios where stations (STAs) use a TCP file transfer application on a WLAN as well as in densely deployed WLANs. Our simulation results indicate that the random AIFSN scheme improves TCP throughput and QoE performances in densely deployed WLANs by 50% compared with the conventional CSMA/CA. Moreover, our research reveals the behavior of the random AIFSN scheme in TCP traffic.