TCP-Aware OFDMA Transmission Based on Traffic Intensity in Downlink and Uplink Directions in IEEE 802.11ax Wireless LANs

Abstract

In recent years, wireless local area networks (WLANs) have become widespread, and the number of mobile stations (MSs) connected to WLANs and the number of WLANs installed have been increasing. In addition, owing to the diversification of applications using WLANs, transmission opportunities have been proportionally greater in the uplink direction, from MSs to base stations (BSs), than ever. Furthermore, most of this data is transmitted using Transmission Control Protocol (TCP). Therefore, WLANs need to provide opportunities for frame transmission in each direction according to the ratio of TCP traffic intensity. In this study, we propose a TCP-aware frame transmission method that makes effective use of Orthogonal Frequency Division Multiple Access (OFDMA) transmission as introduced in the IEEE 802.11ax standard to improve the TCP throughput of the entire WLAN while realizing the allocation of such frame transmission opportunities. In an environment where TCP flows are transmitted in both uplink and downlink directions, the proposed method transmits each frame by using OFDMA transmission and Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) adaptively and selectively according to the buffering status of TCP data segments and ACKs in each direction.