Modified Rate Control for Collision-Aware in Minstrel-HT Rate Adaptation Algorithm

The rate adaptation algorithm in the IEEE 802.11 Wireless Local Area Networks (WLANs) is used to control the rate for frame transmission. In the Linux kernel, Minstrel-HT is used as the default rate adaptation to control the rate in the IEEE 802.11n/ac WLANs. But if there are frames collisions in the channel caused by the hidden terminal problem, then Minstrel-HT degrade data rate resulting in throughput also become decreased. The use of RTS/CTS transmission mode in Minstrel-HT is based on RTS-Threshold, resulting in throughput also decreasing as transmission overhead increases when there are no collisions in the channel. Previous works have proposed dynamic RTS/CTS activation method but it is only used for legacy WLANs. In this paper, we propose a modified rate control in Minstrel-HT that takes into account the development of PHY and MAC in the IEEE 802.11n/ac WLANs and we call it as Minstrel with Collision Detection for High Throughput (Minstrel-CDHT). The modifications we propose are as follows, if the transmission is not successful, then the first retransmission is done by enabling RTS/CTS mode. If the transmission fails again, it is assumed that the failure is not caused by the collision and the following retransmission is done by disabling RTS/CTS mode. We implement and evaluate this algorithm using NS-3 network simulator. The simulation results show, when the collision occurs in the channel, our proposed algorithm produces higher throughput than the original Minstrel-HT and Minstrel-HT with static RTS/CTS.