Characterization of Priority Control based on Media Access Control Method SP-MAC over WLAN

In wireless local area networks (WLAN) based on IEEE 802.11, when the number of wireless terminals connecting to the same access point (AP) increases, data frame collisions cause the decreasing of total throughput for all wireless terminals. To address this problem, we have proposed a new media access control (MAC) method, Synchronized Phase MAC (SP-MAC), based on the synchronization phenomena of coupled oscillators. We have obtained evaluation results that SP-MAC can improve the total throughput of terminals significantly by its mechanism that can avoid data frame collisions among terminals. However, previous studies have addressed the network environment in which only uplink flows from the wireless terminal to an AP exist, but it is necessary to take into consideration the more real network environment in which uplink and downlink flows are generated simultaneously. If many bidirectional data flows exist in the WLAN, the AP receives a large number of frames from both uplink and downlink by collision avoidance of SP-MAC and the buffer overflow occurs frequently in the AP. Especially, when TCP is used as the transport protocol in the bidirectional environment, TCP-ACK segments as well as TCP-Data segments are received by the AP. In this case, strong impact due to the loss of TCPACK segments causes the degradation of the total throughput drastically. In this paper, we propose a priority control method based on SP-MAC for avoiding extreme loss of segments in the AP under the bidirectional environment. Next, we show that the proposed method has an effect for improving communication quality by the simulation. Keywords—Wireless LAN, Media access control, Synchronization phenomena of coupled oscillators, Kuramoto-model, Priority