Joint transmit power and contention window control in dense deployed WLAN

Abstract

In recent years, there has been a rapid rise in wireless networks. Because of the generalization of wireless devices such as smart phones, laptops, smart watches, etc., the use of Wireless Local Area Network (WLAN) is dramatically increased. To support these wireless devices, numerous Access Points (APs) are deployed in limited space and this situation is referred as dense WLAN. Also, the demand of traffic which associated Stations (STAs) requires is increased. Because frequency resource approved for WLAN is limited, dense WLAN system has a problem to support all traffic demands. In such a case, there are many collisions occured between nodes which are associated with the same AP. In addition, performance of the system is decreased by the interference from neighboring Basic Service Set (BSS). To solve this problem, various researches have already studied. Transmit power control algorithm is one of techniques for densely deployed WLAN. In transmit power control algorithm, the received signal strength of the interference from the neighboring AP can be basically reduced. In addition, contention window adaptation algorithm is also one of the method to enhance the performance for dense WLAN. Using the contention window adaptation, the collision probability and the delay can be controlled to afford many STAs in an AP. In this paper, a joint transmit power control and contention window adaptation algorithm is suggested. To manage the channel interference, the AP controls transmit power by monitoring the surrounding environment. With the management of channel interference, contention window adaptation can enhance the throughput by control the channel load. In the proposed algorithm, these behaviors work at distributed system where the AP does not have any information of other APs, and adapt the surrounding environment. We evaluate the performance of the proposed algorithm by simulation. The average per-node throughput, the average cell throughput and the average MAC delay are selected as the metrics of the performance to verify the proposed algorithm and compare the proposed algorithm with the conventional algorithm. In addition, we assumed both saturated condition and unsaturated condition to figure out the efficiency of the proposed algorithm. In the simulation results, the proposed algorithm provided higher average throughputs than the conventional algorithm in case of the large number of STAs per AP what our proposed algorithm targeted. Also, it enabled the average MAC delay to have lower slope than the conventional algorithm. Therefore, it is shown that our proposed algorithm is more efficient in view of both considered metrics compared with conventional algorithm in densely deployed WLAN.