Abstract
Conventional DCF and RTS/CTS mechanisms perform the channel contention by a distributed and independent manner, which can lead to severe cochannel interference and low channel utilization in multiple APs dense deployment scenario. In this paper, we propose a channel scheduling cooperation algorithm called CCT-SDN (centralized concurrent transmission based on SDN) that enables multiple APs (Access Points) to perform cooperatively a centralized downlink transmission control, thus achieving higher system throughput and channel utilization by avoiding cochannel interference and implementing concurrent transmission. This design inherits the merit of the conventional distributed random channel access and adopts standardized OpenFlow protocol and Software Defined Network (SDN) architecture to make a centralized concurrent downlink traffic transmission decision among APs. Meanwhile, we also present a novel neighborhood relation storage scheme called SPRIM to enhance the retrieving efficiency of SDN controller, which enables CCT-SDN to perform a real-time control. Moreover, we also develop a theoretical model to prove the improvement of CCT-SDN. Furthermore, our solution does not require any modifications to existing ubiquitous 802.11 terminal devices and thus is likely to be widely deployed. Finally, extensive simulation results on Mininet-WiFi verify that CCT-SDN can achieve significant performance in terms of aggregate throughput, channel utilization, and packet loss rate in different deployment scenarios.
Highlights
Wireless local area networks (WLANs) have gained signi cant attention in both industry and academia [1] due to their exibility of deployment and cost e ciency
This results in serious cochannel or adjacent-channel interference and severely decreases the overall system performance, especially in dense deployment scenarios. e fundamental reason for this channel ine ciency is the fact that the basic Media Access Control (MAC) protocol utilizes the legacy distributed coordination function (DCF). e DCF based on Carrier Sense Multiple Access/Collision Avoidance (CSMA/ CA) does not always make correct sensing decisions in the presence of exposed/hidden terminal problem [2] and lacks concern to the asymmetry of data tra c on uplink and downlink in many applications. e virtual carrier sensing mechanism such as RTS/CTS uses the RTS or CTS frames to reserve the medium for the actual data transmission, which can handle the hidden terminal problem
In this paper, borrowing the function separation idea of the Software De ned Network (SDN) architecture, we propose CCT-SDN to schedule intensively all downlinks among APs for solving the existing cochannel interference problems in multiple APs deployment scenarios
Summary
Wireless local area networks (WLANs) have gained signi cant attention in both industry and academia [1] due to their exibility of deployment and cost e ciency. With the dramatic increasing popularity of IEEE 802.11 technology, it is widespread in practice to deploy multiple APs (Access Points) with partially overlapping areas for providing ubiquitous continuous coverage This results in serious cochannel or adjacent-channel interference and severely decreases the overall system performance, especially in dense deployment scenarios. Basic DCF has been proven to be severely unsuitable for dense WLANs. erefore, optimization of downlink traffic is often very critical to improve the whole system performance and has become the most important research issue especially in dense deployment scenarios Some existing methods such as smart antennas [6], carrier sense adaptation, and transmission power control [7] improve channel efficiency by a distributed concurrent scheduling manner.
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