UnChannelize the Channels in WLAN

IEEE 802.11-based WLANs use a simple, fixed channelization structure, which divides the available spectrum into a set of channels of equal bandwidth. We argue that the fixed channelization has severely constrained the total capacity and fairness of WLANs. Our argument stems from recent measurements of WLANs in real world [4], [2], [3], which show significant spatial and temporal variations in user and traffic load. More specifically, user populations served by different access points (APs) in a WLAN fluctuate considerably over time, and are extremely unbalanced. Certain APs become hotspots while others remain unused. The fixed channel structure offers very limited flexibility in handling such variations. We propose a radically new channelization structure. Our scheme dynamically creates the appropriate number of channels to accommodate all interfering APs, and adjusts the channel bandwidth (channel-width) depending on the instantaneous traffic loads at the AP and its the neighboring APs. The dynamic channelization is enabled by recent advances in radio technologies, such as cognitive radios, which make it possible to reconfigure the key operating parameters of radios, including center-frequency, bandwidth, and power, with a very low time overhead [5]. The structure of the paper is as follows: The next section presents a motivating example, and Section III describes the system design for creating dynamic channels. We conduct the simulations using real-world traces. Our results, presented in Section IV, show that our dynamic scheme significantly increases network capacity and improves per-client fairness.