The goal of the association policy is to improve the overall system capacity. We do this by picking the ``right'' DAP for a client to associate with, and when needed we select the ``right'' channel for that DAP to operate on.
Intuitively, the way to improve overall system capacity is to have each client to associate with a nearby, lightly-loaded AP. Furthermore, APs that are close to each other should operate on orthogonal channels. We will formalize these notions in the rest of the section.
We do not claim that our association policy is optimal. Rather, our aim is to provide a significant improvement over existing WLAN networks, by taking advantage of the dense deployment of DAPs, and without requiring any changes to the clients.
In this section, we first present a metric we call Available Capacity to rank all possible DAPs that a client can associate with. We then describe the association policy for four scenarios: (i) when a new client shows up, (ii) when the wireless channel conditions change, (iii) when clients move, and (iv) when DAPs fail. A more detailed description of our association policy and related issues is available in [22].