Client-centric heterogeneous access in cognitive WLANs

The spatial and temporal variations of licensed spectrum bands introduce new problems to cognitive wireless LANs. We propose a novel client-centric heterogeneous spectrum access mechanism to deal with these new challenges. All clients in a cell would not have to use the same channel to communicate with access point when there is no common available channel among these clients. In order to achieve channel agreement among nodes on different channels, a new MAC protocol is proposed with no need of common control channel. Considering that AP can only work on one channel at a time, we use a novel technique, subcarrier coding, to enable it to monitor multiple spectrum bands simultaneously. Each client can select its best channel based on local environment and requirement independently. Promising simulation results show that this new access mechanism not only resolve the problem of lacking common data channel in single cell, but also minimizes conflict significantly even in the case of a large number of clients.