Underlay control channel using adaptive hybrid spread spectrum techniques for dynamic spectrum access

The exchange of control messages in medium access control protocols for cognitive radio networks is an important issue, due to the need of keeping transmissions of primary (licensed) users free of interferences occasioned by the presence of secondary users. In an underlay access approach, power constrains must be established in order to allow coexistence between primary and secondary users. In this paper, we propose the implementation of two different types of underlaying control channels, available to the nodes of a cognitive network. One of these channels is used to coordinate the network, while the other type of channel aims to local coordination of each pair of nodes. Code division multiple access based on a direct sequence spread spectrum technique, combined with adaptive frequency hopping is used in order to minimize interferences to primary transmissions, maximize the bit rate of the control messages for the cognitive radio devices.