NeXt generation/dynamic spectrum access/cognitive radio wireless networks: a survey
Computer Networks: The International Journal of Computer and Telecommunications Networking
Cognitive radio: brain-empowered wireless communications
IEEE Journal on Selected Areas in Communications
Achieving Secondary Capacity under Interference from a Primary Base Station
NEW2AN '09 and ruSMART '09 Proceedings of the 9th International Conference on Smart Spaces and Next Generation Wired/Wireless Networking and Second Conference on Smart Spaces
Proceedings of the 7th ACM international symposium on Mobility management and wireless access
A geometric approach to improve spectrum efficiency for cognitive relay networks
IEEE Transactions on Wireless Communications
Overlay Cognitive Radio in Wireless Mesh Networks
Wireless Personal Communications: An International Journal
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In a commonly accepted usage scenario, a cognitive radio appears as a secondary user of certain spectrum which is licensed to another, primary system. A prominent example of cognitive system is a mesh network operating under the interference from primary system. For such a scenario, we propose techniques for efficient secondary usage of spectrum, which rely on the adaptive array antenna in order to reduce the interference between the primary and the cognitive system. In order to keep the hardware complexity as small as possible, the number of antennas at each cognitive node should be small. However, with the simplest 2-element linear adaptive array, the created antenna pattern can result in non-optimized pattern between cognitive nodes in the mesh network. In order to solve such a problem, this paper introduces a simple antenna pattern switching where each cognitive node is equipped with three antennas, and tries to select the antenna configuration constituting 2-element linear array with the best antenna pattern for each link. The proposed configuration requires three antennas but only two transceiver chains, which can reduce the hardware complexity. We also introduce 3-element linear array and design a simple procedure to heuristically select the pattern. Our numerical results show that the proposed techniques can significantly increase the available bandwidth and networking connectivity with small complexity when a cognitive mesh network is located inside the communication area of the primary system.