Queuing Analysis of Opportunistic Access in Multichannel Cognitive Radios

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Due to the propagation characteristics of electromagnetic waves, the frequencies between 10MHz and 6 GHz are the most suitable for wireless communications purposes. With the ever-increasing demand for wireless communications and the popularity of various wireless technologies, the traditional approach to spectrum management based on fixed spectrum allocation, has resulted in scarcity of radio spectrum, due to the fact that most of the available spectrum has been allocated. On the other hand, studies have shown that vast portions of the licensed spectra are rarely used, leading to underutilization of a significant amount of spectrum. As a result, innovative techniques that can offer new ways of exploiting the available spectrum are needed. Cognitive Radio Networks (CRNs), which are based on Cognitive Radio (CR) terminals and wireless networking technologies have been proposed as the solution to current low usage of licensed spectrum problem. CR technology provides unlicensed (also known as secondary) users the capability to share the wireless channel with licensed (also known as primary) users in an opportunistic manner. CR networks are envisioned to provide high bandwidth to mobile users via heterogeneous wireless architectures and dynamic spectrum access techniques, while improving connectivity and self-adaptability of channel environment.