Abstract
Frequency spectrum is a limited resource and the increasing demand caused by emerging services, augmented number of wireless users along with the demand for high-quality multimedia applications have resulted in the overcrowding of the allocated spectrum bands. The overcrowding of spectrum bands has exacerbated by the current spectrum licensing policy which has emerged as a bottleneck to efficient spectrum utilization, due to its inflexibility, resulting in most of the licensed spectrum being severely under-utilized. However, the problem of scarcity of spectrum bands and the inefficient utilization of the already allocated radio spectrum can be smartly addressed through spectrum sharing by enabling opportunistic usage of the underutilized frequency bands. One of the most exciting ways of spectrum sharing is cognitive radio technology which allows a wireless node to sense the environment, detect the network changes, and then make intelligent decisions by dynamically changing its reception or transmission parameters to communicate while ensuring that no interference is affected to the licensed users. It thus improves the spectrum utilization by reusing the unused or underutilized spectrum owned by the incumbent systems (primary systems). In this paper, a comprehensive survey and review of recent research about the advances in cognitive radio technology will be carried out. We will also evaluate the various spectrum sensing techniques in a cognitive radio network in the UHF/VHF bands allocated for TV broadcasting.
Highlights
The rapid growth of wireless communication has exacerbated the problem of scarcity of available spectrum
After receiving the sensing results from the others, a secondary users (SUs) can make its own judgment regarding the status of a spectrum band, basing it on its own sensing results and the data received from the other SUs using a local criterion and without having the need of a controller (Figure 9)
Current spectrum licensing policy has led to most of the spectrum being assigned to various services
Summary
The rapid growth of wireless communication has exacerbated the problem of scarcity of available spectrum. Efficient spectrum utilization is the most challenging hurdle in the evolution of wireless communication systems and radio devices. Cognitive radios (CRs) have emerged as a solution through opportunistic spectrum sharing of spatially and temporally unused spectrum bands. This helps to improve spectral utilization by reusing the unused or underutilized spectrum owned by incumbent systems (primary systems). Spectrum sensing algorithms are used to obtain awareness about spectrum occupancy and the existence of primary users in a given spectrum band. This allows spectrum sharing and gives opportunistic access to unused spectrum and enhances spectrum utilization. Use of spectrum sharing instead of exclusivity has created new opportunities for new technologies such as a smart grid communication network
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