Performance Analysis of a Wireless Network with Opportunistic Spectrum Sharing

Abstract — We analyze the performance of a wireless system that allows opportunistic spectrum sharing. The system consists of a set of primary users sharing a set of channels over a coverage area. The resources allocated to the primary users are shared opportunistically with a set of secondary users. The secondary users are capable of detecting channels that are unused by the primary users and then making use of the idle channels. If no channel is available for a secondary call, the call waits in a buffer until either a channel becomes available or a maximum waiting time is reached. We compute the blocking probabilities, mean reconnection probability, channel utilization, and total carried traffic in the system. Our results suggest that opportunistic spectrum sharing can significantly improve the efficiency of a wireless system, without negatively impacting the performance seen by the primary users. I

Interference Alignment for Cognitive Radio Communications and Networks: A Survey

© 2019 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).Interference alignment (IA) is an innovative wireless transmission strategy that has shown to be a promising technique for achieving optimal capacity scaling of a multiuser interference channel at asymptotically high-signal-to-noise ratio (SNR). Transmitters exploit the availability of multiple signaling dimensions in order to align their mutual interference at the receivers. Most of the research has focused on developing algorithms for determining alignment solutions as well as proving interference alignment’s theoretical ability to achieve the maximum degrees of freedom in a wireless network. Cognitive radio, on the other hand, is a technique used to improve the utilization of the radio spectrum by opportunistically sensing and accessing unused licensed frequency spectrum, without causing harmful interference to the licensed users. With the increased deployment of wireless services, the possibility of detecting unused frequency spectrum becomes diminished. Thus, the concept of introducing interference alignment in cognitive radio has become a very attractive proposition. This paper provides a survey of the implementation of IA in cognitive radio under the main research paradigms, along with a summary and analysis of results under each system model.Peer reviewe