A novel approach of user existence awareness using adaptive spectrum sensing controllers in emergency‐based cognitive radio adhoc networks

Abstract

Summary Spectrum sharing can be considered as an alternative solution to overcome spectrum limitation. Cognitive radio is the most important spectrum sharing technique in wireless communication system, which aims to enhance the utilization of radio frequency spectrum. Identification of spectrum environments like location of both licensed and unlicensed users has been considered in cognitive radio technology. In this paper, cognitive controller is an emergency repairing unit, which is introduced to maximize the number of connected users in an emergency situation. The analysis shows that the sensing efficiency of fixed sensing controller to identify users is limited to its sensing region. A hybrid technique with overlay and underlay accessing to perform data offloading in emergency situations and to connect the disconnected users is proposed to enhance the location sensing efficiency of the controller. A cognitive user node located at the interference region of controller experiences hidden node problem and causes interference to other users. In order to identify such users, an adaptive and cooperative sensing‐based controller is proposed, and efficiency of which is compared with the efficiency of fixed sensing controller. Theoretical and simulation analysis explores that the sensing capacity of adaptive sensing controller provides 42% of higher efficiency than the fixed sensing method.

Distributed algorithm to reduce contention in emergency situations by deploying cognitive radio ad‐hoc controllers

“…As the efficiency of the system can be analysed using throughput and fairness, we have compared the proposed algorithm with heuristic algorithm as mentioned in [10] using those two performance metrics. The transmission range of controllers is assumed to be 25 m. The number of spectrum utilised are 50, 54, 60, 66 and 72 MHz.…”

“…Figs. 1a and b illustrate the offloading of primary data to the nearest controller/relays by co-operation of PUs and cooperative controllers using overlay VMIMO technique [10]. As the primary data relaying occurs, neighbouring SUs and EUs tries to connect in order to obtain spectrum information and transmit their data using underlay technique.…”

“…If the EU is located nearest to a secondary receiver, then it will be affected by serious interference from parallel transmission of both secondary transmitter and EU. The minimum distance between SU and EU at which interference remains higher was illustrated in [10].…”