Proof-of-Concept System for Opportunistic Spectrum Access in Multi-user Decentralized Networks

Abstract

Poor utilization of an electromagnetic spectrum and ever increasing demand for spectrum to support dataintensive services envisioned in 5G have led to surge of interests in paradigms such as cognitive radio,device-to-device communications, unlicensed LTE etc. Such paradigms can improve spectrum utilization viaopportunistic spectrum access (OSA) in which secondary (i.e., unlicensed) users (SUs) are allowed to transmitin the vacant licensed bands given that they do not cause any interference to the active licensed users. Over thelast decade, various spectrum detectors to check the status (i.e. vacant or occupied) of the frequency band havebeen studied and demonstrated but little attention has been paid to the task of frequency band selection fromwideband input signal. This is a challenging task especially in the decentralized network where SUs do notshare any information with each other. In this paper, a new decision making policy (DMP) has been proposedfor frequency band characterization and orthogonalization of SUs into optimal set of frequency bands. Inthe proposed DMP, Bayesian UCB (Bayes-UCB) algorithm is used for accurate characterization of frequencybands. Furthermore, Bayes-UCB based orthogonization scheme is proposed replacing existing randomizationbased schemes. Then, a testbed using USRP has been developed as a proof-of-concept system for analyzingthe performance of DMPs using real radio signals. Based on experimental results, we show that the proposedDMP is superior in terms of improvement in spectrum utilization when compared to existing DMPs. Addedadvantages of fewer number of frequency band switching as well as collisions make the proposed DMP energyefficient and hence, suitable for resource-constrained battery-operated radio terminals.