Channel-Usage Model in Underlay Cognitive Radio Networks
In underlay cognitive radio networks (CRNs), a licensed channel can be shared with its primary users (PUs), provided the resultant interference power level at the primary receiver is below a predefined threshold, known as interference power constraint (IP
- PDF / 342,048 Bytes
- 9 Pages / 439.37 x 666.142 pts Page_size
- 49 Downloads / 184 Views
Abstract In underlay cognitive radio networks (CRNs), a licensed channel can be shared with its primary users (PUs), provided the resultant interference power level at the primary receiver is below a predefined threshold, known as interference power constraint (IPC). Therefore, in such a scenario secondary users (SUs) have to perform the following—(a) perform spectrum sensing to detect the existence of PUs and (b) estimate the IPC to protect the PU from harmful interference. In this paper we develop a channel-usage model of PU’s in underlay mode of CRNs using a Hidden Markov Model (HMM) that allows SU to predict the unused/usable spectra. The model estimates the interference power level of a license channel due to the presence of SUs and decides on the availability of the channel for SU’s transmission imposing IPC. Further, a channel selection scheme is developed so that SUs can decide and select the best channel in the presence of multiple available licensed channels. Simulation results demonstrate the efficacy of the proposed model and its usability in underlay CRN.
1 Introduction In Cognitive Radio Network (CRN), SUs along with the role to sense and discover spectrum opportunities, cognitive radio (CR) [1] has to detect the existence or return of the PUs to protect the PUs from potential interference. The policies for MAC-layer sensing [2] of SUs in underlay CRN require the information about the availability of licensed channels and the estimation of interference level. In such a scenario, the S. K. Deka (B) · N. Sarma Department of Computer Science and Engineering, Tezpur University, Tezpur, Assam 784 028, India e-mail: [email protected] N. Sarma (B) e-mail: [email protected] N. Chaki et al. (eds.), Computer Networks & Communications (NetCom), Lecture Notes in Electrical Engineering 131, DOI: 10.1007/978-1-4614-6154-8_12, © Springer Science+Business Media New York 2013
115
116
S. K. Deka and N. Sarma
SUs require to learn about the channel’s usage pattern of its PUs which will help them in predicting future channel availability, which helps to alleviate the sensing overhead problem of proactive sensing used by SUs. In this paper, we focus mainly on two important issues of MAC-layer sensing for underlay mode CRN—(i) how to estimate and model the channel usage pattern of PUs while tolerating interference from SUs, and (ii) how to discover opportunities in the licensed channel based on learnt channel usage pattern. Accordingly, we propose a novel channel-usage model of PUs for use by the secondary nodes to discover the spectrum opportunity using Hidden Markov Model (HMM) [3]. The model addresses the issue of interference in a license channel due to the presence of SUs through estimated IPC [4, 5] to protect PUs. Based on the proposed model, a channel selection scheme is developed, which helps to decide and select the best channel to be used by a SU for transmission in future. As shown in Fig. 1, for a spectrum underlay scenario, IPCs can be imposed to protect the PUs from interference. IPC [4, 5] is defin
Data Loading...
