Abstract
Cognitive radio (CR) has emerged as a promising technology to solve problems related to spectrum scarcity and provides a ubiquitous wireless access environment. CR-enabled secondary users (SUs) exploit spectrum white spaces opportunistically and immediately vacate the acquired licensed channels as primary users (PUs) arrive. Accessing the licensed channels without the prior knowledge of PU traffic patterns causes severe throughput degradation due to excessive channel switching and PU-to-SU collisions. Therefore, it is significantly important to design a PU activity-aware medium access control (MAC) protocol for cognitive radio networks (CRNs). In this paper, we first propose a licensed channel usage pattern identification scheme, based on a two-state Markov model, and then estimate the future idle slots using previous observations of the channels. Furthermore, based on these past observations, we compute the rank of each available licensed channel that gives SU transmission success assessment during the estimated idle slot. Secondly, we propose a PU activity-aware distributed MAC (PAD-MAC) protocol for heterogeneous multi-channel CRNs that selects the best channel for each SU to enhance its throughput. PAD-MAC controls SU activities by allowing them to exploit the licensed channels only for the duration of estimated idle slots and enables predictive and fast channel switching. To evaluate the performance of the proposed PAD-MAC, we compare it with the distributed QoS-aware MAC (QC-MAC) and listen-before-talk MAC schemes. Extensive numerical results show the significant improvements of the PAD-MAC in terms of the SU throughput, SU channel switching rate and PU-to-SU collision rate.
Highlights
In the recent years, wireless communications and their applications have gained exponential growth, which has raised the demand for radio spectrum resources
We investigate a primary users (PUs) activity-aware distributed medium access control (PAD-MAC) protocol for multi-channel heterogeneous cognitive radio networks (CRNs) with the objective of fully utilizing the advanced capabilities provided by Cognitive radio (CR) to optimize network performance and avoid harmful interference with PUs
We have proposed a MAC protocol (PAD-MAC) that utilizes multiple licensed channels to improve CRN throughput and overall spectrum utilization
Summary
Wireless communications and their applications have gained exponential growth, which has raised the demand for radio spectrum resources. A study conducted in the major cities of the United States in 2002 showed that the radio spectrum below 1 GHz remains mostly unused for long periods of time [2]. The Federal Communication Commission (FCC) in the U.S has begun to consider more flexible uses of the radio spectrum. The aim of the Generation program of the Defense Advanced Research. Project Agency (DARPA) is to redistribute the allocated radio spectrum dynamically. Cognitive radio (CR) was introduced as the key technology for enabling dynamic spectrum access (DSA) [3] with the aim of providing a ubiquitous wireless access environment with seamless wireless connection [4,5]
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