Abstract

As vehicular communication becomes a widespread phenomenon, there will be an increase in spectrum scarcity. Cognitive radio provides an effective solution but requires a robust sensing mechanism that entails a large overhead; this additional sensing data could be detrimental to a system already lacking in bandwidth. This paper proposes novel ways of limiting sensing overhead by improving upon current methods which use cooperative mechanisms and adjustable double thresholds (DTHs). Based on a sliding variable, the proposed thresholds can react to changes in the environment, providing the required primary user detection and false alarm probabilities while limiting the number of vehicles reporting sensing data. Three new DTHs have been proposed: detection-based DTH, decision-based DTH, and independent-threshold DTH. Each has unique properties that make it suited for different environments. Simulations were run on all proposed thresholds to test their validity and endurance under environmental changes. The results indicate that the DTHs would greatly benefit high-contention, dense vehicular networks.

Highlights

  • D UE to recent advances in intelligent transport systems (ITSs), interest in vehicular communications research has increased

  • A model was built that simulated the system without considering how the primary user (PU) would change with time or how the sensing system would react to this

  • Various solutions have been proposed to solve a problem that could become very important as spectrum scarcity in vehicular environments increases

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Summary

Introduction

D UE to recent advances in intelligent transport systems (ITSs), interest in vehicular communications research has increased. Vehicular ad hoc networks (VANETs) generally use the IEEE 802.11p Wireless Access in Vehicular Environments standard to realize communication between vehicles [3]. This standard employs the carrier sense multiple access/collision avoidance protocol, meaning messages can be subject to collisions and losses when there is channel congestion. 75 MHz of dedicated spectrum, from 5.850 to 5.925 GHz, has been assigned for ITS purposes by the FCC [10] This is divided into seven 10 MHz channels: six service channels (SCH) for general purpose messages, and one CCH, which carries safety, coordination, and control messages [17].

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