A Beacon Transmission Power Control Algorithm Based on Wireless Channel Load Forecasting in VANETs.

Yuanfu Mo,Yajuan Guo,Dexin Yu,Jun Song,Kun Zheng,Cheng-Yi Xia

doi:10.1371/journal.pone.0142775

Abstract

In a vehicular ad hoc network (VANET), the periodic exchange of single-hop status information broadcasts (beacon frames) produces channel loading, which causes channel congestion and induces information conflict problems. To guarantee fairness in beacon transmissions from each node and maximum network connectivity, adjustment of the beacon transmission power is an effective method for reducing and preventing channel congestion. In this study, the primary factors that influence wireless channel loading are selected to construct the KF-BCLF, which is a channel load forecasting algorithm based on a recursive Kalman filter and employs multiple regression equation. By pre-adjusting the transmission power based on the forecasted channel load, the channel load was kept within a predefined range; therefore, channel congestion was prevented. Based on this method, the CLF-BTPC, which is a transmission power control algorithm, is proposed. To verify KF-BCLF algorithm, a traffic survey method that involved the collection of floating car data along a major traffic road in Changchun City is employed. By comparing this forecast with the measured channel loads, the proposed KF-BCLF algorithm was proven to be effective. In addition, the CLF-BTPC algorithm is verified by simulating a section of eight-lane highway and a signal-controlled urban intersection. The results of the two verification process indicate that this distributed CLF-BTPC algorithm can effectively control channel load, prevent channel congestion, and enhance the stability and robustness of wireless beacon transmission in a vehicular network.

Highlights

In an “active safety” system of a vehicular ad hoc network (VANET), intelligent vehicles cooperate to avoid dangerous situations and traffic accidents
When the size and generation rate of periodic beacon messages have been reduced to minimum values, the transmission power of periodic beacon messages must be adjusted to effectively decrease the wireless channel load, prevent channel congestion, and guarantee maximal network connectivity
(2) According to a comparison of the channel load that was obtained from the KF-BCLF algorithm and the predefined maximum and minimum threshold values, the beacon transmission power is adjusted when the fairness is satisfactory

Summary

Introduction

In an “active safety” system of a vehicular ad hoc network (VANET), intelligent vehicles cooperate to avoid dangerous situations and traffic accidents. From the standpoint of the channel load surrounding each vehicle, this load is influenced by the expected periodical information generation rate, average message size, configured transmission power, and channel fading conditions but is related to factors such as traffic flow, traffic density, and road incidents. Because a VANET does not have a central communications coordinator, a distributed algorithm must be employed to optimize the beacon message transmission power and ensure fairness among all nodes; otherwise, dangerous conditions may be created for surrounding nodes [46, 47]. When assigning the beacon transmission power, a suitable balance should be achieved to determine the optimal operating strategy The objective of this CLF-BTPC algorithm is to fairly assign the PA (assigned power) to every vehicle in a distributed manner while satisfying the condition that the CL around each vehicle is guaranteed to be within the predefined threshold range.

23. End if Algorithm 1 CLF-BTPC algorithm

Findings

Conclusion