Advances in Multimedia

Volume 2018, Article ID 8729645, 8 pages

https://doi.org/10.1155/2018/8729645

## A Power Control Algorithm Based on Outage Probability Awareness in Vehicular Ad Hoc Networks

^{1}College of Information and Communication, Guilin University of Electronic Technology, Guilin, Guangxi 541004, China^{2}College of Electronic Information and Automation, Guilin University of Aerospace Technology, Guilin, Guangxi 541004, China

Correspondence should be addressed to Yun Li; moc.qq@53293744

Received 30 March 2018; Revised 14 June 2018; Accepted 5 July 2018; Published 1 August 2018

Academic Editor: Shih-Chia Huang

Copyright © 2018 Xintong Wu et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

#### Abstract

This paper addresses the problem of adaptive power control based on outage probability minimization in Vehicular Ad Hoc Networks (VANETs), called a Power Control Algorithm Based on Outage Probability Awareness (PC-OPA). Unlike most of the existing works, our power control method aims at minimizing the outage probability and then is subject to the density of nodes in certain area. To fulfill power control, cumulative interference is assumed to be available at the transmitter of each terminal. The transmitters sent data by maximum power and then get the cumulative interference-aware outage probability. Furthermore, we build the interference model by stochastic geometric theory and then derive the expression between outage probability and cumulative interference. According to the expression, we adjust the transmitter power and optimize the outage probability. Simulation results are provided to demonstrate the effectiveness of the proposed power control strategies. It is shown that the PC-OPA can achieve a significant performance gain in terms of the outage probability and throughputs. Comparing MPC (Maximum Power Control algorithm) and WFPC (Water-Filled Power Control algorithm), the proposed PC-OPA decreased by 23% in terms of the outage probability and increased by 25% in terms of throughputs.

#### 1. Introduction

Vehicular Ad Hoc Networks (VANETs) are a promising intelligent transportation system technology that offers many applications such as traffic and congestion control, safety assistance, and autodriving, all of which will drastically change and provide tremendous benefits to our lives [1–5]. The key technologies for VANETs, called Vehicle-to-Vehicle (V2V) communication, involve the networking of vehicles and other communication devices, e.g., roadside units (RSUs). Power control is the key to maintain the better connectivity of networks among devices, which is used for VANETs. However, unlike the current mobile ad hoc networks, VANETs have a lot of characteristics, such as broadcasting, random node mobility, time-space uncertainty transmission, and interference [6–8]; this makes VANETs more challenging. For example, when the transmitter with the maximum power control sends the data, in certain area big density of nodes brings more interference to the receiver, which results in high outage probability. Addressing this issue, a Power Control Algorithm Based on Outage Probability Awareness, simply named PC-OPA, is proposed.

In VANETs, traffic congestion is easy to happen [9–11]. When congestion happens, more density of nodes results in more interference, which leads to high outage probably. Furthermore, the retransmission results in more consumption, which leads to the poor connectivity in VANETs. If the high channel capacity is pursued, the probability of collision is greater. Therefore, compared to traditional power control algorithm, the PC-OPA aims at the optimal outage probability regardless of the optimal channel capacity. In [12], Power Control based on Broadcasting Messages (PCBM) algorithm is proposed, in which the transmission power is adjusted according to the distance of the nodes. Further, the broadcasting area of nodes is restricted, which reduces the interference among nodes. However, the constant position in nodes is hard to get due to the random mobility in nodes. Therefore, PCBM algorithm has rarely considered the random mobility in reality environment. In [13], in highway scene, Power Control based on Roadside Unit (PSRSU) algorithm is proposed, in which the aim is to be sure of connectivity in nodes of one side. However, Roadside Unit (RSU) costs more. When the congestion happens, PCRSU algorithm is not good to solve the question of more interference because of the more density. In [14], Power Control based on Beacon (PCB) algorithm is proposed, in which action time of driver and access collision in nodes are considered. In long distance communication, the peak power control algorithm based on L beacon is used to obtain the SINR, whereas in short distance communication the minimum power control algorithm based on S beacon is used to satisfy the SINR. According to the communication distance, in PCB algorithm, difference beacon is selected to be adaptive to VANET. Therefore, PCB algorithm is widely used. However, when the speed of a vehicle is very fast, the power in transmitter is used more, which leads to more communication areas. Further, multiuser interference is serious due to more high density in nodes, which leads to high outage probability. At present for more interference of multiusers few powers control algorithm is considered.

In this paper, the performance of improvement of the proposed power control algorithm is achieved in terms of reducing cumulative interference of multiusers. Based on the stochastic-geometry theory in receiver the spatial user interference model is built. Further, the expression of outage probability is deduced. After the outage probability awareness, the transmitter adjusts the power. At last, PC-OPA is subject to obtaining the optimal outage probability and good throughput.

The rest of this paper is organized as follows. Section 2 discussed the related work on the system model, as well as its usage in the analysis of VANETs characteristics. Section 3 describes the mechanism of PC-OPA. Simulation results and the validation of the proposed matching mechanism are presented in Section 4. Finally, concluding remarks are given in Section 5.

#### 2. System Model

VANETs have the obvious characteristics such as randomness and dynamics which makes interference of multiuser difficult to find. Therefore, multiuser’s interference in power control of VANETs is rarely considered. Addressing this issue, the expression about interference is needed to describe the relationship between interference and outage probability, which is the theoretical support for power control algorithm. Therefore, according to the randomness, stochastic-geometry theory is applied to build the system model and then deduce the expression [15, 16]. In Figure 1, we present the model of urban road system.