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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.

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 [

In VANETs, traffic congestion is easy to happen [

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

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 [

Urban road system model [

Due to the fact that characteristics of VANETs are randomness and dynamic, multiple user interference model is established that node random arrived at some region, which can be regarded as stochastic point process. Using identical probability

Within communication coverage area of _{0} is

The multiple user interference [

According to stochastic geometry, we consider a Vehicular Ad Hoc network that has the following key properties.

In short, we introduce theories and properties of random geometric, by space accumulated interference model building in VANETs; it is seen that accumulated interference and outage probability increased with density of nodes, which lead to the network throughput decreasing significantly.

In this section, we consider a power control algorithm that sends data with a maximum power to make a deduction of the formula of outage probability and then adjusts transmission power on the basis of outage probability information of awareness [

SINR is shown as follows:

According to the above properties, when data is sent with a maximum power, outage probability is as follows:

Applying here with

We define

where B is bandwidth.

Adjust transmission power

From function (

Adjusting transmission power, we obtain

Then, the outage probability in a closed-form expression is as follows:

From (

Adjust behind transmission power of outage probability

Taking logarithm on (

By Holder’s inequality,

Applying here with

Calculating the derivatives of (

Function (

Here, we present some numerical results to evaluate the performance our proposed PC-OPA strategies. We compared the outage performance of the proposed strategies with that of WFPC (Water-Filled Power Control Algorithm) and NPC (Non-Power Control algorithm). Assume that simulation area is 2000 m

Simulation parameter setting.

Simulation Area | 2000m |

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Number of Vehicle | 0-160 |

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Transmission Distance | 100m-300m |

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Channel Bandwidth | 5-20MHz |

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Signal-to-Noise Ratio | 15-30dB |

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Doppler Frequency Shift | 100-300Hz |

In Figure

Path loss exponents for different environments.

Environment | Path Loss Exponent, |

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Free space | 2 |

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Urban area cellular radio | 2.7 to 3.5 |

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Shadowed urban cellular radio | 3 to 5 |

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In building line-of-sight | 1.6 to 1.8 |

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Obstructed in building | 4 to 6 |

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Obstructed in factories | 2 to 3 |

Power control exponents

Figure

Outage probability versus

Figure

Outage probability versus

In Figures

Outage probability for different algorithm versus

Outage probabilities versus distance.

The outage probability for different algorithm versus

In Figure

In Figure

The outage probability awareness algorithm is shown in Algorithm

1: set

2:

3:

4:

5:

6:

7:

8:

9:

Throughput for different algorithm versus

In this paper, to address these issues, such as random mobility of nodes, interference in multiusers, and high outage probability, we proposed a power control algorithm, called simply PC-OPA. The PC-OPA analyzes the situation of multiple user interference through stochastic geometry and then establishes relationship between outage probability and channel accumulated interference. At last, the aim of the PC-OPA is to minimize the outage probability. Further, the throughputs increase, while the outage probability declines. Our simulation results validated the derived expression and confirmed the feasibility of the proposed PC-OPA. It is shown that, in general, not all the terminals need to use their maximum power consumption to achieve the best outage probability. If all the terminals use their maximum power consumption, it is easy to increase cumulative interference. Therefore, based on CSI, the PC-OPA in this paper is proposed. The simulation results show that the outage probability of the PC-OPA decreased by 23% and the throughput is increased by 25%, compared to MPC and WFPC.

The data used to support the findings of this study are available from the corresponding author upon request.

The authors declare that they have no conflicts of interest.

This work was supported in part by the following projects: the National Natural Science Foundation of China through Grant 61571318, Guangxi Science and Technology Project (AC16380094, 1598008-29, and AA17204086), the Guangxi Nature Science Fund (2016GXNSFAA380226), Guangxi Nature Science Fund Key Project (2016 GXNSFDA380031), and Guangxi University Science Research Project (ZD 2014146).