Performance Evaluation of 2-Wavelength Cognitive Wireless Network for V2R and V2V Communication

Introduction

Mobility is one of the most important means for economic activity to safely and reliably carry persons, loads, feeds and other materials around world. So far, huge number of human operated cars have been produced and their quality and cost performance are improved year and year. Then, autonomous driving cars have been emerged and running on highways and major public streets on which are well maintained with ideal conditions, such as wide, flat road surface and clear visible center lines in urban area.

On the other hand, in winter season of cold weather countries such as Northern Japan, Northern America and Europe, most of the road surfaces are occupied with heavy snow and iced surface and many slip accidents occurred even though the vehicles attach anti-slip tires. In fact, more than 90% of traffic accidents in northern part of Japan is caused from slipping car on snowy or iced roads (Police Department in Hokkaido, 2018).

Those road state conditions would make difficulty for realizing high-level autonomous vehicle environment such as SAE5 (SAE International, 2018) and even for today’s ordinal driving environment due to increase of traffic accidents. Therefore, safer and more reliable road monitoring and warning system which can quickly transmit the road condition information to drivers and new self-driving system before passing through the dangerous road area are indispensable.

Furthermore, the information and communication environments in local or mountain areas, are not well developed and their mobile and wireless communication facilities are unstable along the roads compared with urban area. Thus, once a traffic accident or disaster occurred, collection, transmission and sharing of road state information are delayed or even cannot be made. Eventually the driver’s live and reliability cannot be maintained. More robust and resilient information infrastructure and proper and quick information service platform with road environmental conditions are indispensable.

In order to resolve those problems, various road sensing methods are possible to understand forward road surface condition using various environmental sensors. For example, road surface temperature or near infra-red laser sensor is a useful equipment to determine the road surface state such as icy, snowy or wet state by collecting and analyzing a set of those sensor data. Furthermore, those sensor data and the analyzed road state information have to be exchanged and shared with other vehicles in realtime by vehicle-to-vehicle (V2V) and vehicle-to-roadside (V2R) communication.

However, only single highspeed wireless network, such as 5G, Local 5G or the next generation Wi-Fi 6 does not provide good end–to-end V2V and V2R performance enough to keep the required performance even though those network provide high throughput and low latency. Usually in wireless network, it tasks longer time to establish the connection between the objective vehicles than the time to pass through one another even using single highspeed network. Eventually the both vehicles pass though without exchanging sensor data and analyzed road state information.

In order to overcome those difficulties, the authors propose an N-wavelength cognitive wireless network for V2V and V2R communication. Both wireless communications can be configured without any public wireless network. Our communication system is consisted of multiple wavelength wireless networks and organized as an N-wavelength wireless cognitive network which can select the best wave-length link to deliver data depending on the network condition and types of data. In typical, connection control data with the host and wireless communication system such as UUID, SSID, key, IP address are transmitted by the long wavelength (low frequency) wireless network from far a longer way while the actual accumulated sensor data are transmitted by short wavelength (high frequency) wireless network in a short distance. In general, the best wavelength wireless communication link is selected by monitoring the network states such as RSSI, bit error rate, packet loss rate, and considering the network performance such as throughput and delay.

In this paper, the authors focus to describe V2V and V2R wireless communication methods and their performance evaluation on field experiment in actual public road when the speed of vehicle is varied. Though the field experiment, the authors could conduct the result that our proposed method has reasonable performance to exchange road state information in actual road environment.