Wireless Access In Vehicular Environment System Research Articles

Interference Rejection Combining Approach in Vehicle Communication Systems for Throughput Enhancement

In this paper, we present interference rejection combining scheme for interference suppression in wireless access in vehicular environments (WAVE) system. WAVE system performances depend on interference traffic since various signals and noises are present due to various vehicles on the road. The IRC scheme can minimize the interference presence from the received signal within the massive interference condition, resulting in the substantial gain of signal-to-interference and noise ratios (SINR) and performance. Based on the experiment of our proposed scheme, given the vehicle speed, SINR and different channel condition, our proposed scheme for interference suppression achieved significant improvements by 2 dB SINR performance gain in the low speed condition and above 0.5 dB performance gain at the high speed case. To extend our scheme for the comprehensive analysis, we also produced the vehicle speed and SINR performance map, which showed the performance pattern over vehicle speed and SINR of our scheme.

A Simulation-Based Analysis of the Loss Process of Broadcast Packets in WAVE Vehicular Networks

The IEEE 802.11p standard operates with the WAVE (Wireless Access in Vehicular Environments) system in vehicular ad hoc networks (VANETs). The broadcast process is used to send messages for safety and non-safety applications. A previous work on broadcast packets over the control channel proposes an analytical model to study the loss process. Even if such work does not consider all of the phenomena affecting the operation of vehicular networks, we can obtain a very good approximation of the performance that VANETs may exhibit. Regardless of its importance, this subject has been barely studied. Moreover, there is in the literature only a couple of contributions on this subject, being both analytical models. Therefore, we present in this paper an analysis of the loss process of broadcast packets on the control channel of VANETs over different scenarios. First, we consider a typical two-way scenario and then we analyze a scenario with intersections, both for different vehicle densities. We conduct a campaign of extensive simulations with the NS-3 simulator to study the average loss rate of broadcast packets, and then we compare our results with an analytical model proposed by Campolo et al. We prove the relationship among the contention window, the packet size, and the number of vehicles with the loss rate, including losses caused by noise, collisions, hidden terminal, and channel switching. Thus, we analyze the loss process validating the results obtained by Campolo et al. We find that there are additional factors affecting the loss rate, which cannot be captured with the analytical model. One key finding in this work is that the loss rate due to channel switching differs between both approaches. Also, we find bounds on the use of the control channel, with the loss rate and the traffic load in the network as parameters.

Safety Communication Based Adaptive Multi-channel Assignment for VANETs

Dedicated short-range communication technology has been proposed for wireless access in vehicular environment (WAVE) standard. With this technology, road users can benefit from utilizing inter-vehicle and infrastructure to vehicle communication services, which are crucial for enhancing road safety and facilitating efficient transportation. WAVE standard provides different channel assignment patterns. In addition to the baseline standard IEEE 802.11p, which provides continuous access channel operation, WAVE offers the MAC extension to support multi-channel operation with the standard IEEE 1609.4. By using standard channel assignments, WAVE system suffers from decreasing service performance especially for safety applications in the scenario with high vehicle density. Moreover, fixed channel assignment may not offer best solution for different traffic situations. This paper proposes a mechanism called safety communication based adaptive multi-channel assignment, which allows flexible multi-channel usage based on real-time communication traffic condition. Several test scenarios have been implemented and the system performance has been observed via simulations. The results show that our proposed method can optimize and maintain good system performance in all test cases, while other channel assignment mechanisms can only offer good performance for certain traffic conditions.

MAC 계층에서의 IEEE 802.11p 기반 WAVE 통신 시스템의 성능 평가

Vehicular communications have been receiving much attention in intelligent transport systems(ITS) by combining communication technology with automobile industries. In general, vehicular communication can be used for vehicle-to-vehicle(V2V) and vehicle-to-infrastructure( V2I) communication by adopting IEEE802.11p/1609 standard which is commonly known as wireless access in vehicular environment(WAVE). WAVE system transmits signal in 5.835~5.925 GHz frequency band with orthogonal frequency division multiplexing(OFDM) signaling. In this paper, after 32 bit processed the channel monitoring in MAC(Media Access Control) layer of WAVE system implemented according to IEEE 802.11p standard, data were received and we evaluated the performance, we built the test bed consisting of OBU(On Board Unit) in the real expressway. We transmitted WSM(WAVE Short Message) and received WSM between OBU wirelessly. And then, we calculated channel occupancy time per one frame and throughput, and evaluated the performance.

Design of u-Transportation Communication Systems for Next-Generation ITS Services

Next-generation ITS(Intelligent Transportation System) adopts WAVE(Wireless Access in Vehicular Environment) system which is capable of the bidirectional communication system in vehicular environments. u-Transportation system adopted WAVE communications system to show the optimal performance in terms of various services with regard to vehicle safety and traffic. In this paper, we introduce testbed of ubiquitous-Transportation system and its service. Then, we describe WAVE system for supporting next-generation ITS service. Also, we carried out tests in real road environments in order to verify communication functions of WAVE systems and its performance. We confirmed that our communication systems for supporting services meet the communication performance.

Performance Analysis of a Multi-Channel MAC with Dynamic CCH Interval in WAVE System

To improve the throughput performance of the Wireless Access in Vehicular Environment (WAVE) system, we propose a multi-channel MAC protocol that is able to adaptively adjust the intervals of Control Channel (CCH) and Service Channel (SCH) according to the probability distribution of the reservation time for service packet in CCH Interval. Numerical results show that our protocol can significantly improve the performance of WAVE system.

Mobility management of unicast services for wireless access in vehicular environments

Wireless Access in Vehicular Environments (WAVE) provides seamless and interoperable services for vehicles. In WAVE, the WAVE Short Message Protocol (WSMP) provides broadcast services but does not define unicast/multicast services that require mobility management to track the locations of the vehicles. To resolve this issue, this article proposes a location estimation-based mobility management mechanism by utilizing positioning systems (e.g., GPS) for a WAVE system deployed in highway environment with a large volume of high-speed vehicles. Performance study indicates that under the same paging cost, our approach can reduce 40-90 percent of the network traffic as compared with the traditional cellular mobility management approach.

Simulation Performance of WAVE System with Combined DD-CE and LMMSE Smoothing Scheme in Small-Scale Fading Models

This paper investigates the performance of IEEE 802.11p wireless access in vehicular environments (WAVE) system in small-scale fading models reported by Georgia Institute of Technology (Georgia Tech). We redesign the small-scale fading models to be applied to the computer simulation and develop the IEEE 802.11p WAVE physical layer simulator to provide the bit error rate and packet error rate performances. Moreover, a new channel estimator using decision directed channel estimation and linear minimum mean square error smoothing is proposed in order to improve the performance of the conventional least square channel estimator using two identical long training symbols. The simulation results are satisfactorily coincident with the scenarios of Georgia Tech report, and the proposed channel estimator significantly outperforms the conventional channel estimator.

Saturation throughput analysis of WAVE networks in Doppler spread scenarios

IEEE 802.11p, also known as wireless access in vehicular environment (WAVE), extends the applications of IEEE 802.11 to a fast fading vehicular communication environment. In WAVE systems, Doppler effect should not be ignored because of the high velocity of vehicles. Hence, in this paper the authors study the characteristics of physical layer WAVE system in the presence of the Doppler spectrum, such as symbol error rate performance and inter-subcarrier interference power. The throughput performance expression of a WAVE system is derived theoretically, which is the function of the frame size, number of the nodes, transmission probability, frame error rate and Doppler spread. Based on the obtained expressions, the optimal frame size, transmission probability and the number of nodes supportable in the WAVE system are derived to evaluate the maximum throughput performance. Finally, to validate the analytical results, simulations have been conducted to show the effectiveness of the proposed scheme.