Road-vehicle Communication Systems Research Articles

Performance Evaluation of Inter-Vehicle Packet Relay for Road-Vehicle Communication in Fast Mobile Environment

In conventional road-vehicle communication systems, user terminals in the vehicles have to directly connect to wireless access points (APs). However, vehicle speeds are so fast that the channel condition between the terminals and the APs constantly changes because of changing path loss and time-varying fading. In this paper, to compensate for such deterioration, we propose to reduce the relative speed between the terminals and the APs by an inter-vehicle packet relay technique. If a terminal can send data via other vehicles running at lower speeds, the relative speed will decrease, which suppresses the dynamic range of path loss and deterioration by fading. We, first, validate our method by a numerical analysis using a statistical path-loss model. The numerical analysis verifies that our method is able to suppress deterioration caused by path loss and time-varying fading. However, in the numerical analysis, geometric propagation of paths is not considered; instantaneous and rapid loss changes are not considered. Therefore, we evaluate our method by computer simulations using a geometric propagation model. In the simulations, phase difference between multiple paths and loss fluctuation within one frame duration affect the performance. From the results of the simulations, we validate our method. Furthermore, we investigate the combination of our method and the selection diversity technique, which can suppress channel fluctuation and may enhance the performance of our method. Moreover, we measure interference in the overlapped zone between two AP areas. From the measurement, we show that our packet relays do not cause a problem in interference between areas.

Channel Quality Improvement by Inter-Vehicle Packet Relay in Road Vehicle Communication Systems

In road-vehicle communication systems, the transmission rate between user terminals in the vehicle and the access points degrades due to changing path-loss and time-varying fading. In this paper, we used an inter-vehicle packet relay technique to improve channel quality in road-vehicle communication systems. We evaluated this method using numerical analysis to validate our method.

Cyclic Shifted-and-Extended Codes Based on a Quasi-Orthogonal Sequence for a CDM Transmission Scheme

We have developed a code-division-multiplexing (CDM) transmission scheme for future road-vehicle communication systems, which uses cyclic shifted-and-extended (CSE) codes generated from a basic code with superior auto-correlation characteristics. This paper proposes to use a Quasi-Orthogonal (QO) sequence as the basic code. Its auto-correlation values are zero except at zero and middle shifts. When the CDM transmission is performed by the CSE codes based on the QO sequence, a desired correlation value is, at a receiver, interfered by the auto-correlation value at middle shift. Therefore, an elimination technique for the interfered correlation value is proposed and realizes zero cross-correlation characteristics within the cyclical shift interval. The new CDM transmission scheme based on the proposed scheme is evaluated by computer simulations in terms of the bit-error-rate performance.

Enhanced Soft-Handoff Scheme for Real-Time Streaming Services in Intelligent Transportation Systems Based on CDMA

Code division multiple access (CDMA)-based radio-on-fiber road-vehicle communication systems were proposed to support real-time streaming services in intelligent transportation systems (ITSs). Soft handoff should be provided for real-time streaming services because these services are required to guarantee real-time property and quality of service (QoS). However, soft handoff of real-time streaming services causes the shortage of resource in view of the system. In this paper, the double-adjustment soft-handoff (DASH) scheme is proposed to support seamless service regardless of the shortage of resource and maximize the resource efficiency when real-time streaming services are served in CDMA-based ITSs. The DASH scheme adjusts the data rate of a call when it starts and finishes soft handoff. The performance of the DASH scheme is evaluated by analytical and simulation methods. Performances are evaluated with respect to the blocking probability, the handoff failure probability, and the carried traffic. Numerical results show that the proposed scheme can give relative good maintenance of calls and good throughput.

Performance evaluation of soft handoff for multimedia services in intelligent transportation systems based on cdma

To support multimedia services in intelligent transportation systems (ITS), CDMA based radio-on-fiber road-vehicle communication systems were proposed. Soft handoff should be provided for multimedia services because these services are required to guarantee real-time property and quality of service (QoS). The performance evaluation of soft handoff is important in view of system management such as determination of optimal resource allocation, cell configuration, and admission strategy. But, the performance evaluation of soft handoff when multimedia services are serviced has not been previously researched, even though there have been some previous works for voice-call service. In this paper, we develop a new analytical model of soft handoff when multimedia services are served in CDMA based ITS. We evaluate the performance of soft handoff scheme by analytical and simulational method. Blocking probability, handoff failure probability and carried traffic are obtained.

A radio-on-fiber based millimeter-wave road-vehicle communication system by a code division multiplexing radio transmission scheme

A radio-on-fiber (ROF) based road-vehicle communication system is described in which several radio base stations (RBSs) communicate with a control station (CS) over ROF connections. The RBSs use the same millimeter-wave frequency band to communicate with mobile stations (MSs). The result is one large virtual cellular zone encompassing several RBSs controlled by one CS. However, in one virtual cellular zone, interference arises at the bound between adjacent cellular zones because the RBSs in each zone transmit their signals using the same frequency band. To minimize this interference, code division multiplexing is used to modulate the signals sent between the MSs and RBSs. Testing using an experimental course demonstrated that by using this system, we can achieve an error-free continuous communication system with a maximum transmission rate of 4.608 Mbps.

The Performance of Fiber-Radio Road Vehicle Communication System with Macro-Diversity

This paper proposes a road-to-vehicle communication system based on fiber-radio extension link (FREx link). Since the proposed road-to-vehicle communication system interconnects a cell control station with base stations by FREx link, optical fiber link noise should be taken into account to evaluate the system. This paper analyzes the outage probability and frequency utilization efficiency performance of the fiber-radio road-to-vehicle communication system with macro-diversity. It also shows that the proposed system with macro-diversity can improve performance, although it should be designed with the effect of optical fiber link noise in mind.

Road vehicle communication system for vehicle control using leaky coaxial cable

A new road vehicle communication (RVC) system that provides continuous communication between vehicles and control centers using a leaky coaxial cable is presented. The system operates in the quasi-microwave band providing high-quality communication through a well-designed communication protocol. An experimental setup and future directions are also included in this article.