现代有轨电车通信关键技术指标研究

有轨电车在国内蓬勃发展,对城市发展和行业进步起到了积极的促进作用,但有轨电车行业目前还未能发布全国统一的行业规范,对比现行的《江苏省有轨电车工程技术规程》、《上海有轨电车工程设计规范》及《有轨电车交通工程技术标准(报批稿)》3部行业规范中的通信篇章,并针对其中通信的关键技术指标进行分析,研究有轨电车行业通信技术发展趋势。     

Analytical model for information flow propagation wave under an information relay control strategy in a congested vehicle-to-vehicle communication environment

Vehicular traffic congestion in a vehicle-to-vehicle (V2V) communication environment can lead to congestion effects for information flow propagation. Such congestion effects can impact whether a specific information packet of interest can reach a desired location, and if so, in a timely manner to influence the traffic system performance. Motivated by the usefulness and timeliness of information propagation, this paper aims to characterize the information flow propagation wave (IFPW) for an information packet in a congested V2V communication environment under an information relay control strategy. This strategy seeks to exclude information that is dated in the communication buffer under a first-in, first-out queue discipline, from being relayed if the information flow regime is congested. It trades off the need to enable the dissemination of every information packet as far as possible, against the congestion effects that accrue because of the presence of multiple information packets. A macroscopic two-layer model is proposed to characterize the IFPW. The upper layer is formulated as integro-differential equations to characterize the information dissemination in space and time under this control strategy. The lower layer adopts the Lighthill-Whitham-Richards model to capture the traffic flow dynamics. Based on the upper layer model, a necessary condition is derived which quantifies the expected time length that needs to be reserved for broadcasting the information packet of interest so as to ensure the formation of an IFPW under a given density of V2V-equipped vehicles. When the necessary condition is satisfied under homogeneous conditions, it is shown that the information packet can be propagated at an asymptotic speed whose value can be derived analytically. Besides, under the proposed control strategy, only a proportion of vehicles (labeled asymptotic density of informed vehicles) can receive the specific information packet, which can be estimated by solving a nonlinear equation. The asymptotic IFPW speed, the asymptotic density of informed vehicles, and the necessary condition for the IFPW, help in evaluating the timeliness of information propagation and the influence of traffic dynamics on information propagation. In addition, the proposed model can be used to numerically estimate the IFPW speed for heterogeneous conditions, which can aid in the design of traffic management strategies built upon the timely propagation of information through V2V communication.     

Accurate and cost-effective traffic information acquisition using adaptive sampling: Centralized and V2V schemes

The new generation of GPS-based tolling systems allow for a much higher degree of road sensing than has been available up to now. We propose an adaptive sampling scheme to collect accurate real-time traffic information from large-scale implementations of on-board GPS-based devices over a road network. The goal of the system is to minimize the transmission costs over all vehicles while satisfying requirements in the accuracy and timeliness of the traffic information obtained. The system is designed to make use of cellular communication as well as leveraging additional technologies such as roadside units equipped with WiFi and vehicle-to-vehicle (V2V) dedicated short-range communications (DSRC). As opposed to fixed sampling schemes, which transmit at regular intervals, the sampling policy we propose is adaptive to the road network and the importance of the links that the vehicle traverses. Since cellular communications are costly, in the basic centralized scheme, the vehicle is not aware of the road conditions on the network. We extend the scheme to handle non-cellular communications via roadside units and vehicle-to-vehicle (V2V) communication. Under a general traffic model, we prove that our scheme always outperforms the baseline scheme in terms of transmission cost while satisfying accuracy and real-time requirements. Our analytical results are further supported via simulations based on actual road networks for both the centralized and V2V settings.     

基于随机网络演算的CBTC车-地无线通信时延分析

以往对城市轨道交通无线网络性能评估较多采用实验室仿真方法,该方法需要花费大量的时间和经济成本,给实际应用带来了很大的局限。提出一种能够分析车-地无线通信性能的理论方法——随机网络演算。通过随机网络演算对地铁CBTC无线业务分析并建立相应的业务到达模型和信道服务模型,根据随机网络演算的理论知识,推导出车地无线通信的时延边界,最后运用MATLAB工具对理论结果和仿真结果进行对比验证。通过对理论结果和仿真结果对比分析,可得两者误差相对较小,从而得出基于MGF的随机网络演算是可以分析CBTC车-地无线通信时延的结论。     

加快推进我国交通一体化发展的建议

本文首先提出推进我国交通一体化发展既是必然选择,也具备较好基础,其次分析目前我国交通一体化发展不足的主要制约因素,提出我国交通一体化的内涵和目标,并从基础设施一体化、客运服务一体化、货运服务一体化、天地一体的交通通信和信息支撑保障体系、区域交通一体化几个方面提出推进我国交通一体化的发展重点。     

重载铁路MESH自组网一跳节点空口碰撞算法

重载列车车车通信可以采用长距离自组网通信技术实现.基于TDMA原理,针对自组网过程中一跳节点间频点资源碰撞概率进行数学建模,提出重载铁路MESH自组网通信节点空口碰撞概率的计算方法,通过关键参数的设置即可计算出系统一跳节点间的碰撞概率,利用蒙特·卡罗方法,在MATLAB中进行统计学仿真验证,对系统设计及工程设计优化均有...     

对利用AP数据库排除车载无线电台干扰的研究

介绍CBTC系统的数据通信网,根据CBTC系统骨干网的双网特性,为轨旁AP建立2个AP数据库,与列车车头和车尾的2套车载无线电台相对应.车载设备中设计一个车载无线电台管理模块,利用轨旁AP数据库排除非法的无线干扰,实现无线覆盖区域间的越区切换,保证切换的安全性和稳定性.     

基于OTDM的铁路区间光纤通信系统复用电路设计

根据铁路区间通信的需求,本文提出一种基于OTDM(光时分复用)技术的铁路区间光纤通信系统的复用与解复用电路设计方案.对车站发送的同步码进行检测,根据检测结果实现各个无源光接口之间的时钟同步,实现了数据的复用与解复用,不同码率间的转换.试验结果表明设计具有可行性,可提供2M和64 k两种数据接口.     

铁路区间通信系统中的数字语音终端设计

针对目前铁路区间通信的需求,本文提出了一种铁路区间光纤通信系统.介绍了用于该系统的语音终端的设计,MC145481芯片的结构及功能设计,为满足语音终端数据处理和MC145481芯片时序要求的CPLD设计.     

轨道交通乘客信息系统车地无线传输方案设计与优化

本文简要介绍轨道交通乘客信息系统车地无线传输技术.分析车地无线传输工程应用中的几种外界干扰:同频干扰、多径干扰、其他电磁干扰,提出相应的抗干扰对策.提出轨旁AP布点设计原则以及部署方案,并提出优化建议.