车载网络概述及相关路由算法分析
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车载网络综述及相关路由算法分析
Overview of V ANET and analysis of relevant routing algorithm
软网1301 王建帮 201192181
软网1301 张凯源
1车载网络综述
1.1相关概念
随着相关技术的发展,越来越多的无线设备开始被应用在汽车上,如远程钥匙、PDAs、
智能手机等,车载网络(英文术语为Vehicular Ad hoc Network,即VANET)的概念因而被
提出。在Vehicular ad hoc networks(VANETS):status, results, and challenges一文中,作者从
以下四个方面对VANET作出了较为全面的阐述:
1)Intelligent transportation systems (ITSs)
VANET中节点可分为vehicles和Roadside Units(RSUs), 它们各自都有接收,存储,转发数据
以及路由的功能。两者区别在于,vehicles代表着移动的车辆,其位置是不断变化的,而
RSUs则是固定在路边的节点。
Fig. 1 Inter-vehicle communication
Fig. 2 Vehicle-to-roadside communication
Fig. 3 Routing-based communication
由于实际应用的需要,在ITSs中存在三种可能的通信结构(communication configure-tion):inter-vehicle, vehicle-to-roadside, and routing-based communication。这三者的实现都依赖于有关周围环境的精确且即时的信息,而要获取这样的信息,则需要精确的定位系统(如Bluetooth, Ultra-wide Band, ZigBee等)以及智能的通信协议(如GPS, DGPS)来提供支持。
2)Inter-vehicle communication
The inter-vehicle communication configuration (Fig. 1) uses multi-hop multicast/broadcast to transmit traffic related in- formation over multiple hops to a group of receivers.
3)Vehicle-to-roadside communication
The vehicle-to-roadside communication configuration (Fig. 2) represents a single hop broadcast where the road- side unit sends a broadcast message to all equipped vehicles in the vicinity.
4)Routing-based communication
The routing-based communication configuration (Fig. 3) is a multi-hop unicast where a message
is propagated in a multi-hop fashion until the vehicle carrying the desired data is reached.
1.2应用背景
Typically, applications are categorized as safety, transport efficiency, and information or enter-
tainment applications.
1)Road safety
For safety-related applications, the Vehicle Safety Communications (VSC) consortium identified
eight high potential applications : traffic signal violation warning, curve speed warning, emerg-
ency electronic brake light, pre-crash sensing, cooperative forward collision warning, left turn
assistant, lane-change warning, and stop sign movement assistant.
2)Transportation efficiency
For transportation efficiency applications, the Car-to-Car Communication Consortium (C2C- CC)
analyzed exemplarily enhanced route guidance and navigation, green light optimal speed advisory,
and lane merging assistants.
3)information and entertainment
Ideas for information and entertainment applications consist of quite a diverse set: tolling (one of
the initial motivators for vehicle-to-infrastructure communications), point-of-interest notifications,
fuel consumption management, podcasting, and multi-hop wireless Internet access, to name a few. 2路由算法简介
针对车载网络路由算法的研究已经持续了很多年,期间有不少创新、有效的成果被陆续提
出。相对于移动自组网(Mobile Ad hoc Network,即MANET)来说,车载网络具有网络
拓扑变化快,节点运动模式多样,车辆密度分布随时空动态改变,新增与删除节点速度快
等特点。因此若直接将以往为移动自组网设计的路由协议应用于车载网络中,显然是不合
适的。下面介绍的是在车载网络中讨论较多的三类路由算法:proactive routing protocols,
reactive routing protocols, position-based routing。
2.1 Proactive routing protocols
Proactive routing protocols employ standard distance-vector routing strategies (e.g., Destination-
Sequenced Distance- Vector (DSDV) routing) or link-state routing strategies (e.g., Optimized
Link State Routing protocol (OLSR) and Topology Broadcast-based on Reverse-Path Forwarding
(TBRPF)).They maintain and update information on rout- ing among all nodes of a given
network at all times even if the paths are not currently being used. Route updates are periodically
performed regardless of network load, band- width constraints, and network size. The main
drawback of such approaches is that the maintenance of unused paths may occupy a significant