Towards an Inter-vehicle Communication Algorithm
Abstract –– This article examines the potential role of wireless ad-hoc networks and the LORA-CBF routing algorithm for inter-vehicular communications in the context of optimizing traffic flow and increasing vehicular safety. The LORA-CBF algorithm is discussed in detail and preliminary test bed results are provided, followed by recommendations for future research. Finally, some reflections are offered on how to meet the challenges of implementing Vehicular Ad hoc Networks (VANET) in real-world conditions.
Keywords –– Inter-vehicular communication, Location Routing Algorithm with Cluster-Based Flooding (LORA-CBF), wireless ad-hoc Networks, Vehicular Ad-hoc Networks (VANET).
I. I NTRODUCTION
How to optimize traffic flow has been one of the primary challenges of specialists studying congestion and safety on streets and motorways because of the different economic, health and safety issues related to inefficient traffic circulation. Traditional solutions to address traffic congestion, caused in part by inefficient traffic flow, have proven largely temporary or ineffectual as between 1990 and 2000, highway travel times for personal vehicles increased in 70 of 75 important urban areas. [1]
Economic costs due to transportation delays are reflected in the billions of dollars spent on construction projects and the resulting loss of productivity caused by billions of man hours of lost time on the congested streets and freeways of major United States cities, not to mention health costs related to increased air pollution levels and fuel consumption of stationary automobiles. Presently, according to model simulations, the most common cause of transportation delay in the United States is vehicular accidents, representing nearly 40 percent of nonrecurring delays of freeways and principal arteries[1].
Although the economic costs are great, the human cost of vehicular accidents is staggering, as shown by the following United States Department of Transportation Bureau statistics for 2001, which recorded a total of 6,181,000 accidents, 3.1million injuries, and 45,130 fatalities [1]. I n 2004, an average of 117 people died each day in automobile accidents, or one person every 12 minutes. Total economic costs related directly to motor vehicle accidents cost the United States economy an estimated $231 billion dollars, $820 dollars per person or 2 percent of the Gross Domestic Product (GDP) [2].
Although passive safety systems such as seat belts and air bags have been used to significantly reduce the total number of major injuries and deaths due to motor vehicle accidents, they do not improve traffic flow or lower the actual number of automobile collisions. In order to actually lower the number of vehicular accidents, computer and network experts propose active safety systems, including Intelligent Transportation Systems (ITS) that are based on Inter-vehicle Communication (IVC) and Vehicle-to-Roadside Communication (VRC). Presently, technologies related to these architectures and their related technologies may, in the future, significantly optimize traffic flow, which, in turn, can have important economic and safety ramifications.
Active vehicular systems employ wireless ad-hoc networks and Geographic Positioning System (GPS) to determine and maintain the inter-vehicular separation necessary to insure the one hop and multi hop communications needed to maintain spacing between vehicles. Location based routing algorithms form the basis of any Vehicular Ad-hoc Network (VANET) because of the flexibility and efficiency they provide with regards inter-vehicular communication. Although several location-based algorithms already exist, including Grid Location Service (GLS), Location Aided Routing (LAR), Greedy Perimeter Stateless Routing (GPSR), and Distance Routing Effect Algorithm for Mobility (DREAM) to name a few.
This paper proposes a Location-Based Routing Algorithm with Cluster-Based Flooding (LORA-CBF) [3] as an option for present and future automotive applications due to the following two advantages:
?it employs local information to improve the traditional routing used in non-positional algorithms
?it minimizes flooding of its control traffic by using only the selected nodes, called gateways nodes, to disseminate its messages.
The rest of the paper is organized as follows: a brief introduction to inter-vehicle and vehicle to roadside communication is presented in section 2. The description of some vehicular ad-hoc network test beds is reported in section 3. The Location-Based Routing Algorithm with
Towards an Inter-vehicle Communication Algorithm R. A. Santos, A. Edwards, O. álvarez
College of Telematics, University of Colima, C.P. 28040, Colima, México Phone (312) 31-61075 Fax (312) 31-61075 E-mail: aquinor@ucol.mx
Cluster-Based Flooding (LORA-CBF) is explained in section 4. Section 5 describes the implementation of the LORA-CBF test bed. Details of the measurements and results made on the LORA-CBF algorithm are explained on Section 6. Finally, Section 7 discusses conclusions and offers suggestion for future research.
II. INTER-VEHICLE AND VEHICLE TO ROADSIDE
COMMUNICATIONS
The last half decade has witnessed an increased interest in inter-vehicle and vehicle to roadside communication, in part, because of the application, growth and proliferation of wireless networks. Most research in this area has focused on vehicle-roadside communication, also called beacon-vehicle communication [4-5].Some common applications for vehicle to roadside communications with limited communication zones of less than 60 meters include: Automatic Payment, Route Guidance, Cooperative Driving, Parking Management, etc.
The introduction of IEEE 802.11, along with technological advances related to wireless ad-hoc networks and location-based routing algorithms, makes vehicle-to-vehicle communication viable [6-8]. Applications for inter-vehicle communication include intelligent cruise control, maneuvering control, lane access and emergency warning systems, among others. Because network flooding is of major concern, the authors in [6] propose using Grid,which employs a geographic forwarding and scalable distributed location service to route packets from car to car. The authors
in [7] compare a topology-based approach and a location-based routing scheme. The authors chose Greedy Perimeter Stateless Routing (GPSR) as the location-based routing scheme and Dynamic Source Routing (DSR) as the topology-based approach. In [8], the authors compare two topology-based routing approaches, DSR and Ad-Hoc On-Demand Distance Vector (AODV), versus one position-based routing scheme, GPSR, in an urban environment.
The integration of on-board computers with wireless network capabilities in vehicles will, in the future, permit instantaneous communication between similarly equipped vehicles in their immediate area. By exchanging information related to different parameters, vehicles will be able to obtain information about the actual mechanical and safety conditions of the vehicle, as well as external factors such as traffic conditions, route alternatives, and additional GPS information related to the location of different public and private services, all of which will contribute to increasing driver comfort and safety.
The focus of this work is inter-vehicle communication because there are no existing standards for wireless inter-vehicle communication and because vehicle-roadside communication has already been proposed for standardization in Europe (CEN TC 278 WG 9)and North America (IVHS).
III. VEHICULAR AD-HOC NETWORK TEST BEDS Some test beds have been deployed to evaluate the performance of wireless networks for inter-vehicle communication [9-11]. Authors in [9] report deploying eight nodes within a 700m by 300m site, with each node running the Dynamic Source Routing (DSR) protocol. In this study, each vehicle was equipped with a Lucent Wave LAN Wireless LAN radio on the roof. The ad-hoc network included five moving car-mounted nodes. In this experiment, cars followed each other with a separation of 90m. Authors in [10] describe their experiences building a real-world ad-hoc network test bed using cars as mobile nodes. These cars were equipped with computing and communication devices. A position-based forwarding algorithm was implemented on Linux-based laptops to exploit position information gathered by on-board navigation systems supported by GPS. In [11] authors propose and incorporate improvements of the OLSR protocol. In this test bed, authors deploy a topology consisting of vehicles bearing laptop computers equipped with IEEE 802.11b compliant equipment. Experiments were conducted in a typical environment and routing performance was evaluated based on the UDP packet throughput and round trip time.
IV. LOCATION ROUTING ALGORITHM WITH
CLUSTER-BASED FLOODING (LORA-CBF) LORA-CBF is formed with one cluster head, zero or more members in every cluster and one or more gateways to communicate with other cluster heads. Each cluster head maintains a “Cluster Table,” which is a table that contains the addresses and geographic locations of the member and gateway nodes.
When a source attempts to send data to a destination, it first checks its routing table to determine if it knows the location of the destination. If it does, it sends the packet to the closest neighbor to the destination (Figure1). Otherwise, the source stores the data packet in its buffer, starts a timer and broadcasts Location Request (LREQ) packets. Only gateways and cluster-heads can retransmit the LREQ packet. Gateways only retransmit a packet from one gateway to another in order to minimize unnecessary retransmissions, and only if the gateway belongs to a different cluster-head.
Upon receiving a location request, each cluster head checks to see if the destination is a member of its cluster. Success triggers a Location Reply (LREP) packet that returns to the sender using geographic routing, because each node knows the position of the source and the closest neighbor based on the information from the LREQ received
and the Simple Location Service (SLS). Failure triggers retransmissions by the cluster head to adjacent cluster-heads (Reactive Location Service, RLS). The destination address is recorded in the packet. Cluster-heads and gateways, therefore, discard a request packet that they have already seen.
Figure 1: Flow diagram for LORA-CBF.
Upon receiving a location request, each cluster head checks to see if the destination is a member of its cluster. Success triggers a Location Reply (LREP) packet that returns to the sender using geographic routing, because each node knows the position of the source and the closest neighbor based on the information from the LREQ received and the Simple Location Service (SLS). Failure triggers retransmissions by the cluster head to adjacent cluster-heads (Reactive Location Service, RLS). The destination address is recorded in the packet. Cluster-heads and gateways, therefore, discard a request packet that they have already seen.
Once the source receives the location of the destination, it retrieves the data packet from its buffer and sends it to the closest neighbor to the destination.
Basically, the algorithm consists of four stages: 1. Cluster formation
2. Location discovery (LREQ and LREP)
3. Routing of data packets
4. Maintenance of location information
Similar work for cluster-based flooding can be found in [12]. The main difference is that in [12] the gateways are selected among the borders nodes. For internal traffic, just cluster-head and gateways should re-broadcast. Re-broadcasting by CH guarantees broadcast coverage inside the cluster because of 1-hop clustering considered in this method. Re-broadcasting the internal traffic guarantees
flowing the traffic to all the adjacent clusters because of the coverage of all adjacent clusters by the gateway selection method.
V. IMPLEMENTATION OF THE LORA-CBF
ALGORITHM TEST BED
We deployed LORA-CBF on a test bed using Linux and equipped each node with an Enterasys wireless card, employing sockets to allow the communication between neighbor nodes. Five laptops with ad-hoc routing capability and were deployed in an outdoor environment to represent a small-scale ad-hoc network. To validate LORA-CBF first statically (Figure 2), we compared LORA-CBF against the results of another wireless ad-hoc network test bed [13]. In [13], each node ran the Associativity-based routing (ABR) protocol. The ABR and LORA-CBF algorithms employed periodic beaconing to inform neighboring nodes about their presence and both used source-initiated on-demand ad-hoc routing protocols to discover routes. The main difference here is that ABR selects the route based on its longevity. On the other hand, LORA-CBF makes use of its predictive algorithm to select the best route based on the geographic locations of their neighbor nodes.
Figure 2. Test bed used in deploy LORA-CBF algorithm.
Figure 3. End-to-End Delay for one hop.
64100048856
Size of packets (bytes)E E D (m s )
64
1000
1448
Size of packets (bytes)
E E D (m s )
Figure 4. End-to-End Delay for two and three hops.
Figures 3 and 4 show 1, 2, and 3 hop results for LORA-CBF and ABR. Results show very similar behavior for the different packet sizes selected for the study. Each value on the graphs represents results for 100 packets sent with a margin of error of <15%. Discover time for the first hop is 0 seconds due to the Hello mechanism. For 2 hops, the discovery time is 1.6 seconds and for three hops, discovery time increases to 1.74 seconds due to route discover mechanism of the two algorithms.
VI. CONCLUSIONS AND FUTURE WORK
In the near future, automobiles may have factory installed wireless ad-hoc network capabilities to improve traffic flow and safety, in part, because it is more cost effective than continually undertaking massive construction projects, which are proving to have limited success. Consequently, future developments in automobile manufacturing will include new communication technologies to help provide more effective spacing and collision avoidance systems. In order to avoid communication costs and guarantee the low delays required for the exchange of safety-related data between cars, inter-vehicle communication (IVC) systems based on wireless ad-hoc networks represent a promising solution for future road communication scenarios, as it permits vehicles to organize themselves locally in ad-hoc networks without any pre-installed infrastructure.
LORA-CBF is an algorithm that can possibly be used in future wireless ad-hoc networks because of its reactive geographic routing algorithm, which employs GPS in conjunction with its predictive algorithm, both of which are necessary in mobile networks. Furthermore, LORA-CBF uses a gateway selection mechanism to reduce contention in dense networks, which is a predictable scenario in highly congested traffic conditions. Finally, the hierarchical structure of LORA-CBF facilitates its deployment as part of vehicular ad hoc networks because it requires minimal deployed infrastructure.
Future work related to the development of LORA-CBF will include the integration of GPS, predictive algorithms
and geographical maps into a sole architecture and deploy it on a test bed.
REFERENCES
[1] Transportation Statistics Annual Report. U.S. Department of
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[3] Santos, R. A., Edwards, A., Edwards, R. M. and Seed, N. L. (2005) ′performance evaluation of routing protocols in vehicular ad-hoc networks′, International Journal Ad Hoc and Ubiquitous Computing, vol. 1, nos. 1/2, pp. 80-91.
[4] Carl-Herbert Rokitansky and Christian Wietfeld. Comparison of Adaptive Medium Access Control Schemes for Beacon-Vehicle Communications . IEEE-IEE Vehicle Navigation & Information Systems Conference, 1993.
[5] G. Brasche, C. –H. Rokitansky, and C. Wietfeld. Communication Architecture and Performance Analysis of Protocols for RTT
Infrastructure Networks and Vehicle-Roadside Communications . IEEE 44th Vehicular Technology Conference, 1994.
[6] Robert Morris, John Jannotti, Frans Kaashock, Jinyang Li and Douglass De couto. CarNet: A ScalableAd-hoc Wireless Network System . In Proceedings of the 9th ACM SIGOPS European workshop: Beyond the PC: New Challenges for the Operating System, Kolding, Denmark, September 2000.
[7] Holger Fü?ler, Martin Mauve, Hannes Hartenstein, Michael K?semann and Dieter Vollmer. MobiCom Poster: Location-Based Routing for Vehicular Ad- Hoc Networks . ACM SIGMOBILE Mobile Computing and Communication Review, volume 7 issue 1, 2003.
[8] Christian Lochert, Holger Fü?ler, Hannes Hartenstein, Dagmar Hermann, Jiang Tian and Martin Mauve. A Routing Strategy for Vehicular Ad-hoc Networks in City Environments . IEEE Intelligent Vehicles Simposium, 2003.
[9] David A. Maltz, Josh Broch and David B. Johnson. Lessons from a Full-Scale Multihop Wireless Ad-hoc Network Testbed . IEEE Personal Communication, 2001.
[10] Michael M?ske, Holger Fübler, Hannes Hartenstein and Walter Franz. Performance Measurements of a Vehicular Ad-hoc Network. IEEE 59th Vehicular Technology Conference (VTC2004-spring), vol. 4, pp. 2116- 2120, 2004.
[11] Jatinder Pal Singh, Nicholas Bambos, Bhaskar Srinivasan and Detlef Clawinn. Proposal and Demonstration of Link Connectivity Assessment based Enhancements to Routing in Mobile Ad-hoc
Networks. IEEE 58th Vehicular Technology Conference (VTC2003- Fall), vol. 5, pp. 2834-2838.
[12] Reza Purtoosi, Hassan Taheri, Abbas Mohammadi, Foroohar
Foroozan. A High Performance Cluster-Based Flooding Algorithm for Wireless Ad Hoc Networks. Proccedings of the fifth International Conference on Computer and Information Technology (CIT′05). 2005. [13] C. –K. Toh, Minar Delwar, and Donald Allen. Evaluating the
Communication Performance of an Ad Hoc Wireless Network. IEEE Transactions on Wireless Communications, vol. 1, no. 3, July 2002.
福建省福州格致中学2014-2015学年高一上学期期中考试英语试题 Word版无答案
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春风送暖，如丝般的触感滑过脸际，送来温暖的气息。像圣洁的天使飘落的羽毛，又似冬日的火光映照着脸颊，勾起心底潜藏着的那暖暖的记忆。 “怦”，好险，好险。将将赶上这班车，不然，可又得等上半小时呢! “呼”，长舒一口气，抓好扶手。提着袋子，心头嘟囔：大夏天的还得去给表弟送书，什么世道，补课竟然都不带书，学的好才怪!心里愤愤的咒骂着。 “喂，我说这个女生，不想买票哟!”售票员不耐的声音总算唤回了我的神思。吐吐舌头，开始找钱包、掏钱、买票。等等!我钱包呢?糟了，莫不是跑得急忘在家里了?! 天哪，别开玩笑了。不过很可惜，上帝爷爷今天似乎睡觉去了，我全身上下摸不出一毛钱。 售票员看着我着急的样子冷笑着：“你这样的学生我见多了，什么‘钱包没带’‘钱掉了’的，我听得多了。小小年纪什么不学，学人家坐霸王车，害不害羞哟。撒起慌来脸都不红，羞不羞!” 我长这么大，什么时候被这样当众骂过。委屈的泪水一下子涌上了眼眶：“阿姨，对不起，我下车总行了吧。” “哟，装撒。现在的小孩哟，太会演了，怕是都已经到了要去的地方了吧。” 我咬着唇，拼命忍住眼里酸涩的泪水，自知理亏，也没办法反驳。 “阿姨，她是个女生，不过忘了带钱嘛，谁不没有点难处。你话也不能这样说啊。不就一块五嘛，我帮她买了。” 闻言侧头，身边是个和我差不多大的男孩儿。看着我，他轻轻眨了眨眼。清澈的目光既像关心，又像安慰，却更像春风拂过面庞，在炎炎夏日里带来阵阵温暖的清凉。眼里充盈的泪水，在此时，落了。 “谢谢，你叫什么名字。”我低低道着谢。 “呀，我叫什么呢?嗯，说‘雷锋’太老土了。有了!”他故意顿了顿，眼里满是狡黠，“我叫‘春风’。呵呵……” 春日，细雨蒙蒙。我望着窗外如丝般的雨，发着呆。忽的，我的童年记忆像一缕春风拂面而来，将我带回童年时代……
2020学年高一英语上学期期末考试试题(新版)新人教版
阜蒙县第二高中2017--2018学年度上学期高一期末考试 英语试卷 时间：100分钟总分：150分 第一部分：阅读理解（共两节，满分40分） 第一节（共15小题；每小题2分，满分30分） A A teenager needs to have a sense of independence in their life to feel secure （安全的）. To some teenagers independence means a lot to them, and I think that some parents don’t allow their teenagers enough independence. Independence has something to do with freedom. Some kids are not allowed to go anywhere alone, and the only thing their schedule includes is going to school, coming home, going to sleep, and repeating the process the next day. Parents tend to be afraid that their kids can get hurted if they go outside into the world. But if parents control their kids too much, they may never learn to live on their own. The best way for a teenager to learn lesson is through experience. I think it is beneficial for teenagers to have freedom. Teenagers’ lack of freedom can also stop them from having good friendship at school. Some might say that this is a good thing, because it helps them focus more on their school work. I argue that this can only discourage them not to do their school work. Some parents do not allow their children to be around their friends outside the school, thinking that this will get them into trouble. But I don’t think so. Instead, isn’t this a good reason for parents to get their children a cellphone? Cellphones allow teenagers to stay in touch with their parents, and communicate better with their friends. Privacy is another issue between parents and their teenagers. Teenagers tend to enjoy relaxation by themselves in their own room. This also gives them a sense of independence. It often annoys teenagers when their parents enter their room when they are not home. I know that my mom always goes in m y room when I’m not home, and this has brought me to the point where I have asked many times to get a lock on my door. 1. What is the main idea of the second paragraph? A. Kids know how to live independently. B. Some parents allow their kids no freedom. C. It benefits teenagers to have freedom. D. Kids have a dull routine every day 2. In the opinion of the author, ___________. A. parents should make it easy for kids to communicate with their friends B. good friendships between kids harm their school work C. it is unnecessary for a kid to have a cellphone D. kids should focus on the school work 3. How do teenagers usually feel when their parents enter their rooms in their absence?
小学语文教学论文 想象作文教学浅谈
小学语文教学论文：想象作文教学浅谈 作文是语文教学的重点，也是难点，而想像作文更是难中之难，小学生大都有“恐作症”，老师也常常为此头疼不已。那么怎样才能让学生在想象作文中有内容可写，有话可说呢？我认为可以从以下几方面训练。 一、观察现实生活，激发相关想象。 想像离不开现实，离开现实的想象是空洞的，无论哪一类想象作文都脱离不了现实生活。例如童话式想象作文，它是根据小学生喜爱动物的特点，用动物代替人类的形象来表达他们对世界的认识，在想像力作用下的动物附上了人的动作、语言、神态和思维。这类作文实际上是对现实的再现。 如想像作文“未来的×××”，这一类写未来生活的想象作文对学生而言有难度。未来是什么样的，学生除了接触到一些科幻片、科幻小说以外，其他的十分抽象，不知如何写。教师可引导学生仔细观察现实生活，展开想像的翅膀。例如现在的房屋，一旦完工，它便固定下来。如果让学生大但想象，让未来的建筑由一个个组装件构成，根据不同的需要进行不同的组合，这样既适合不同人的需求，又便于搬迁、移动，还可以维修，那该多好。又如当看到学校操场只有一处，空间过于狭小时，可以引导学生想象地下或空中操场，用电梯或升降机来回启用……这些现实中人们追求的更加便捷、完美的东西，都可以大胆想象它的样子、形状、功能。如果激发了学生想象的火花，那么展现在学生面前的空间不知有多大！ 二、结合课文内容，进行再造想象。
课文是学生学习文化知识的重要材料，也是学生写作的典型范例。教师可充分利用课文资源，结合课文内容，让学生练习改写、续写、扩写等想象性作文，是一种行之有效的再造想象途径，能有效提高学生的想像能力。 例如《凡卡》一文，当凡卡满怀希望地把信寄出去后，爷爷能收到吗？爷爷在乡下会怎样想念凡卡呢？小凡卡后来的命运又会如何呢？让学生大胆去想象，续写出符合事情发展的故事，这样既加深了对课文内容的理解，又激活了学生想象的火花。 另外，还可以根据文中的插图进行补充或扩写。如《我的战友邱少云》一文在的插图，邱少云被烈火烧身时的巨大痛苦，是通过作者的心理活动侧面描写的，那么邱少云的心理感受会怎样呢？可引导学生观察他的神态、动作进行想象。 三、填补一些空白，设置整体形象。 在教学中选取一些相关的事物或词语，让学生进行整合，填补其中的空白，也是提高学生想象能力的重要手段。例如：画下几种不同的小动物，让学生按照自己的思维说出它们之间的关系，并想象出这些小动物之间会发生什么样的故事，然后进行口述表演，这样激起学生的童趣，他们的想象力就会更活跃。或者随便写下几个词语，让学生编上一段故事，用上这几个词语。这类填空白的训练，可以让学生的想象能力得到逐步提高。坚持长期训练，会收到意想不到的效果。 总之，学生作文能力的提高与教师的训练密不可分。我们应该在平时的作文教学中善动脑子，力求科学、有效，为学生作文插上想像的翅膀，让他们飞得更高、更远。