S Kamakshi, V S Shankar Sriram
Centre for Information Super Highway (CISH), School of Computing, SASTRA Deemed University, Thanjavur, Tamil Nadu 613401, India.
Sensors (Basel). 2019 May 12;19(9):2191. doi: 10.3390/s19092191.
"Vehicular Ad-hoc Networks" (VANETs): As an active research area in the field of wireless sensor networks, they ensure road safety by exchanging alert messages about unexpected events in a decentralized manner. One of the significant challenges in the design of an efficient dissemination protocol for VANETs is the broadcast storm problem, owing to the large number of rebroadcasts. A generic solution to prevent the broadcast storm problem is to cluster the vehicles based on topology, density, distance, speed, or location in such a manner that only a fewer number of vehicles will rebroadcast the alert message to the next group. However, the selection of cluster heads and gateways of the clusters are the key factors that need to be optimized in order to limit the number of rebroadcasts. Hence, to address the aforementioned issues, this paper presents a novel distributed algorithm CDS_SC: Connected Dominating Set and Set Cover for cluster formation that employs a dominating set to choose cluster heads and set covering to select cluster gateways. The CDS_SC is unique among state-of-the-art algorithms, as it relies on local neighborhood information and constructs clusters incrementally. Hence, the proposed method can be implemented in a distributed manner as an event-triggered protocol. Also, the stability of cluster formation is increased along with a reduction in rebroadcasting by allowing a cluster head to be passive when all its cluster members can receive the message from the gateway vehicles. The simulation was carried out in dense, average, and sparse traffic scenarios by varying the number of vehicles injected per second per lane. Besides, the speed of each individual vehicle in each scenario was varied to test the degree of cohesion between vehicles with different speeds. The simulation results confirmed that the proposed algorithm achieved 99% to 100% reachability of alert messages with only 6% to 10% of rebroadcasting vehicles in average and dense traffic scenarios.
“车载自组织网络”（VANETs）：作为无线传感器网络领域一个活跃的研究方向，它们通过以分散方式交换有关意外事件的警报消息来确保道路安全。在为VANETs设计高效传播协议时，一个重大挑战是广播风暴问题，这是由于大量的重传所致。防止广播风暴问题的一个通用解决方案是以这样一种方式基于拓扑、密度、距离、速度或位置对车辆进行聚类，即只有较少数量的车辆会将警报消息重传给下一组。然而，聚类的簇头和网关的选择是需要优化的关键因素，以便限制重传次数。因此，为了解决上述问题，本文提出了一种新颖的分布式算法CDS_SC：用于聚类形成的连通支配集和集合覆盖算法，该算法采用支配集来选择簇头，并使用集合覆盖来选择簇网关。CDS_SC在现有算法中是独特的，因为它依赖于局部邻域信息并逐步构建聚类。因此，所提出的方法可以作为一种事件触发协议以分布式方式实现。此外，通过允许簇头在其所有簇成员都能从网关节点接收消息时处于被动状态，聚类形成的稳定性得以提高，同时重传次数也减少了。通过改变每条车道每秒注入的车辆数量，在密集、平均和稀疏交通场景中进行了模拟。此外，在每个场景中改变每辆车的速度，以测试不同速度车辆之间的凝聚程度。模拟结果证实，在平均和密集交通场景中，所提出的算法实现了警报消息99%至100%的可达性，同时只有6%至10%的车辆进行重传。
