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Using Heterogeneous Networks for Intersection Collision Avoidance

Abstract

Vehicular Ad-Hoc Network (VANET) is one of the most active research areas in ad hoc networks. In VANETs, each vehicle is equipped with wireless device so that it can communicate with other vehicles. With this capability, new applications targeting safety, entertainment, and better driving experience can be developed.

The most urgent applications that arise much attention are the vehicular safety applications. Most safety applications can be achieved by exchanging small data packets called beacons. Beacons contain the position information of vehicles. By analyzing the position information, a warning can be issued when a potential collision is identified.

However, some applications require warning messages to be disseminated multiple hops away, so a multiple hop data dissemination protocol is needed in these cases. To disseminate data efficiently, directional broadcast was proposed. The key idea is to select one relay node in each selected directions so that data can be propagated to all vehicles. However, it causes misclassification problem which results in inefficient and unreliable data propagation.

For intersection collision avoidance, new concerns need to be taken care of. In urban area, the wireless communication can be blocked by buildings around the corner. Previous research shows that the line-of-sight condition in urban area is not good enough for identifying potential collisions within sufficient time before impact. Therefore, a road side unit installed in the center of an intersection is necessary in order to rebroadcast beacons to vehicles around the intersection. This incurs additional cost of the deployment of VANET infrastructure.

The first part of this thesis explores the details of directional broadcast in terms of performance, and proposes a novel map-based directional broadcast protocol. We also incorporate a retransmission mechanism if transmission is regarded as failed to overcome the unreliable wireless communication. Store-carry-forward approach is used to increase the delivery ratio and efficiency. Moreover, we propose a solution to improve the safety of bicyclists using camera and DSRC. Simulations show that the map-based relay selection protocol can select relay nodes efficiently, and the retransmission combined with store-carry-forward approach increases delivery ratio significantly.

For intersection collision avoidance, the original plan of connected vehicle project includes the deployment of massive number of road-side units at intersections. Due to the cost, the deployment of road-side units has been indefinitely postponed. Without road-side units, data cannot be propagated well at intersections in urban area because the line-of-sight transmission could be blocked by buildings around the corner. Aiming on this, LTE has been proposed as an alternative to overcome this problem. We analyze and evaluate the possibility of using LTE for intersection collision avoidance service. Based on our study, LTE should be able to provide satisfactory delay and bandwidth for limited number of users. In order to improve the bandwidth usage, we propose a cluster architecture using both short range and long range communication technology. Meanwhile, a prioritization scheme can also be used to provide service to users who need it most. We envision a world with safe and entertaining journey in the future with the popularity of VANET applications.

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