| Summary: | 博士 === 逢甲大學 === 資訊工程學系 === 103 === Current driving assistant systems are not just used for safety concerns only. Entertainment, data sharing, and advertisement are additional services offered by driving assistant systems, and these services are receiving considerable attentions. Many modern vehicles are equipped with various sensors to provide different information services in intelligent transportation systems. Data sharing has several problems to be solved, including data request and data dissemination. The data dissemination is used to broadcast the data in specific area or entire networks. Most studies on data dissemination schemes have focused on avoiding the problem of broadcast storm.
The major topic of this work consists of the hybrid geo and mobile grid scheme, data dissemination and sharing scheme, and service tracking protocol. In the hybrid scheme, geo grid scheme is the basis of our methods. The geo grid scheme is used to divide a map into grid structure. Each grid elects its grid header to manage the information of the grid. However, geo grid is limited in fixed grid size of the initial design, which may cause more cost for network maintenance. We design the mobile grid sequence (MGS) scheme as follows. The mobile grid structures utilize the characteristic of group mobility to increase the flexibility of grid structure and lower its maintenance cost. This scheme also designs inter-MGS data exchanging method to provide efficient data circulation in the mobile grid structures. In a mobile environment, the service provider is not fixed in a location. When the service provider moves to another location of the road, the users may need to perform the discovery process again.
The data dissemination and sharing scheme is based on a virtual backbone mechanism for vehicular communications. Coordinators store information and manage resource information in the backbone area. To reduce control packets for information exchange, headers can support effective resource management in mobile environments. The data structure design can create a local resource of routing table information based on a virtual backbone to locate and record resources. The tracking protocol is used to manage the service footprints information and keep tracking the target service. We choose a set of grid headers, called indicators, to manage the footprints. Indicators act as seigniors, which manage service providers in their territories. Corresponding users can easily find target services based on footprints if each service leaves its footprints on the branches.
In the experimental results, mobile grid sequences effectively extend the service time, and the information is reliably shared in mobile grid sequences. Data dissemination and sharing schemes are efficient and outperforms other schemes in terms of satisfactory ratio and download time. The service tracking scheme outperforms both AODV and the centralized scheme regarding the tracking success rate and service-tracking time.
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