18-12-2012, 05:29 PM
Cooperative download in vehicular environments
Cooperative download in vehicular.pdf (Size: 135.9 KB / Downloads: 41)
Abstract
We consider a complex (i.e., non-linear) road scenario where users aboard
vehicles equipped with communication interfaces are interested in downloading large
files from road-side Access Points (APs). We investigate the possibility of exploiting
opportunistic encounters among mobile nodes so to augment the transfer rate experienced
by vehicular downloader’s. To that end, we devise solutions for the selection of carriers
and data chunks at the APs, and evaluate them in real-world road topologies, under
different AP deployment strategies. Through extensive simulations, we show that carry &
forward transfers can significantly increase the download rate of vehicular users in
urban/suburban environments, and that such a result holds throughout diverse mobility
scenarios, AP placements and network loads.
Algorithm
Carrier’s selection algorithm
Contacts maps can be exploited by APs to select local cars as data carriers in the
cooperative download process, by retrieving their contact probability estimates with
respect to downloader vehicles. Firstly, it is necessary that APs know which cars in their
surroundings are interested in some content. Thus, every time a downloader vehicle
starts a production phase, the fact that it is requesting data, as well as the nature of the
desired content, is attached to the usual information on the production phase that the
local AP shares with other APs.
Existing System
The cooperative download of contents from users aboard vehicles, that
introduced SPAWN, a protocol for the retrieval and sharing of contents vehicular
environments. SPAWN is designed for unidirectional traffic over a highway, and is built
on the assumption that all on-road vehicles are active downloader’s of a same content.
Disadvantages:
1. Low Network Capacity.
2. Access only simple files not large files.
Proposed System
In this paper, we focus on one of the latter tasks, namely the download of largesized
files. We identified and proposed solutions to the problems of carrier’s selection
and chunk scheduling, and extensively evaluated them. The main contribution of this
work lies in the demonstration that vehicular cooperative download in urban
environments can bring significant download rate improvements to users traveling on
trafficked roads in particular.