A Data Dissemination Protocol for Vehicles with Temporary Cellular Network Inaccessibility

Abstract

The cellular network coverage in sparsely populated and mountainous areas is often patchy. That can be a significant impediment for services based on connections between vehicles and their environment. In this paper, we present a method to reduce the waiting time occurring when a vehicle intends to send a message via a cellular network but is currently in a dead spot without sufficient coverage. We use a hybrid network approach combining cellular network access with ad-hoc networks between vehicles that are nearby. In particular, we introduce a data dissemination protocol that allows the vehicles connected through an ad-hoc network to find out which one will most likely leave the dead spot first. Messages can then be sent to this vehicle that forwards them as soon as it regains cellular network access. Further, we developed an initial implementation of this protocol using the technology WiFi Direct that is realized on many mobile phones. Implementation details of the prototype as well as analysis results regarding data transmission time limits of fast driving vehicles are discussed in the article as well.

Utilizing Connectivity Maps to Accelerate V2I Communication in Cellular Network Dead Spots

“…Eltahir et al [5] use vehicles as relay stations such that a car in a dead spot may transmit messages via a number of other vehicles until reaching one that has cellular network access. In contrast to our approach [14], however, they neither allow to store data in vehicles nor to utilize their directions and positions in a dead spot. Therefore this approach can mitigate only smaller dead spots that contain sufficient traffic.…”

“…To reduce the waiting time for message transmissions between vehicles and their fixed infrastructure in areas where the cellular network coverage is weak, we developed a special data dissemination protocol [14]. In addition to the communication between vehicles and the infrastructure (V2I) via a cellular network, it uses short-lived ad-hoc vehicular networks (VANET) between close-by vehicles.…”

“…Also mountainous terrain makes the network coverage frail as mountains and hills tend to cause echoes deteriorating the radio reception [4]. Own tests showed that the size of dead spots in very remote areas like the Australian Outback can be really large and extend hundreds of kilometers (see [14]).…”

“…To mitigate the effect of dead spots, we developed a data dissemination protocol for the transport of data from vehicles to the fixed infrastructure [14]. When vehicles have no cellular network access, they build ephemeral ad-hoc networks with other cars in their area.…”

“…A problem to be solved by the data dissemination protocol, is to find out which vehicle in an ad-hoc network has the highest probability to leave the dead spot first. In the original version, we select the car that lost cellular network access first since, assuming similar average speeds, it is supposed to be also the first one having crossed the dead spot [14]. This approach is easy to realize since we only need local connectivity measurements in the vehicles.…”