Abstract

Abstract
The constant need of operators to ensure a high quality of service requires an adequate estimation of signal level in the service area. Drive Tests (DTs) are used to monitor signal level. Still this is an expensive task, not being able to cover all areas. A methodology to build complete path loss grids for a given site is proposed. Starting from available DTs measurements for certain pixels, path loss is estimated for the remaining ones by tuning a propagation model and extrapolating the path loss for neighboring pixels. This allows to provide a complete path loss estimation for the desired area around the cell.

Abstract
We propose to use Vehicular ad hoc networks (VANET) as the infrastructure for an urban cyber-physical system for gathering up-to-date data about a city, like traffic conditions or environmental parameters. In this context, it is critical to design a data collection protocol that enables retrieving the data from the vehicles in almost real-time in an efficient way for urban scenarios. We propose Back off-based Per-hop Forwarding (BPF), a broadcast-based receiver-oriented protocol that uses the destination location information to select the forwarding order among the nodes receiving the packet. BFP does not require nodes to exchange periodic messages with their neighbors communicating their locations to keep a low management message overhead. It uses geographic information about the final destination node in the header of each data packet to route it in a hop-by-hop basis. It takes advantage of redundant forwarding to increase packet delivery to a destination, what is more critical in an urban scenario than in a highway, where the road topology does not represent a challenge for forwarding. We evaluate the performance of the BPF protocol using ns-3 and a Manhattan grid topology and compare it with well-known broadcast suppression techniques. Our results show that BPF achieves significantly higher packet delivery rates at a reduced redundancy cost. © 2011 IEEE.