# Intersection-Based Link-Adaptive Beaconless Forwarding in Urban Vehicular Ad-Hoc Networks
## 1 Introduction
However, if the duration for which relay vehicle acts as a default forwarder is too long, the chances of a relay vehicle moving out of the forwarding zone will be high and may lead to multiple relay vehicles forwarding redundant data packets at the same hop level. In addition, the urban traffic environment comprises several road intersections leading to roads with different directions, and a relay vehicle acting as default forwarder for long time can lead to data packets being forwarded in the wrong direction, hence resulting in either packet drops or longer routes to destination. Therefore, assigning an appropriate duration for the relay vehicles to stay in a default forwarding state is vital and using the geographic information of road intersections present in urban VANETs can greatly contribute towards solving the issue. This article proposes a receiver-based data forwarding protocol that uses geographic information of road intersections to assign a duration for which a relay vehicle stays in default forwarding state. The key contributions of the article are as follows:  
* A novel receiver-based data forwarding protocol called intersection-based link-adaptive beaconless forwarding for city scenarios (ILBFC) is proposed. ILBFC exploits geographic information of road intersections in limiting the duration for which a relay vehicle stays as a default forwarder. Also, the maximum duration for which a relay vehicle can be a default forwarder is fixed based on the maximum road length between the two road intersections. * An urban road traffic adaptive winner relay management scheme is employed, where the relay vehicle when acting as default forwarder decides on every data packet reception whether or not to continue as default forwarder. The decision is based on the relative geographic progress of current and previous relay vehicles towards destination. This is done with the aim to take into account the drastic decay in the speed of vehicles due to the road intersections and traffic signals encountered in urban VANETs. * The proposed ILBFC is then simulated in realistic traffic conditions and its performance is compared with other existing state-of-the-art routing protocols. The comparison is done in terms of three performance metrics: packet delivery ratio (PDR), average ETE delay, and a new metric called packet redundancy coefficient (PRC), where PRC gives a measure of routing protocol's ability to disseminate the data packet in unicast fashion. The rest of the article is organized as follows. Section 2 gives the background information highlighting various remote monitoring applications, characteristics of remote monitoring in urban environment, different aspects of routing, and an overview of receiver-based data forwarding in VANETs. Section 3 explains all the features of the proposed ILBFC protocol in detail. Section 4 analyzes the performance of ILBFC in comparison to routing protocols from existing state-of-the-art. Specifically, this section details the scenario setup, the performance metrics, and the routing protocols used in the comparisons, and provides an in-depth discussion of the simulation results. Finally, Section 5 concludes the paper.