# Intersection Routing Based on Fuzzy Multi-Factor Decision for VANETs
## 2 Related Work
More and more researchers proposed protocols considering urban traffic characteristics and intersections. The shortest-path-based traffic-light-aware routing (STAR) protocol [13] considers the status of traffic lights. In STAR, packets are attempted to forward to a connected road segment based on the status of traffic lights. Similarly, the intersection-based connectivity aware routing (iCAR) [14] obtains the road connectivity proactively and decides the next intersections by evaluating the lifetime of a link based on real-time traffic information. However, both STAR and iCAR only consider the traffic conditions of the current road segment and ignore the subsequent routing. The infrastructure-based connectivity aware routing (iCAR-II) [15] not only adopts the intersection-based connectivity-aware routing, but also makes the routing direction based on the global network topology. The strategy of iCAR-II is to construct a global network topology by predicting the network connectivity and update location servers with real-time network information. It then selects the shortest path from source to destination. Though iCAR-II enables multi-hop vehicular application, it also loses packets when roads are disconnected. Furthermore, based on the name of iCAR-II, it is known that iCAR-II is very dependent on infrastructure. The notable DTN vehicular routing protocols are VADD and GeOpps. In vehicle-assisted data delivery (VADD) [16], each vehicle maintains a matrix of estimated delay based on the information of the distance between intersections and the vehicular density on the road. Then, the routing path is decided by the delay matrix. The enhancement of VADD is called static-vehicle assisted adaptive data distribution protocol in VANETs (SADV) [17] and SNs are employed at intersections to store-and-forward packets in due time. Geographical opportunistic routing (GeOpps) [18] determines a vehicle which is closer to the destination based on a navigation system. It calculates the shortest distance from the packet's destination to the nearest point (NP) and estimates the arrival time to the destination. During the travel of vehicles, if there is another vehicle that has a shorter estimated arrival time, the packet will be forwarded to that vehicle. The process repeats until the packet arrives at the destination. The GeOpps was equipped with local infostations at the intersections. The traffic-aware routing protocol (TAROC) [19] proposed a cooperative collection method. A real-time traffic condition map is drawn by cooperation between information aggregators at intersections and information collectors on road segments, and a data route with a weight score is constructed. While many geographic routing protocols have been proposed, all of them forward the packets based on the greedy forwarding strategy, which means the packet should be forwarded as far as possible inside the range of communication radio. However, as we know, the biggest characteristic of the VANETs is the high mobility, meaning the link is easily broken. The biggest advantage of the greedy forwarding strategy is that it reduces the hop counts, but the link break rate is increased. The link should be recovered or rebuilt when the link is broken. At that condition, the hop counts must increase and more time must also be spent. Due to the fact that the routing decision is made at the intersection, the packet forwarded should return the last intersection along the road segment and find another route if the link is unconnected between two intersections. Therefore, if the vehicles know the connection status in advance, the vehicles can choose the best segment to forward the packets such that the hop count can be reduced. In addition, most of the existing proposals only consider a single factor, such as velocity. This is another reason why the link is fragile and easy to break. In recent years, more and more researchers have focused on fuzzy routing protocols.