# Intersection-Based Routing with Fuzzy Multi-Factor Decision for VANETs
## 1 Introduction  
The Vehicular Ad hoc Network (VANET) is created by applying the principles of the Mobile Ad Hoc Networks (NANETs) to the vehicle, which is an important part of the Intelligent Transportation System (ITS) framework [1, 2, 3]. VANET can be regarded as a special practical application of wireless ad hoc networks (Ad Hoc Network). However, due to the network characteristics of VANET, such as high dynamic topology, strict delay requirements, high mobility, predictable trajectory, unlimited energy, accurate positioning, etc., its application prospects are bright and broad. The research scope spans three traditional research fields of the intelligent transportation system, computer network, and wireless communication, which makes the research on VANET attach the attention of many academic and industrial circles. VANET is now generally divided into three types of networks, namely Vehicle-to-Vehicle (V2V) ad hoc network, Vehicle-to-Infrastructure (V2I) network, and Hybrid network [4, 5, 6]. The main task of VANET is to transmit the collected or received data in a timely and efficient manner; however, due to the constraints of the urban environment, data transmission and forwarding between vehicles can only proceed along existing roads, and the direction changes during the data transmission and the forwarding can only appear at intersections. Therefore, vehicle routing decisions largely depend on the data forwarding decisions at the intersection; the data forwarding decision at the intersection determines the forwarding direction and the road section of the data in the next stage, which affects the data delivery rate and delay rate of the overall routing, and it also affects the quality of the routing decision. It can be said to a large extent that the decision of intersection data forwarding determines the overall routing. The quality of a decision is affected by many factors, and if there are many factors, it is difficult to quantify them specifically in the process of evaluation and implementation. Moreover, it is difficult to give relative weight because it is difficult to judge the importance of the impact factors at the same level. The actual situation of humans evaluating things is that it is very difficult to estimate the real original value of each evaluation object, but it is easy to make a fuzzy evaluation of it with natural language, and it is easy to make a roughestimation of the relative size or the quality of its weight through a fuzzy number [7; 8; 9]. In this case, it is more appropriate to use the method of Triangular Fuzzy Number (TFN) for evaluation [10; 11]. TFN number is a method to transfer fuzzy and uncertain linguistic variables to definite values. Using TFN in the evaluation method can solve the contradiction that the performance of the evaluated object cannot be accurately measured, but it can only be evaluated by language. At intersections, there are many factors that affect the data forwarding decision, such as vehicle density, signal lights, destination location, road width (number of lanes), etc. Here, we select three factors including vehicle density, direction, and traffic to complete the decision making of the intersection. Firstly, a complete link is established in advance using vehicle speed between every two adjacent intersections, if it exists. Secondly, using a triangular fuzzy number, each intersection node determines the next road segment after fuzzing and defuzzifying the three factors received. Figure 1 shows the architecture of this scheme. We assume that data transmission among vehicles with IEEE 802.11p and the next-hop vehicle selection is based on the contact time. The base station (BS) provides the traffic information to the roadside unit (RSU), and the RSU determines which road segment the packet should be forward to. The following content of the article is as follows. In Section 2, the related works are described. In Section 3, the details of the scheme proposed are elaborated.