# Weight-Based PA-GPSR Protocol Improvement Method in VANET
## 2 Related Work  
At present, many research have been proposed to improve the selection of forwarding nodes for geographic location routing protocols. In the geographic perimeter stateless routing protocol (GPSR) proposed by [PERSON] et al. [14], the source node forwards the data packet to the neighbor node closest to the destination. When the source node does not find any neighbor node closer to the destination node, the perimeter forwarding strategy based on the right-hand rule is used for transmission. Due to its stateless routing, GPSR may encounter a situation where the route is disconnected and the message delivery fails. The GPSR+ predict protocol (GPSRJ+) proposed by [PERSON] et al. [15] uses the estimated future location of the neighbor node to select the next hop node and improves the greedy forwarding and perimeter forwarding strategies of GPSR. Both protocols regard the distance to the destination as the only indicator for forwarding data packets,which are prone to routing voids. [PERSON] et al. [16] proposed the MM-GPSR, which uses pre-defined \(\lambda\) parameters in greedy forwarding to control the communication area in which to find the next hop node and uses the minimum angle value in perimeter forwarding to select the next hop. However, its pre-defined parameters reduce the performance of the scheme. [PERSON] et al. [16; 17] proposed PA-GPSR, adding additional information to the location table, as well as using the rejection table and the most recent forwarding table to mark the nodes where routing voids occur to reduce the number of data retransmissions and achieve the purpose of reducing network overhead. However, PA-GPSR does not use basic routing indicators, such as link connectivity and relative speed, and the data packets copied in perimeter forwarding increase network overhead. The predictive geographic routing protocol (PGRP) proposed by [PERSON] et al. [18] selects the next hop according to the direction, predictive position, and angle of neighbors. The Kalman filter-predictive geographic routing protocol (K-PGRP) proposed by [PERSON] et al. [19] yields the Kalman filter as a prediction module in the PGRP routing protocol. The mobility prediction-based routing protocol (MPBRP) proposed by [PERSON] et al. [20] improved the greedy forwarding strategy and perimeter forwarding strategy based on predictive position. These studies did not consider the impact of neighbor node density and link reliability. [PERSON] et al. [21] proposed the weighted greedy perimeter coordinator routing protocol (W-GPCR) based on weight selection, which calculates the next hop node in greedy forwarding and perimeter forwarding by considering the multi-parameter formula designed based on distance, direction, and neighbor node density. The research considers the influence of all neighbor nodes found in the communication range. The Hybrid Relay Node Selection Scheme for Message (HRNS) protocol proposed by [PERSON] et al. [22] uses message reachability, communication delay, and bandwidth utilization to select the next hop node, though while increasing the packet arrival rate, it also increases the end-to-end delay. The Geo-LU proposed by [PERSON] et al. [23] selects the next hop node based on the two-hop neighbor information, the minimum remaining bandwidth, and its packet loss rate. The trust-based geographic routing protocol for VANETs (TGRV) proposed by [PERSON] et al. [24] uses trust to evaluate the packet forwarding rate while considering the distance, speed, and direction of neighbors, and it selects the next hop node based on the information and trust of the two-hop neighbors. The smart forwarding method-based data dissemination protocol (SFTD) proposed by [PERSON] et al. [25] evaluates the link quality based on the link duration and the received signal strength indication and selects the next hop node. [PERSON] et al.