# Weight-Based PA-GPSR Protocol Improvement Method in VANET
## 2 Related Work
[26] proposed reliable and efficient RSU-enabled relay vehicle selection protocol (ReUse) to select the next hop node based on various parameters, such as mobility, link quality, buffer size, and the number of neighbors. The Obstacle Prediction-Based Routing Protocol (OPBRP) proposed by [PERSON] et al. [27] uses mobility prediction and mobility to improve the prediction-based routing protocol to select the next hop node. The cross-layer enhancement of geographic routing protocol (Geo-CAP) proposed by [PERSON] et al. [28] considers the packet loss rate, physical interference, and media access control layer overhead to establish a link model and select the next hop node. The multi-criteria-based broadcast suppression scheme protocol (MCBS) proposed by [PERSON] et al. [29] uses multiple node attributes, including relative speed, traffic density, link stability, movement angle, and distance to the sender, to estimate the quality of the node and select the next hop node. A position-based reliable emergency message routing (REMR) protocol proposed by [PERSON] et al. [30] uses vehicle motion information (for example, position, speed change, and movement angle) to minimize possible link interruptions and select the next hop node. [PERSON] et al. [31] proposed a multi-intersection selection based on the probability routing protocol (MISP) of the road section connection. This protocol considers the distribution of vehicles affected by traffic lights and completes the data transmission by selecting the optimal path and the relay node in the road section. The trunk line based geographic routing protocol (TLBGR) proposed by [PERSON] et al. [32] uses the traffic flow of the trunk line and the surrounding road network to provide real-time data, and it completes the data transmission through the selection of the next intersection and the next hop of the selected path between the current and the next intersection. The improved road segment-based geographical routing protocol (ISR) proposed by [PERSON] et al. [33] divides the forwarding area into a number of road segments and selects a head node on each segment by focusing on the location, direction, and link quality-centric score for every vehicle on each road segment. These studies mainly consider node motion and channel state for link performance modeling to improve location-based routing protocols. These protocols are prone to routing voids in sparse networks, resulting in high transmission delay. In addition, the computational complexity of some studies is high and is not suitable for sparse network scenarios. The relay node selection mechanism of routing protocols can be divided into sender- or receiver-oriented protocols [34; 35]. Table 1 presents a summary of reviewed location-based routing protocols based on their taxonomy, with most of them considered to be sender-oriented protocols. \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline  
[21] & & & & & & \\ GRP & Urban & & & & & \\
[21] & & & & & & \\ HRNS & \begin{tabular}{c} Distance, traffic \\ load, speed, and \\ density \\ \end{tabular} & V2V & \begin{tabular}{c} Hybrid relay \\ node selection \\ scheme \\ \end{tabular} & – & & & & & \\ Geo-LU & Urban & \begin{tabular}{c} Residual \\ bandwidth and \\ link quality \\ \end{tabular} & V2V & \begin{tabular}{c} Two-hop \\ information- \\ based greedy \\ forwarding \\ \end{tabular} & – & & & & \\ TGRV & Urban & \begin{tabular}{c} Distance, speed, \\ direct trust, \\ recommendation \\ trust, and \\ direction \\ \end{tabular} & V2V & \
\begin{tabular}{c} Trust-based \\ greedy \\ forwarding \\ \end{tabular} &
\begin{tabular}{c} Packet delivery \\ rate, delay, and \\ hop count \\ \end{tabular} \\ \hline \hline \end{tabular}
\end{table} 
Table 1: A summary of the reviewed location-based routing protocols.