# A Geographical Heuristic Routing Protocol for VANETs
## 2 Related Work  
Heuristic optimization techniques have been used in some works to improve the operation of routing protocols. In [10], the authors propose a new routing protocol called the Tabu Search-based Routing Protocol (TSRP), which introduces an implementation of the Tabu search meta-heuristic to avoid nodes previously selected in the routing process of the data from the sensor (that has previously sensed the event) to the sink. TSRP is based on maximizing the cost function, which considers the energy and the visibility of that sensor compared to the sink. TSRP keeps a 0/1 string that indicates whether a node forwarded a packet or not. Simulation results show that TSRP extends the network lifetime compared to the protocols Gossiping [11] and MFR [12].  
The authors in [13] propose a routing optimization algorithm to minimize the route cost from a source to a destination within a reasonable time. The proposed algorithm is designed by using a tabu search mechanism that is a representative meta-heuristic algorithm. The tabu search algorithm carries out two neighborhood-generating operations in order to determine an optimal path and minimize algorithm execution time. The proposed tabu search algorithm is compared with other meta-heuristic algorithms, which are the genetic algorithm and simulated annealing, in terms of the routing cost and the algorithm execution time. The comparison results show that the proposed tabu search algorithm outperforms the other algorithms and that it is suitable for adapting the routing optimization problem.  
The optimal parameter setting of the Optimized Link State Routing (OLSR) is analyzed in [14], also as an optimization of routing in ad hoc networks. The authors use a series of representative meta-heuristic algorithms (particle swarm optimization, differential evolution, genetic algorithm and simulated annealing) in order to find automatically optimal configurations of this routing protocol. This study is focused on VANETs and is tested with realistic scenarios based on the city of Malaga. In the experiments, the evaluated OLSR configurations obtain better Quality of Service (QoS) than the standard RFC 3626 [15].  
Position-based routing relies on Global Position System (GPS) coordinates. In [16], the authors focus the study on the fact that the GPS measured data will always be corrupted by noise and other factors. The authors use the simulated annealing optimization technique for finding lower bounds on how much improvement is possible given the inaccuracies in the measurements. They use two algorithm previously proposed, VLOCI [17] and VLOCI2 [18], in order to improve the initial GPS coordinates.  
In general, there are several routing protocols proposed for wireless mobile ad hoc networks. Particularly in vehicular networks, depending on the particular scenario, one protocol or another might lead to a better result. However, we have not found any routing protocols that use other heuristic optimization techniques in the routing decision process apart from the greedy approach of geographical routing protocols. All of the position-based protocols surveyed in [3; 5; 6; 7; 19] work with local search and follow a greedy approach in the selection step of the next forwarding node. Hence, there is room for performance improvement of geographical protocols by using other heuristic optimization techniques like Tabu search and simulated annealing.