# Adaptive QoS-Aware Multi-Metrics Gateway Selection Scheme for Heterogenous Vehicular Network +
## 2 Related Work  
The majority of the suggested gateway collection schemes in the VANET domain are either cluster-based or non-cluster-based [20]. This distinction depends on how the vehicles are organized prior to selecting the MGW. The authors of [15; 21; 22; 23] proposed a cluster-based gateway selection mechanism in a VANET-LTE integration architecture. Based on a VANET universal mobile telecommunication system (VANET-UMTS) convergence architecture, the authors of [24] suggested a cluster-based multimetric adaptive mobile gateway management mechanism (CMGM). The proposed CMGM mechanism aimed to cut down on the number of vehicles that directly link to the UMTS network. This is accomplished by encouraging a limited number of vehicles equipped with both UTRAN and IEEE 802.11p interfaces to be considered as possible MGW applicants, capable of relaying the traffic from the other vehicles to the UMTS network. The potential MGW candidates are required to form a cluster depending on the movement direction of the vehicles and UMTS receive signal strength (UMTS-RSS). The MGW candidate that is nearest to the center of the cluster is constantly chosen as the CH. Furthermore, in the case of the ordinary vehicle that wants to communicate to the UMTS network, the algorithm proposed a multicriteria gateway selection algorithm based on the receive signal strength (RSS), mobility, speed, and link stability criteria for selecting the best gateway. However, this process is more complicated, as it involves the development and maintenance of unstable clusters in response to the rapidly changing environment in a VANET. Furthermore, the time required to build the clusters and make the CH decision is longer than the time required for information exchange. To make this algorithm easier to understand, the authors suggested a simpler gateway selection (SGS) scheme in [15], which aimed to simplify the CMGM proposed in [24] by eliminating cluster creation within the 3G active zone. The vehicles that are located inside the UMTS service area used the UMTS-UTRAN interface to directly link to the UMTS network. When the vehicles are going out of the coverage range or are going into a dead zone, they must form a cluster and use the IEEE 802.11 interface to search for MGW and relay vehicles that are still inside the coverage region. Next, the best relays and gateway vehicles are selected to connect to the UMTS infrastructure network. Three parameters are utilized in selecting the best MGW inside the UMTS active zone, including the UMTS-RSS, route lifetime, and available route capacity metrics. Nevertheless, the SAW technique is used to weigh each potential MGW based on the above-mentioned metrics. The vehicle with a higher weight is always selected as the MGW on the infrastructure. When the SGS scheme required all vehicles to link directly to the UMTS network, however, the authors did not consider the overload issues. It ignored the conditions for delay and packet loss for the various application classes. In [24], the authors suggested a GWS mechanism built upon an enhanced hybrid wireless mesh protocol (E-HWMP). The proposed protocol is a cluster-based protocol that uses LTE, RSS, accessible route power, and connection stability metrics to shape clusters and elect cluster heads. In the work, the elected CH is announced as the MGW responsible for relaying the traffic sent by the vehicles that are located outside of the 4G active zone and need to communicate with the infrastructure network. However, problems of cluster reliability and maintenance were not discussed, even though they are critical for improving network communication efficiency. The authors in [23; 25] proposed a fuzzy logic system for the gateway selection decision. However, [18] proposed a fuzzy mulimetric QoS-balancing gateway selection (FQGwS) algorithm. The FQGwS algorithm adopts the cluster formation techniques proposed by [24]. When the cluster is formed and the CH is elected, the MGW is selected based on the type of traffic class.