Integration of vehicular ad-hoc network (VANET) and cellular network is a promising architecture for future machine-to-machine applications. This integration helps the vehicles have steady internet connection through cellular network (i.e., LTE), and at same time communicate with other vehicles. However, dead spot areas and unsuccessful handoff processes due to the high speed of vehicles that can disrupt the implementation of this kind of architecture. In this chapter, simplified cluster-based gateway selection (SCGS) scheme for multi-hop relay in VANET network is proposed. The scheme is achieved by utilizing a new routing protocol called an enhanced hybrid wireless mesh protocol (E-HWMP). The simulations results show that SCGS scheme through E-HWMP protocol performed better than ad-hoc on demand distance vector (AODV) routing protocol. Furthermore, SCGS scheme through E-HWMP is compared with other cluster-based gateway selections used in the previous works; the result shows that SCGS scheme through E-HWMP protocol outperforms the other cluster-based gateway selections schemes.
TopIntroduction To V2v
Along with the ongoing advances in dedicated short-range communication and wireless technologies, inter-vehicular communication and road–vehicle communication have become possible, giving birth to a new network-type called Vehicular Ad-hoc Network (VANET). VANETs aim to improve road safety and transportation efficiency, as well as to reduce the impact of transportation on environment. Vehicle communication networks are formed by connecting devices inside public and private vehicles with each other (vehicle–to–vehicle communications) and with fixed communication infrastructure (vehicle–to– infrastructure communication) (Eltahir, & Saeed, 2015; Elathir, & Saeed, 2016). Providing internet access to devices (end users) in vehicles enables various applications in safety and emergency warning, traffic management and entertainment. The key role that VANETs can play in the realization of intelligent transport systems has attracted the attention of major car manufacturers. Heterogeneous wireless network is the one of the hot research topics in wireless domain. Recent research in wireless networking has been focusing upon the heterogeneous integration of IEEE 802.11-based wireless ad hoc networks with 3GPP cellular networks (Liu, Jia, Wang, Lu, & Wu, 2015; Saeed, Alawi, & Hassan, 2011; Eltahir, Saeed, & Mokhtar, 2014). The 3GPP cellular networks such as Universal Mobile Telecommunications System (UMTS), are predominantly used for wide-area wireless data and voice services via access to a Base Station Transceiver (BST), also referred to as UMTS Node B. On the other hand, VANETs are used for short range, high-speed communication among nearby vehicles, and between vehicles and roadside infrastructure units. Vehicle to- Vehicle (V2V) communication supports services such as car collision avoidance and road safety by exchanging warning messages across vehicles (Eltahir, Saeed, Mekherjee, & Kamrul Hasan, 2016; Eltahir, Saeed, & Alawi, 2013).
The major weakness of IEEE 802.11 radio is its very limited transmission range which is typically 200-300 meters (Jiau, 2015; Wan, Tang, & Wolff, 2008). In order to cover the wide area, a large number of access point is needed which results in high deployment cost. From this it is understood that the better solution is to use a small number of access points (Aps) along the roadside and form an ad-hoc network among vehicles and apply a relay mechanism to forward the packets for vehicles outside of the AP range or to integrate VANET to the network that can provide high coverage range (i.e. cellular network) in order to reduce the number of access points and the switching process from one access point to another.
The unique characteristics of VANET are the high mobility and rapidly changing network topology caused by the high travelling speed of the nodes; the constrained pattern due to the restricted roads; limitations of bandwidth due to the absence of a central coordinator that controls and manages communications between nodes; disconnection problems owing to the frequent fragmentation in the networks and signal fading caused by objects that form obstacles between the communicating nodes.
Consequently, the main challenges facing VANET are to decide upon the routing protocol that should be used to control the process of forwarding packets through nodes on the network; determining how to select the next-hop node to use to forward packets to their final destination, particularly in a sparse environment, depending on the presence of the unique characteristics of VANET. Therefore, providing a robust routing protocol is considered to be the most crucial solution in VANET (Matthew, 2012). This involves using new parameters to take the decisions regarding selecting the next-hop node to enhance the efficiency of the routing process and increase performance. As a result, it is anticipated that designing an efficient routing protocol will aid in accomplishing the task of delivering packets to their destinations in VANET via a more realistic method, which promises to apply road safety efficiently.
VANET is a specific circumstance of MANET. Many routing techniques have been designed in MANET to tackle the limitations with transmission packet delivery delay, involving packets being dropped, wasting bandwidth, mobility and security. These techniques could not be appended to VANET owing to its particular characteristics, such as the restricted mobility pattern.