You are presented with multiple paper abstracts, alongside the associated literature review and chapter titles. Given the provided information, you are going to do a literature review. Please generate a coherent literature review that synthesizes the content, draws connections between different works, highlights major findings, and identifies any gaps in the existing research.

Literature Review Title: Beaconing Approaches in Vehicular Ad Hoc Networks: A Survey 
Chapter Title:  Heterogeneous Vehicular Networks 
1. Abstract of Cited Paper (BIB001):  This paper considers the provision of broadband wireless access (BWA) for users on the road. A Wi-Fi based system, which utilises a three-tier network architecture, is suggested as a readily available way of achieving BWA for road vehicles. However, the use of this approach and technology still poses a number of specific challenges. We identify and examine in greater depth a number of the challenges, and propose possible solutions to overcome them. 
2. Abstract of Cited Paper (BIB002):  Wireless-communication technology can be used to improve road safety and to provide Internet access inside vehicles. This paper proposes a cross-layer protocol called coordinated external peer communication (CEPEC) for Internet-access services and peer communications for vehicular networks. We assume that IEEE 802.16 base stations (BS) are installed along highways and that the same air interface is equipped in vehicles. Certain vehicles locating outside of the limited coverage of their nearest BSs can still get access to the Internet via a multihop route to their BSs. For Internet-access services, the objective of CEPEC is to increase the end-to-end throughput while providing a fairness guarantee in bandwidth usage among road segments. To achieve this goal, the road is logically partitioned into segments of equal length. A relaying head is selected in each segment that performs both local-packet collecting and aggregated packets relaying. The simulation results have shown that the proposed CEPEC protocol provides higher throughput with guaranteed fairness in multihop data delivery in vehicular networks when compared with the purely IEEE 802.16-based protocol. 
3. Abstract of Cited Paper (BIB003):  The intelligent transportation system (ITS), a worldwide initiative program utilizes novel information and communication technology for transport infrastructure and vehicles. Among extensive ITS components, efficient communication system is the most important role which connects numerous vehicles with roadside infrastructure and management center in the ITS program. Vehicular ad hoc network (VANET) has been a cornerstone of the envisioned ITS without infrastructure. However, multihop data delivery through VANET is difficult by the fact that vehicular networks are highly mobile and frequently disconnected. Thus, traditional ad hoc routing protocols are not well suited for these high dynamic network. In this paper we propose a new heterogeneous vehicular network (HVN) architecture and a mobility pattern aware routing for HVN. HVN integrates wireless metropolitan area network (WMAN) with VANET technology and reserves advantages of better coverage in WMAN and high data rate in VANET. Vehicles in HVN can communicate with each other and access Internet ubiquitously. We mainly focus on the routing issue for HVN, because the routing protocol for HVN is different from those used in MANET or VANET. With the WMAN infrastructure support in HVN, the mobility pattern aware routing protocol can adopt the whole information of the vehicular network and unique characteristics of vehicle mobility to establish a reliable route path in high dynamic vehicular network. 
4. Abstract of Cited Paper (BIB004):  Cellular networks have gained a lot of popularity in the context of vehicular communication within the last few years. Existing reference architectures such as CALM already consider them to provide enhanced connectivity to vehicles for data communication. Their capabilities, especially 3G and next-generation, translate into great potential in the vehicular environment, far beyond the provision of data connectivity. In this context we present a solution that uses 3G cellular networks not only as a backup for data communication among vehicles, but also and especially as an efficient mechanism for the dissemination of relevant control information for multiple applications, services, and protocols. Our simulation results demonstrate that by using our 3G-based solution to disseminate connectivity information, vehicular ad hoc routing protocols improve their route selections, which results in a higher packet delivery ratio in urban scenarios.

Literature Review:
The applications of vehicular network are commonly categorized into two different groups: public safety and comfort-related applications. The undergoing studies in VANET only consider single type of applications. In the other words, none of them could achieve the requirements of all types of safety, traffic information system and comfort applications at the same time. Thus, it is necessary to enable a heterogeneous vehicular network in order to let a vehicle use multiple radio access technologies, i.e., (Worldwide Interoperability for Microwave Access) WiMAX, WiFi, IEEE 802.11p, 3G cellular networks, Long Term Evolution (LTE) and satellite communication. The authors in BIB004 , BIB003 , BIB005 , BIB001 , BIB002 have studied the integration of ad hoc network with infrastructure to achieve the public safety and comfort-related applications. In BIB004 , Hung et al. proposed mobility pattern-aware routing protocol for VANET. In this study, vehicles are equipped with IEEE 802.16e and IEEE 802.11 radio access technologies so they can communicate with each other and access internet ubiquitously. Another heterogeneous architecture that integrates IEEE 802.16 radio access technology and ad hoc communication between vehicles was proposed in BIB003 . This study supports public safety applications and Internet access. The results shows that the proposed design reduces tracking error as compared to the de-facto fixed algorithm