1. Cloud-Assisted Gateway Discovery for Vehicular Ad Hoc Networks Yen-Wen Lin, Jie-Min Shen, and Hao-Jun Weng Department of Computer and Information Science, National Taichung University of Education, Taichung, Taiwan, R.O.C. Speaker: Lin-You Wu

2. Outline I. Introduction II. System Overview III. Simulations IV. Conclusions

3. I. Introduction Cloud services are charming for vehicular ad hoc network (VANET) users. Advances of wireless networks make access to the Internet from VANETs possible. However, the features of VANETs hinder the delivery of cloud services to VANETs.

4. It is important to find proper Internet gateways to connect the VANET users to the cloud. Thus, Internet access in VANET is quite necessary to effectively acquire cloud services. Internet gateway here is defined as the portal to the Internet.

5. The efficiency of gateway discovery in VANETs remarkably affects the experience of employing cloud services. A cloud-assisted gateway discovery scheme is proposed in this paper to get connection to Internet and advance routing performance.

6. In our design, a few cloud servers are designated for maintaining vehicles’ routing information. The gateway with longest link lifetime is selected and reserved by the cloud servers for the requesting vehicle in advance.

7. II. System Overview A.System Model The system model is depicted in Fig. 1. The elements involved in the system include:

8. Cloud Server: Cloud Server is the service provider in the cloud. In this paper, to support DaaS (Discovery as a Service; described later) services to the vehicle users, two special servers, namely, the DaaS Registrar and the DaaS Dispatcher, are facilitated in the system. DaaS Registrar maintains related information of the gateways. DaaS Dispatcher is responsible of discovering and dispatching the gateways for the client vehicles.

9. Gateway: Gateway is the entity which is able to connect to the Internet directly. According to the mobility of the gateways, two types of gateways are considered in this paper, namely the Stationary Gateway and the Mobile Gateway.

10. The Stationary Gateway (SG) is part of the roadside infrastructure such as access points (APs) of WiFi or WiMAX, or base stations (BSs) of cellular networks. The Mobile Gateway (MG) is the vehicles on the road which can directly connect to the Internet.

11. Client Vehicle: Client Vehicle (CV) is the vehicle which wants to connect to the Internet.

12. Relay Vehicle: In case that a CV locates outside the coverage of any gateway, one or more Relay Vehicles (RVs) forward packets from/to a CV to/from a gateway.

13. B. Gateway Registration The gateway willing to support gateway service registers its state information with the DaaS Registrar in advance. The state information of the gateway includes current location, speed, direction, and QoS level. The DaaS Registrar then assigns a GID (Gateway ID) to the gateway.

15. C. Gateway Discovery A CV offloads the overheads of gateway discovery to the cloud servers by sending a REQ-DaaS message to currently serving gateway. The DaaS Dispatcher takes over the gateway discovery and dispatching for the requesting CV.

18. D. Gateway Selection If more than one gateways are available, the DaaS Dispatcher selects a best gateway for serving the portal to the cloud.

19. III. Simulations The simulations are collected in Table I.

20. A. Packet Delivery Rate The packet delivery rate of both the AODV and the proposed scheme decreases as the velocity of vehicle increases.

21. B. End to End Delay In the AODV, the gateway with least hop count is selected for handoff while in the proposed scheme, the gateway with longest link lifetime is chosen as the next-hop gateway.

22. C. Signaling Load In the AODV, the gateway with least hop count is chosen for handoff. Oppositely, in the proposed scheme, the gateway with longest link lifetime is selected as the next-hop.

23. IV. Conclusions A cloud-assisted gateway discovery scheme is proposed in this paper. Related cloud servers maintain the state information of the gateways in the system.

24. The gateway with longest link lifetime is dispatched by the cloud servers for the requesting vehicle ahead. Thus, the cloud servers are responsible of discovering proper gateways for the requesting vehicles.

25. END