Wai Chen

A survey and challenges in routing and data dissemination in vehicular ad hoc networks

In this paper, we survey recent results in VANET data dissemination. We structure the survey into three broad categories: geocast/broadcast, multicast, and unicast approaches; and describe key ideas of representative technologies in each category. In addition, we consider location service and security issues that are crucial for data dissemination in VANET. We conclude by sharing our thoughts on further challenges.

MarconiNet supporting streaming media over localized wireless multicast

Flexible multi-media streaming such as advertisment insertion, location based services, mobility and wireless access are vital components that make existing Internet Radio and TV networks more attractive for the roaming users. All of these applications also provide added value to telematics, and military usage including coordination, education, situation awareness, distributed simulation, battlefield communication and multi-player games. While content distribution over a wired network can be realized by instituting proxies and gateways at several parts of the access network, providing mobility over heterogeneous wireless access need to consider many operational issues such as handoff, join and leave latency and desired level of quality of service for the mobile clients. This paper discusses some novel application layer techniques that provide a platform for Mobile E-Commerce with a multi-tiered payment and security scheme that supports a business model for a global streaming network. The proposed streaming network called MarconiNet is based on standard IETF protocols such as SIP, SAP and SDP for signaling, RTSP for stream control and RTP/RTCP for media delivery and feedback control.

Survey of Routing Protocols for Inter-Vehicle Communications

Inter-vehicle communications is a topic of growing interest, with a number of target applications under consideration. One significant application for inter-vehicle communications is dissemination of vehicle safety information such as road and traffic-related events and conditions. To support vehicle safety information, a reliable and efficient intervehicle communications system which can meet stringent safety application performance requirements is needed. This paper reviews developments in routing schemes targeted for ad hoc vehicle networks and considers them in the context of safety communications

A survey and challenges in routing and data dissemination in vehicular ad-hoc networks

In this paper, we survey recent results in VANET data dissemination. We structure the survey into three broad categories: geocast/broadcast, multicast, and unicast approaches; and describe key ideas of representative technologies in each category. In addition, we consider location service and security issues that are crucial for data dissemination in VANET. We conclude by sharing our thoughts on further challenges.

Fast-handoff schemes for application layer mobility management

In order to ensure proper quality of service for real-time communication in a mobile wireless Internet environment it is essential to minimize the transient packet loss when the mobile is moving between different cells (subnets) within a domain. Network layer mobility management schemes have been proposed to provide optimized fast-handoff for multimedia streams during a clients frequent movement within a domain. This paper introduces application layer techniques to achieve fast-handoff for real-time RTP/UDP based multimedia traffic in a SIP signaling environment. These techniques are based on standard SIP components such as user agent and proxy which usually participate to set up and tear down the multimedia sessions between the mobiles. Unlike network layer techniques, application layer techniques do not have to depend upon any additional components such as home agent and foreign agent. It thus provides a network access independent solution suitable for application service providers.

Mobility-aware MPLS in IP-based wireless access networks

Many domain-based micro-mobility schemes have been proposed to improve deficiencies of Mobile IP. The micro-mobility schemes provide efficient and fast handoff by localizing mobility impacts when the movement is within a domain. However they lack QoS support. This paper proposes mobility-aware MPLS as a micro-mobility scheme. The proposed scheme provides an efficient micro-mobility with continuous QoS support by combining the advantages of MPLS, such as IP QoS support, with the advantage of host-based micro-mobility schemes, such as low-latency handoffs.

Multicasting streaming media to mobile users

Content distribution in general, and multicasting in particular, over a wired network to static hosts can be realized by placing proxies and gateways at several parts of the network. However, if the end hosts are mobile over heterogeneous wireless access networks, one needs to consider many operational issues such as network detection, handoff, join and leave latency, and desired level of quality of service, as well as caching and load balancing. This article surveys a set of protocols and technologies that offer multicast-based services for streaming multimedia in a mobile environment. It also brings forth some of the issues related to mobile content distribution in the wireless Internet that may be helpful during its deployment by application service providers.

Application-layer multicast for mobile users in diverse networks

As multicast services become prevalent, it is important to find viable solutions for multicasting to mobile nodes. This problem is complicated by the necessity to support multicast services over existing backbone and access networks which may have varying network and/or link layer multicasting capabilities. While most work on supporting multicast services focuses on the IP layer solution, we propose an application-layer approach for providing multicast services to mobile users traversing networks with diverse multicast capabilities. We propose placing multicast proxies in the backbone and access networks to support several multicast-related functions at the application layer including the creation of virtual networks for dynamically tunneling through non-multicast-capable networks. We describe our proposed application-layer multicast architecture and its advantages to third-party service providers for multicasting to mobile users in diverse networks.

Scalable request routing with next-neighbor load sharing in multi-server environments

Load balancing for distributed servers is a common issue in many applications and has been extensively studied. Several distributed load balancing schemes have been proposed that proactively route individual requests to appropriate servers to best balance the load and shorten request response time. These schemes do not require a centralized load balancer. Instead, each server is responsible for determining, for each request it receives from a client, to which server in the pool the request should be forwarded for processing. We propose a new request routing scheme that is more scalable to increasing number of servers and request load than the existing schemes. The method combines random server selection and next-neighbor load sharing techniques that together prevent the staleness of load information from building up when the number of servers increases. Our simulation shows that it outperforms existing schemes under a piggyback-based load update model.

A distributed traffic navigation system using vehicular communication

Traffic congestion leads to significant cost in terms of time, money and influence on the environment. To alleviate the effect through situational awareness, various traffic service providers aggregate traffic information using a variety of inputs such as probes, toll collection etc. This aggregated information is fed back to the drivers to achieve congestion avoidance and provide arrival-time estimates. In this paper, we outline a framework for a distributed vehicle traffic navigation system. The proposed system leverages a multi-hop vehicular network to gather local information. Such information can be elusive to traffic service providers in terms of timeliness and accuracy. Based on the gathered information, a distributed scheme is proposed that locally determines the shortest time travel paths. The proposed system can function independently or can complement an existing infrastructure-based system and can capture the dependence between route decisions of different vehicles in a given area. Based on performance evaluations, we observe that the proposed protocol can significantly enhance local route decisions leading to better traffic flow and road utilization.