Sunil Madhani

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.

Implementing a testbed for mobile multimedia

In an effort to realize wireless Internet telephony and multimedia streaming in a highly mobile environment a testbed emulating a wireless Internet has been built. This allows the setting up of multimedia calls between IP mobiles and integration between IP and PSTN end-points in a wireless environment. Different functionalities and components involved with the wireless Internet streaming multimedia have been prototyped and experimented in the testbed. These include signaling, registration, dynamic binding, location management as well as supporting the QoS features for the mobile users. This paper describes some of the components of the testbed and highlights the experiences while building this testbed which could be beneficial to some who plan to build a similar testbed to realize several features and capabilities of Mobile Wireless Internet, before actually bringing to the market.

Secure universal mobility for wireless internet

The advent of the mobile wireless Internet has created the need for seamless and secure communication over heterogeneous access networks such as IEEE 802.11, WCDMA, cdma2000, and GPRS. An enterprise user desires to be reachable while outside ones enterprise networks and requires minimum interruption while ensuring that the signaling and data traffic is not compromised during ones movement within the enterprise and between enterprise and external networks. We describe the design, implementation and performance of a Secure Universal Mobility (SUM) architecture. It uses standard protocols, such as SIP and Mobile IP, to support mobility and uses standard virtual private network (VPN) technologies (e.g., IPsec) to support security (authentication and encryption). It uses pre-processing and make-before-break handoff techniques to achieve seamless mobility (i.e., with little interruption to users and user applications) across heterogeneous radio systems. It separates the handlings of initial mobility management and user application signaling messages from user application traffic so that VPNs can be established only when needed, thus reducing the interruptions to users.

Realizing mobile wireless Internet telephony and streaming multimedia testbed

Streaming real-time multimedia content over the Internet is gaining momentum in the communications, entertainment, music and interactive game industries as well as in the military. In general, streaming applications include IP telephony, multimedia broadcasts and various interactive applications such as multi-party conferences, collaborations and multiplayer games. Successfully realizing such applications in a highly mobile environment, however, presents many research challenges. In order to investigate such challenges and demonstrate viable solutions, we have developed an experimental indoor and outdoor testbed laboratory. By implementing standard IETF protocols into this testbed, we have demonstrated the basic functionalities required of the mobile wireless Internet to successfully support mobile multimedia access. These requirements include signaling, registration, dynamic configuration, mobility binding, location management, Authentication Authorization and Accounting (AAA), and quality of service over a variety of radio access network (RAN) technologies (e.g. 802.11b, CDMA/GPRS). In this paper, we describe this testbed and discuss important design issues and tradeoffs. We detail the incorporation and inter-relation of a wide catalog of IETF protocols-such as SIP, SAP, SDP, RTP/RTCP/RTSP, MGCP, variants of Mobile-IP, DRCP, HMMP, PANA, and DSNP-to achieve our goals. We believe that the results and experiences obtained from this experimental testbed will advance the understanding of the pertinent deployment issues for a Mobile Wireless Internet.

Reducing energy consumption on mobile devices with WiFi interfaces

Emergence of mobile handheld devices with WiFi (IEEE 802.11) interfaces such as WiFi phones, WiFi-cellular dual-mode phones and PDAs (personal digital assistants), allow users to take full advantages of heterogeneous radio technologies. WiFi, however, was not originally designed for energy-constrained handheld devices. As a result, the standby times of a handheld device with a WiFi interface is significantly lower than what people typically experience with todays cellular phones. This paper presents and evaluates a system-level power management method devices with WiFi, or other high energy-consuming network interfaces, to significantly increase their standby times without modifications to WiFi and upper layer protocols and implementations.

Network Discovery Mechanisms for Fast-handoff

Proactive handoff mechanisms involving secure pre-authentication and proactive configuration help reduce the delay and transient data loss for real-time communication during movement between homogeneous or heterogeneous access networks. Pre-authentication is meant to perform authentication with a network before a mobile moves into the network. To achieve secure pre- authentication with a target neighboring network, a mobile needs to obtain an IP address of the authentication server from the target network when the mobile is still outside the target network and then to establish a security association with the authentication agent in the target network. This requires the mobile to discover the parameters of various network elements in the target network ahead of time so that the mobile can communicate with these network elements to establish proactive security associations. We describe several approaches for a mobile to discover the network elements in target networks before moving into these target networks. We also describe how network discovery can help provide fast-handoff using secure pre-authentication and proactive IP address acquisition during handover between different access networks.

Sensors on patrol (SOP): using mobile sensors to detect potential airborne nuclear, biological, and chemical attacks

Sensors have been developed for environmental monitoring including detecting potential airborne nuclear, biological, and chemical attacks, monitoring air pollutions, and road and traffic conditions. Many cities in the U.S. are deploying or considering the deployment of sensors for environmental monitoring. Today, a typical approach is to use fixed sensors. This usually requires a large number of sensors with large and complex network infrastructures to connect sensors to data processing centers. This paper proposes and evaluates a new approach-Sensors on Patrol (SOP)-which uses sensors mounted on vehicles (e.g., buses, taxis, police cars) and people (e.g., policemen) to monitor the environment. This could reduce the number of required sensors and the size and the complexity of the network infrastructure required to connect the sensors. This paper also presents a method for estimating the number of mobile sensors required to cover a region of interest and analyze the volume of information reporting.

Collaborative sensing using uncontrolled mobile devices

This paper considers how uncontrolled mobiles can be used to collaboratively accomplish sensing tasks. Uncontrolled mobiles are mobile devices whose movements cannot be easily controlled for the purpose of achieving a task. Examples include sensors mounted on mobile vehicles of people to monitor air quality and to detect potential airborne nuclear, biological, or chemical agents. We describe an approach for using uncontrolled mobile devices for collaborative sensing. Considering the potentially large number of mobile sensors that may be required to monitor a large geographical area such as a city, a key issue is how to achieve a proper balance between performance and costs. We present analytical results on the rate of information reporting by uncontrolled mobile sensors needed to cover a given geographical area. We also present results from testbed implementations to demonstrate the feasibility of using existing low-cost software technologies and platforms with existing standard protocols for information reporting and retrieval to support a large system of uncontrolled mobile sensors

GPS Assisted Fast-Handoff Mechanism for Real-Time Communication

Reducing transient data loss during a mobiles frequent subnet handoff depends upon several factors such as layer 2 handoff detection, faster IP address discovery, and registration and media re-direction. We present a new methodology that can provide faster IP address discovery using GPS coordinate of the mobile. This mechanism provides a suitable approach for high-speed vehicular users. It discusses several issues involved with this handoff process such as layer 2 detection, IP address assignment, and duplicate address detection. It also describes the experiment carried out in an external testbed.

Secure universal mobility for wireless Internet

The advent of the mobile wireless Internet has created the need for seamless and secure communication over heterogeneous access networks such as IEEE 802,11, WCDMA, cdma2000, and GPRS. An enterprise user desires to be reachable while outside ones enterprise networks and requires minimum interruption while ensuring that the signaling and data traffic is not compromised during ones movement within the enterprise and between enterprise and external networks. We describe the design, implementation and performance of a Secure Universal Mobility (SUM) architecture. It uses standard protocols, such as SIP and Mobile IP, to support mobility and uses standard virtual private network (VPN) technologies (e.g., IPsec) to support security (authentication and encryption.) It uses pre-processing and make-before-break handoff techniques to achieve seamless mobility across heterogeneous radio systems. It separates the handlings of initial mobility management and user application signaling messages from user application traffic so that VPNs can be established only when needed, thus reducing the interruptions to users.