Yoshihiro Ohba

IEEE 802.21: Media independent handover: Features, applicability, and realization

Providing users of multi-interface devices the ability to roam between different access networks is becoming a key requirement for service providers. The availability of multiple mobile broadband access technologies, together with the increasing use of real-time multimedia applications, is creating strong demand for handover solutions that can seamlessly and securely transition user sessions across different access technologies. A key challenge to meeting this growing demand is to ensure handover performance, measured in terms of latency and loss. In addition, handover solutions must allow service providers, application providers, and other entities to implement handover policies based on a variety of operational and business requirements. Therefore, standards are required that can facilitate seamless handover between such heterogeneous access networks and that can work with multiple mobility management mechanisms. The IEEE 802.21 standard addresses this problem space by providing a media-independent framework and associated services to enable seamless handover between heterogeneous access technologies. In this article, we discuss how the IEEE 802.21 standard framework and services are addressing the challenges of seamless mobility for multi-interface devices. In addition, we describe and discuss design considerations for a proof-of-concept IEEE 802.21 implementation and share practical insights into how this standard can optimize handover performance.

Media-independent pre-authentication supporting secure interdomain handover optimization

Handovers may cause delays and packet losses that affect real-time communication performance. Mobility protocols at several layers are designed to support handover, but they need to be optimized to ensure high-quality application performance. Existing optimization techniques are not sufficient to take care of interdomain and intertechnology handovers involving different access technologies, such as Wi-Fi, GSM, CDMA, and WiMAX. We categorize several types of handover, describe handover delay components, and propose a handover optimization framework called media independent pre-authentication that can provide optimizations for interdomain and intertechnology handover in a manner that is transparent to mobility management protocols. In addition, we also present experimental results demonstrating that this framework can achieve a significant reduction in handover delays for both network-layer and application-layer mobility management protocols.

Seamless proactive handover across heterogeneous access networks

Dual-mode handsets and multimode terminals are generating demand for solutions that enable convergence and seamless handover across heterogeneous access networks. The IEEE 802.21 working group is creating a framework that defines a Media Independent Handover Function (MIHF), facilitates handover across heterogeneous access networks, and helps mobile users experience better performance during mobility events. In this paper, we describe this 802.21 framework and also summarize a Media-independent Pre-Authentication (MPA) mechanism currently under discussion within the IRTF that can further optimize handover performance. We discuss how the 802.21 framework and the MPA technique can be integrated to improve handover performance. Finally, we describe a test-bed implementation and validate experimental performance results of the combined mobility technique.

Dynamic service negotiation protocol (DSNP) and wireless DiffServ

This paper presents the design principles of dynamic service negotiation protocol (DSNP). DSNP is a protocol to negotiate the SLS (service level specification) in the IP layer. It can be used for service negotiation from host to network, network to host, and network to network. The automated negotiation makes service negotiation efficient in terms of time, cost, and correctness. The dynamic negotiation not only allows users to adapt their needs dynamically, but also lets providers utilize the network better. DSNP can be used in both wireline and wireless networks. It is, however, particularly useful in the mobile environment. To demonstrate the usefulness of DSNP, a reference wireless QoS architecture based on DiffServ is presented. Example applications and experimental results are illustrated.

A key management framework for AMI networks in smart grid

The environments in which current electric grids operate as well as the requirements for the emerging smart grid differ substantially from those of todays Internet and telecommunication networks. For example, typical electric or gas meters in the advanced metering infrastructure (AMI) are low-power, low-capability wireless devices utilizing personal area wireless network technology (e.g., IEEE 802.15.4). These devices are low-cost, typically with 4-12 kbytes of RAM and 64-256 kbytes of flash memory, and are often connected to the backhaul via low-bandwidth links. Comparing this to the high-powered, high-capability devices of the Internet with gigabytes of RAM and storage, the differences are striking. Security solutions designed for capability-rich Internet devices will not be suitable for the capability-poor devices of the smart grid; thus, new requirements are needed that can efficiently operate in resource constrained devices. With this operating environment in mind, we present a smart grid key management framework with application to AMI networks. Specifically, we describe how this key management model can be realized in such a resource-constrained environment using existing standard protocols and provide preliminary performance results.

Kerberized handover keying: a media-independent handover key management architecture

This paper proposes a media-independent handover key management architecture that uses Kerberos for secure key distribution among a server, an authenticator, and a mobile node. With the proposed architecture, signaling for key distribution is based on re-keying and is decoupled from re-authentication that requires EAP (Extensible Authentication Protocol) and AAA (Authentication, Authorization and Accounting) signaling similar to initial network access authentication. In this framework, the mobile node is able to obtain master session keys required for dynamically establishing the security associations with a set of authenticators without communicating with them before handover. By separating re-key operation from re-authentication, the proposed architecture is more optimized for proactive mode of operation. It is also optimized for reactive mode of operation by reversing the key distribution roles between the mobile node and the target access node. This paper discusses how the proposed architecture is applicable to the existing link-layer technologies including IEEE 802.11 and 802.16 and across multiple AAA domains. This paper also describes how Kerberos is bootstrapped from initial access authentication using an EAP method.

An Experimental Study of Location Assisted Proactive Handover

Traditionally, signal-to-noise ratio of a mobile determines the handoff dynamics of the mobile. But in certain cases, precise location of the mobile augmented by information services, such as IEEE 802.21 MIS, can expedite the handoff with similar performance results. We illustrate an experimental system that takes advantage of the mobiles relative location with the neighboring access point to perform proactive handoff. It keeps track of the current location of the mobile and then uses the information from the neighboring networks to help perform the proactive handoff. Proactive handover technique helps the mobile to communicate with these networks before the handover is complete thereby reducing the delay and packet loss. In some cases, location-assisted handover could prove to be more useful compared to the handover technique based on signal-noise-ratio.

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.

Network-Layer Assisted Mechanism to Optimize Authentication Delay during Handoff in 802.11 Networks

Secured and seamless mobility across heterogeneous access networks needs optimization at all layers. Authentication and security association at the link layer is one of the major components of delay during handoff. We propose a network- layer assisted proactive handoff scheme that helps to optimize the handoff process involving link-layer security across multiple subnets. We demonstrate this proactive scheme and analyze the results for IEEE 802.11-based networks for both roaming and non-roaming scenarios. We then compare these results with the pre-authentication techniques offered by IEEE 802.11i.