27-03-2012, 12:50 PM
MEDIA INDEPENDENT HANDOVER
MEDIA INDEPENDENT HANDOVER (MIH) TECHNOLOGY.docx (Size: 22.09 KB / Downloads: 45)
ABSTRACT
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.
INTRODUCTION
The growing demand for mobile broadband services is the catalyst for an ever-increasing variety of air interface technologies targeting local area to wide area connectivity. We envision that the network of tomorrow will be a “network of networks” that enables uninterrupted services when roaming across many different independent radio access solutions – a mega network transparent to the users.InterDigital has been a pioneer in the development of Media Independent Handover (MIH) and helped define the IEEE 802.21 standard for seamlessly connecting GSM, WCDMA, WiMAX, WiFi, cdma2000 and virtually any other radio access technology. In practical terms, MIH technology provides operators with a virtual network extension and a platform for a range of new services – with minimal investment and low technical complexity – offering a better user experience with increased reliability and transparent coverage.A typical MIH solution consists of a simple MIH client in the mobile device, an MIH server in the IP backhaul and requires no changes to the existing radio access network. Our seamless connectivity roadmap is rapidly evolving to enable additional services and capabilities that include LTE, IMS, Mobile TV and Cognitive Radio.
Ubiquitous Internet access is one of the main challenges in telecommunications. The number of Internet users is growing at a very fast pace. At the same time, the average customer uses more than one device to connect to the Internet, and downloads and uploads digital media of an unprecedented magnitude. The network access paradigm of “always connected, anytime, anywhere” is a central requirement for next generation networks. This places a tall order to operators that ought to find ways to provide broadband connectivity to their subscribers irrespective of their location and access device. Therefore, taking into account the convergence scenario envisioned in the telecommunications area, it is essential that different wired and wireless access technologies can work together, allowing mobile users to handover between them seamlessly.
IEEE has been working on a standard which enables Media Independent Handovers (MIH) – IEEE 802.21 [1]. IEEE 802.21 defines an abstract framework that optimizes and improves horizontal and vertical handovers by providing information about the link layer technologies to the higher layers. For the successful support of seamless, make-before-break handovers, one of the most important requirements is QoS support. Presently, MIH provides QoS resources querying for the candidate access technologies and, after the target access technology is selected by the mobility decision algorithm, MIHoffers the capability to enforce the QoS resources. Since the time interval between the resources query and activation may not be negligible and the network conditions in the target access technology can change during this period, the MIH framework must be able to provision QoS resources in the target network prior to their activation, guaranteeing their availability for future activation. Moreover, the MIH framework is a general framework, but needs to be integrated with the specific access technologies and their mobility processes, allowing for a coherent inter-technology handover process .
This paper presents novel handover procedures to address seamless mobility in heterogeneous environments. The proposed scheme is an enhanced version of the IEEE 802.21MIH platform, called enhanced Media Independent Handover Framework (eMIHF). The proposed eMIHF extends the original MIH version by adding the capacity to efficiently provision and activate QoS resources in the target radio access technology during the handover preparation phase. We show that eMIHF interacts efficiently with the mobility process of the different technologies in place, and therefore guarantees a reliable make-before-break handover. Furthermore, the proposed scheme addresses the translation and adaptation of QoS parameters from the serving to the target access technology, enabling the enforcement of QoS policies in the target network during the handover preparation phase. Moreover, eMIHF triggers the correct MAC layer primitives in the radio access technology for mobility and QoS management purposes.
To evaluate using simulation the efficiency of the proposed solution we implemented eMIHF and extended version 9 of the IEEE 802.21 MIH platform for ns-2 [2]. Amobile initiated handover has been implemented between Wi-Fi [3] and WiMAX [4], and was integrated with the Fast Mobile IPv6 (FMIPv6) [5] mobility management protocol, demonstrating the value of our solution for forthcoming IPv6 mobile heterogeneous network environments with QoS requirements.
The remainder of this paper is organized as follows. Section II describes the most relevant related work published by vendors, standardization bodies, research projects and the academic community. Section III provides a high-level description of the eMIHF entities and services. Thereafter, Section IV describes the proposed seamless mobility scheme, focusing on the integration of the eMIHF within a Wi-Fi to WiMAX handover process. Section V presents our performance evaluation results and, finally, Section VI concludes the paper and discusses open issues for future work
MEDIA INDEPENDENT HANDOVER (MIH) TECHNOLOGY
Converged devices are already capable of handling multiple wireless technologies – such as GSM/WCDMA, WiFi, WiMAX or cdma2000 – in a single device. However, it has been challenging to deliver popular Web-based services, voice over IP (VoIP), e-mail, video and TV, across multiple locations, devices, network access technologies and operators.
The IEEE 802.21 MIH standard comprises a set of mechanisms that facilitatemobility across heterogeneous or hybrid networks by abstracting the link layer intelligence to higher layers, creating a common interface that treats all access technologies in a generic manner.
MIH specifies three media-independent services: Event Service, Command Service and Information Service. The Event Service (ES) provides a unified reporting mechanism that indicates, or may anticipate, changes in state or status of the link layers. The Command Service (CS) allows either the mobile client or the network function (MIH server) to control the parameters of a link, modify the behavior of the ES and initiate and coordinate the network switching. The Information Service (IS) provides database access and retrieval of network availability, parameters and services for both serving and neighboring access networks. Examples include information about heterogeneous geographical network maps, service costs, QoS functionalities and roaming partners. The IS also provides neighboring network information about user and network operator policies for optimal initial network attachment or network re-selection in idle mode.
The intelligent MIH connection-monitoring manager middleware sits between the application and the device radio modems to monitor the wireless accesses, network status and availability. The middleware interacts with the higher layers in a consistent manner to ensure seamless connection handover with minimal delays across different access protocols’ coverage areas, with varying speeds and levels of quality of service (QoS) support.
Currently, IP mobility is typically provided by Proxy Mobile IP (PMIP) or Mobile IP (MIP) solutions. MIH provides the low layer mechanisms required for enhancing the performance of the IP-level mobility protocol, and it can equally be used with PMIP, MIP, Session Initiation Protocol (SIP) and even Dynamic Host Configuration (DHCP)-based solutions. The flexibility of MIH provides network operators with the ability to not only enhance current mobility solutions, but also future ones such as Voice Call Continuity (VCC), Service Continuity, and other IMS- and IP-based service.
HETEROGENEOUS NETWORKS
The wireless industry has evolved rapidly, moving from the simple voice and text messaging to the next generation of services, devices and applications. Mobile voice, data and multimedia at high reliable speeds have become the norm and users’ expectations on these services are higher than ever before.
While most new individual wireless technologies are capable of providing these services, the scarce and expensive frequency spectrum forces network operators to rely on heterogeneous wireless networks to satisfy the users’ needs in different locations.
MIH satisfies today’s customer expectations by enabling predictable and ubiquitous service – that’s network and technology agnostic – when switching between networks. The technology overcomes the challenges of seamless network integration, requiring no user intervention, saving battery life and selecting the lowest cost connection.