A survey on applications of IEEE 802.21 Media Independent Handover framework in next generation wireless networks

Abstract

Integration of various wireless access technologies is one of the major concerns in recent wireless systems in which multi-technology mobile devices are provided to users to roam between different access networks. Being an essential part in heterogeneous wireless systems, vertical handover is more complex than conventional horizontal handover. As IEEE 802.21 Media Independent Handover (MIH) is the standard addressing a uniform and media-independent framework for seamless handover between different access technologies, many works have been carried out in the literature to employ MIH services in handover management This paper presents a comprehensive survey of the proposed mobility management mechanisms that are using this framework. As a comparative view, the paper categorizes the efforts according to the layer of mobility management and evaluates some of the representative methods discussing about their advantages and disadvantages The paper also looks into recent handover decision and interface management methods that are exploiting MIH Moreover, the extensions and the amendments proposed on MIH are overviewed.

Introduction

The upcoming generation of wireless mobile networks is an integration of different access technologies including 802 family such as WiFi and WiMAX, and non-802 family such as UMTS and LTE. This complex mix of technologies needs global seamless roaming among a diverse range of mobile access networks. Nowadays, device manufacturers are integrating more network interfaces into their devices. Many cell phone models now support both WiFi and 3G, and notebook computers are available with built-in support for WiFi, WiMAX and 3G technologies. In this context, vertical handover is a key challenge that allows a Mobile Node (MN) to transfer its traffic from one network interface to another when the provided quality of connection in the serving network is poor [1]. Due to the heterogeneity of such networks, vertical handover is a complex procedure requiring comprehensive standards to facilitate seamless handover between diverse access networks and to work with multiple mobility management mechanisms. The IEEE 802.21 [2] addresses this issue by providing a Media Independent Handover (MIH) framework and associated services to enable seamless handover between different access technologies [1]. Officially started from March 2004, IEEE 802.21 working group produced the first draft in 2005. The standard finally approved on November 2008 after subsequent revisions.

IEEE 802.21 defines a media-independent entity that provides a generic interface between different link layer technologies and upper layers [3]. Link layer technologies include media types specified by the Third Generation (3G) Partnership Project (3GPP), 3G Partnership Project 2 (3GPP2), and both wired and wireless media in the IEEE 802 family of standards [2].

The MIH standard aims to facilitate the integration of heterogeneous networks by providing a uniform information about layer 2 (L2) triggers to the upper layers in order to help the handover decisions [4]. In addition, MIH provides facilities for inter-technology candidate network discovery, target network preparation, and L2 handover initiation and execution [5]. Note that the 802.21 standard does neither specify rules (or policies) for handover decision nor determines whether the handover has to be terminal or network initiated [6].

Recently, important modifications emerged on both standardization bodies and manufacturers that clearly indicate that the IEEE 802.21 will soon take off and be implemented in real networks. For example, InterDigital, British Telecom (BT) and Intel have recently deployed experimental testbeds with MIH functionalities to optimize seamless handover [7]. Also, some open source implementations of MIH protocol are emerging to be used by developers.

The rest of this paper has been organized as the followings; in the next section, the MIH framework and its services will be introduced. Section 3 discusses on recent efforts that have exploited the MIH on different mobility management protocols and the improvements achieved. Section 4 investigates some of the representative vertical handover decision and management methods that are employing MIH services. Section 5 discusses on amendments and extension proposed on MIH. Section 6 is a comparative summary on representative methods and finally Section 7 concludes the paper.