IEEE 802.21 Media Independent Handover [1]

The emerging IEEE 802.21 standard, Media Independent Handover, has the ability to seamlessly handover networks for both wired and wireless networks, which is addresses a prevalent problem when roaming. Interoperability between homogenous network types of 802 and non 802 networks is also a key feature of the 802.21 standard. This report consists of the understanding of 802.21 services and its functionality, specifically at the Data Link and Network Layers of the OSI Networking Model. Currently at the stage of proposal, the 802.21 working group hopes to finalize the standard’s document and begin implementation shortly thereafter. Future outlook of this standard is good when comparing with the existing proprietary UMA (Unlicensed Mobile Access), which is a similar technology, but fails to offer interoperability. The expectations for this standard are, but are not limited to: ability to roam between 802.11 and 3G networks, allowance for use by multiple vendors and users, application for both wired and wireless networks, and ability to engage in a teleconference.


Introduction
Wireless networking has provided us the ability to freely utilize our mobile devices (i.e. computer notebook, cellular phones, PDA, GPS) wherever and whenever a wireless access point is available. With the multitude of existing wireless standards (Wi-Fi, GSM, etc), a smooth transition from one network to another is utterly impossible with the current technology. Existing IEEE 802 standards go through a series of failures before acquiring the correct network access. For instance, as soon as a user unplugs the Ethernet cable from his or her computer, an error appears indicating that the user is no longer connected to a LAN network. If the computer has wireless capability (i.e. 802.11b), then the user may be able to connect to a wireless network, but network discovery would take some time to establish. An interruption of service is inevitable, thus, a network handover standard is necessary. This emerging standard is the IEEE 802.21, which working efforts debuted in March 2004 and implementation is still in progress [4].
IEEE 802.21 is a developing standard which enables handover and interoperability between heterogeneous network types including both 802 and non 802 networks [6]. The standard provides information to allow handing over to and from cellular and wireline, GSM, GPRS, WiFi, WiMAX, Personal Area Network (PAN), Bluetooth and 802.11 networks through different handover mechanisms [1].

Background
Initiated in March 2004, the working group for the 802.21 standard was chaired by Ajay Rajkumar from Lucent Technologies. The members involved include over 50 companies. These companies are the “largest vendors of end-to-end network infrastructure, device companies, chipset developers, and even service providers” [1]. One of the contributing companies, Intel Corporation, expressed enthusiasm towards providing users with the ability to move from a hotspot to a cellular connection without noticing. Envisioned is the idea of a future that unites network connectivity across a wide range of networks. Figure 1 shows a prototype mobile phone that has four different wireless networks: Bluetooth, GPS, GPRS, and Wi-Fi. With the implementation of 802.21, this device is expected to intellectually select available networks, with an ease of transition and without any interruption, when roaming [3].

standards: Bluetooth, GPS, GPRS, and Wi-Fi [3].

Objective
The objective is to enable an innovative fast Layer 2 and Layer 3 handoff algorithm between networks (for both wired and wireless networks). Network discovery and selection are factors that affect the quality of service during a handover decision. With this technology, end-user devices will have the ability to “automatically choose the best available network connection type and to seamlessly hand off sessions among networks during roaming without user involvement” [2]. 802.21 is expected to unite the multitude of existing networks.

Organization
The next immediate section describes the proposed 802.21 standard in detail. The specifics include the four Media Independent Handover services provided, packet format and information, and functionality in Layers 2 and 3 (Data Link and Network, respectively) of the OSI Networking Model. We will discuss the current progress, including accomplished milestones towards completing the 802.21. In addition to this standard’s expectations, we will also mention its future outlook. The report concludes with comparison of 802.21 and existing similar technologies.