IEEE 802.21

802.21 is an IEEE emerging standard. The standard supports algorithms enabling seamless handover between networks of the same type as well as handover between different network types also called Media independent handover (MIH) or vertical handover. The standard provides information to allow handing over to and from cellular, GSM, GPRS, WiFi, Bluetooth, 802.11 and 802.16 networks through different handover mechanisms.

The IEEE 802.21 working group started work in March 2004. More than 30 companies have joined the working group. The group produced a first draft of the standard including the protocol definition in May 2005. The letter ballot process began and subsequent revisions to the draft are in progress as of September 2006, with almost all comments resolved.

Reasons for 802.21

Cellular networks and 802.11 networks employ handover mechanisms for handover within the same network type (aka horizontal handover). Mobile IP provides handover mechanisms for handover across subnets of different types of networks, but can be slow in the process. Current 802 standards do not support handover between different types of networks. They also do not provide triggers or other services to accelerate mobile IP based handovers. Moreover, existing 802 standards provide mechanisms for detecting and selecting network access points, but do not allow for detection and selection of network access points in a way that is independent of the network type.

ome of the expectations

*Allow roaming between 802.11 networks and 3G cellular networks.
*Allow users to engage in ad hoc teleconferencing.
*Apply to both wired and wireless networks.
*Allow for use by multiple vendors and users.
*Compatibility and conformance with other IEEE 802 standards.
*Include definitions for managed objects that are compatible with management standards like SNMP.
*Although security algorithms and security protocols will not be defined in the standard, authentication, authorization, and network detection and selection will be supported by the protocol.

Implementation

Many vendors are building wireless products and participating in the development of the 802.21 standard. Current technologies such as 802.11 that accomplish handover use software to accomplish handovers and suggest that software will also be the way that handover will be implemented by 802.21. The use of software as a means to implement 802.21 should not cause large increases in the cost of networking devices.

Examples

*A user should be able to unplug from an 802.3 network and get handed off to an 802.11 network.

*A cellular phone user in the midst of a call should be able to enter an 802.11 network hotspot and be seamlessly handed off from a GSM network to the 802.11 network and back again when leaving the hotspot.

imilar technologies

Unlicensed Mobile Access (UMA) technology is basically a mobile-centric version of 802.21. UMA is said to provide roaming and handover between GSM, UMTS, Bluetooth and 802.11 networks. For more information on UMA you can go to http://www.umatoday.com/.Since June 19 2005, UMA is a part of the ETSI 3GPP standardization process under the GAN (Generic Access Network) Group.

WiOptiMo technology enables any application running on a device to use the best internet connection among all the wired/wireless access providers available, guaranteeing persistence in case of weak or no signal and managing the switch among them (when needed/convenient) in a transparent way, without interrupting the active application/session.For more information you can read [http://hal.inria.fr/inria-00001015/en/ A Cross-Layering and Autonomic Approach to Optimized Seamless Handover ] or "WiSwitch: Seamless Handover between Multi-Provider Networks" on [http://ieeexplore.ieee.org/Xplore/guesthome.jsp IEEE Explore] .

ee also

*Mobility management
*Mobile IP
*Handover
*Radio resource management
*Roaming
*Vertical handoff

External links

* [http://www.ieee802.org/21/ IEEE 802.21 web site]
* [http://www.wi-fiplanet.com/columns/article.php/3310401 Is Cellular Handoff Nigh? article]