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TheIEEE 802.21 standard forMedia Independent Handoff (MIH) is anIEEE standard published in 2008. The standard supports algorithms enabling seamlesshandover between wired and wireless networks of the same type as well as handover between different wired and wireless network types also calledmedia independent handover (MIH) or vertical handover. The vertical handover was first introduced by Mark Stemn and Randy Katz at U C Berkeley.[1] The standard provides information to allow handing over to and from wired802.3 networks to wireless802.11,802.15,802.16,3GPP and3GPP2 networks through different handover mechanisms.
The IEEE 802.21working 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 standard was published in January 2009.
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. Current802 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.
Implementation is still in progress. Current technologies such as802.11 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. An open-source software implementation is provided by ODTONE.[citation needed]
Crossing different administrative connectivity domains will require agreements among different network operators. Currently, such agreements are still not in place. In smartphones today, a user can manually select to use WiFi or cellular LTE, but the connections are not automatically maintained should a disconnection of one network occurs.
Hence, seamless handovers across different wire/wireless networks are still not available today.
Unlicensed Mobile Access (UMA)[citation needed] technology is a mobile-centric version of 802.21. UMA is said to provide roaming and handover betweenGSM,UMTS,Bluetooth and802.11 networks. Since June 19, 2005, UMA is a part of the ETSI 3GPP standardization process under the GAN (Generic Access Network) Group.
TheEvolved Packet Core (EPC) architecture for Next Generation Mobile Networks (3GPP Rel.8 and newer) provides theAccess Network Discovery and Selection Function element (ANDSF)[citation needed] (see 3GPP TS 23.402 and 3GPP TS 24.312). Its S14 interface provides the communication path between the Core Network and the User Endpoint device on which to exchange discovery information and inter-system mobility policies, enabling as such a network-suggested reselection of access networks.
