Editing Mobility management (section)

==Types of area==
===Location area===
A "location area" is a set of base stations that are grouped together to [[Engineering optimization|optimize]] signaling. Typically, tens or even hundreds of base stations share a single [[Base station subsystem#Base station controller|Base Station Controller]] (BSC) in GSM, or a [[Radio Network Controller]] (RNC) in UMTS. The BSC / RNC is the intelligence behind the base stations; it handles allocation of radio channels, receives measurements from the mobile phones, and controls handovers between base stations.

Each location area has an assigned unique identifier, made up of numbers, called a "location area code" (LAC). The LAC is broadcast by each base station at regular intervals. Within a location area, each base station is assigned a distinct "cell identifier" (CI) number, see also [[Cell Global Identity]].

If the location areas are large and moderately populated, there will likely be a high number of mobiles operating simultaneously, resulting in very high paging traffic. This is due to the fact that every paging request has to be broadcast to every base station in the location area. Ultimately, this wastes [[Bandwidth (signal processing)|bandwidth]] and power on mobile devices by requiring them to listen for broadcast messages too often. Similarly if on the other hand, there are too many small location areas, the mobile device must contact the network very often for changes of location, which will also drain the device’s battery. Therefore, it is important to strike a balance between the size of the location area and the number of mobile device users in the location area{{Citation needed|date=April 2009}}.

===Routing area===
The routing area is the packet-switched domain equivalent of the location area. A "routing area" is normally a subdivision of a "location area".  Routing areas are used by mobiles which are [[GPRS]]-attached. GPRS is optimized for "bursty" [[data communication]] services, such as wireless internet/intranet, and multimedia services. It is also known as GSM-IP ("[[Internet Protocol]]") because it will connect users directly to [[Internet Service Providers]]

The bursty nature of packet traffic means that more paging messages are expected per mobile, and so it is worth knowing the location of the mobile more accurately than it would be with traditional circuit-switched traffic.  A change from routing area to routing area (called a "Routing Area Update") is done in an almost identical way to a change from location area to location area.  The main differences are that the "Serving GPRS Support Node" ([[SGSN]]) is the element involved.

===Tracking area===
The tracking area is the [[3GPP Long Term Evolution|LTE]] counterpart of the location area and routing area. A tracking area is a set of cells. Tracking areas can be grouped into lists of tracking areas (TA lists), which can be configured on the [[User equipment|User Equipment]] (UE). Tracking area updates are performed periodically or when the UE moves to a tracking area that is not included in its TA list.

Operators can allocate different TA lists to different UEs. This can avoid signaling peaks in some conditions: for instance, the UEs of passengers of a train may not perform tracking area updates simultaneously.

On the network side, the involved element is the [[Mobility Management Entity]] (MME). MME configures TA lists using [[Non-access stratum|NAS]] messages like Attach Accept, TAU Accept or GUTI Reallocation Command.