Monday 1 October 2012

LTE: What is a Tracking Area

Even though I have known tracking area for a long time, the other day I struggled to explain exactly what it is. I found a good explanation in this new book 'An Introduction to LTE: LTE, LTE-Advanced, SAE and 4G Mobile Communications By Christopher Cox'. An extract from the book and Google embed is as follows:

The EPC is divided into three different types of geographical area, which are illustrated in Figure 2.6. (see Embed below).

An MME pool area is an area through which the mobile can move without a change of serving MME. Every pool area is controlled by one or more MMEs, while every base station is connected to all the MMEs in a pool area by means of the S1-MME interface. Pool areas can also overlap. Typically, a network operator might configure a pool area to cover a large region of the network such as a major city and might add MMEs to the pool as the signalling load in that city increases.

Similarly, an S-GW service area is an area served by one or more serving gateways, through which the mobile can move without a change of serving gateway. Every base station is connected to all the serving gateways in a service area by means of the S1-U interface. S-GW service areas do not necessarily correspond to MME pool areas.

MME pool areas and S-GW service areas are both made from smaller, non-overlapping units known as tracking areas (TAs). These are used to track the locations of mobiles that are on standby and are similar to the location and routing areas from UMTS and GSM.


Kit Kilgour said...

Cannot an eNB belong to more than one Tracking Area 'though?

Zahid Ghadialy said...

Kit, it is possible but not sure if we would see multiple TA's in an eNodeB

Aitsam Goraya said...

one eNodeB is only assigned with single TAC. It's MME which has TA List which can have more than 1 TACs. So, if UE moves from one eNodeB to another eNode of different TAC, which is in the same TAL. UE will not make any TAU as MME always do paging on TAL.