LA and TA

Lac:location Area code location codes (in mobile communication systems) are a region that is set up for paging, covering a geographical area, initially divided by administrative area (a county or a district), and is now flexible, divided by paging volume. When the paging volume in a lac reaches an alarm threshold, it must be split. To determine the location of the mobile station, each GSMPLMN coverage is divided into a number of location areas, and the location area code (LAC) is used to identify the different location areas. A location area can contain one or more cells.

Location Area identification Number (LAI)

Lai is used to identify the location area, and its number structure is:

Mcc+mnc+lac

Among them: MCC and MNC with IMSI MCC and MNC.

Lac is the location area code, which uniquely identifies each location in our digital PLMN, is a 2-byte, 16-binary BCD code that is represented as L1L2L3L4 (range 0000~ffff, which defines 65,536 different location areas. ）

The LAC is sent in a system message on each cell broadcast channel. When the mobile station is powered on, plugged into a SIM card, or discovers that the lac in the current cell is not the same as what it originally stored, it advertises its current location area to the network through the IMSI combination (Imsiattach) or the location update process. The network stores the location area of each mobile station and serves as the location information for future paging of the mobile station.

Settings and impact

Lac Coding method Each country has the corresponding regulations, China Telecom's own GSM Internet Lac encoding method also has a clear stipulation (see the Ministry of PTT on GSM system specification). The distribution and coding of the LAC have been identified in the early stages of the construction network, with few changes during operation. The size of the location area (LAC), which is the size of the range covered by a location code (LAC), is a fairly critical factor in the system. If the LAC coverage is too small, there will be an increase in the location update process on the mobile station, which increases the signaling traffic in the system. Conversely, if the location area coverage is too large, then the network paging Mobile station, the same paging message will be sent in many cells, which will cause the PCH channel overload, but also increase the signaling traffic on the Abis interface. Because the mobility and burst are quite strong in mobile communication, there is no uniform standard for the adjustment of the position area size. The operating department can determine whether to adjust the size of the location area based on the current network, the PCH load situation in each area and the signaling link load. If the former phenomenon is serious can be appropriate to adjust the location of small, conversely, the appropriate adjustment of the large location area. In general, it is recommended that the location area be as large as possible.

Precautions

Location code settings must be strictly in accordance with the relevant provisions of China Telecom, should not be in the network (nationwide) appear in two or more than two locations using the same location area

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Trace area code--Tracking region code

TA and related basic concepts

Ta:tracking area, tracking zone. TA is the new concept of LTE system for the location management of UE.

Related concepts:

LA Location Area

RA Routing Area Routing Zone

LAI LA Identity Location Area identification

RAI RA identity Route zone identification

TAI TA identity Tracking Area identification

LAC LA Code Location Area code

RAC RA Code Routing area encoding

TAC TA Code Tracking area code

LA (location area: LAI = PLMN + LAC) is the concept of the 2G and 3G era circuit domain, which enables the mobile switch (msc/sever) to know the location of the terminal in time, and when the paging terminal, the Mobile Exchange center in the terminal's location area of all the cells to search. The terminal does not need to be updated in one location; When moving across LA, the LA update process needs to be initiated so that the network knows the location of the terminal, and the terminal needs a periodic LA update process in order to maintain close contact with the network side.

RA (routing area: RAI = plmn+ LAC + RAC) is the concept of the 2G ERA and 3G ERA grouping domain, it enables SGSN to know the location of the terminal in time, before the terminal to initiate data transmission, must register with SGSN and HLR, and paging the terminal in the routing area. The terminal may not need to do an RA update within an RA, an RA update occurs when moving across the routing area, and periodic RA updates are required.

TA's role

The Tracking zone (Tracking area) is a newly established concept for the location management of the LTE system for UE. When the UE is idle, the core network can know the tracking area where the UE resides, and when the UE in idle state needs to be paged, it must be paged in all cells in the tracking area registered by the UE.

TA is a community-level configuration, multiple cells can be configured with the same TA, and a cell can only belong to a TA.

The Tai is the tracking area identification for LTE (Tracking Zone Identity), which is composed of PLMN and TAC.

TAI = PLMN + TAC (Tracking area Code)

Multiple Ta form a TA list, while assigning to a ue,ue in the Ta list (TA lists) do not need to perform TA update, in order to reduce the frequent interaction with the network;

When the UE enters the new TA area that is not in its registered TA list, it needs to perform TA update, the Mme assigns a set of TA to the UE, and the newly assigned TA can also contain some TA from the original TA list;

Each cell belongs to only one TA.

The influence of CSFB on TA list

When the CSFB is on, the location information of the mobile phone needs to be updated with the Mme and MSc, so TA and La must ensure a certain correspondence. For this reason, the Mme cannot turn on the smart TA list function, because once this function is turned on, the MSC side is unable to update the response La information (the LTE user in TA list does not need to interact with the core network signaling) in order to be able to respond to the voice paging message in a timely manner.

LA and TA