LAC: Location Area Code Location Code

LAC: Location Area Code Location Code
　　

 

A location code (in a mobile communication system) is an area set for paging. It covers a geographical area and is generally divided by administrative area (one county or one District) in the initial stage ), now it is flexible, divided by page size. when the paging volume under a lac reaches an alert threshold, it must be split.
　　

 

Definition
　　

To determine the location of the Mobile Station, each coverage area of gsmplmn is divided into many location areas, and the location code (LAC) is used to identify different location areas.
　　

 

Format
　　

The location code (LAC) is included in Lai and consists of two bytes. It is encoded in hexadecimal notation. The available range is 0001-fffeh, and the code group limit H and ffffh are not available (see GSM specifications 03.03, 04.08 and 11.11 ). A location area can contain one or more residential areas.
　　

 

Transfer
　　

The LAC sends messages to the system message on the broadcast channel of each cell. When the mobile device is started, SIM card inserted, or finds that the LAC in the current residential area is different from the original storage content, it notifies the network of its current location through imsi combination (imsiattach) or 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
　　

Each country has relevant provisions on the LAC encoding method. China Telecom also has specific provisions on its GSM online LAC encoding method (see the Ministry of Posts and Telecommunications's GSM system specifications ). Generally, the allocation and encoding of the LAC have been determined at the initial stage of network construction, and few changes are made during the running process. The size of the Location Code (LAC) is a critical factor in the system. If the LAC coverage is too small, the location update process of the mobile station increases, increasing the signaling traffic in the system. Otherwise, if the range of the Location Area is too large, the same paging message will be sent in many communities when the network paging mobile station, which will lead to heavy load on the PCH channel, it also increases the signaling traffic on the Abis interface. Due to the strong mobility and burstable nature of mobile communication, there is no uniform standard for adjusting the location area size. The operation department can determine whether to adjust the size of the Location Area Based on the current network and the PCH load and the signaling link load in each region for a long time. If the former is serious, the location area can be adjusted to a smaller value; otherwise, the location area can be adjusted to a greater value. Generally, it is recommended that the location area be as large as possible.
　　

 

Notes
　　

The location code must be configured in strict accordance with China Telecom's relevant regulations. Do not use the same location code in two or more locations in the network (nationwide ).