Brief description of PLMN (a little messy note)

About PLMN

• PLMN (Public Land Mobile Network): public land mobile (communication) network
• A network established and operated by the government or an operator approved by it to provide the public with land mobile communication services. This network is usually interconnected with the Public Switched Telephone Network ( PSTN ) to form a regional or national-scale communications network.
• There are currently 3 PLMNs in Mainland China:
  1. China Mobile's GSM/GPRS/EDGE network
  2. China Unicom's GSM/GPRS network
  3. China Telecom's CDMA-1X network
• PLMN = MCC + MNC , PLMN is composed of MCC mobile country code and MNC mobile network code, for example:
  1. The PLMN of China Mobile GSM is: 46000 (MCC: 460, MNC: 00)
  2. The PLMN country code MCC of China Unicom GSM is 460, and the network code MNC is 01: 46001
  3. Mobile network codes related to mainland China: China Mobile uses 00 , 02 , 04 , 07 , China Unicom GSM system uses 01 , 06 , 09 , China Telecom CDMA system uses 03 , 05 , Telecom 4G uses 11 , China Railcom uses 20
• PLMN is synonymous with mobile communication network. Specific to our country, the network of each mobile communication operator is considered a PLMN, so the networks of China Mobile, China Unicom and China Telecom are different PLMNs.
• With the rise of virtual operators, virtual operators can also be regarded as a PLMN.
• In order to let users know which PLMN they are in, each PLMN should have a clear identification (number), which is broadcast by the base station as system information so that all terminals under the base station can receive it.
• The mobile country code ( MCC ) is used in combination with the mobile network code ( MNC ) (called a combination of "MCC/MNC tuple " ) to uniquely identify the mobile network operator (operator) using GSM (including GSM-R ), UMTS and LTE public land mobile networks.
• Some but not all CDMA , iDEN and satellite mobile networks are also identified as MCC/MNC tuples
• For a specific terminal ( UE/ mobile phone), it is usually necessary to maintain / save several different types of PLMN tables, and there will be multiple PLMNs in each list . as follows:
  1. RPLMN (Registered PLMN): The PLMN registered before the terminal was shut down or offline
  2. EPLMN (Equivalent PLMN equivalent PLMN): A PLMN that is in the same position as the PLMN currently selected by the terminal has the same priority; this PLMN is configured on the MSC or MME , if the user is at the home location then EPLMN=EHPLMN . If you are roaming, EPLMN ! =EHPLMN
  3. EHPLMN (Equivalent Home PLMN equivalent local PLMN): It is a local PLMN with the same status as the PLMN currently selected by the terminal; the operators corresponding to HPLMN may have different number ranges, for example, China Mobile has three numbers: 46000 , 46002 , 46007 Number segment.   46002 is EHPLMN relative to 46000 ; it is written into the USIM card when the operator burns the card
  4. HPLMN (Home the PLMN home PLMN): the PLMN belongs to the end user; terminal USIM on the card IMSI number included in MCC and MNC to the HPLMN on the MCC and MNC are consistent
  5. VPLMN (Visited PLMN): PLMN visited by end users. The PLMN and the MCC and MNC of the IMSI stored in the SIM card are not exactly the same
  6. UPLMN (User Controlled PLMN User Controlled PLMN): a parameter related to PLMN selection stored on the USIM card
  7. OPLMN (Operator Controlled PLMN): a parameter related to PLMN selection stored on the USIM card
  8. FPLMN (Forbidden PLMN): It is a PLMN that is forbidden to access. Generally, the terminal will add it to this list after trying to access a PLMN and is rejected
  9. APLMN (Approve PLMN can capture PLMN): It is a PLMN on which the terminal can find at least one cell and can read its PLMN identification information.
• When the UE is turned on, the first task is to search for the network and register, that is, the network selection operation. The UE 's network selection operation can be divided into two processes, PLMN selection and cell search. In the PLMN selection process, the UE maintains some PLMN lists, which sort the PLMNs according to their priority, and then search downwards from the high priority. The priority order is: RPLMN , HPLMN , UPLMN , OPLMN , VPLMN . Except for VPLMN , each type of PLMN list stores the corresponding RAT (Radio Access Technology), that is, it identifies GSM/GPRS technology, UMTS technology or E-UTRA technology, so as to realize which access technology is preferred under the same PLMN .
• When users access the network, they must not only consider access to the operator's network, but also consider the access time.
• RPLMN as the last registered network from the access success rate and access time is certainly the best, EPLMN is the last registered network of peer to peer network is equivalent to RPLMN .
• Other PLMNs are all PLMNs that can be searched by the current terminal. If none of the current PLMNs match, the terminal will try to access according to the signal strength.
• Due to various reasons, the network accessed is not necessarily the user’s home operator network, so after the user accesses the network, the cell reselection process will be initiated. At this time, if there is HPLMN, EHPLMN signal coverage, they will choose to return to home Operator network.
• Both the mobile phone and the base station must be set up with a PLMN. The mobile terminal needs to know which operators’ PLMNs I can access , and the base station needs to know which operators’ mobile phones I allow to roam in

supplement:

• PLMN and PSTN are both communication networks. The biggest difference between PLMN and PSTN is the difference between wired and wireless. PSTN users are connected to the switch in the network by a subscriber line, and the location of the telephone terminal is fixed and inconvenient to move; PLMN users use mobile terminals and base stations They are connected by wireless signals, and finally through the switch in the network to realize convenient communication during the movement
• PSTN (Public Switched Telephone Network) definition: Public Switched Telephone Network, a commonly used old telephone system. That is the telephone network commonly used in our daily life