Definition
HPLMN (Home PLMN, Home Network) is the network of the operator to which the SIM card is subscribed, determined by the MCC/MNC in the IMSI. It is the counterpart of VPLMN (Visited PLMN, Visited Network): the device accesses the HPLMN when in the home area and accesses the VPLMN when roaming abroad. The identification of HPLMN and VPLMN is the basis for Roaming Policy, PLMN Selection, and billing distinctions (local vs. roaming).
Technical Principle
The first few digits of the IMSI are the MCC (Mobile Country Code) and MNC (Mobile Network Code), which together identify the HPLMN. When the device is powered on or enters a new area, it scans available networks according to the PLMN Selection strategy, prioritizing the HPLMN (if in the home area) or the Preferred Network preferred network. When roaming, the device attaches to the VPLMN and interacts with the HPLMN via signaling to complete authentication and billing.
Application in ICMP
ICMP needs to identify the HPLMN of each card for: Roaming Determination—distinguishing local and roaming usage based on whether the current PLMN matches the HPLMN; Billing—recording the HPLMN and VPLMN in the CDR, supporting Geo-Based Pricing and Cross-Border Billing; Policy—Roaming Policy can restrict or prioritize certain VPLMNs. For Multi-IMSI cards, different profiles may correspond to different HPLMNs.
How the Home Identity Assigns the Tariff
The home network is the public land mobile network where this SIM’s subscription identity sits, not the country where the device happens to be standing. The mobile country code and mobile network code in the identity form the home network. The network the device is attached to now is the visited network. When the two match, usage is handled as a local relationship. When they differ, the relationship is roaming: signaling returns to the home side for authentication, and the CDR carries both network identities. The home network is therefore the reference field for tariff, roaming policy, and report grouping. The current visited network is the field coverage. One does not stand in for the other.
Use the concept when the platform can already read the country code and network code from the SIM record or the CDR, and the product rules state how “same as the home network” and “different from the home network” are priced. A shipping address is not enough, because a SIM can be subscribed in one country and used for a long time in another. On a multi-identity SIM, first confirm which identity is enabled now. The home network changes with the enabled identity. When diagnosing a failed connection, read the current network in card diagnostics together with the home network on the SIM record, then decide whether this is a local rejection, roaming that was never opened, or a policy that forbids that visited network.
Writing the Visited Place as the Subscribed Place
A common slip is to overwrite the home network with the location the device reports, or with the visited network. After a fleet crosses into another country, the current position has changed and the subscription identity has not. If a report writes “country of presence” as the home country, local and roaming tariffs are applied to the wrong place for the whole month. The reverse also happens: roaming CDRs seen inside the home country are treated as bad master data. Near a border, or indoors where only a neighboring country’s signal is found, a device can attach to another network. A CDR whose visited network differs from the home network is then normal. Policy decides whether to allow it. The SIM’s subscription identity should not be rewritten.
Another bias is to store only a country field. The same country code can still point, through different network codes, at different carriers in that country, with different tariffs and different allowed visited networks. After a multi-identity switch, if usage aggregation still groups by the home network from before the switch, traffic on the cheaper identity is counted into the expensive one. Keep identity, country code, network code, and enabled status separate. Before a CDR is posted, check it against the identity that was enabled at the time, not only against the country name in the aggregate.
Where one country code has several network codes, grouping should land on the specific network, not only on the country name. When a temporary test identity ends, disable it at once, or later production usage will keep hanging on the test home network. Before and after an identity switch, keep the time of the last CDR on the old identity and the time of the first attach on the new identity. Records on the boundary can then be explained, and a site that stays attached to a neighboring network across the border will not be rewritten into a different subscription.
Both domestic roaming and international roaming can make the current network differ from the home network, and the billing meaning is not always the same. A device that attaches, inside the home country, to another licensed network may still be treated as local under some contracts and as domestic roaming under others. International roaming prices apply only after the device leaves the home country. Comparing country codes alone treats a domestic off-net attach as travel abroad, and treats a network just across the border as local. The rule has to look at country code, network code, and the contract’s definition of “local.”
The home network on a CDR should be the identity in force when the usage occurred, not the identity on the SIM record on the day of posting. A late CDR may arrive after an identity switch. If the posting job overwrites the home network carried on the CDR with the “current identity,” charges from the old identity are booked on the new tariff. When storing the CDR, do not rewrite the carrier’s original home and visited fields. Keep the platform’s grouping beside them, so reconciliation can still return to the network codes the carrier saw.
If the inquiry screen shows only one “network” column, support cannot tell whether the subscribed place is wrong or the device simply attached somewhere else. Show the home network, the current visited network, and the time of the latest attach side by side. Only when the three agree is the device online at home. A visited network that is empty while the home network has a value means the record is still there. It does not mean the device is connected now.