Glossary of Terms and Technologies
Cellular network identifiers, radio terms, how GeoCell draws coverage, and the searches — for reference while searching or reading results.
Location and Cell Identifiers by Technology
Each generation of mobile network identifies a cell's location differently, but the underlying idea is the same: a location-management code plus a cell code, prefixed by the operator's network code (MCC+MNC), together form a globally unique cell identifier.
| Technology | Location Management | Area Identifier | Area ID Composition | Cell Identifier | Global Cell ID |
|---|---|---|---|---|---|
| 2G (GSM) | Location Area (LA) | LAC (Location Area Code) | MCC + MNC + LAC | CI (Cell Identity) | CGI = MCC + MNC + LAC + CI |
| 3G (UMTS) | Location Area (LA) | LAC (Location Area Code) | MCC + MNC + LAC | CID (Cell ID) | CGI = MCC + MNC + LAC + CID |
| 4G (LTE) | Tracking Area (TA) | TAC (Tracking Area Code) | MCC + MNC + TAC | ECI (E-UTRAN Cell ID) | ECGI = MCC + MNC + ECI |
| 5G NR | Tracking Area (TA) | TAC (Tracking Area Code) | MCC + MNC + TAC | NCI (NR Cell ID) | NCGI = MCC + MNC + NCI |
| NB-IoT | Tracking Area (TA) | TAC (Tracking Area Code) | MCC + MNC + TAC | NCI (NR Cell ID) | NCGI = MCC + MNC + NCI |
- 5G NR & NB-IoT share the same identifiers (TAC, NCI, NCGI) — NB-IoT is a subset of the 5G NR specification, not a separate identifier scheme. The 5G TAC is 24 bits, versus 16 bits in LTE.
- NCI (NR Cell ID) is a 36-bit identifier: the higher bits identify the gNB, the remaining bits identify the specific cell.
eNB, gNB and CI
eNB (Evolved Node B)
The 4G base station — the hardware that connects LTE devices to the mobile network.
- Radio — sends and receives signals to/from LTE devices.
- Scheduling — decides which radio resources each device uses, and when.
- Mobility — handovers, measurement reports, idle-mode cell reselection.
- Core interface — MME and SGW via S1; neighbouring eNBs via X2.
Each eNB has an eNB ID (20 bits for macro cells, 18-28 bits for home eNBs) — the most significant part of the ECI.
gNB (Next Generation Node B)
The 5G base station — the 5G counterpart of the eNB, for 5G NR devices.
- All the eNB functions, enhanced for higher speeds, lower latency and massive IoT.
- CU/DU split — can be split into a Central Unit and a Distributed Unit.
- Dual connectivity — can combine 4G and 5G with an eNB (EN-DC).
- Core interface — 5G Core (5GC) via NG; neighbouring gNBs via Xn.
Each gNB has a gNB ID (22-32 bits, operator-configurable). The NCI includes the gNB ID plus a cell sector ID.
CI (Cell Identity) in LTE
The identifier of a single cell within an LTE network — not the same as the older 2G/3G Cell ID (CID). It is 28 bits long and, on its own, only identifies the cell within one operator's PLMN (MCC+MNC), not globally.
- Most significant bits (20, 18 or variable): the eNB ID — which base station.
- Least significant bits (8, 10 or variable): the Sector ID — which cell on that eNB (sector 0, 1, 2...).
A common macro setup is a 20-bit eNB ID + 8-bit Sector ID (up to 256 cells per eNB, typically 3). CI and ECI are used interchangeably for this 28-bit value; the ECGI adds MCC+MNC to make it global.
Quick Reference
| Term | Full Name | Network | Role |
|---|---|---|---|
| eNB | Evolved Node B | 4G LTE | Base station |
| gNB | Next Generation Node B | 5G NR | Base station |
| CI | Cell Identity | 4G LTE | 28-bit ID of a single cell (within a PLMN) |
| TAC | Tracking Area Code | 4G / 5G | Groups cells for paging (16 bits LTE, 24 bits 5G) |
| LAC | Location Area Code | 2G / 3G | Groups cells for paging |
| Identifier | Length | Contains | Globally Unique? |
|---|---|---|---|
| CI (LTE) | 28 bits | eNB ID + Sector ID | No (needs MCC+MNC) |
| ECI (LTE) | 28 bits | Same as CI | No |
| ECGI (LTE) | CI + MCC+MNC | PLMN + CI | Yes |
| NCI (5G) | 36 bits | gNB ID + Sector ID | No |
| NCGI (5G) | NCI + MCC+MNC | PLMN + NCI | Yes |
Coverage on the Map
A cell's coverage is never known exactly — every polygon GeoCell draws is an estimate of the area a sector may serve, not a measured boundary. GeoCell can show three kinds, from roughest to most specific:
Default polygon
A polygon around the antenna, oriented by the cell's azimuth, whose reach depends only on the technology and is generated when the cell is imported (about 300 m for 2G, 275 m for 3G, 250 m for 4G, 225 m for 5G and 200 m when the technology is unknown).
Always available, but the same size for every cell of a technology — a rural macro cell and a city small cell look alike.
Real polygon "Real" button
Built from the aperture (beam width, degrees) and radius (distance, metres) the operator supplied for that sector. When the operator gave no data, the Real polygon is simply the default one.
Use the Real button on the map to switch. Searches that compare polygons (Advanced “touching”, Geo by point) calculate with the real polygon but draw the default one unless you switch.
Combain coverage
A polygon measured from crowdsourced device reports by the Combain service, shown for a searched cell or an Operation cell that has one.
Closest to reality where there is data, but it depends on external availability and on how many devices reported that cell — treat it as a second opinion next to the operator's figures.
Reading coverage with care
- A device is usually served by a nearby sector, but not always the closest one: terrain, buildings, load balancing and indoor/outdoor position can put it on a farther cell.
- Neighbouring polygons overlap by design so devices can hand over; a point inside two polygons is normal.
- An antenna's real beam is not a sharp wedge: the edges fade, and back-lobes can reach behind the antenna.
- Several cells on one site (different sectors, bands or technologies) share the same location but have different azimuths and CGIs.
Map buttons
A blue button is on; a white one is off. Your choice is remembered.
- Grid — geohash grid (labels appear when zoomed in enough).
- Real — switches between default and real polygons.
- Counties — CAOP administrative boundaries.
- PoI — Points of Interest (Operations).
- 3D — Google's photorealistic 3D map (rotate and tilt freely); press 2D to come back. Cell polygons, PoIs and the Counties overlay are shown on it, click any of them for the same balloon as in 2D, and Grid, Real, Counties, PoI and Full screen have buttons on the right of the 3D map.
Network and Radio Terms
Public Land Mobile Network — an operator's network, identified by MCC + MNC.
Mobile Country Code and Mobile Network Code — together identify the country and the operator (e.g. 268-01 = Portugal, MEO).
Same idea in different generations: LAC (Location Area Code) groups 2G/3G cells; TAC (Tracking Area Code) groups 4G/5G cells. GeoCell stores both in the same
lac_tac field.Radio Access Technology — the kind of radio a cell uses: GSM (2G), UMTS (3G), LTE (4G), NR (5G). GeoCell's "technology" field.
One directional antenna face of a site. A typical site has three sectors about 120° apart; each sector is a separate cell with its own CI and azimuth.
Macro cells cover hundreds of metres to kilometres from a mast; small cells and femtocells cover streets, buildings or a single home/office, so their polygons are much smaller than the default one.
Physical Cell ID — a small identifier (0-503 in LTE) broadcast over the air so a device can tell a cell from its immediate neighbours. Unlike CI/ECI it is not globally unique and is reused across the network.
A range of radio frequencies a cell uses (e.g. B3, B20, n78), with separate uplink (device→network) and downlink (network→device) frequencies. Lower bands reach farther; higher bands carry more data over shorter distances.
The channel number of a carrier frequency in 2G/3G (ARFCN, UARFCN), LTE (EARFCN) and 5G (NR-ARFCN) — a compact way to name the exact frequency and, with it, the band.
Several operators sharing the same physical radio equipment or site. GeoCell shows this as a cell's
ran_cgi: the CGI of the actual RAN owner when it differs from the serving operator's own.5G can run Non-Standalone (anchored on a 4G eNB and core, using EN-DC dual connectivity) or Standalone (its own 5G core). In NSA the device may show both an LTE and an NR cell at once.
Passing an active call or data session from one cell to another as a device moves, without dropping it.
How an idle device picks the cell to camp on; it can change without any activity, so the last serving cell is not always the closest one.
Cells a device reports as candidates for handover from its serving cell — useful for locating a device when the serving cell alone isn't precise enough.
A value telling a device how early to transmit so its signal arrives on time; it reflects the distance to the serving antenna (about 550 m per step in GSM), so it narrows a position to a ring around the site. Not to be confused with the Tracking Area.
LTE/5G signal measurements: reference signal power (RSRP), reference signal quality (RSRQ), total received strength (RSSI) and signal-to-interference-plus-noise ratio (SINR). Higher (less negative) is generally better.
The compass bearing (0-360°) an antenna sector points towards — shown on a cell's map polygon and info window.
A sector's horizontal beam width (aperture, degrees) and estimated coverage distance (radius, metres) — the inputs to the Real polygon.
A way of encoding a lat/lng point as a short base32 string, where nearby points share a common prefix. The map's "Grid" is a geohash grid whose cell size follows the zoom level, and an Operation map can jump to a geohash you type.
Subscriber and Device Identifiers
These are not stored by GeoCell; they are the identifiers that usually appear in operator records next to a cell.
International Mobile Subscriber Identity — the subscriber's identity on the SIM: MCC + MNC + a subscriber number (15 digits at most).
International Mobile Equipment Identity — a 15-digit identifier of the handset itself (per radio modem), independent of the SIM.
The subscriber's phone number, in international format.
Temporary identities the network assigns instead of the IMSI over the air (TMSI in 2G/3G, GUTI in 4G/5G), so a subscriber cannot be followed by a fixed identifier.
A device on another operator's network is in its visited network (VPLMN); the operator that issued the SIM is its home network (HPLMN). The cell's MCC+MNC is the visited network's, so it can differ from the SIM's.
GeoCell Searches
One or more cells by their CGI/ECGI/NCGI, or all the most recent cells of a LAC/TAC. If the local database has no answer it can fall back to external sources (Google, then Combain).
A main cell plus the cells around it — within a circle, or all cells whose polygon touches the main cell's polygon.
Cells by place: inside a circle or rectangle you draw, or those whose polygon touches a point.
Cells inside a CAOP area (district, county or parish), matched by containment in the official polygons.
Browse an operator's cells filtered by LAC/TAC, eNB/gNB, band, technology and date range.
Look a cell up in several external sources at once and compare where each one places it.
GeoCell-specific Concepts
The globally unique cell identifiers from the table above — what you search by, and what GeoCell stores as a cell's
cgi.A cell's identifier as reported by the Paragon data source, kept alongside the standard CGI when the two use a different numbering convention.
A third-party crowdsourced cell/Wi-Fi geolocation provider GeoCell queries for a cell's measured coverage polygon.
A public, crowdsourced database of cell tower locations — one of the external sources for a cell that isn't in the local database.
Carta Administrativa Oficial de Portugal — Portugal's official administrative boundaries. GeoCell can overlay them on Administrative search and Operation maps (the Counties button).
An Operation is a working session grouping cells and PoIs added over time by a group; a Target is a named, coloured grouping within it (e.g. a person or device), shown in the map legend.
Point of Interest — a marker placed on an Operation's map (an address, a meeting point...), separate from any cell.
When several rows describe the same cell name or CGI over time, searches show the most recently modified one, so results reflect the operator's latest data.