Field Guide · term

Also known as: base station, eNodeB, eNB, gNodeB, gNB, cell site

A base station is the fixed radio node that connects mobile handsets to the operator’s core network over the air interface. In LTE it is called the eNodeB (evolved Node B), and in 5G NR the gNodeB (next-generation Node B); both terms name the same functional thing — the tower-side radio that a cell site presents to phones.12 A single physical site is usually divided into sectors, each a separate cell facing a different direction.

mast + 3 sector antennas basebandeNB / gNB core network backhaul
A cell site divides into sectors, each a cell served by directional antennas; the base station's baseband unit links those radios via backhaul to the core network.

How it works

Physically, a base station combines antennas (usually mounted high for line of sight), radio units that up- and down-convert between baseband and RF, and a baseband unit that runs the modem and scheduler. In modern deployments the radio is often a remote radio head at the antenna, connected by fibre to a baseband unit at the base of the tower or pooled in a central office (a “cloud RAN” split). The base station schedules the shared air interface, assigning time-frequency resources to each handset, manages handovers as users move, and increasingly steers energy with massive MIMO and beamforming, especially in 5G.

A cell is the coverage area of one sector on one carrier; a typical macro site hosts three sectors at 120° spacing, and dense areas add small cells. Naming has tracked the generations: BTS in GSM, NodeB in 3G, eNodeB in 4G LTE, and gNodeB in 5G NR — the “e” and “g” prefixes marking each generation’s evolution of the same node.

Relevance to SDR

The base station is the counterpart, in cellular, of the trunking site in land-mobile radio: a fixed, sectored radio node that hands mobiles between coverage areas and coordinates access to shared spectrum. That parallel is the useful one for SDR readers — the sectored-site, neighbour-list, handover architecture GopherTrunk follows on P25 and DMR trunked networks is conceptually the same as a cellular eNodeB/gNodeB, just narrowband and (often) in the clear.

GopherTrunk does not decode cellular base stations. eNodeB and gNodeB air interfaces are wideband, licensed, and encrypted, and lie outside the scope of a land-mobile trunking scanner. The term is documented here so the cellular network structure a scanner shares the spectrum with is clear, and to draw the analogy to the trunking sites GopherTrunk does follow.

Sources

  1. Base station — Wikipedia, for the general definition of a base station and cell-site sectorisation. ↩

  2. eNodeB — Wikipedia, for the LTE eNodeB and its relationship to the NodeB/gNodeB lineage. ↩

See also