Field Guide · protocol

Also known as: NB-IoT, Narrowband IoT, Cat-NB1, Cat-NB2

NB-IoT (Narrowband IoT) is a licensed-spectrum, cellular low-power wide-area network standardized by 3GPP for the Internet of Things.1 It squeezes a complete cellular link into a single 180 kHz carrier — the width of one LTE resource block — and layers on deep coverage extension and aggressive sleep modes so a sensor can reach a basement meter and still run for years on a battery. Unlike unlicensed IoT radios, NB-IoT runs inside operators’ licensed bands.

LTE carrier in-band guard standalone refarmed each NB-IoT block is 180 kHz wide — one LTE resource block
NB-IoT fits in one 180 kHz resource block: inside an LTE carrier, in its guard band, or standalone on a refarmed (e.g. GSM) channel.

Overview

NB-IoT trades throughput and latency for reach and battery life. It uses OFDMA on the downlink and single-carrier FDMA on the uplink, where a device may transmit on a single 3.75 or 15 kHz tone to concentrate all its power for the best link budget. Coverage enhancement repeats transmissions many times so a signal survives roughly 20 dB deeper into buildings than plain LTE.

Technical characteristics

Property Value
Bandwidth 180 kHz carrier
Downlink OFDMA, 15 kHz subcarriers
Uplink SC-FDMA, single-tone (3.75/15 kHz) or multi-tone
Duplex Half-duplex FDD (typical)
Peak rate tens to ~250 kbps (Cat-NB1); higher for NB2
Power saving PSM and extended DRX (eDRX)
Coverage up to ~164 dB maximum coupling loss

Because it reuses LTE numerology and the operator’s core network, NB-IoT inherits SIM-based security, authentication, and global roaming — advantages the unlicensed LPWANs lack.

History

3GPP introduced NB-IoT in Release 13 (frozen in 2016) as Cat-NB1, alongside the related LTE-M.2 Release 14 added Cat-NB2 with higher data rates and positioning, and later releases folded NB-IoT into the 5G ecosystem as a recognized mMTC (massive machine-type communications) technology.

Deployment

Operators worldwide have deployed NB-IoT for smart metering, environmental sensing, smart parking, and asset tracking — applications that send small, infrequent reports and value deep indoor coverage. It competes with unlicensed LoRaWAN and Sigfox on one side and, for higher-rate or mobile use, with its sibling LTE-M on the other.

Decoding it with GopherTrunk

NB-IoT is out of scope for GopherTrunk, a trunked land-mobile voice scanner. NB-IoT is encrypted, SIM-authenticated cellular traffic on licensed spectrum; receiving user payloads is not something an SDR scanner does. GopherTrunk implements no LTE/NB-IoT PHY or core-network stack. On a waterfall you would simply see it as a narrow carrier within an operator’s band.

Sources

  1. Narrowband IoT — Wikipedia, for the 180 kHz carrier, deployment modes, and coverage-enhancement design. ↩

  2. NB-IoT — 3GPP, for the Release 13 origin and the standard’s positioning in cellular IoT. ↩

See also