NB-IoT vs LTE Cat-1: Choosing a Cellular IoT Link

Key Takeaways

• NB-IoT is a 3GPP narrowband LPWAN standard using a 180 kHz licensed carrier, aimed at small, infrequent uplinks.
• LTE Cat-1 is a full LTE device category with wider bandwidth, higher throughput, voice support and continuous handover.
• NB-IoT wins on link budget and battery life; Cat-1 wins on latency, payload size and mobility.
• An NB-IoT product buys an operator subscription, not a private network, so band support comes first.
• Every cellular figure is conditional on band, antenna gain, repetition count and operator configuration.

1. What Is NB-IoT?

NB-IoT is a 3GPP narrowband cellular radio standard for low-power wide-area devices that send small payloads infrequently over licensed spectrum.

It is also written Narrowband IoT and LTE Cat-NB1, and it arrived with 3GPP Release 13 as part of the Low Power Wide Area (LPWAN) family. The operator deploys it in licensed spectrum, so the device needs a SIM and a subscription instead of a gateway.

Core characteristics

• Narrow 180 kHz channel: one carrier occupies 180 kHz, the width of a single GSM carrier. That concentrates transmit energy and keeps the radio simple, so the device draws far less current than a wideband LTE device.
• Operator-managed licensed spectrum: interference is managed by the network, so no site survey or channel plan is needed. The user cannot move the frequency or set the output power.
• Coverage extension by repetition: the same transport block is repeated and a higher power class is available, pushing the link budget beyond a normal cellular link. The cost is time on air, and time on air is drawn from the battery.
• Power saving built into the standard: Power Saving Mode (PSM) and extended DRX (eDRX) keep the device registered while its radio sleeps, which is where multi-year operation comes from.

2. How Does NB-IoT Work?

NB-IoT works through a narrow carrier that the operator allocates in licensed spectrum.

1. A 180 kHz carrier, introduced in 3GPP Release 13. One carrier occupies 180 kHz in both directions and uses low-order modulation, so peak rates stay in the tens of kilobits per second. The link suits readings, alarms and setpoints rather than file transfer.
2. Three deployment modes, also per 3GPP Release 13. Stand-alone mode refarms a former GSM carrier, in-band mode sits inside the resource blocks of an existing LTE carrier, and guard-band mode uses the unused edge of an LTE carrier. Performance therefore depends on the local deployment.
3. Repetition and higher transmit power stretch the coverage. The device retransmits the same transport block and a higher power class is available - 23 dBm alongside 20 dBm per 3GPP. At the cell edge the same payload takes longer to send, and that time comes out of the power budget.
4. The device attaches to the operator core network. Registration and authentication run through the SIM against the operator's Evolved Packet Core (EPC), and the application server sits behind the operator network. There is no private gateway to install.
5. PSM and eDRX produce the battery life. In Power Saving Mode the device stays registered with its radio off for a configured interval, and eDRX lengthens the paging cycle beyond the normal LTE cycle. Battery life is a timer and payload decision, so two products on one module can differ by years.
6. Mobility and latency are deliberately limited. An NB-IoT device is expected to stay put, so continuous handover during an active transfer is not in the profile, and a repeated uplink can take from a fraction of a second to several seconds. A moving product needs another technology.

3. What Is LTE Cat-1?

LTE Cat-1 is a 3GPP device category that carries a full LTE connection at reduced throughput, giving IoT products higher data rates, voice capability and continuous mobility.

Cat-1 is not a separate radio standard: it is UE category 1 within LTE, with the same carrier structure and core network as a phone, and it sits above NB-IoT in capability and below Cat-4 in cost. Typical peak rates are 10 Mbit/s downlink and 5 Mbit/s uplink per 3GPP category 1.

Core characteristics

• Full LTE bandwidth and throughput: the device works inside a normal LTE carrier, so payloads of kilobytes to megabytes are practical. Firmware updates and log uploads stop being a special case.
• Voice support: VoLTE is available in the category, which matters for products with a human interface or an audible alarm path. NB-IoT carries data and no voice.
• Continuous mobility and handover: the device keeps its session while moving between cells at speeds a vehicle reaches. Trackers, vehicles and handheld terminals depend on this.
• Higher current, standard hardware: round-trip latency is typically tens of milliseconds in connected state and reconnection is quick, but idle and connected currents are higher. A multi-band LTE module, a 50 ohm feed and a normal data SIM cover most deployments.

4. NB-IoT vs LTE Cat-1: What Is the Difference?

The difference is a deliberate trade: NB-IoT spends throughput and mobility to gain coverage and battery life, while LTE Cat-1 keeps full LTE behaviour and pays in current.

The decision rule: choose NB-IoT when the device is fixed, the payload is small and infrequent, and the site has poor coverage or no mains power; choose LTE Cat-1 when the product needs larger payloads, voice, low latency or movement.

5. NB-IoT Configuration and Key Parameters

These parameters decide whether an NB-IoT design works in the field.

• Band support and operator band plan: deployments commonly use 800 MHz and 900 MHz, with 1800 MHz in some regions. A module whose band list misses the local carrier never attaches.
• Antenna gain and band coverage: 2.5 to 3 dBi is typical on meter enclosures. An antenna rated outside the operator band gives a link that works in strong signal and fails at the cell edge.
• 50 ohm impedance and VSWR: 1.5 or lower is the usual target at the connector. A poor match reflects transmit power back into the radio, cutting radiated power.
• Cable loss and antenna placement: a thin pigtail plus a metal cabinet can cost several dB. The symptom is a link that passes on the bench and fails in the enclosure.
• PSM and eDRX timers: active time is often a few seconds to tens of seconds, with the periodic update timer at minutes to hours. Set too long, downlink commands arrive late; set too short, the cell drains.
• SIM form factor and provisioning: 4FF plastic SIMs and embedded MFF2 parts are both common. An unprovisioned SIM produces an attach loop that fails the first data session.
• Attach and registration retries: backoff grows with every failed attempt. Without a retry limit, a badly placed device retransmits at full power and drains in days rather than years.
• Payload size versus upload interval: tens of bytes every few minutes or hours is the efficient zone. Once payload growth forces back-to-back transfers, average current climbs and the battery case must be redesigned.

6. When to Use NB-IoT and When Not To

Good fit for NB-IoT

• Fixed meters and sensors in basements, manholes or rural sites, where coverage matters more than speed.
• Battery products with a target life of several years and an uplink of tens of bytes.
• Sites with no mains power and no wired backhaul, such as water and gas metering.
• Applications that tolerate seconds of latency, such as daily consumption reports.

Good fit for LTE Cat-1

• Devices that move: vehicle trackers, handheld terminals and mobile equipment.
• Payloads of kilobytes to megabytes, including firmware updates and log uploads.
• Interactive applications that cannot tolerate multi-second replies, such as control panels.
• Designs that also need voice, since Cat-1 carries VoLTE.

Poor fit for NB-IoT

• Tracking or roaming assets, because continuous handover during transfer is outside the profile.
• Streaming or large-file transfer, where the narrow channel becomes the bottleneck.
• Sub-second control loops, given the repeated uplink profile.
• Regions where the local operator runs no NB-IoT carrier.

Poor fit for LTE Cat-1

• Battery products with a multi-year target and no mains connection.
• Installations in very weak coverage, where the extra link budget of NB-IoT is decisive.
• Cost-driven designs where a few tens of bytes per hour is the whole data model.

7. Real-World Applications

In metering, environmental sensing and infrastructure monitoring, the uplink decision comes down to coverage and power first. A water meter or gas meter reports a small reading at a fixed interval and must survive on a battery with no mains supply, which is the profile NB-IoT was written for.

The Ebyte store currently lists no NB-IoT module, and that should be stated plainly. The NB-IoT band coverage in the catalogue comes from the antenna range rather than from a radio: the TXGN-JW-5 elbow gel-stick antenna covers NB-IoT, GPRS and GSM bands with 2.5 dBi gain, an SMA-J connector, 50 ohm impedance and VSWR of 1.5 or lower, and the TXGN-JZ-5 is its straight stick equivalent. The cellular terminal line is LTE Cat-1, represented by the E840-DTU(EC05-485)E-V2, an industrial LTE Cat-1 4G RS485 modem for the Asia-Pacific market with TCP, UDP, MQTT and HTTP support, 8 to 28 V DC power, DIN-rail mounting and transparent bidirectional serial transmission over LTE-TDD and LTE-FDD bands. It is a Cat-1 product, not an NB-IoT product.

For built-in designs the TXGN-FPC-3407 is an FPC antenna with 3 dBi gain, an IPEX-1 interface, 50 ohm impedance, VSWR of 1.5 or lower and 824-960 MHz plus 1710-1990 MHz coverage, described for NB, GSM, GPRS and NB-IoT use; where the enclosure is metallic, the TXGN-JKD-20 rubber sucker antenna offers 3 dBi gain, SMA-J, 50 ohm, VSWR of 1.5 or lower and 800, 900, 1800 and 1900 MHz coverage for GPRS and NB-IOT links. Installed gain is usually lower than datasheet gain, so band coverage, feed-line loss and mounting should be checked before the enclosure is signed off.

8. FAQ: NB-IoT in Practice

Q1: What is the difference between NB-IoT and LTE Cat-1?

NB-IoT is a narrowband 3GPP standard built for small, infrequent uplinks in licensed spectrum, while LTE Cat-1 is a full LTE device category with higher throughput, voice support and continuous handover. NB-IoT gives more link budget and lower power consumption; Cat-1 gives speed, low latency and mobility.

Q2: How much data can NB-IoT send and how fast?

Practical NB-IoT payloads are tens to a few hundred bytes, and peak rates stay in the tens of kilobits per second depending on the deployment mode and repetition count. A transfer typically completes in under a second in good coverage, but at the cell edge repeated transmissions can stretch one uplink to several seconds.

Q3: Does NB-IoT support voice or mobility?

No, NB-IoT carries data and it is designed for static devices. Voice calls need VoLTE on an LTE category such as Cat-1, and continuous handover during an active transfer is not part of the NB-IoT profile. A moving asset such as a tracked vehicle needs a full LTE category.

Q4: How long does an NB-IoT device last on battery?

Multi-year operation is achievable but conditional, not guaranteed. Life depends on payload size, upload interval, sleep current of the whole board, and the repetition count the network sets for the installed coverage. A device reporting tens of bytes once a day with well configured PSM and eDRX timers can reach several years.

Q5: Why does my NB-IoT device fail to attach to the network?

Most attach failures are band, SIM or coverage issues.

• Never attaches → check the band list against the operator's live band plan.
• Attach rejected or looping → check the SIM is provisioned for NB-IoT.
• Drops in the cabinet → check antenna coverage and feed loss.
• Drops after a timer expires → check PSM and eDRX timers.

Q6: Can I use the same antenna for NB-IoT and LTE Cat-1?

Not reliably, because the two radios do not use identical bands. An antenna specified for NB-IoT, GPRS and GSM bands covers the lower cellular bands well but may miss the higher LTE bands a Cat-1 module uses. Check the antenna frequency range against both band plans.

9. Pre-Flight Checks Before You Choose a Cellular Link

1. Confirm the network exists on site. Check that the local operator runs a live NB-IoT carrier in a band your module supports, and test it with the final antenna before freezing the design.
2. Size the payload and interval first. Note bytes per report and reports per day; if the answer is kilobytes or minutes, move to LTE Cat-1.
3. Build the power budget before the hardware. Average current comes from sleep current, transmit current, time on air at the expected repetition count, and the PSM and eDRX timers; compare it with the cell capacity plus margin.
4. Treat the antenna as part of the radio design. Verify band coverage, gain, 50 ohm impedance, VSWR, connector type and feed-line loss, because installed gain sets the real link quality.
5. Check SIM provisioning last. Confirm the SIM profile, the form factor that fits the enclosure, and the tariff for the expected report volume.