LTE and 5G Categories
and Bands Explained
LTE categories, carrier aggregation, frequency bands, 5G NSA and SA, NB-IoT, LTE-M, SIM formats and eSIM – the complete picture, without the jargon.
You bought a router that says “5G”. You put a SIM in. It connected at 4G. What happened?
Or you are standing in front of a spec sheet trying to work out whether CAT-12 is worth it over CAT-6 for your application. Or why your device works indoors on 800 MHz but not on 2100 MHz. Or why a 5G NSA router needs a strong 4G signal to stay connected.
This guide answers all of it. We start with frequency bands – the actual radio frequencies your device uses and what each one means for range, speed and penetration. Then we work through LTE categories, carrier aggregation, 5G NSA and SA, and the IoT-specific standards NB-IoT and LTE-M. We finish with SIM formats and a quick summary of eSIM and eUICC.
What we cover
- Frequency bands explained
- UK 4G and 5G bands in use
- How to look up your local mast
- LTE categories – what they mean
- Does category matter in practice?
- Carrier aggregation explained
- 5G NSA – why it still needs 4G
- 5G SA – the real thing
- NB-IoT and LTE-M for IoT
- SIM formats and eSIM summary
1. Frequency Bands – The Foundation of Everything
Before any of the LTE category or 5G discussion makes sense, you need to understand frequency bands. They are the actual radio frequencies that mobile networks use to carry your data through the air. Every piece of cellular hardware – your router, your module, your phone – is built around the bands it can receive and transmit on.
Mobile network frequencies are grouped into numbered bands by 3GPP (the international standards body that defines mobile network specifications). Band 20 is 800 MHz. Band 3 is 1800 MHz. Band 1 is 2100 MHz. Band 78 is 3.5 GHz. Each band has its own set of physical properties that determine how it behaves in the real world.
The physics that matter
There is a fundamental trade-off in radio physics: lower frequencies travel further and penetrate obstacles better, but carry less data per second. Higher frequencies carry more data per second but have shorter range and struggle with walls, buildings, and foliage.
This is why operators deploy multiple bands simultaneously. Low bands like 800 MHz provide coverage – they reach rural areas, basements, and the inside of buildings. High bands like 3.5 GHz provide capacity – they carry the heavy data loads in cities and dense areas. Your device uses whichever band gives the best combination of signal and speed at that moment.
2. UK 4G and 5G Frequency Bands in Use
In the UK, Ofcom licenses spectrum to mobile operators in specific frequency bands. Not every operator uses every band, and not every band is available at every mast. Here is the full picture of what is in use in 2026.
4G LTE bands
| Band | Frequency | Common name | Range | Building penetration | Primary use | UK operators |
|---|---|---|---|---|---|---|
| B20 | 800 MHz | Digital Dividend | Excellent | Excellent | Rural coverage, indoor fill | EE, Vodafone, Three |
| B8 | 900 MHz | GSM 900 refarmed | Excellent | Very good | Coverage, rural areas | O2, Vodafone |
| B3 | 1800 MHz | DCS 1800 refarmed | Good | Moderate | Urban capacity, most common CA band | All four operators |
| B1 | 2100 MHz | UMTS 2100 | Moderate | Moderate | Urban capacity | EE, O2, Three |
| B7 | 2600 MHz | 2.6 GHz | Short | Poor | Dense urban capacity, stadiums | EE, Vodafone, Three |
| B32 | 1500 MHz | L-band / SDL | Good | Good | Supplementary downlink only (CA) | EE |
5G NR bands
| Band | Frequency | Common name | Range | Typical peak speed | UK operators | Notes |
|---|---|---|---|---|---|---|
| n28 | 700 MHz | 700 MHz 5G | Excellent | 50-200 Mbps | EE, Vodafone, O2 | Rural 5G coverage, best building penetration |
| n78 | 3.4-3.8 GHz | C-band / 3.5 GHz | Urban/suburban | 200-800 Mbps | All four operators | Primary 5G band in UK cities – most 5G you see is this |
| n258 | 26 GHz | mmWave | Very short (<200m) | 1-4 Gbps | Limited trials | Dense venues only – no meaningful UK rollout yet |
| n1 / n3 | 2100 / 1800 MHz | DSS bands | Moderate | 20-100 Mbps | Various | Dynamic Spectrum Sharing – shared with 4G, lower performance |
UK Mobile Spectrum at a Glance
Bar length represents relative frequency position (not speed or capacity). Green = best penetration/range. Teal = 5G bands.
What this means for device specification
When you are buying a cellular router or modem for a specific deployment, the band support matters as much as the category. A CAT-12 device that does not support Band 20 will struggle in rural areas. A device that only supports Band 1 and Band 3 will work fine in an office in Manchester but may have no signal in a field in Yorkshire.
Always check the band list in the spec sheet against the bands your operator uses in the deployment area. This is not optional – it is the most common source of “the modem doesn’t work on site” calls.
3. How to Look Up Your Local Mast – Using CellMapper
Understanding bands in theory is useful. Seeing what your local masts actually broadcast is better. CellMapper is a free crowd-sourced database of mobile network cell towers. It shows you exactly which operator runs which mast, which bands it broadcasts, and often the exact physical location of the antenna.
Try This Now – CellMapper Walkthrough
Go to cellmapper.net/map and do the following:
- Select your country (UK) and operator (EE, O2, Vodafone, or Three) from the dropdowns at the top
- Select the network type – start with LTE (4G)
- Navigate to your location – the map will show blue dots for reported cell towers
- Click on a tower dot near you
- A panel will appear showing the eNB ID (the base station number), the bands in use at that site, and the reported signal data from devices that have driven or walked past
What you are looking for in that panel: does the site show Band 20 (800 MHz)? Band 3 (1800 MHz)? If it shows both, that site can support carrier aggregation – your CAT-6 or higher device will combine both bands for higher speeds. If it only shows Band 3, carrier aggregation is not possible at that location.
For 5G: switch the network type to NR (5G) and repeat. You will see which masts have n78 (3.5 GHz) 5G active. Notice that many 5G masts share a physical location with an LTE mast – this is what 5G NSA looks like on the ground. The 4G mast and the 5G mast are often co-located on the same structure.
CellMapper data is crowd-sourced. Coverage varies. Rural areas may have sparse data. For IoT deployment planning, it is a useful first check – but always verify on-site with a router and a signal diagnostic tool.
4. LTE Categories – What They Actually Mean
LTE categories are 3GPP standards that define the maximum capability of an LTE modem. The category defines three things:
- Maximum downlink speed – how fast data can come to your device
- Maximum uplink speed – how fast your device sends data up
- MIMO layers and carrier aggregation capability – how those speeds are achieved
| Category | Max DL | Max UL | MIMO | CA bands | Where you see it |
|---|---|---|---|---|---|
| CAT-4 | 150 Mbps | 50 Mbps | 2×2 | None | Budget routers, M2M modems, older hardware |
| CAT-6 | 300 Mbps | 50 Mbps | 2×2 | 2x DL (2CA) | Mid-range routers, tablets |
| CAT-9 | 450 Mbps | 50 Mbps | 2×2 | 3x DL (3CA) | Advanced routers |
| CAT-12 | 600 Mbps | 100 Mbps | 4×4 | 3x DL (3CA) | High-end routers, mobile broadband |
| CAT-16 | 1,000 Mbps | 150 Mbps | 4×4 | 4x DL (4CA) | Premium routers, pre-5G devices |
| CAT-20 | 2,000 Mbps | 200 Mbps | 4×4 | 5x DL (5CA) | High-end 5G NSA anchor modems |
5. Does the Category Actually Matter in the Real World?
For IoT and M2M: mostly no. If you are sending telemetry, GPS pings, or control messages, you will never hit the ceiling of even CAT-4. The data volumes do not justify a higher category modem.
For mobile broadband and failover: sometimes. A CAT-6 device can genuinely pull more than a CAT-4 on a multi-band site. But on a single-band rural site, both devices get the same speed – the category becomes irrelevant.
What actually limits your speed, in order:
The practical rule: For general IoT and M2M, CAT-4 is sufficient. For mobile broadband where speed genuinely matters – CCTV, video backhaul, high-throughput data – CAT-6 or CAT-12 is worth specifying, but only if the deployment location and network can actually support it. Check CellMapper first. Then check on site.
6. Carrier Aggregation – How the Speed Adds Up
Carrier aggregation (CA) is how LTE achieves speeds above a single band’s limit. Instead of one block of spectrum, your device uses two, three, or more simultaneously – combining the data streams for higher effective throughput.
Think of it as lanes on a motorway. Band 20 (800 MHz) is one lane. Band 3 (1800 MHz) is a second. Carrier aggregation lets your device use both at once. The number of bands a device can aggregate is what drives the category number – CAT-6 does 2CA, CAT-9 does 3CA, and so on.
Important: CA only works if the base station supports it. This is where CellMapper becomes useful. If you look up a site and it only shows one band active, CA is not available there regardless of what your device supports.
7. 5G NSA – Why It Still Needs 4G
5G Non-Standalone (NSA) is the first version of 5G deployed at scale. It is called Non-Standalone because it relies on the existing 4G LTE core network and requires a 4G anchor cell to function. This was a deliberate engineering shortcut – building a completely new 5G core takes years and massive investment. NSA let operators overlay 5G radio on top of existing 4G infrastructure quickly.
What this means in practice: If the 4G signal at a location is poor, 5G NSA will not help you. The device will fall back to 4G only, or may struggle to maintain a stable connection at all. A 5G NSA router in a weak 4G coverage area will underperform a well-positioned 4G CAT-12 device. Check CellMapper – if the 4G site near you only shows Band 20 with a single band and no 5G NR active, a 5G NSA router will give you no benefit over a quality 4G router.
8. 5G SA – The Real Thing
5G Standalone (SA) has its own core network (the 5GC) and does not depend on 4G for signalling. It is a complete, independent mobile network generation. This unlocks the features that 5G was originally designed to enable.
| Feature | 5G NSA | 5G SA |
|---|---|---|
| Core network | 4G EPC | 5GC (new core) |
| Needs 4G anchor | Yes – mandatory | No |
| Network slicing | Not supported | Full support |
| Ultra-low latency (URLLC) | Limited | Full support |
| UK rollout (2026) | Widely deployed | Major cities, rolling out |
Network slicing is the SA feature with the most industrial relevance. It lets an operator carve the physical network into multiple virtual networks, each with guaranteed characteristics – a factory floor gets a dedicated low-latency slice, a fleet gets a high-reliability slice, consumer traffic runs on a separate slice. This only works with a 5GC core.
9. NB-IoT and LTE-M – Built for IoT
Most IoT devices send tiny amounts of data infrequently. A temperature reading every 10 minutes. A meter reading once a day. Building those devices on CAT-4 hardware is wasteful in every sense – power, cost, hardware complexity. 3GPP defined specific low-power standards within LTE for these applications.
| Category | Max DL | Max UL | VoLTE | Mobility | Battery life | Best for |
|---|---|---|---|---|---|---|
| CAT-NB1 | 26 kbps | 66 kbps | No | Static only | 10+ years | Meters, sensors, static devices |
| CAT-NB2 | 127 kbps | 158 kbps | No | Limited | 10+ years | Improved NB-IoT – use this for new deployments |
| CAT-M1 (LTE-M) | 1 Mbps | 1 Mbps | Yes | Full handover | Several years | Trackers, wearables, mobile assets |
| CAT-1 / CAT-1bis | 10 Mbps | 5 Mbps | Yes | Full | Months | POS, alarms, smart metering |
| CAT-4 | 150 Mbps | 50 Mbps | Yes | Full | Hours/days | Routers, CCTV, general M2M |
CAT-1bis is a Release 13 variant of CAT-1 that removes the requirement for two receive antennas (MIMO). A single-antenna module qualifies, which reduces hardware cost and simplifies PCB design. For embedded industrial IoT where you need more than LTE-M but cannot justify CAT-4 power draw, CAT-1bis is frequently the correct answer and often overlooked.
10. SIM Card Formats and eSIM Summary
The SIM (Subscriber Identity Module) authenticates your device to the network. The format has evolved significantly. Here is the complete picture.
eSIM and eUICC in brief
An eUICC (Embedded Universal Integrated Circuit Card) is a SIM chip that stores multiple operator profiles and can switch between them remotely via OTA update. The operator credentials are downloaded rather than physically installed. This is the technology behind what marketing departments call “eSIM”.
There are two main GSMA standards:
- SGP.02 (M2M eUICC) – enterprise/operator managed. The platform pushes profile changes remotely. Standard for managed IoT fleets on MFF2 chips. Your connectivity platform controls which profile is active.
- SGP.22 (Consumer eSIM) – user-initiated. You scan a QR code or select a carrier in settings. Used in phones, tablets and wearables.
Why it matters for IoT: If you deploy 500 devices and need to change connectivity provider, eUICC means you push the new profile over the air. No truck rolls. No SIM swaps on site. For fleet deployments crossing borders, devices can attach to local operators automatically rather than roaming. A dedicated guide covering SGP.02, SGP.22, SGP.32 and how to evaluate connectivity platforms is coming separately.
MFF2 does not automatically mean eUICC. A soldered MFF2 can contain either a fixed traditional SIM profile or an eUICC chip. They look identical on a PCB. Always check the spec sheet for eUICC capability if remote provisioning is part of your requirement.
LTE, 5G and Bands Quiz
Ten questions drawn at random from a bank of 30. You will get a different set each time.