Why Cellular Dominates Industrial IoT Connectivity

There are dozens of wireless connectivity technologies available to IoT developers and system designers. WiFi, Bluetooth, Zigbee, LoRaWAN, Sigfox, satellite – each has its advocates and its genuine use cases. But in the UK industrial IoT market, cellular connectivity – 4G LTE, 5G, LTE-M, and NB-IoT – accounts for the large majority of deployed connected devices. The reasons are practical rather than dogmatic.

Cellular networks already exist everywhere that industry operates. The infrastructure investment has already been made by the mobile network operators. A cellular device can connect in a car park, on a rooftop, in a substation, on a construction site, in a vehicle, in a field, and in the middle of an industrial estate with no infrastructure investment from the deploying organisation beyond the device and the SIM card. No gateways to install, no frequency planning, no spectrum licences.

Cellular also scales without the architectural complexity of private wireless networks. Adding the thousandth device to a cellular deployment requires the same setup as adding the first – provision a SIM, configure the device, connect. The network handles everything between the device and the destination. And cellular networks are managed, maintained, and upgraded by the operators, meaning coverage and capability improve over time without the deploying organisation doing anything.

For applications that require wide-area coverage, mobility, reliable uptime, and known security properties, cellular is the default choice for good reason. The questions worth asking are not “should we use cellular?” but “which cellular technology?” and “what hardware, SIM, and architecture?”

The Cellular Technology Landscape

Cellular is not a single technology – it is a family of standards, each optimised for different combinations of data rate, power consumption, range, and cost. Understanding which technology fits which application is the starting point for any serious IoT deployment.

4G LTE – The Industrial IoT Workhorse

4G LTE remains the foundation of industrial IoT connectivity in the UK and will continue to be for at least the next decade. The network is mature, coverage is comprehensive, hardware is well-established and cost-effective, and the ecosystem of industrial routers, gateways, SIM cards, and management platforms built around 4G LTE is deeper than any other technology.

LTE device categories define the modem capability. Cat 4 is the workhorse category for industrial routers – up to 150 Mbps downlink, suitable for high-bandwidth applications including CCTV backhaul, high-frequency SCADA telemetry, and general WAN connectivity for remote sites. Cat 6 adds carrier aggregation for higher sustained throughput. Cat 1 reduces the modem complexity and power draw significantly at the cost of peak throughput – appropriate for asset tracking, basic telemetry, and devices where the LTE connection is used intermittently rather than continuously.

Dual-SIM and WAN Resilience

The most important architectural decision for a 4G LTE IoT deployment is WAN resilience. A single SIM on a single operator provides no redundancy against network outages or localised coverage issues. Industrial routers with dual SIM slots – such as the Milesight UR35 and UR75 – allow two independent WAN paths to be configured, on different mobile network operators, with automatic failover between them. For critical applications – SCADA outstations, BESS control systems, security monitoring – dual-SIM on different MNOs is the minimum viable resilience architecture.

Some deployments add a third WAN path – an Ethernet WAN port connected to a fixed broadband or leased line circuit – giving three independent failure modes to overcome before connectivity is lost entirely. The Milesight UR75 supports this hybrid cellular-plus-Ethernet topology natively.

5G for Industrial IoT

5G NR (New Radio) is in active deployment across the UK. The UK’s four main operators all have 5G networks, with EE and Vodafone leading on geographic coverage and O2 and Three expanding rapidly. For IoT applications, 5G brings three capabilities that 4G cannot match: significantly higher peak throughput, substantially lower latency, and – in 5G Standalone (SA) architecture – network slicing.

5G Standalone and Network Slicing

5G Non-Standalone (NSA) uses a 5G radio layer with a 4G core network. This delivers higher throughput but not the latency improvements or advanced features of full 5G. 5G Standalone uses both a 5G radio and a 5G core network, unlocking the full capability of the standard including sub-millisecond latency, network slicing, and guaranteed quality of service.

Network slicing is the capability most relevant to critical infrastructure IoT. A 5G slice is a logically isolated portion of the network with dedicated capacity and defined performance characteristics – guaranteed bandwidth, maximum latency, and traffic isolation from other users on the same physical infrastructure. For utility SCADA communications, emergency services, and other applications where QoS guarantees matter, a dedicated 5G slice provides a level of service assurance that shared network infrastructure cannot.

The commercial availability of network slicing for enterprise IoT customers is developing through 2025 and 2026. For current deployments, 5G Sub-6GHz with 4G LTE fallback on hardware like the Milesight UR75 provides the performance headroom of 5G with the coverage reliability of the mature 4G network as a fallback. For more on 5G network slicing developments, see 5G Slicing.

5G Fixed Wireless Access

5G FWA (Fixed Wireless Access) uses 5G as a replacement for fixed broadband – delivering high-bandwidth internet connectivity to premises without a physical cable connection. For industrial sites, temporary deployments, and locations where fixed broadband infrastructure is poor or unavailable, 5G FWA is a compelling option. For dedicated coverage of 5G FWA technology, hardware, and UK deployment considerations, see 5G FWA.

LTE-M and NB-IoT – Low-Power Cellular for Battery Devices

LTE-M and NB-IoT are cellular technologies designed from the ground up for low-power, low-data-rate IoT devices. Both operate on licensed spectrum within the LTE network, use the MNO’s existing infrastructure, and require a SIM card per device – but they are architecturally distinct from LTE Cat 4 and serve a very different set of applications.

LTE-M (LTE Cat-M1)

LTE-M provides data rates up to around 1 Mbps, supports voice, and crucially supports device mobility – devices can move between cells without dropping the connection. Power consumption is dramatically lower than Cat 4 through power saving mode (PSM) and extended discontinuous reception (eDRX), which allow the device to sleep for extended periods while remaining registered on the network. Battery-operated devices using LTE-M can run for years on a single charge, transmitting periodic updates and waking for inbound messages on a schedule.

LTE-M is appropriate for asset tracking (the device moves), wearables, medical monitoring devices, and sensors that need occasional two-way communication rather than purely uplink reporting. In the UK, EE and Vodafone have active LTE-M networks; coverage is good but not as comprehensive as standard LTE.

NB-IoT

NB-IoT trades mobility and data rate for even lower power consumption and better penetration into challenging RF environments – basements, thick-walled buildings, underground installations. It is specifically designed for fixed, low-data-rate devices that transmit small amounts of data infrequently and may be in locations with marginal signal. Smart utility metering is the archetypal NB-IoT application – a meter in a basement cupboard, reporting a reading once a day, running on an internal battery for 10 years.

NB-IoT does not support mobility – it is a fixed-device technology. And the higher latency (seconds rather than milliseconds) makes it unsuitable for any application requiring responsive communication. For everything else within its parameters, it is an extremely efficient technology for the deployment economics it enables.

For a detailed comparison of LTE-M and NB-IoT application scenarios, see the iotportal guide to Cat-M and NB-IoT applications.

5G RedCap – Bridging the Gap

5G RedCap (Reduced Capability, also known as NR-Light) is a 3GPP Release 17 technology that occupies the space between NB-IoT/LTE-M and full 5G NR. It provides data rates of up to around 150 Mbps – comparable to LTE Cat 4 – with significantly lower modem complexity and power consumption than full 5G. The target is industrial IoT sensors, wearables, and devices that need more capability than LTE-M can provide but do not need the full throughput of 5G NR.

Enhanced RedCap (eRedCap, 3GPP Release 18) extends the specification further toward the ultra-low-power end, targeting LTE Cat-1 replacement scenarios where a device needs more than NB-IoT but far less than full 5G. RedCap is beginning to appear in commercial hardware – the Teltonika RUT276 was among the first RedCap routers to launch in the UK market.

For comprehensive coverage of 5G RedCap technology, chipsets, hardware, and UK deployment timelines, see 5G RedCap.

Hardware – Routers, Gateways and Modules

Cellular connectivity hardware falls into three categories. Industrial cellular routers provide WAN connectivity for a site or a cluster of devices via Ethernet and WiFi – they are the cellular WAN access point for devices that connect over wired or local wireless networks. IoT gateways combine cellular connectivity with a sensor collection layer – typically LoRaWAN, Modbus, or Zigbee – aggregating data from multiple end devices and forwarding it upstream via cellular. Cellular modules are embedded components that add cellular connectivity to a custom device design – appropriate for OEM integration where a self-contained router form factor is not suitable.

Industrial Cellular Routers

An industrial cellular router differs from a consumer mobile broadband router in every dimension that matters for long-term unattended deployment. Operating temperature range is typically -40 to +70 degrees C rather than the 0 to +40 of consumer hardware. Mean time between failures is rated in years of continuous operation. Serial interfaces (RS232, RS485) allow direct connection to legacy industrial equipment using Modbus or DNP3. Dual SIM slots provide WAN redundancy. VPN support – IPsec, OpenVPN, WireGuard – is built in as standard rather than as an optional feature. And management platforms allow fleet-level configuration, monitoring, and firmware management without site visits.

The cellular router classifications guide covers the full range from compact Cat 4 devices through to 5G multi-WAN models with edge computing capability. For the Milesight industrial router range specifically – UR32, UR35, UR75, UF51 – see the Milesight routers page.

IoT Gateways with Cellular Backhaul

Where the application involves collecting data from distributed sensors rather than providing WAN connectivity for networked devices, an IoT gateway is the appropriate hardware. Milesight LoRaWAN gateways – the UG65 and UG67 – combine 8-channel LoRaWAN sensor collection with cellular or Ethernet backhaul. The UG67 is self-contained: LoRaWAN collection on the sensor side, LTE cellular on the backhaul side, in a single IP67 outdoor enclosure. One device, one SIM card, coverage for hundreds of sensors across a multi-kilometre area. See the Milesight LoRaWAN gateways page for full specifications.

Edge Computing on Cellular Hardware

Higher-specification industrial routers and gateways increasingly include on-device edge computing capability. Milesight UR75 and UF51 routers include an embedded Node-RED runtime – a flow-based programming environment that allows local data processing, protocol conversion, and conditional logic to run on the device itself without a cloud dependency for the compute layer. This is significant for applications where network latency matters, where connectivity is intermittent, or where processing data locally reduces the volume of traffic that needs to travel over the cellular link. The Milesight Development Platform guide covers how Node-RED integrates with the wider Milesight management ecosystem.

SIM Cards and Connectivity Options for Cellular IoT

The SIM card is the cellular identity of the device. For IoT deployments, the SIM selection is as important as the hardware selection – a poorly chosen SIM can undermine the connectivity resilience of even well-specified hardware.

M2M and Industrial SIM Cards

Consumer SIM cards are not appropriate for industrial IoT deployment. M2M SIM cards are provisioned with tariffs designed for persistent, low-volume data sessions, physical specifications suited to industrial temperature ranges, and management platforms that provide fleet-level visibility and control. The industrial SIM cards guide covers the full range of M2M SIM options and selection criteria.

Multi-Network Roaming SIM Cards

For outdoor deployments, rural locations, and large distributed device estates where no single MNO provides consistent best coverage, a multi-network roaming SIM provides coverage resilience on a single SIM card. The SIM connects to whichever of several partner networks offers the strongest signal at the device location, without a fixed home network preference. Combined with a dual-SIM router running two different multi-network SIMs, this creates a connectivity architecture that is highly resilient to operator-level outages and coverage gaps. See the multi-network SIM guide for how steering works and what to look for in a multi-network SIM tariff.

Fixed IP SIM Cards

A fixed IP SIM assigns the same IP address to the device permanently. This is required when a remote system needs to initiate an inbound connection to the device – SCADA polling, CCTV stream access, direct management access. Fixed IP SIMs are typically paired with a private APN that routes device traffic through an isolated network path rather than the public internet. See the fixed IP SIM guide and the private APN explainer for when these are and are not needed.

eSIM and eUICC

eUICC (embedded Universal Integrated Circuit Card) allows SIM profiles to be provisioned and changed over-the-air without physically swapping hardware. For fleets deployed across wide geographies, the ability to switch MNO remotely – to respond to coverage changes, network sunsets, or better tariff availability – is a significant operational advantage over the lifetime of a deployment. The SGP.02 standard covers existing M2M eUICC implementations. SGP.32 is the newer IoT-specific specification designed for constrained devices. Both are covered in depth at eUICC Explained and SGP.32.

Antenna and Signal Optimisation

The cellular modem and SIM card determine what networks the device can access. The antenna determines how well it accesses them. In a well-designed installation with a good antenna, signal levels will be 10-20dB better than a poorly specified installation – the difference between a marginal connection that drops under adverse conditions and a stable link that performs reliably in all weather.

Industrial cellular devices use SMA or FME antenna connectors. Most ship with a basic stub antenna. For panel or cabinet installations, a roof-mounted external antenna connected by low-loss cable gives significantly better performance – particularly in metal enclosures where the case itself attenuates the signal from an internal antenna. For outdoor pole-mounted installations, a weatherproof external antenna rated for the operating environment is the correct specification. MIMO antenna configurations (2×2 for LTE, 4×4 for 5G) use multiple antenna elements to increase throughput and resilience on the cellular link.

For antenna selection guidance covering mounting options, cable types, MIMO configurations, and gain calculations for specific deployment scenarios, see the IoT antennas section and the specialist resource at IoT Antenna.

VPN and Secure Cellular Connectivity

Cellular connectivity gets data from the device to the mobile network. VPN gets it securely from the mobile network to the destination – a control centre, a cloud platform, a data centre. For industrial and critical infrastructure applications, transmitting operational data over the public internet without encryption is not acceptable under most cybersecurity frameworks, including the NIS Regulations and NCSC CAF for UK-regulated operators.

The three VPN protocols in common use on industrial cellular hardware are IPsec, OpenVPN, and WireGuard. IPsec is the traditional choice for site-to-site VPN in industrial applications – widely supported by hardware from all manufacturers and by enterprise VPN concentrators. OpenVPN is more flexible and works through NAT and firewalls that block native IPsec, making it reliable even on cellular networks that do not permit IPsec passthrough. WireGuard is the newest protocol, with significantly better performance and simpler configuration than either IPsec or OpenVPN, and is increasingly the preferred choice for new deployments on hardware that supports it.

For a detailed treatment of VPN options for IoT deployments, network segmentation, and the cybersecurity requirements imposed by NIS and CAF, see the security section and the IoT security guide.

Remote Device Management

A cellular IoT device that cannot be managed remotely is a liability. Firmware vulnerabilities need patching. Configuration changes need deploying. Signal levels need monitoring. When a device goes offline, the operations team needs to know immediately – not when someone notices a missing data point 48 hours later.

Remote management platforms for cellular IoT hardware address all of these. For Milesight hardware, the Milesight Development Platform provides fleet-level device management, OTA firmware updates, real-time monitoring, comms-loss alerting, and webhook integration with external systems. The platform is free for up to 10 devices and $1 per device per year at Professional tier – competitive pricing that reflects the fundamental shift away from manual site-visit management that a capable platform enables. See the full explainer at Milesight Development Platform.

Sector Applications

UK Cellular Network Landscape

The UK has four national mobile network operators – EE (part of BT Group), Vodafone, O2 (Telefonica UK), and Three (now merged with Vodafone as of 2024). Coverage varies significantly between operators in rural areas. EE consistently performs strongest in rural and geographic coverage in Ofcom’s annual connected nations reports. Vodafone and O2 lead in dense urban areas. Three has historically had the weakest rural coverage but is expanding rapidly as part of the Vodafone-Three merger integration.

For IoT deployments across mixed geographies, testing actual signal strength with each candidate operator at representative deployment locations – rather than relying on published coverage maps – is the only reliable approach. Coverage maps are optimistic by design. The test modem in the actual intended mounting position is the ground truth.

2G (GPRS/EDGE) has been sunset by most UK operators. Vodafone switched off its 2G network in 2023; EE followed in 2024. Any IoT devices still dependent on 2G fallback connectivity should be treated as at risk and prioritised for hardware refresh. 3G sunset has also progressed – all four UK operators have shut down 3G networks, meaning devices relying on 3G-only modems are now offline. The transition pressure to 4G LTE as the baseline cellular technology is complete.