Cellular Backhaul for SCADA, RTU & Industrial Telemetry Networks

SCADA systems, RTUs, and PLCs depend on continuous low-latency data exchange to maintain visibility over distributed process control infrastructure. Modbus, DNP3, and IEC 60870-5-104 polling cycles, alarm propagation, and historian backhaul require reliable transport with minimal jitter and guaranteed recovery after outages.

Cellular connectivity provides backhaul for telemetry networks spanning water treatment plants, remote pumping stations, pipeline monitoring, substation automation, tank farms, and industrial sites where leased-line deployment is cost-prohibitive or geographically impractical.

Common Challenges in Telemetry Deployments

• Maintaining sub-second polling cycles for time-critical alarms (pump failures, pressure excursions, level overruns)
• Buffering and forward-recovery of timestamped measurements during temporary signal loss
• RF attenuation in concrete pump houses, steel tank enclosures, and below-grade chambers
• DC-only power availability at remote RTU cabinets and solar-backed outstations
• Multi-year unattended operation with no site access for maintenance
• Integration with legacy RS485/RS232 serial equipment and Modbus RTU networks
• Isolation of process control traffic from IT networks and internet-facing systems

Where Industrial Connectivity Enables Telemetry

• Backhaul of Modbus TCP/RTU, DNP3, and IEC 104 telemetry streams to master stations and historians
• Real-time alarm propagation (digital inputs, contact closures, discrete state changes)
• Time-series buffering with store-and-forward during WAN disruption
• Remote setpoint adjustment and control output commands from HMI/SCADA consoles
• Secure VPN tunnelling isolating operational technology from corporate IT and public internet

Typical Telemetry & Monitoring Use Cases

• Water and wastewater: pump station automation, flow metering, reservoir level monitoring, chlorine residual tracking
• Oil and gas: pipeline pressure monitoring, cathodic protection, wellhead telemetry, tank gauging
• Power utilities: substation RTU backhaul, load monitoring, transformer temperature, sectionaliser status
• Industrial plants: boiler controls, compressor telemetry, cooling tower monitoring, process variable logging
• Rail and highways: signal box monitoring, crossing alarms, drainage pump control, environmental sensors
• District heating: flow/return temperature, pressure balancing, heat meter aggregation, valve control

Deployment Considerations

• Protocol conversion: Modbus RTU/ASCII to Modbus TCP, serial-to-IP gateways for legacy PLCs
• Local historian storage (MQTT broker, InfluxDB, SQLite) with forward-on-reconnect
• 12/24 VDC operation with <2W idle power for solar or battery-backed RTU cabinets
• Dual-SIM failover or multi-IMSI eSIM for operator diversity across geographically dispersed sites
• High-gain directional antennas (Yagi, panel) for fringe-coverage and RF-shielded enclosures
• Zero-touch provisioning and centralised firmware management for 100+ node deployments

Security and Data Integrity

SCADA and process control networks operate under strict segmentation requirements (IEC 62443, NERC CIP). Cellular backhaul must provide:

• IPsec tunnels with AES-256-GCM and certificate-based IKEv2 authentication preventing unauthorised master station access
• Private APNs with fixed IP addressing and firewall-restricted routing (no internet breakout)
• X.509 certificate management via local CA or HSM-backed credential storage
• Link heartbeat monitoring, session persistence tracking, and tamper-evident logging for audit compliance

Network Topology

Field instruments (4–20mA, digital I/O, Modbus RTU sensors) connect to a local RTU or protocol gateway. The gateway polls devices, timestamps readings, and forwards Modbus TCP or DNP3 over Ethernet to an industrial cellular router with external LTE/5G antennas. The router establishes an IPsec tunnel to a master station or SCADA front-end, isolating operational traffic from corporate VLANs. Separate out-of-band management tunnels allow remote router access without exposing the process control plane.

Data Buffering, Recovery and Consistency

SCADA systems require deterministic recovery. Gateways buffer timestamped polls in local non-volatile storage during cellular outages, then replay stored samples in chronological order once the tunnel re-establishes. Sequence numbering and change-of-value filtering prevent duplicate alarm annunciation. TCP keepalives and application-layer heartbeats (DNP3 integrity polls, Modbus watchdog registers) detect stale sessions before control commands are issued.

Why Cellular Connectivity Is Used Instead of Fixed Lines

Leased lines to remote pumping stations, pipeline valve sites, and rural substations incur £200–500/month per circuit plus installation lead times exceeding six months. Cellular provides sub-£20/month connectivity with same-day deployment. LTE latency (30–70ms) and 5G latency (10–30ms) meet SCADA polling requirements (typically 1–10 second cycles) when edge buffering absorbs temporary signal fades. Dual-SIM failover across operators provides resilience comparable to secondary fixed links.

Why Connected IoT

• Specialisation in SCADA backhaul and RTU connectivity (water, power, industrial process control)
• Experience architecting 100+ node Modbus/DNP3 networks with centralised VPN termination
• Hardware selection focused on DIN-rail routers, protocol gateways, and industrial Ethernet switches
• UK-based support with understanding of UK water, power, and industrial operational environments

Discuss Your Remote Monitoring & Telemetry Requirements

For related deployment guidance, see our water & wastewater, wind & remote assets, DeviceHub management and VPN and antenna optimisation pages.

If you operate systems that require stable, secure connectivity, we can help specify the correct industrial router, antenna setup and connectivity approach for your deployment.