The transition from GPRS to 4G LTE is becoming urgent for many industrial sites: remote meter reading, RTUs, substations, remote PLCs, meters, Modbus gateways, and RS-232 or RS-485 devices still rely on 2G modems that were installed, in some cases, as long as twenty years ago. The goal is not to replace the entire SCADA system, but to modernize mobile connectivity without modifying the PLCs, field protocols, or existing monitoring applications.
The Problem
The GPRS network, based on 2G technology, has long served as a discreet connectivity solution for isolated industrial equipment. It has enabled the connection of energy meters, meter reading stations, pumping stations, remote management cabinets, RTUs, Modbus/RTU gateways, and remote SCADA systems. However, this infrastructure is now reaching the end of its lifecycle.
French carriers have announced the phased shutdown of their 2G and 3G networks, with timelines that should be checked regularly with official sources. As of now, Orange has indicated that 2G service will be shut down by 2026 and 3G by 2029 in metropolitan France. SFR has announced a 2G shutdown in 2026 and a 3G shutdown in 2028. Bouygues Telecom has also announced the phased shutdown of its 2G and 3G networks. Exact dates may vary depending on the operator, region, and service plan; therefore, you should confirm the timeline with ARCEP and the operators before finalizing a migration plan.
There are numerous impacts on the ground.
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GPRS modems are often built into older equipment that still works perfectly well for business purposes.
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Some RTUs from the 2000s have only an RS-232 or RS-485 serial connection.
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SCADA applications have sometimes been configured using legacy addresses, ports, timeouts, and AT commands.
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Replacing the SCADA system or the PLC is much more expensive than replacing the connectivity module.
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3G equipment must also be taken into account to avoid having to undertake a second migration project a few years down the line.
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An unplanned migration creates the risk of an emergency: disruption of remote meter reading, loss of monitoring, on-site visits, and pressure on maintenance teams.
So the real issue isn’t just “moving from 2G to 4G.” We need to make the transition without disrupting existing usage patterns.
Why Direct Replacement Is Rarely Simple
An industrial GPRS modem is not always just a simple network device. It can be deeply integrated into the existing architecture: power supply, DIN rail, antenna, serial port, AT commands, APN settings, SCADA timeouts, Modbus protocol, alarm monitoring, and maintenance procedures.
| Existing component | Risk during migration | Best practice |
|---|---|---|
| RS-232 or RS-485 interface | Physical or serial incompatibility | Verify pinout, baud rate, parity, and stop bits |
| Modbus RTU | SCADA polling failure | Test frames before migration |
| AT commands | Incompatible connection script | Emulate or adapt the necessary commands |
| Carrier APN | Loss of connectivity | Preconfigure SIM profiles |
| IP address or port | SCADA unable to reach the site | Maintain or redirect existing data flows |
| 12–24V DC power supply | Unplanned electrical work | Choose a compatible gateway |
| Antenna | Insufficient 4G signal | Audit coverage and replace if necessary |
The migration must therefore begin with a detailed technical assessment, not with the purchase of equipment.
Our Approach
The Eziwan gateway is designed to replace industrial GPRS modems while preserving the existing architecture as much as possible. On the field side, it can integrate with serial interfaces, Modbus communications, and industrial power requirements. On the network side, it uses 4G LTE connectivity, with monitoring, dual SIM support as needed, centralized configuration, and secure tunnels.
The approach involves a three-tier migration.
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Field layer: Retain existing RS-485, RS-232, Modbus RTU, RTU, and PLC equipment as long as their business functions remain valid.
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Connectivity layer: Replace the GPRS connection with a supervised LTE connection, using a suitable antenna and a multi-carrier SIM card or dual SIM cards if necessary.
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Operations layer: Provide automatic provisioning, logging, alerts, availability monitoring, and centralized fleet management.
This approach makes it possible to modernize connectivity without requiring a complete overhaul of the SCADA system.
Target Architecture for Migration from GPRS to LTE
A successful migration architecture clearly separates the legacy serial network from the new secure IP transport network. The gateway acts as an industrial bridge, while also providing monitoring and security.
The SCADA system continues to receive business data, but connectivity becomes monitored, maintainable, and compatible with the phase-out of 2G and 3G networks.
RS-485 and RS-232 Backward Compatibility
Serial backward compatibility is often the critical issue. Much industrial equipment was never designed for native IP connectivity. It communicates via Modbus RTU, uses fixed serial parameters, or relies on a legacy modem.
The settings to check include:
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Interface type: RS-232, 2-wire RS-485, or 4-wire RS-485.
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Serial baud rate: for example, 1200, 2400, 9600, 19200, 38400, or 115200 baud.
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Parity: none, even, or odd.
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Number of data bits.
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Number of stop bits.
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Modbus addresses of the devices.
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Delays between requests.
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Half-duplex support in RS-485.
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Termination resistors and bus bias.
The migration must replicate the expected behavior of the existing modem. Even a slight difference in timing can be enough to disrupt older equipment.
Compatibility with Modbus and Existing SCADA Systems
On many sites, the SCADA system queries remote devices according to a pre-validated model: the same list of registers, the same polling frequency, the same alarms, and the same historical data. The migration must avoid modifying this model unnecessarily.
| Key Point | Why It’s Important |
|---|---|
| Modbus registers | Avoids having to reconfigure SCADA screens |
| Device address | Preserves scripts and historical data |
| Polling frequency | Limits ripple effects in the field |
| Existing alarms | Avoids a time-consuming functional revalidation |
| Routing or application port | Reduces changes on the monitoring side |
| Site identifiers | Maintains continuity of historical data |
The goal is not to “take advantage of the migration” to change everything. We must first restore reliable transportation and then consider optimizations at a later stage.
AT Commands: Watch Out for Hidden Dependencies
Some devices control the modem directly using AT commands. They can initialize the connection, check the signal, establish a data session, read the network status, or restart the modem. These dependencies are sometimes poorly documented.
Examples of commands or behaviors to audit:
AT
ATI
AT+CSQ
AT+CREG?
AT+CGATT?
AT+CGDCONT
ATD
ATH
AT+CFUN
Not all legacy AT commands necessarily have a direct equivalent in LTE. The best approach is to identify the commands actually used by the device, and then determine whether the gateway can emulate them, adapt them, or work around the need through transparent configuration.
Multi-carrier SIM and dual SIM
The transition to LTE should not create a new, fragile dependence on a single carrier. A site that was operating on GPRS may be located in an area where 4G coverage varies depending on the carrier, the antenna’s location, the terrain, or the building.
There are two possible approaches.
| Option | Benefit | Limit |
|---|---|---|
| Single-carrier SIM | Easy to manage | Dependence on a single network |
| Multi-carrier SIM | Better coverage depending on location | Network policy varies depending on agreements |
| Dual SIM | Clearer redundancy | Requires a failover strategy |
| Multi-carrier dual SIM | Enhanced resilience | Cost and monitoring must be managed |
| Backup satellite | Locations outside mobile coverage | Installation and cost constraints |
For critical sites, it is recommended to test multiple carriers on-site using the terminal antenna, not just a cell phone.
Fleet Audit Before Migration
A network audit helps prioritize sites, avoid surprises, and plan migration phases. It should cover equipment, operators, interfaces, protocols, and on-site access constraints.
The following information is useful:
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Site, location, and criticality.
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Current mobile carrier.
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Modem type: GPRS, EDGE, 3G, HSDPA, or other.
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Modem serial number and model.
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Field interface: RS-232, RS-485, Ethernet.
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Protocol: Modbus RTU, Modbus TCP, AT commands, proprietary protocol.
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Power supply available.
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Antenna type and location.
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Mobile coverage quality.
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SCADA dependencies.
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Potential window of opportunity.
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Field contact and validation procedure.
This inventory can be imported into a planning tool to rank sites by urgency, complexity, and risk.
Example of a migration matrix
| Site Type | Existing Equipment | Complexity | Recommended Strategy |
|---|---|---|---|
| Remote meter reading | GPRS RS-232 modem | Low | Direct replacement with frame testing |
| Pumping station | RS-485 Modbus RTU | Medium | Parallel migration and SCADA validation |
| Substation | Legacy RTU + AT controls | High | Control audit, pilot project, dedicated procedure |
| Remote site | GPRS with limited coverage | High | Multi-carrier testing and external antenna |
| Recent 3G network | HSDPA Ethernet modem | Medium | Bulk migration to LTE with ZTP |
This matrix helps avoid a one-size-fits-all approach for sites that do not share the same constraints.
Risk-Free Parallel Migration
Parallel migration involves installing the new gateway without immediately disconnecting the old modem. During a validation period, data can be compared, communications tested, and SCADA teams reassured.
This method reduces the risk of service disruption. It is particularly useful for critical or hard-to-reach sites.
Zero-Touch Provisioning for Mass Deployment
When a network has several dozen or hundreds of modems, manual configuration becomes a risk factor. Zero Touch Provisioning allows each gateway to be pre-enrolled with its serial number, site, profile, and variable settings.
When powered on, the gateway:
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Logs in to the Eziwan cloud.
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Restores its configuration.
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Applies its network settings.
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Initializes its certificates.
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Opens its secure tunnel.
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Raise his status.
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Triggers monitoring checks.
This approach reduces field errors and allows installers who are not network specialists to replace modems using a standardized procedure.
Security: Avoid Repeating the Weaknesses of GPRS
The transition to LTE also provides an opportunity to address long-standing vulnerabilities: poorly documented access, shared APNs, lack of application-level encryption, weak passwords, exposed interfaces, and monitoring without logging.
Best practices to adopt:
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Use an encrypted VPN tunnel for sensitive data.
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Avoid any direct exposure of industrial equipment to the Internet.
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Implement individual certificates.
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Log connections and events.
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Segment data flows between SCADA, maintenance, and telemetry.
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Disable unnecessary services.
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Monitor network quality and access attempts.
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Revoke old access rights after migration.
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Document the new architecture.
A successful migration is not just about restoring service. It must improve control over industrial connectivity.
Performance: What 4G LTE Changes
4G LTE generally offers higher data speeds and lower latency than GPRS, but it’s important to exercise caution: the actual improvement depends on coverage, the carrier, the antenna, network load, the industrial environment, and the traffic profile.
4G can enable:
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More frequent data uploads.
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More detailed logs.
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More responsive oversight.
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More convenient remote access.
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Faster updates or diagnostics.
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Greater capacity to handle multiple data streams.
However, it is not always necessary to increase the volume of data right from the start of the migration. To minimize risks, it is often better to first replicate the existing GPRS behavior and then optimize the collection frequencies once the system has stabilized.
Antennas and Radio Quality
The transition to 4G may require an antenna upgrade. An older GPRS antenna is not always optimal for the LTE bands used locally. In addition, metal cabinets, industrial buildings, terrain, and electromagnetic interference can degrade reception.
Scheduled inspections:
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Antenna frequency compatibility.
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Install outside the cabinet if necessary.
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Length and quality of the coaxial cable.
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Appropriate connectors.
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RSRP, RSRQ, SINR, and latency measurements.
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Testing multiple operators.
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Testing under actual conditions, with the cabinet closed.
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Mechanical fastening and environmental protection.
Radio quality must be monitored over time. A good signal on the day of installation does not guarantee continuous availability.
Example Migration Configuration
A migration configuration must be explicit. It must specify the site, profile, serial interface, protocol, and connectivity.
site:
id: station_pompage_042
criticite: haute
interface_terrain:
type: rs485
protocole: modbus_rtu
baudrate: 9600
parite: paire
stop_bits: 1
equipements:
- nom: rtu_principal
adresse_modbus: 1
connectivite:
lien_principal: lte
sim:
mode: multi_operateurs
vpn:
actif: true
type: openvpn
supervision:
scada:
mode: transparent
port: 502
alertes:
perte_lien: active
signal_degrade: active
tunnel_coupe: active
This type of model makes it possible to standardize sites while retaining the parameters specific to each installation.
Recommended Migration Plan
A migration from GPRS to LTE should be organized in phases. The timeline depends on the size of the network, the criticality of the sites, on-site accessibility, and the operator’s phase-out dates.
| Step | Objective | Deliverable |
|---|---|---|
| Inventory | Identify 2G and 3G modems | List of sites to be migrated |
| Qualification | Classify by carrier, interface, and criticality | Priority matrix |
| Pilot | Test a few representative sites | Validated procedure |
| Pre-enrollment | Associate gateways, profiles, and sites | Fleet ready for ZTP |
| Phase 1 Deployment | Migrate simple sites | Initial field feedback |
| Phase 2 Deployment | Migrate critical sites | SCADA validation |
| Decommissioning | Remove legacy GPRS access points | Infrastructure cleaned up |
| Reporting | Document availability and incidents | Migration report |
The pilot study is essential. It helps identify hidden dependencies before moving to a broader implementation.
Checklist Before Replacing a GPRS Modem
| Check | Question | Priority |
|---|---|---|
| Operator | Which 2G or 3G network is currently in use? | High |
| End Date | What is the shutdown date for this network? | High |
| Interface | Does the equipment use RS-232, RS-485, or Ethernet? | High |
| Protocol | Modbus, AT commands, or a proprietary protocol? | High |
| SCADA | Do the ports and addresses need to be retained? | High |
| Antenna | Is the existing antenna LTE-compatible? | High |
| Power | Does the site provide compatible 12–24V DC power? | Medium |
| Coverage | Has 4G been tested with the end antenna? | High |
| Security | Are data streams encrypted and logged? | High |
| Rollback | Can we switch back to the old modem during the test? | High |
This checklist helps prevent last-minute migrations to sites where every move is costly.
Common Mistakes to Avoid
Wait for the service outage
An emergency migration leaves little time for auditing, testing, ordering, installing, and validating. Isolated or critical sites must be given priority.
Forget About 3G Devices
Focusing solely on GPRS could lead to a second project shortly thereafter. 3G modems should be inventoried as part of the same initiative.
Replacing the SCADA System Too Soon
If the SCADA system is functioning properly, it is often best to maintain its current behavior during the migration. Optimizations can be implemented once LTE connectivity has stabilized.
Ignoring AT Commands
Older equipment may rely on specific modem commands. Without an audit, the migration may fail even though the cabling and coverage are correct.
Using an unsuitable antenna
An old or poorly positioned antenna can turn a high-performance LTE gateway into an unstable connection. The antenna must be part of the design.
Do not log the new connectivity
The upgrade should provide greater visibility into: connection status, signaling, active operator, tunnel, events, failovers, and availability.
How Eziwan Facilitates the Migration from GPRS to 4G LTE
Eziwan offers a structured solution for replacing GPRS modems without overhauling the industrial infrastructure.
| Need | Eziwan’s Response | Benefit |
|---|---|---|
| Replace GPRS | Industrial LTE Gateway | Ensure long-term connectivity |
| Maintain field infrastructure | Serial and Modbus interfaces | Fewer PLC modifications |
| Avoid manual configuration | Zero-Touch Provisioning | Faster deployment |
| Secure data flows | VPN tunnel and certificates | Reduced exposure |
| Manage the fleet | Eziwan Cloud | Multi-site monitoring |
| Anticipate outages | Signal and link alerts | Proactive maintenance |
| Reduce risks | Parallel migration | Validation before switchover |
| Maintain operations | Monitoring and logs | Simpler diagnostics |
This approach can be integrated with the Eziwan gateway, monitoring via the Eziwan cloud, and industrial connectivity architectures.
Useful References
To confirm the schedules and prepare a migration plan, it is recommended that you consult official sources and up-to-date carrier websites.
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ARCEP for the French telecommunications framework and background information.
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Orange Networks for Orange 2G and 3G calendars.
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SFR Support for information on the SFR network migration.
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Bouygues Telecom for announcements regarding network upgrades.
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ANFR Radio Map to identify registered radio sites around an industrial site.
These sources must be supplemented by on-site measurements, as actual coverage depends on the location, the antenna, the building, and the radio environment.
Conclusion
The migration from GPRS to 4G LTE is an ongoing industrial project. 2G and 3G modems still in service must be inventoried, prioritized, and replaced before network shutdowns cause losses in remote meter reading or monitoring. The best strategy is to preserve the SCADA system and RS-485 equipment whenever possible, while modernizing connectivity, security, and monitoring.
Eziwan enables the replacement of GPRS modems with industrial LTE gateways designed to meet field requirements: serial interfaces, Modbus, automatic provisioning, multi-carrier SIMs, secure tunnels, cloud-based monitoring, and parallel migration. This approach reduces the risk of service interruptions and turns an operator-imposed constraint into an opportunity to ensure the long-term reliability of industrial connectivity.
Further Reading
- Industrial Connectivity — an overview of connectivity technologies available after the end of 2G/3G
- Industrial 4G Router — Replace your GPRS modems with an RS-485-backward-compatible 4G router
- Industrial LTE Router — industrial LTE routers certified for critical OT environments
- Industrial 4G Backup — Take advantage of the migration to add a 4G backup link
- Guide to Connectivity in White Spots — Solutions for sites with poor coverage during the 4G migration