Whether it’s wearable health monitors, environmental sensors, or fleet management systems, IoT devices have become essential tools across public sector services
IoT devices rely on a stable network connection to deliver critical data, but what happens when the signal drops? For many organisations, this is less a hypothetical scenario than a daily challenge. The solution is frequently sought through multi-network SIMs, which are widely seen as the ideal choice for maintaining connectivity in areas with variable network coverage, promising uninterrupted service by connecting to whichever network has the strongest signal. However, not all multi-network SIM solutions are equal, and understanding the technology behind them is key to choosing a reliable and secure solution.
The pitfalls of unsteered multi-network SIMs
Unsteered multi-network SIMs, which lack a predefined preference for any individual network, appear to offer the ultimate flexibility. They can connect to any available network, seemingly ensuring that devices always latch onto the “strongest” signal. However, the actual process of network selection, governed by 3GPP standards, is more intricate – and less reliable – than it appears.
When an unsteered SIM searches for a network, it does not necessarily prioritise the highest signal quality. Instead, it operates within a set of criteria that frequently results in connections to networks with “acceptable” rather than optimal signal strength. The lack of “permanent roaming agreements” with certain networks can also be an issue, potentially resulting in SIMs being randomly disconnected or barred.
Combined with potentially higher costs, unsteered SIMs often fall short of their promises.
The rise of dual IMSI SIMs
To address these challenges, a new generation of SIM technology has emerged: dual IMSI SIMs. Unlike unsteered SIMs, these are programmed with two distinct profiles – a primary “home” IMSI and a secondary IMSI for backup. This configuration provides a balanced approach that delivers both stability and resilience.
The primary IMSI network offers low latency and cost efficiency. If unavailable or the signal quality drops below an acceptable threshold, the secondary IMSI activates, maintaining uninterrupted service. Once the primary network is available again, the SIM switches back, optimised for cost and performance.
The ability to maintain seamless operations even in challenging network environments generally makes dual IMSI SIMs the best choice for critical IoT applications, especially where downtime is not an option.
Beyond connectivity: Security and scalability
Security is as important as reliability, especially when dealing with sensitive public data. Many commercial SIMs connect and send data over the public internet, increasing exposure to cybersecurity risks. Devices are visible, and data packets may be intercepted.
Advanced IoT SIM solutions route data through secure, private infrastructure. This approach significantly reduces the attack surface, ensuring that IoT devices and data are invisible and unreachable to external threats.
An example is Spitfire’s One Network, a fully private network with MPLS that combines the benefits of dual-IMSI mobile technology with private routing, security, and management. SIMs can connect to multiple UK radio access networks but route all data traffic through Spitfire’s own network infrastructure.
One Network also enables direct connectivity to IoT cloud platforms and other sites through fixed-line circuits. It allows central management through a single customer portal, simplifying provisioning, monitoring, and reporting.
Managing large-scale deployments
Public sector organisations often manage hundreds or thousands of devices across different locations. One of the key advantages of dual-IMSI SIMs in an MPLS private network is operational simplicity. There’s no need to manually reconfigure devices or switch APNs when the network changes. The IP address space can remain consistent across both IMSIs, ensuring smooth handovers and predictable device behaviour.
This reduces the administrative burden on IT teams and helps avoid errors that can lead to service disruptions. Whether you’re managing a city-wide sensor network or mobile workforce, this level of automation and control is a major benefit.
A smarter approach to IoT connectivity
The integration of dual IMSI SIMs with private, secure network platforms represents a significant step forward in the evolution of IoT connectivity.
Combining the flexibility of multiple networks with the stability and security of a single, managed environment, organisations can be confident in the knowledge that their infrastructure is robust, secure and future-ready.
