What is a dual SIM modem and how does it enable wireless-to-wireless failover?
When developing a Wireless WAN (WWAN) strategy for manufacturing floors, shipping ports, classrooms, fleets, and more, executives and IT professionals are presented with a slew of decisions they must make, including the choice between dual SIM vs. dual modem routers.
What is a dual SIM modem?
Dual SIM technology means that a single modem can accommodate two SIM cards. In this scenario, there is only one radio, meaning only one SIM will be active at a time. The presence of a second SIM within a software-defined modem enables IT teams to easily and remotely change the WAN connection from one cellular carrier to another.
Dual SIM modems are often used for installation flexibility. For example, imagine a large national retailer deploying hundreds of Wireless WAN routers to branches across the country. The retailer can place two SIM cards into each modem, representing two different carriers. Upon installation, IT teams can survey the performance of each SIM and — based on the results of the survey — switch to the carrier that provides the best network experience at that location before deactivating the other SIM.
In addition to using a dual SIM modem to test coverage at a target site, this technology is also useful if an enterprise wants the ability to automatically switch to a second SIM when the first reaches a data plan cap.
Although there are viable use cases for dual SIM modems, they are not recommended for wireless-to-wireless failover when uptime is crucial, as switching to the second SIM requires new carrier settings to be downloaded which can take minutes to achieve. Further, the system cannot predict whether the second carrier will offer a better connection. If a shift back to the first carrier is necessary, the deployment could be offline for several minutes.
What is a dual modem router?
Dual modem technology means there are two active radio connections, allowing SIM cards from different carriers to be active at the same time without the downtime of switching between the two. Benefits of a dual modem include:
Wireless-to-wireless failover and WAN redundancy
The ability to connect to two carriers at the same time is the only way to provide true wireless-to-wireless — or cellular-to-cellular — failover. The automatic switch from one carrier to another occurs almost instantaneously, making dual modems particularly beneficial for those driving connected vehicles that travel in and out of coverage areas such as delivery drivers or first responders.
At locations where wired-line connectivity is available, some enterprises use dual-modem functionality to further enhance their failover by utilizing three carriers at once. For example, they might use wired-line connectivity and SIMs from two different cellular providers to reach “four-nines” connectivity, or nearly 100% uptime.
Enterprise businesses can increase network bandwidth by taking advantage of SD-WAN functionality through routers that have dual active modems. IT professionals can also use SIM management services to monitor data usage and make appropriate data plan changes in response to high-usage events.
SIM-based auto carrier selection
Dual-modem functionality is an excellent way to achieve instant, seamless carrier redundancy in your network. However, in situations where a dual modem is not the most cost-effective option, and a few-minute lapse is acceptable, SIM-based auto carrier selection can prove beneficial. Enterprises can designate a backup carrier that the single modem will fail over in the event of an outage.
Auto carrier selection allows a wireless router to detect the carrier of an installed SIM, load the correct firmware and configuration settings automatically, then connect to the network — all without accessing the Internet, because all carrier profiles are locally stored.
The ability to simply insert an active SIM and power up without manual modem configuration significantly simplifies deployments and can greatly reduce inventory complexity by removing the need for a different SKU for each carrier.