1 minute read
Roaming SIMs
Roaming Sims fall into two categories. The first is a true roaming SIM that will connect to any network available to it. The second category is a managed or steered SIM. The steered sim has a list of partner networks that it will choose over any over other network open to it. This can create a problem when the preferred partner network is not available for the transmission of data in any given location.
A roaming SIM is designed to give you the best connection available in the location it is used in. The SIM allows access to the available networks, but it is the router/modem that chooses the network. The roaming SIM allows the router/modem to run a site survey when it is first powered up to see what networks are available to it. Networks that have a poor signal or offer low throughput are blacklisted and the ones that are left are put in a preferred order (based on signal strength and throughput). When the preferred network has low signal or throughput this is also black-listed and then the next network from the preferred list is selected. Once all networks are black-listed the whole process starts again. This process is perfect for a fixed device.
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One common issue that can be experienced with a Managed Roaming SIM is where the home network applies a set of rules on how the connection is managed, so called steered roaming. Steered Roaming is where the SIM checks against an onboard Public Land Mobile Network (PLMN) list. It may then, for example, steer the router away from a strong Vodafone signal to a weaker Three signal because the supplier has a better deal with Three than they do with Vodafone.
Within the EU, and in the consumer market, charges for roaming are mandated to be equivalent to those applied on the home market. Since Brexit, there is no longer a requirement for this rule to apply to UK MNO’s. If a device will be crossing borders or deployed overseas, roaming charges could form most of the cost of the subscription. It is wise to check any contracts carefully, including for penalties should allowances be exceeded.
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