Roaming versus local SIM cards

Roaming Subscriber Identity Module (SIM) cards can access different networks around the world if the SIM manufacturer has a roaming agreement with the network outside their local network.

This means that the network looks at the device as roaming in their network and often have some different configurations compared to a local device. For example, many roaming SIM cards lack agreements around the world to access the important Power Saving Mode (PSM) and Extended Discontinuous Reception (eDRX) features. You must check with your SIM card provider if these features are available. If your device cannot get in to PSM or use eDRX intervals in a network, you need to make sure your application turns the modem completely OFF if the device is going to sleep for a long time.

Figure 1. SIM card form factors
SIM card form factors

See this blog post to learn more about the different types and form factors of SIM cards.