Prepare for Production Deployments with Super SIM

Key issues you need to address on your journey to volume production with Twilio Super SIM

You've built and tested your prototype, you've fine-tuned it into a product that can be manufactured in volume and shipped out to delight end-users. Now you're getting ready to deploy it to the first of your chosen target markets.

Or perhaps you're still in the planning stage but are beginning to consider the hardware and connectivity choices you will have to make when you reach the later phases of your IoT project.

Whatever stage you've reached in the journey from prototype to product, you will certainly need to consider how to work with Super SIM at scale. So far you've likely worked with one or two individual SIMs, each one manually managed in the Twilio Console for use in evaluation and prototype hardware. Though you will use the same processes to manage a fleet of Super SIMs — either using the Super SIM API or Console Bulk Actions — you will find that real-world locations pose some connectivity challenges that you may not have faced in the lab and for which you should now prepare.

To help you do so, this guide will introduce you to the obstacles that taking your IoT project to the next level will place before you, and provide you with strategies to overcome them and set you up for success. It's much better to face these issues now rather than when you have already released your product and devices are being used in the field.

You might even like to view this guide as a checklist of key points you need to address on your journey to volume production.

1. Have you selected the right cellular module?

You may already have selected a modem that you know works well with Super SIM through your own evaluation and testing. If not, we're here to help. Use our Cellular Module Knowledgebase not only to choose your project's connectivity hardware, but as a guide to configuring your chosen module for successful data connectivity.

Each of the modules in the Knowledgebase has been tested with Super SIM and are known from the experience of customers to support Super SIM's IMSI-switching technology: they provide the REFRESH proactive command, and either the STATUS proactive command, Location Status Event (LSE) or Location Information (LOCI) file updates that are required to allow Super SIM to access the widest range of networks in a given location.

Modules which support only some or none of the proactive commands listed above will not be able to access as many networks as modules that support all of them. Some networks will not be accessible to them at all because they require IMSI switching to be available to the device.

2. Will you deploy to a 'permanent roaming' country?

SIMs that spend a significant amount of time attached to visited cellular networks rather than their home networks are said to be permanently roaming. This applies to any SIM, from any provider. To be deemed roaming permanently, the SIM must spend 1-3 months attached to the visited network. The exact duration depends on the visited carrier and local regulation.

Most countries don't prevent permanent roaming, but a small number of nations, listed below, restrict or even forbid it. They do so typically to prevent businesses and individuals in those countries from sourcing connectivity from non-local providers. However, such restrictions also impact products like Super SIM.

Super SIMs are always roaming. If you intend to use a Super SIM-connected device in a country for more than 30 days, especially those listed below, you should consider the risks of being blocked from a network due to permanent roaming restrictions.

Countries with permanently roaming regulations include, but are not limited to:

• Canada †

• China

• Brazil

• India

• Russia

• Saudi Arabia

• Singapore

• Turkey

• United Arab Emirates

† Speak with sales to discuss options and eligibility for permanently roaming in Canada.

In these countries, SIMs can roam initially, but if they continue to do so for between one and three months, depending on the territory, they may be blocked. These restrictions are not specific to Super SIM, all non-local connectivity providers are subject to the same rules.

The local networks typically determine if a SIM is permanently roaming by checking the IMSI. Super SIMs hold multiple IMSIs and if the IMSI normally used in a country is blocked from accessing a network due to permanent roaming restrictions, you may be able to get reconnected, at least temporarily, on one of the backup IMSIs. If you find yourself blocked by a network, you may still be able to connect to other networks enabled in your Network Access Profile (NAP) if coverage is available.

If you are looking to use Super SIM in one of the above countries with permanent roaming restrictions, we encourage you to discuss your plans with one of our IoT Sales Specialists.

3. Have you set the correct APN?

The default Super SIM APN is super.

Support for distributed Internet breakouts are now available to all customers. Using a distributed breakout is key to achieving low latency. We offer a breakout in Frankfurt for Super SIM customers in Europe and Africa, and a breakout in Singapore for Super SIM customers in Asia Pacific. More locations will follow.

The APN you use determines your breakout point. The default APN, super, causes traffic to break out to the Internet from the Twilio Mobile Core in Ashburn, Virginia in the US. To make use of the Frankfurt breakout, set your device's APN to de1.super. To make use of the Singapore breakout, set your device's APN to sg1.super.

You should use super in all other circumstances.

You may be tempted to code your application to sample the SIM's current IMSI and use its Public Land Mobile Network (PLMN) ID prefix to create and set an alternative APN. We do not recommend this approach, which is not only unnecessary but also risks loss of connectivity. Super SIM leverages multiple IMSIs to upgrade SIMs or for failover and they may be changed over-the-air. The current IMSI being used may change in the future. The generated APN may fail to resolve. In this case, the device won't be able to communicate with the Twilio Mobile Core's Packet-data Network Gateway (PGW) and so won't gain access to the public Internet.

Instead, set your modem to use super so that the full APN remains correct no matter what country in which it is trying to connect, or what IMSI the SIM applies. This includes not only the IMSIs that are currently available to the SIM, but others that may be added in future via over-the-air (OTA) updates.

4. Does your device's OS set the APN for you?

Not all Super SIM-enabled products are custom-built devices. Some make use of new off-the-shelf hardware or repurpose older consumer devices — a great way to extend the life of unwanted electronics and to reduce e-waste.

However, mobile operating systems may alter the APN you have applied. They do so to make life easier for consumers, but this also means that you will need to adopt a strategy to deal with APN changes and, in extreme cases, being prevented from setting the APN at all.

Most Android devices let you enter super in the Cellular networks > Access point names section of the Settings app, or similar depending on the version of Android in use or the degree of vendor modification.

However, some versions of Android require you to provide a Mobile Country Code (MCC) and Mobile Network Code (MNC) for an APN. This is to help match the APN to the IMSI being used by the device. You should make sure you enter this information. Super SIM can switch IMSI, of course, so you may need to add MCC, MCN, SPN, and APN combinations to your device, one for each of the four IMSIs that Super SIM currently makes available.

You can find details of the combinations in How to Set a Device's APN for Super SIM.