Roaming Explained

Roaming in general

As the IoT-enabled devices of large scale, IoT networks are scattered across the globe, crossing many borders, companies are looking for roaming solutions to allow their devices to transmit data at the cheapest rate possible. Roaming steering is a process that allows home networks to identify the ideal roaming partner for its subscribers. From the consumer’s perspective, this is a seamless process, which is all the more important if the subscriber happens to be a large-scale IoT network.

The increasing deployment of IoT environments is happening worldwide. Thus IoT device manufacturers need to provide global connectivity solutions in order to attain market shares beyond their main region of operations. It is very likely that providers who can guarantee connectivity across the globe will end up dominating this new market. Roaming capabilities are virtually synonymous with global connectivity. Roaming is the ability to access the network providers beyond the ones who issued a SIM.

How does roaming work?

While most of us have likely benefited from roaming at one point or another, very few understand how roaming is made possible. Roaming becomes available thanks to roaming agreements between two operators. In order for these two operators to reach an agreement and enter a partnership, they have to consider the following questions:

  • For which type of connection will roaming be allowed? (e.g., 2G, 3G, 4G or 5G)
  • Can the roamer accept calls, and at what cost?
  • Can the roamer send or receive SMS?
  • Can the roamer use data? If yes, at what speed and at what cost?

The pricing of the roaming is typically based on the number of expected roamers and the operating costs. To allow subscribers to roam in other countries, the operator has to negotiate agreements with other operators for every country. So roaming costs will always vary strongly from country to country.

The process of roaming is typically very similar across different types of networks:

  • After a device containing a SIM is turned on in a country with a roaming partner from the SIM issuer, an IMSI will be sent to the partner network. The roaming network detects that the IMSI was not issued by the network itself. The roaming network will then identify the issuer. In case there is no roaming agreement, the roaming network will deny its services to the SIM, and thus, no connection can be established.
  • If there is a roaming agreement between both operators, the roaming network will contact the network from home and will query for more information to find out whether this particular subscriber is allowed to roam.
  • If there is roaming permission, the device can connect to the roaming network. The network starts keeping temporary records of the device’s network usage. From the consumer’s perspective, this is a seamless, uncomplicated process.

What is Roaming Steering?

As mentioned previously, the costs for roaming vary strongly from country to country and also between operators of the same country. Thus if there are multiple roaming partners within a region, it would be ideal for subscribers to be able to connect to the roaming network with the cheapest rates for calls, SMS, and, most importantly, data.

This ability is known as roaming steering. The mobile operator can decide which partner network subscribers can use. There are two different ways or roaming steering, SIM-based steering and network-based steering.

SIM-based steering

SIM-based steering uses the list of preferred networks directly stored in the SIM in order to decide for the best roaming partner in a given situation. This list, however, has to be updated continuously as roaming agreements are subject to change at any time.

Network-based steering

This system is remotely integrated into one’s issuing network. As a device tries to connect to a roaming partner, the roaming partner will establish contact with the home network. Then, based on current agreements, the steering system decides whether this roaming partner is the right choice for the subscriber. If this is the case, the roaming request is granted. If not, then the system will send a “roaming request denied” message. After the device receives this message from the home network, it will automatically try to connect to the next available roaming partner.

Network steering is crucial for IoT

Many IoT networks will deploy IoT-devices that will cross countries’ borders. For this reason, roaming and roaming steering is absolutely crucial, as the price for data is a massive cost factor, especially for large-scale environments with hundreds or thousands of IoT-enabled devices.