Why continuous monitoring of international roaming quality is becoming more important for mobile operators

International roaming in digital mobile communications hasn’t just been invented. Customers across the globe have been enjoying mobile services abroad for over 30 years already, and without any doubt, it is one of the key drivers for the success of GSM and all related standards. This raises the question: If international roaming is such a success story, why has the continuous monitoring of the roaming performance gained more importance compared to 5, 10, or even 20 years ago? 

Without claiming that the list is exhaustive, here are at least 4 reasons to underline the increased importance:

1) 5G increases complexity further

In 2024, in almost all developed countries, consumers can enjoy high-speed 5G data services. Even if the technology behind it is “only” 5G NSA (non-stand-alone), download rates up to 500 Mbps can be achieved in ideal conditions. 5G coverage, though, is not yet available everywhere, and even where there is 5G coverage, there is 4G as well. Despite all 2G/3G sunsetting efforts, many operators still keep at least one of the legacy technologies, some even continue to have both 2G and 3G in place. For services such as voice and SMS, this means that they might be provided in many different flavors:

– Circuit-switched voice over 2G and/or 3G.
– CSFB, if 4G is available but no VoLTE or no VoLTE roaming in place.
– VoLTE
– 5G NR if 5G SA is available and if a roaming agreement for 5G NR exists.
– 2G/3G SMS (using MAP protocol)
– 4G SMS (over MAP)
– 4G SMS over Diameter
– 4G IMS SMS over MAP or Diameter
– 5G SMS using MAP or Diameter

Thus, the multitude of possible technologies and protocols used to enable voice and SMS increases the potential points of failure in the home, visited, and intermediary networks. Do all network providers always make sure their services work across all different technologies?

2) New regulatory directives

Preventing consumers from telco fraud such as Robocalls with spoofed numbers has become a number one priority for both operators and regulators. The German regulator, in late 2022, imposed all German mobile operators not to deliver the CLI of calls originating from abroad and containing a German mobile number – except for German subscribers in roaming. In the beginning, German operators were challenged on how to distinguish a call being originated from a German roaming subscriber or from a fraudster calling from abroad and faking a German CLI, as there are no simple, standardized ways to do so. The British regulator, Ofcom, for that reason, still has not imposed a rule to flag or even block such calls (only calls originating outside the UK with spoofed UK fixed network numbers are blocked). Do German mobile operators monitor if they strip off the CLI from the right (= spoofed) calls, or do they treat roamers like fraudsters?

3) IREG is not sufficient

Having successfully opened a roaming relation for a service does not mean the service will work forever. Core network upgrades in HPLMN and VPLMN, changed MAP/Diameter routing, new or different interconnect partners could easily lead to a situation where a once successfully opened service will fail over time, or it will not be delivered with the expected quality. Despite this fact, many operators ignore monitoring their roaming relations after successful openings, so they don’t have certainty whether their roaming services work as they should.