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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.
– 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.

4) Cheap wholesale agreement – good service quality?

One of the main tasks of roaming and wholesale managers is the optimization of their wholesale deals. But optimization usually means: best roaming footprint as cheap as possible. To what extent does quality matter? The GSMA is pushing a lot to encourage MNOs to define SLAs for roaming services and to monitor them, but the truth is the industry so far is still quite reluctant to apply appropriate measures. Even more, MNOs in most cases do not know if they get the best roaming quality for their customers – or if customers of their competitors get even better service quality!

Well, now someone might think, isn’t this all just pure theory? Does roaming not work well since more than 30 years since we introduced GSM in the early 90s of the past century? The answer is: It is not theory, there are plenty of live examples we see day-by-day when monitoring international roaming relations using our Global Service Enabler (GSE) platform. 

Example 1:
Sending SMS over IMS in 4G, on average, takes around 4 seconds in terms of end-to-end transmission time – this is an average value measured in Europe, in all networks which support this technology in roaming (mind that a VoLTE roaming agreement needs to be in place to send SMS over IMS). In a Norwegian network, though, for German roamers from an MNO_X, the E2E transmission time is double that average value. For roamers belonging to another German MNO_Y, and roaming to the same network, the E2E transmission time is around 4 seconds, as expected. The even more surprising fact is that using legacy SMS technology over 2G provides faster SMS transmission for the said MNO_X than using the latest innovative technology.

This observation is not just a one-time snapshot; we could observe it now for several months already, so it looks like MNO_X still is not aware of this problem, or not able to solve it, or does not care at all about it.

Example 2:
Incoming voice calls to Germany, originating from German subscribers in roaming, show up with an empty CLI: This phenomenon was seen quite often in early 2023 when the German regulator imposed the new anti-fraud/anti-spoofing law. Recent checks, again done on the SEGRON GSE platform, have revealed that the problem still exists when calling from certain networks in Belgium, Italy, and Poland – this is not an exhaustive list, as not all roaming destinations across the globe have been checked in our internal campaigns.

Example 3:
In Poland, we have seen that the data throughput for a German subscriber is higher in a non-preferred visited network than in the preferred network. Also, this phenomenon is not just seen temporarily; it can be tracked back for several weeks and even months.

Example 4:
Tests carried out in the Netherlands at the end of last year have shown rather high 2G/3G call setup rates (VoLTE Roaming is often still not in place) for German roamers in some of the mobile networks. While the GSMA recommends a call setup time of less than 8 seconds for intra-continental calls, we have measured a significant number of calls with a setup time of more than 10 seconds. Compared to call setup times in other German neighboring countries, the measured values in the Netherlands are almost 100% higher.

To cut a long story short, there is no other way for mobile network operators than to implement permanent monitoring strategies if they want to maintain roaming quality at the level customers expect it. SEGRON Global Service Enabler (GSE) gives mobile operators the possibility to get all the insights they need to know how to manage roaming quality across the globe.


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