Roaming Report – Part 6 – 5G Roaming in the US fixes the lack of no LTE-CA on some Devices!

When I was last in the US back in 2019, I noticed that quite a number of the test smartphones (from the EU) I had with me would not do LTE Carrier Aggregation (CA). Even worse, my devices where often sent to a 5 or 10 MHz Carrier, so data transfer speeds were abysmally slow in the single digit Mbps range. Already back then, I found such a device behavior pretty strange but hoped that time would fix this. Fast forward to 2024 and my recent visit to the US, where I could have another look:

Continue reading Roaming Report – Part 6 – 5G Roaming in the US fixes the lack of no LTE-CA on some Devices!

Roaming Report – Part 5 – Double Inter-Continental Voice Delay

And yet another roaming story from my recent trip to North America: For voice and video calls to family and friends, I use my Prosody XMPP server in Germany, a voice stream reflector that is also located in the country and the ‘Conversations’ messenger app. By having all components close together, the speech path delay is minimal. But when roaming to North America, the round trip delay time to and from Germany is around 300 milliseconds when connected to an LTE network. That’s quite a bit longer than what I would have expected, as the RTT time from one of my servers in Germany to ‘’ that is hosted in San Francisco is around 160 ms.

But let’s stick with the 300 ms round trip time for now, which means there is a 150 ms one way delay, i.e. the delay between mouth to ear. However, if both ends of the conversation are at the far end of North America, e.g. in California, while the voice reflector is in Europe, the mouth to ear delay doubles, i.e. it is around 300 milliseconds. ITU G.114 recommends a mouth to ear delay of less than 150 ms for conversational calls, so the 300 ms are way beyond this recommendation. So how does that sound like in practice?

To find out, I established a ‘Conversations’ voice call over two LTE/5G ENDC connections between two smartphones and observed the delay. And indeed, the delay is quite obvious, but it is still possible to have a normal conversation, albeit with a bit of silence when the direction of the conversation changes.

If I was at the North American west coast for a longer time than just for a week or two and wanted to use ‘Conversations’ for local calls, I would obviously change my setup: SIM cards with LTE P-GWs on the continent and a media reflector somewhere here as well. In other words: The Edge is still important!

Roaming Report – Part 4 – When the SIM card talks to the Internet

Here’s a quick follow-up to my recent blog post on using an eSIM when roaming in the US: After I installed the eSIM, I noticed with my trace tools that whenever my smartphone connected to an LTE network, the phone would, in addition to the LTE PDU session for Internet connectivity, request another PDU session with another APN (Access Point Name). This was not configured anywhere in the device. The PDU session just lived for a few seconds and was then terminated again. I was a bit puzzled at first but soon had a suspect… the SIM card.

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Roaming Report – Part 3 – Airalo – 5 Minutes to the eSIM

After a bit of a disappointing prepaid eSIM (non-) experience directly from US network operators, I switched to plan B and had a look if I could get an eSIM for use in the US from one of the global eSIM roaming platforms. Two years ago, I checked out Airalo when I was roaming in Europe, and was quite happy with the result.

Continue reading Roaming Report – Part 3 – Airalo – 5 Minutes to the eSIM

Roaming Report – Part 2 – Getting a Local US eSIM – How Hard Can it Be?

While I was in the US, I was using my German SIM card to roam through the different networks. When using a German SIM card, however, all IP data traffic goes back from the US to Germany and from there to the Internet. As the servers for my self-hosted services are in Europe, that’s not much of a problem. However, I also wanted to test some of the US specific features / limitations of mobile Internet access, and was prepared to spend some money to get a Prepaid eSIM from one of the US network operators. Prices in the US are significantly higher than in most countries in Europe, but it would not have kept me away. It turned out, however, that getting a prepaid eSIM from US network operators is not straight forward.

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Roaming Report – Part 1 – Roaming with Verizon – A First!

It’s March 2024 and for the first time in 5 years (thank you Covid pandemic), I was in the US again. So far, so good, but there is one significant difference this time, at least from a technical point of view: For the first time ever, I’m roaming with Verizon!

Most travelers won’t even notice, but until recently, Verizon in the US could not be an international roaming partner for most travelers, because their 2G and 3G CDMA networks were incompatible with the majority of international networks. Even with the introduction of LTE, this did not change. This was because for GSM/UMTS/LTE/5G network operators, international roaming depended on the 2G/3G circuit switched voice core and the CS-fallback mechanism from LTE/5G to GSM or UMTS. And this is what Verizon could not offer to international operators. But finally, VoLTE roaming is on the rise and it seems my home operator has made a roaming agreement with Verizon. Agreed, most people use Internet based voice calling apps these days, including me, but VoLTE roaming support in devices and networks is still crucial for emergency calling and calls to people that don’t share the same messenger / calling app.

So here we go, one of those rare ‘firsts’! And as the title indicates, I made good use of my time in North America and had a look at a lot of other things while roaming. So stay tuned for more posts to come!

Sony WF-1000XM5 In-Ear Headset – Review

In my life there is a time before noise cancellation headsets and the time ever since, as noise cancellation has brought so much more silence, peace and concentration when I’m in noisy city, home and office environments. As my current first generation Bose in-ear noise cancellation headset I’ve had for many years are showing signs of battery fatigue and charger connector problems, it was time to look for something new. After shopping around a bit, the two contenders for my refresh where either the latest generation Bose in-ear Bluetooth headset, or the latest Sony variant. In the end, I decided to go for the Sony WF-1000XM5 and I’ve been using them for around 2 weeks now. Was it a good choice? I’m not so sure…

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