Author: Martin

Many network operators these days are trying to get their VoLTE system off the ground in their home countries so perhaps by 2016 we'll finally see a significant number of networks using the system beyond the few that are silently up and running today. While VoLTE at the beginning will only work in the subscriber's home country, many network operators are now thinking about implementing the next step which is to also offer VoLTE when the user roams abroad instead of falling back to CS-fallback to 2G or 3G networks for voice calls. Problem is, it adds quite some complexity to an already very complex system.

The solution favored by many so far is to have VoLTE work abroad in pretty much the same way as circuit switched calls. The concept is referred to as RAVEL (Roaming Architecture for Voice over IMS with Local Breakout) and LBO (Local Breakout) and its core idea is to use part of the IMS infrastructure in the visited network (i.e. the P-CSCF) that then communicate with the S-CSCF in the home network. Further, calls can be routed directly to another subscriber instead of going back to the home network first. Docomo wrote a good article with further details that can be found here. One of the advantages of the approach is that the P-CSCF has interfaces to the visited core and radio network and can thus establish a dedicated bearer for the speech path and hand-over the call into a circuit switched channel when the subscriber looses LTE coverage. The downside of the approach is that interaction of the P-CSCF with the IMS in the home network is not a trivial matter.

As a result, network operators have started thinking about a simpler solution in the GSMA REVOLVER group which has resulted in a 3GPP study item referred to S8HR (S8 Home Routing). S8 is the packet switched interface for LTE between a home network and a visited network. The 'Home Routing' part of the abbreviation already indicates that this solution is based on routing all IMS related things back into the home network without any involvement whatsoever of IMS network components in the visited network, thereby drastically reducing VoLTE roaming complexity. In fact, apart from the MME having to set a parameter in the Attach accept message, the visited network is not aware of the UE's VoLTE capabilities and actions at all, everything is sent transparently to the P-CSCF in the home network via the home network's PGW. In other words, IMS signaling and voice traffic takes the same path as other LTE data from roaming subscribers today. Another interesting thought: VoLTE roaming via S8HR would be like an OTT (over the top ) service…

Needless to say that reduced complexity results in a number of disadvantages compared to local breakout. Another Docomo paper, an article by Telecom Italia and a recent post over at the 3G4G blog give a good introduction. One major issue is how to handle emergency calls by roaming subscribes. The challenge of emergency calls for the network is to direct the call to a local emergency responder (e.g. the local police station). As S8HR does all things related to IMS in the home network there is no way to do that. As emergency calling is a regulatory requirement and unarguably an important feature it needs to be dealt with. The simplest solution is to instruct the mobile to do a CS-fallback call in case of an emergency. A more complex solution is to use the IMS in the visited network for emergency calling. But I wonder if the additional complexity is worth the more elegant solution? After all, 2G or 3G network overlays will be present in most parts of the world for a very long time to come, so why bother? Or if one bothers, perhaps bother later?

The second, equally problematic drawback is that calls in the visited network can't be handed over to a circuit switched channel (SR-VCC) when the subscriber runs out of LTE coverage. Again, the IMS in the home network has no way to communicate with network components in the visited network. 3GPP is investigating solutions but it's likely that in case they come up with something it's not going to be a simple solution. Perhaps S8HR is not less complicated with SR-VCC support than RAVEL? It remains to be seen.

The big question is whether not supporting SR-VCC is a showstopper for S8HR? After all the OTT competition (Skype, etc.) can't do it either. But I suspect it's going to be a showstopper for many network operators as this is a clear disadvantage over traditional circuit switched voice roaming. On the other hand, mobile devices could have an option for the user to disable VoLTE roaming if they are really bothered by it. I suspect most people won't as SR-VCC mainly plays a role in high mobility scenarios, e.g. in moving cars and trains. One could even think about putting logic in mobile devices to detect roaming and high mobility scenarios and then preferring CS calls over VoLTE if S8HR is used. That would push the issue from the network to the mobile side, but still, perhaps it is worth a relatively minor effort on the mobile side instead of going to great lengths to implement it on the network side. And again, after all, the competition can't do SR-VCC in the first place…

Until September 2010 I must have been one of the most outspoken and enthusiastic Nokia fan around. The future was great, the future was bright, Nokia was embracing open source and promised to migrate from the somewhat aging Symbian OS to the open source Meego operating system for its upcoming devices. The day Nokia announced that an 'Ex'-microsoft manager is to become the new CEO of Nokia was more than just a shock for me. How could an 'Ex'-Microsoft manger possibility continue with open source!?

The day of the 'burning platform' memo marked the not quite unexpected but still abrupt end of my Nokia fandom. Meego and open source to be abandoned and to be replaced by a closed source Microsoft Windows Mobile, you can't imagine a more drastic 180 degrees in a company strategy and what I would have liked Nokia to do for me. 5 years later Nokia is no more, bought and destroyed by Microsoft and now completely written off from their books due to a complete failure to make Windows Mobile a success.

While I don't mind that Windows is not getting a foothold in mobile it's a shame Nokia and its great ideas withered away. While most of the tech press has already written of Nokia the smartphone company, my favorite mobile analyst Tomi Ahonen has three great scenarios for Nokia the smartphone coming back but not as a Microsoft subsidiary but as a part of Nokia the network infrastructure company. Microsoft wants to get rid of what's left of Nokia mobile while the original and still existing Nokia wants to make a comeback in mobile. Based on lots of insight and historical knowledge it's a brilliant piece of analysis of what could now happen. I just wished those in charge would listen and show dome good sense, at least this time…

A couple of weeks ago I finished reading "Commodore – A Company On the Edge", a book by Brian Bagnall about the early years of Commodore in the computer business up to 1984 and the success of the C64. I could hardly resist as the C64 was the first computer I owned. At the end of the book I wished the sequel about the later years of Commodore and the Amiga, which was my second computer I owned, would also have been already published. Now it seems that my wish could be fulfilled rather sooner than later as Brian has a campaign over at Kickstarter for his upcoming project.

Originally set out for a sum of 15.000 Canadian dollar, the project has attracted quite some attention and the pledged sum, as of this writing and including my own backing is at 73.800 Canadian dollars! A respectable sum and I'm really happy to see that even books for such an arguably niche audience can still get great funding this way and make it worthwhile for the author to work on such a monumental project.

There's less than 3 days left to participate in the Kickstarter campaign as I write this post so if you are a computing history buff you better hurry!

via The Digital Antiquarian

Every now and then I travel the world and stay in places where I'm charged 2.50 Euros a minute for the privilege of making traditional mobile voice calls with my mobile phone to someone back home. Needless to say that long calls for €150 per hour have to be avoided if at all possible. These days, however, Skype or other VoIP clients that run on smartphones come to my rescue in combination with a 15 Euros for 150 MB roaming data package.

So what's the price difference to those 2.50 Euros a minute circuit switched mobile calls? When not using video, Skype uses around 20 kbyte of data per second which is around 72 MB an hour. In other words, that 150 MB data roaming package for 15 Euros buys me around 2h worth of Skype calls, i.e. a Skype call to another Skype user costs me €7.50 when roaming. When used to call a fixed line phone, add a euro or two. In other words, despite using an expensive data roaming package, that Skype call costs 20x less and I'm sure my home network operator still has a good margin on roaming data. Hour long mobile calls 10.000 miles away from home have just become sweet again.

And a nice bonus: When calling other Skype users, voice quality is way beyond what's possible with circuit switched mobile calls between networks and continents. No WB-AMR anywhere… The only downside: Should your connection drop down to 2G during the call that's rather an abrupt end of the conversation. So in mobility scenarios, circuit switched mobile calls still have an advantage, at least until that 98% coverage requirement is reached.

This year, both the Atari ST and the Commodore Amiga celebrate their 30th birthday. To me they represent the height of the home computer evolution that paved the way to computing for many adolescents at the time. Many, like me, had a C64 or similar computer before an Atari or an Amiga and most migrated to PCs at the beginning of the 1990s once Microsoft got their act together in 1991 and shipped Windows 3.1. That, in no way, however, diminishes their importance at this point in time.

While reading a book about the Amiga recently and doing some background research, I stumbled over the web page for the Amiga 30th anniversary event in Neuss, Germany, which will take place on the 10th of October. That's not too far away from where I live so I will most likely attend and relive history for an afternoon. Should be great fun!

For those of you living in the US, there's a 30th anniversary event on the 25th and 26th of July at the Computer History Museum in Mountain View, California. The UK will celebrate on the 2nd of August in Peterborough and the event in Amsterdam has already taken place at the end of June.

Some people would probably still say today that they don't need or want Internet access when going on vacation on a cruise ship or to a remote island. But I suppose their number is on a steep decline and cruise ship operators are investing in Wi-Fi Internet access on their ships not only in special areas but in cabins as well. According to this article (in German) the pleasure costs between 25 euros per week for "social media" access to 99 euros for 3 GB of data for a week on a ship of one of the major cruise lines.

The article doesn't mention what kind of backhaul is used but it's likely to be satellite. There's different kinds of technologies and (one of?) the latest and greatest seems to be from O3b, a company about which I wrote a post in 2008. It looks like in the meantime their medium earth orbit satellites (at an altitude of 8.062 km) are up and running and their public list of customers includes a cruise ship operator (though not the one mentioned in the first post linked to above) and remote islands. The specs advertised on their web page is a top speed of a single transponder of 1.6 Gbit/s and round trip times of around 150 ms. Each satellite has many independent transponders that can direct their beam to a specific area which hints at the capacity and user experience that can be achieved even if several hundred people on a ship need access simultaneously. Here's a video that demonstrates how the system works with two antennas that track the satellites.

And a final thought: I wonder if the uplink/downlink ratio on a cruise ship with lots of people posting their pictures and videos to social media websites is significantly different from the "land" average!? So apart from pleasing customers, a cruise line you probably can't get any better advertising than people posting their pictures in real time to Facebook…

Some heart warming nostalgia today: For some time now, the GSM logo initially designed at the end of the 1980s and used on a lot of GSM related products in the decades afterwards is rarely to be seen these days anymore. But there are some who still use it on new products. Have a look at the new 2015 Telecom Italia SIM card I've recently been given. It's not big and prominent anymore but still there. I wonder what the intention was to put it there. Perhaps by someone with nostalgia in his or her heart? We'll probably never find out but it made me smile nevertheless. And just in case you wonder what the meaning is behind the for dots in the logo, have a look here.

For about half a year I ran a somewhat outdated version of Selfoss on my server at home for RSS feed reading for a simple reason: At the time a change was proposed to integrate marking all displayed entries as "read" into the scrolling mechanism. I much preferred this over the solution that made it into the following release with which you had to disable scrolling to get a new button to mark entries as read. As other changes were minor I decided to remain on the old version and keep the suggested patch running on my system. Github makes it possible.

Over the weekend, however, I updated to the latest version once more despite the feature not being integrated because of two very interesting new features: There's a new feature to read full posts for those RSS feeds that only show the first part of the original entry. For a previous version I came up with dedicated code for a specific web site. Now, however, someone seems to have cracked the nut of how parsing a full web page and stripping out the text and pictures in a more generalized way. I gave it a try with one of my feeds and it worked perfectly. Enough a reason to switch and great to have a choice 🙂

Once per year I review which software I've used most and to which projects I'd like to donate some money to in return. After all, free software is not "free as in beer" but "free as in freedom". This time around I donated to six projects which had the most impact on my daily use of computers and smartphones.

As I use Ubuntu on countless devices including several servers my first donation went to them this year. Also, I think their push for a single OS and user interface for all devices from smartphone to TV is an important project that should be funded and supported.

Firefox and Thunderbird are my web browser, email client and calendar of choice and Mozilla is far too much dependent on donations from the advertising industry. My donation will change little in that regard but every penny counts.

Without Libreoffice, Linux on the desktop is hardly imaginable and so I decided to donate something to the TDF (The Document Foundation) as well. Great job done guys, thanks very much!

A website I visit several times a day is Wikipedia so I decided to donate to the Wikimedia foundation as well.

Again, my world without that project would be quite different. Another big thanks goes to Openstreetmap. In addition to regularly updating and contributing to the database I felt it would be a good thing to donate some money for to keep their infrastructure running.

And finally I made small donation to the KeypassX project as I rely on their software to keep my passwords save day in and day out.

Thanks to all people working on these projects, paid or volunteering, the computing world would be not as great as it is today without you!