Author: Martin

This week, another network operator in Germany announced that they will start LTE data roaming on 1 August. For two reasons, however, the announcement is more than a little bit strange.

First, they are not only a year late to the game but they will only start with three foreign networks while their competition already have roaming agreements with several dozen networks around the globe. The second restriction is even weirder: LTE Roaming data speeds are limited to 1 Mbit/s and nobody knows what that is good for!? While my LTE data roaming speeds easily surpass 20 Mbit/s they want to limit their customers to 1/20 of that. No way this would work for me because I regularly use LTE data roaming for notebook tethering.

Hm, that makes me wonder if they are bundling a couple of old E-1 lines to connect to their roaming hub and are afraid of massive overload if customers want to use the technology as it was designed!? 😉 Sorry, an announcement like that needs to be ridiculed.

On my commute to work I make good use of the excellent network coverage along the railway track. LTE coverage is almost perfect, but just almost as there are a few locations where my data session is handed over to the 3G network. Once on 3G the only way back to LTE, at least for now, is for the network to set the device into Cell-PCH or Idle state so it can search for LTE and return autonomously. That unfortunately doesn't happen in my case as my OpenVPN Server sends a UDP keep-alive packets every 10 seconds, thus preventing my smartphone I use for tethering to return to LTE. It's not that big of a deal as 3G is quite fast as well so I hardly notice the difference. But I'm a perfectionist… So I had a closer look at the OpenVPN sever configuration (in /etc/openvpn/server.conf) and noticed an option for keepalive timers:

keepalive 10 120

The "10" suspiciously looked like the 10 seconds interval that keeps my 3G connection in Cell-DCH state. After changing the line to

keepalive 30 120

the UDP keepalive packets are now spaced 30 seconds apart. That's more than enough time for the network now to set my device to Cell-PCH or Idle state, which in my case, happens after around 12 seconds of inactivity. Shortly after, my tethering smartphone then changes back to LTE.

Perfect! And on top of all this I might even save some battery power as fewer packets are sent and received now.

In a previous post I wrote about what has changed in desktop computing in the last 6 years. In summary not very much, I still use my notebook from back then for some purposes with an up to date operating system for multimedia consumption.  So what about mobile computing and mobile devices, how have things evolved in this domain in the same time frame?

Back in 2008 I wrote a review of how well an entry level phone at the time, a Nokia 5000, could be used for email and web browsing. Back then, the point was to show that even with an entry level device, it had become possible to surf the web and use the device for email communication. It was a sensation. So let's have a look at how the 7 year old Nokia 5000 compares to a similar device that can be bought today.

Price

For my comparison I chose the Android based LG D160, released back in 2014 and which is currently available for around 56 euros, contract free, VAT included. That is only around 60% of the price I paid for the Nokia 5000 at the time, which cost 90 euros. I could have made a comparison to a device that also costs 90 euros today but I wanted to compare two entry level devices and the cost of such a device has come down significantly over the years.

Connectivity

At the time, being able to browse the web with an entry level device was spectacular, today it's a given, nobody would think otherwise anymore. Back then I used Opera Mini with a compression server in the cloud to reduce the size and complexity of the web page. This was necessary on the one hand because the Nokia 5000 only came with a 2G EDGE network interface that could at best transport around 250 kbit of data per second. 3G networks did exist at the time and already covered bigger cities, but entry level devices were still limited to 2G networks. Compression was also necessary due to the processing power and memory having been quite low on the Nokia 5000 compared to today's devices. The LG D160 of 2014 on the other hand comes equipped with a 3G HSPA network interface with data transfer speeds of up to 14.4 Mbit/s. LTE networks are available nationwide today but it's the same story as with 3G for the Nokia 5000 then, LTE hasn't moved down into entry level category yet. What is included today that was considered a high end feature at the time is Wi-Fi, so the device can be used at home without a cellular network. Also, the device supports tethering, so it can be used as a gateway to the Internet for a notebook or tablet on the move.

Screen and Web Browsing

The image on the left shows the Nokia 5000 and the LG D160 side by side and next to a Samsung Galaxy S4, a flagship device back in 2013. While the Nokia 5000 back in 2008 came with a 320×240 pixel screen capable of 65k colors, the LG D160 now has a 320×480 pixel screen with 16 million colors. By today's standards that is a very low resolution but compared to 2008 it is still twice the number of pixels. Opera is still my browser of choice but I have moved-on from Opera Mini to Opera, a full web browser that no longer requires a compression server on the backend as the device has enough RAM and processing power to show mobile optimized and even full web pages without any magic applied in between. At the time it took around 12 seconds to launch the browser and there was no multitasking. Still acceptable then but today, the browser launches in 4 seconds and even stays in memory if no other big apps are running despite the 512 MB RAM, which is a massive amount compared to 2009, but rather little today. GSMArena doesn't even specify how much RAM was built into the Nokia 5000 but the 12 MB of Flash memory for file storage compared to the 4 GB in the D160 today are a pretty good indication of what it must have been. Another aspect I focused on at the time was how fast and smooth scrolling and I noted that compared to the flagship Nokia N95 at the time it was slower and not as smooth. Still usable was the verdict. Today, scrolling of normal web pages via a touchscreen is quite smooth on the D160 and light-years away from what was possible on entry level devices in 2008/9.

eMail

At the time, the email client in the Nokia 5000 was quite rudimentary, with important options such as partial downloads missing. Also, there were few if any email apps for non-smartphone devices at the time to improve the situation. Today, even the 40% cheaper D160 easily runs sophisticated email clients such as K9 mail that, apart from a proper PGP implementation, leaves little to be desired.

Camera, Navigation and Apps

When it comes to built-in cameras, the Nokia 5000 from back in 2009 has a 1 MP camera at the back while today's D160 has a 3 MP camera built in. Both take pictures but they would both be rated pretty much worthless by the standards of each period. But still, the camera is significantly better at a much reduced price compared to 2009. One big advantage of today's entry level smartphones compared to 2009 is the built in GPS chip for a variety of uses from finding the closest Italian restaurant to car navigation. I didn't install Osmand on the D160 but Google maps pinpointed my location in seconds and presented me with a route to a destination almost instantly. An incredible improvement over the state of the art in 2009 in this price category. I mentioned the price tag on purpose as Nokia Maps with car navigation existed in 2008/9 (see here and here) but could only be used on much more expensive Symbian OS based devices. And a final point to make in this review is the availability of apps now and then. Few apps and games existed for entry level devices back then. Today, even the very low cost D160 can handle most Android apps and many if not most games (I'm no expert when it comes to gaming). Also, SMS messaging is quickly dissapearing with most people not caring about privacy and using Internet based multimedia replacement solutions such as WhatsApp instead.

Summary

So while I still use the notebook I bought back in 2009 with the latest operating system version on the market today, the entry level phone from back then is so outdated by today's entry level state of the art that I find quite shocking. Incredible how things have advanced in mobile in this short amount of time.

When I recently checked out a "very low end" smartphone of 2015 I couldn't help noticing how vastly different and improved things are compared to smartphones sold a couple of years ago. I'll write a follow up article about this but I think the scene should be set first with a comparison: What happened in desktop/laptop computing since 2009?

I chose 2009 for this post as this was the year I bought a 17" laptop mainly for stationary use to replace an aging tower PC. Since my usage became more mobile since then I had to replace this laptop for everyday use with a smaller device in the meantime. Nevertheless I still use that laptop today, 6 years later (!), for streaming Netflix, Youtube and other things. So while I still use this 6 year old computer any phone from that era has long gone to digital oblivion.

So is that 6 year old laptop old and outdated? I guess that depends on how you look at it. At the time I bought the laptop for 555 euros with an Intel Core 2 Duo processor, 4 GB of RAM, a 256 GB hard disk, USB 2, a 17" display and Windows Vista. Even if I hadn't upgraded the machine, Windows Vista pretty much looks like Windows 7 which is still widely used today. I could even upgrade the machine to Windows 8 or Windows 10, to be shipped in a few weeks from now and it would still run well on a 4 GB machine. As a matter of fact, many low end laptops sold today still come equipped with 4 GB of RAM. Hard disk sizes have increased a bit since then, USB 3 ports are now standard, CPUs are perhaps twice as powerful now (see here and here) and the graphics capabilities required for gaming are more advanced. But for my (non-gaming) purposes I don't feel a lot of difference.

As I switched to Linux in the meantime my software evolution path was different. Windows was banished from the machine at some point and replaced by Ubuntu Linux. Ubuntu's graphical user interface looked different in 2009, a lot of eye candy has been added since then. Today I run Ubuntu 15.05 on the machine and I upgraded to a 256 MB SSD which makes it in effect look no different from my almost up to date notebook. It also still behaves pretty much the same when it comes to program startup and reaction times. The major difference is that the fan is louder compared to my current laptop due to the still higher power requirements of laptops of the 2009 time frame compared to today's machines.

So what has changed since 2009 in the laptop world? Prices have certainly come down since then a bit and many people these days buy laptops in the €300 to €400 range (taxes included). Technical specs have improved a bit but the look and feel is pretty much the same. Companies have started experimenting with touch screens and removable displays to create a more "tablet-like" experience, trying to import some of the fascinating advances that have happened elsewhere since. But that's still a niche at best. In other words, hardware and software evolution on the desktop have very much slowed down compared to the 1990's which was the second half of the home computer area and the decade of the rise of the PC and Windows. Things already slowed in the 2000's but that decade still saw the rise of easier to use Windows and prices for laptops coming down significantly.

Now try to remember what kind of mobile phone or smartphone you had in 2009 and compare that to what you have today and you'll see a remarkable difference to the story above. More about that in a follow up post.

While 3G networks are still doing pretty well in most parts of Europe due to HSPA+, 64QAM, dual-carrier, etc. etc., I was recently at an airport where the 3G cell covering my location seemed to have severe uplink congestion problems. Ping times were normal while only little data was transmitted in the uplink direction but immediately skyrocketed to several seconds whenever the uplink was somewhat more loaded with screen sharing and a VoIP calling. A bit of a let down.

But then I remembered that my phone I used for tethering was on LTE just a couple of minutes before and must have been redirected to 3G due to a low signal level. So I decided to lock the phone to LTE-only with an app I discovered recently. Who needs circuit switched mobile telephony anyway…!? Despite the signal level being really really low (a single signal bar was just barely shown every now and then), both uplink and downlink were much faster than what I could get over the 3G cell that was very strong in my location. Signal strength isn't everything.

Generally, I think the network operator bases thresholds for moving between network technologies are a good thing to rely on. In some cases such as this one, however, I'm glad I can make the choice myself.

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…