Category: Uncategorized

An interesting reverse strategy happening at the moment on my smartphone:

Instead of having Wi-Fi activated on my smartphone by default to benefit from cheap internet access at home and access to local resources I am rather opting now to have it switched-off by default unless I really need it, e.g. to download podcasts, videos etc.

Why? Because my current smartphone's Wi-Fi reception is quite restricted and I've experienced a couple of times that while it could still see the Wi-Fi access point it had difficulties to transfer data due to the reception level. Instead of switching to the cellular network, however, it got stuck. Not good, this is not yet implemented well. Also, I usually don't use any local resources such as a NAS server with my smartphone and I also don't use it as a remote control for any gadgets residing in the home network. I travel too much so my home network is rather basic compared to others.

When comparing the reception quality of smartphone with larger devices such as notebooks it seems that it is in general much weaker. While my notebook sized devices still receive the Wi-Fi network very well in remote corners in my apartment, mobile devices already have difficulties. So unless that changes and I have an all-you-can-eat 3G data package anyway and don't hit the throttling limit, my smartphone Wi-Fi will stay off at home.

What about you, do you use Wi-Fi at home and what are your experiences concerning reception and range?

Nokia's recently produced a couple of Dual-SIM phones which I haven't seen around much in Europe. When visiting the Philippines, however, I could observe them being marketed by the local Nokia stores alongside pretty much anything else in the Nokia portfolio, including the Nokia N9 and, as a major absentee, the Nokia Lumia.

While observing the people in a park in Makati, Manila's business district, I noticed that quite a number of people had at least two phones with them, some of them even three. When asking why, I was told that most people use on-net "all you can eat" packages while voice calls and SMS messages are rather expensive. So it seems to be cheaper to get a couple of prepaid SIMs from different networks and extra phones rather than to pay for inter-operator charges. So for people with a quite restrictive budget, a Nokia Dual-SIM phone probably makes a lot of sense.

People in the Makati district, however, probably have a significantly higher income than the average consumer in the country and I could observe that one of the two phones was usually a smartphone while the other was a what many people a low end phone. The smartphone was usually either an iPhone or a high end Samsung or HTC Android based device. I failed to see anyone using a Nokia smartphone.

… asks David Talbot in a recent article on the Technology Review website. An interesting question and I'd really like to see a solution that shows who receives what kind of information from apps or the operating system itself that is originally shipped with the device.

But not through a cloud of fine print as is often the case today but detailed and to the point please. With a number of discoveries over the past few months of location information and private data being harvested and sent off mobile devices lately without users being aware of the fact, I think it is really time for this. Also I think it would be a good idea to put some law behind this to ensure that there are consequences if the devices does more than actually described in such a list.

Obviously such a feature would have a difficult time to track what kind of data third party applications send out but I think the point of such a feature would be to ensure that the user knows what he gets at the time he buys the device. Anything installed from a third party later on is his own responsibility. And Android, for example, makes it quite clear what kind of capabilities an app requests during installation and it doesn't take much imagination what an app can do when it requests Internet connectivity and access to calendar and address book.

3GPP standardization is well ahead of real life deployments and it has to be, as developing and testing the ever more complicated features takes time. Currently, Release 8 of the specifications has made it into the real world, with HSPA+ Dual Carrier deployments and first LTE networks now in commercial use. So from a radio access, speed and capacity point of view, what's in store between this and what will Release 11, that is currently under development, put on top of it?

A detailed resource listing the new features of each Release can be found here. If you have a look you'll immediately see that my list below is but a tiny fraction of what has been done in each release. My focus for this post, however, is very narrow and only looks at how the capacity of the macro base stations is enhanced as we go forward.

In Release 9, HSDPA gets enhanced by adding MIMO to Release 8's combination of Dual Carrier + 64-QAM, pushing theoretical peek data rates from 42.2 MBit/s to 84.4 MBit/s. To make things more flexible, the two 5 MHz carriers can now be in different frequency bands. In the uplink direction, dual carrier operation is introduced (while having been present in the downlink since Release 8), thus pushing theoretical uplink data rates beyond 20 MBit/s.

With Release 10, 3 and 4-carrier HSDPA is specified in up to two different frequency bands. Like the already existing dual-carrier feature, aggregating carriers has little impact on overall capacity of the network but offers higher peak data rates to individual users. On the LTE side, carrier aggregation beyond the initial 20 MHz is introduced and the number of antennas for MIMO in the downlink direction is increased from 4 to 8. Again, this is well beyond what is used in life networks today with up to two independent streams in the case of LTE. In the uplink direction, up to 4 antennas are now specified to increase data rates under ideal conditions.

From a raw maximum throughput point of view it seems that a limit has been reached. It is unlikely anything more than 64-QAM modulation makes sense and 8 MIMO data streams will keep engineers busy for a long time to figure out how to put such a high number of antennas on roof tops and crammed into small devices.

But ultra high data rates are not everything when it comes to overall maco network capacity. A major issue is interference between cells, especially for users that are at a location where they get a strong signal from more than one cell. Here, higher order modulation and MIMO is not much help.

Therefore, one of the major topics in 3GPP Release 11 in this respect is Coordinated Multi-Point (CoMP) transmission. Nomor's current LTE newsletter shows this quite clearly by giving an overview of currently active work items in the different RAN working groups.

Here's an abbreviated list of the objectives of CoMP from the current version of the work item description (RP-111117):

• Specify the support of intra- and inter-cell CoMP
• Joint transmission
• Coordinated scheduling/beamforming

And, in case that has sparked your interest, further details can be found in the study item 3GPP TR 36.819 that preceded the current work item.

Coming back to the title of the post "the air is getting thin", it's interesting to observe that after years of specifying how to get ever faster data rates, significant work is now done around improving data rates in places far away from a good signal. Not only will this help individual users to get a higher data rate in such places, but network capacity in general is increased by spending less time transmitting and repeating lost data slowly with a very low modulation and coding scheme. It will take a few years before we see this in practice but I think chances are high that the result of this work item will see the light of day.

I've been to a hotel recently that was just newly built and which had the latest window technology for heat insulation. That's all nice and well but for mobile networks on the outside, such windows are almost impenetrable.

The path loss through these windows were 30 db, so even a base station pointing directly at the hotel having a great 3G signal outside the hotel (-60 dbm) dropped to still acceptable (-90 dbm) just inside the hotel to a complete "nothing" just a few meters inside. Without dedicated in-house coverage via leaky cables, femtos, repeaters, etc., hotel guests are having a hard time if they want to use the networks outside.

Interestingly enough, standing close to a window helps but standing to a wall is actually much much better, the path loss in my case was only 10 db instead of 30. Quite a counter intuitive thing to do.

Having your Skype client open on your PC also means that your network can be used for relaying other Skype calls if the system detects incoming TCP/UDP connections can go through your NAT firewall (e.g. due to UPnP opening a few ports). It seems this doesn't happen very often as I haven't observed a relay session over my PC until recently, when I suddenly had a 200 kbit/s data stream in both direction running over my PC for several minutes.

Wireshark is always close at hand so I could quickly confirm that the data stream was indeed to and from the Skype client. A Reverse DNS lookup then revealed that the call was between two other PCs in Germany in networks of different providers. That probably means that the DSL routers in those networks do not have UPnP enabled, otherwise the IP packets could have been exchanged directly between the two parties. Also interesting to note was that the relaying went over my Wi-Fi. So unknowingly to those on the call their data packets went over a wireless link at least twice, probably even four times if you assume that both parties used Wi-Fi at their end as well.

ARCEP, the French regulator has reportedly given the go ahead to Iliad, also known as "Free" to officially launch their 3G network as they have fulfilled the initial minimum coverage condition as they now cover 27% of the French population with their own network. A national roaming agreement with France Telecom / Orange will do the rest for now. The Free network launch is the first in many years in Europe and it's actually the exception from the current norm of networks being combined in other countries to reduce competition. It's going to be interesting to see how well Free will be doing and what kind of effect it will have on competition and pricing in France. I wish them all the best, perhaps I can become a customer soon if they offer interesting prepaid packages!

The European Union is going through a difficult phase right now with lots of challenges but also lots of opportunities to further strengthen the integration of the European states. Obviously there are also the critics, mainly nationalists who are looking for salvation in isolation, doubting the benefits of a common market and a common future. But the madness of everyone going their own path can be shown in many areas and railways is a particular good example. What does this have to do with telecoms? Bear with me for a minute and find out.

Up until 10-15 years ago, every country in Europe used their own system for electric train power and signaling. The only thing that railways seemed to have in common was the same track width and even this changes when you go towards Eastern Europe. In other words, trains crossing country borders have to have several power adaptations, several different radios the driver has to know and understand several different signaling systems and the list goes on. An interesting example are the Thalys high speed trains that operate between France, Belgium, the Netherlands and Germany. Four countries and four different communication and signaling systems, and all within a journey time of 3 hours. Just crazy but a result of national planning and implementation without neighbors in mind.

To some this might seem but a small inconvenience but image the same would apply when you cross the border with your car. And it actually did until the early 1990’s. Before, each country had its own mobile communication system and mobile phones became pretty much useless when crossing the border. In some instances it was even forbidden to take the mobile device with you to prevent you from using it in the other country because radio waves could not be made to stop at the border. Crazy nowadays but perceived as normal only 20 years ago. And then GSM came along, one of the first children of European collaboration in the then young European Community. And evidently it has changed every country in Europe and pretty much the rest of the world afterwards. But when looking at how radio communication worked in Europe before the days of GSM, it has had the most profound influence here from a cooperation point of view. If nationalists had gotten their way back then I wonder how mobile communications would look today.

Now back to railway communication. Also here, GSM was accepted as the basis for voice and data communication and new pan-European railway tracks that are partly funded by the EU have to have a common signaling and communication system based on GSM, or it’s enhanced flavor GSM-R (GSM Railways). The data and signaling part of it is called ERTMS (European Rail Traffic Management System) and is used to replace national signaling systems. Thalys is one of the beneficiaries, using ERTMS as train control system on its journey through the different countries. The picture above recently taken in Cologne shows the ERTMS logo on a Thalys train.

Some where hesitant to join the club back then and some are hesitant to join it now. But if you are into telecoms history, here’s an account of someone late to the party, who has joined nevertheless and still made a profound positive impact despite of it. Enjoy and think about the story there and this blog entry here next time someone sees the end of the EU in sight.

The topic of providing Internet access at meetings keeps me interested and I have continued experimenting with different setups. One somewhat more sophisticated setup I've been working on lately is to physically separate the Wi-Fi and traffic shaping module for the meeting participants from the device that provides Internet connectivity (e.g. a 3G/LTE Router).

The best setup is of course to connect them via an Ethernet cable. In some situation this might not be possible, however, for example, when the 3G/LTE router has to sit outside the meeting room as there is no or insufficient coverage in the room. For such a scenario, a Wi-Fi link can provide the solution. But this is a bit more difficult than I thought at first. In my first setup I could only get a few megabits per second through the link.

Eventually, I figured out that the Wi-Fi access point that communicates with the participants and the Wi-Fi access point communicating with the 3G/LTE router interfere with each other, despite being on completely different Wi-Fi channels (one on channel 1, the other on channel 10). Separating the two devices by a meter and a half and the channel was suddenly much better and I could get around 15 MBit/s over the end to end channel (i.e. twice over Wi-Fi). After some more experimentation I figured out that I could even have the devices close together and get almost the full channel bandwidth (around 24 MBit/s), it's just a matter of how the antennas are placed.

Kind of reminds me of first HSDPA tests I did almost 5 years ago where slight changes in antenna orientation of the HSDPA card had stunning effects.

Here's two links today that give a very interesting overview of GSM, UMTS and LTE coverage in Germany today from two of the four network operators. I've chosen to link those two, because Vodafone and T-Mobile have built up significant LTE coverage over the past 18 months, especially in rural areas to bring high speed Internet coverage to small towns and villages. This was part of the license conditions for the 800 MHz digital dividend band and as can be seen on the maps it has born fruit.

On the T-Mobile map one can also see LTE coverage that will be switched on soon, most of it in big cities this time. The special thing about the Vodafone map is that UMTS and LTE coverage can be shown separately or together on the map and it's interesting to observe how LTE fills the gaps in UMTS coverage. 

I've been saving screenshots those coverage maps for years and it is quite interesting to see how 3G coverage expanded over the years. Initial 3G deployments looked quite different from the initial LTE deployments now as at that time, it was the big cities that were covered first rather than rural areas. This time around, license conditions have made the picture different and also, 3G in big cities with HSPA+, 64QAM and Dual Carrier extensions still has ample capacity to serve the needs there so there was no disadvantage to go for rural coverage first where often, only 2G was available.