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One of the things that is just as important as capacity on the UMTS or LTE air interface is the ability to shuffle the data back and forth between a base station and the rest of the network. This link is called the "backhaul" and for data rates beyond just a couple of megabits, fiber connections or microwave Ethernet links are required. Recently, Ericsson has released an interesting paper that describes the state of the art and the future of microwave backhaul.

So here are some technical details I found quite interesting: Like everywhere in telecoms, it seems there is an ETSI version (European Technical Standards Institute) of the equipment used globally and an ANSI version (American National Standards Institute) for the Americas. The current state of backhauling uses up to 56 MHz wide channels, and 256 QAM modulation and the maximum transmission power is given as around 2 watts. Traditional (virtual) E1 connections can be mixed with Ethernet connectivity and the Ethernet line rate on such a link is 345 MBit/s, equaling 80 traditional E1 lines. That is good enough for a combined GSM, UMTS and LTE base station today with three sectors, as 100 MBit/s per sector is unlikely to be achieved simultaneously in all three sectors. For more technical details see their data sheet.

The smallest channel offered by Ericsson's current product is a 3.5 MHz Channel and QPK modulation, resulting in a line rate of 2 E1s, equaling 4.1 MBit/s. The spec sheet that can be found here also reveals that dish antennas can be used with a diameter from 0.2m and single polarization up to dishes with 3.7m diameter and dual polarized antennas inside.

Used frequencies in ETSI land are anywhere between 6 and 38 GHz today, so far above the current frequency bands used between the base station and actual user devices, which transmit and receive anywhere between 700 MHz and 2600 MHz today. As high frequencies and high modulation are sensitive to rain a bandwidth adaptation feature ensures that during bad weather the line rate is reduced to ensure the link stays up.

I also had a quick look a competing microwave solution from Dragonwave to see where they are at the moment. They claim that their current microwave compact product is capable of speeds in the order of 800 MBit/s. That's about twice that of the Ericsson product and is likely because they use XPIC (cross polarization interference cancelation), which allows two data streams to be sent over the same channel simultaneously. Some but unfortunately not very detailed information can be found here.

So what does the future hold? Ericsson says that the 80 GHz band looks promising for microwave in the future, 112 MHz channels should be introduced shortly and 4×4 MIMO via two separate antennas and XPIC in each antenna will push microwave backhaul datarates beyond 1 Gbit/s.

 

I just don't get it!? I just had a look at a number of books on Amazon when I realized that each and every one of them was significantly more expensive in the Kindle version than in print!? Too successful already? I guess I will stick to printed books then, like them much more anyway. It leaves me clueless…

And another follow up on the history trail of the first GSM call in a commercial network 20 years ago to the post about the state of GSM back in 1991 to one of the first GSM phones, the Siemens P1. Obviously, the Siemens P1 big and heavy but even then it was clear that the next step in miniaturization were real "handheld" devices as shown in this video clip from the 1991 international radio exhibition (IFA) in Germany. One one of the first truly mobile phones was the Nokia 1011, announced at the end of 1992. And here's the TV commercial from back then. Enjoy!

Here is some very interesting information concerning the number of 3G base stations NTT DoCoMo in Japan. According to this report from UnwiredInsight, the company currently has 62.800 outdoor HSPA base stations and in addition 29.200 indoor installations.

These numbers are incredibly high, especially when compared for example to the number of base stations Vodafone says it has in Germany (and provides very good coverage with!). According to reports, Vodafone has around 20.000 GSM base stations in Germany and 13.000 HSPA base stations (I assume most are co-located with GSM). Now Germany and Japan are almost equal in size so the number of base stations should also in the same area. But they are clearly not. So I thought that perhaps what they meant was number of sectors. But no, even NTT DoCoMo themselves have released similar numbers and also says it's "base stations".

Well then, looks like they are not beaten anytime soon in this number game.

If you are a frequent reader to this blog you have probably noticed that I am running Ubuntu on my netbook for a couple of years now as it is fast and slick on such limited hardware and, of course, it's open source. But there are a few tasks for which I still prefer Windows software, for which I use Wine to use it in Ubuntu.

One of these is the Windows TightVNC Remote Desktop Client, which for my purposes is much better suited than Ubuntu's built in Vinagre VNC Client. Especially the "scaling" option that let's me scale down the remote desktop which tremendously helps if it is vastly bigger than the small netbook screen is sadly missing. Also, the built-in client does not show me the local mouse pointer which kills usability as it makes moving the remote mouse pointer precisely very arduous.

But o.k. I use Wine to run the Windows application in Ubuntu and it does the trick, even if the scaled down image of the desktop does not look as nice as if the program ran on a real Windows machine. However, it has its limits, too. When I recently tried to remotely administer another Ubuntu machine with it, I found it to be unstable with Vine as the VNC server on the other end. So I switched back to Vinagre just to be disappointed again by the missing local mouse pointer. Time to do search for an alternative. And the alternative I found is quite stunning. It's called Remmina and can be installed right via the Ubuntu package manager.

Not only does Remmina have a seamless scaling option that beautifully reduces the size of the remote desktop but it also has a full screen view in which the desktop moves when the mouse pointer hits the screen limit in case the remote desktop is still biger even after scaling down. Also, it handles both Windows 7 and Ubuntu client desktops without any hicups. Perfect! Furthermore, it has a reverse VNC functionality, i.e. the remote desktop can establish a connection to the client. I use this quite frequently when the remote desktop is behind a NAT in which the TCP port required for the incoming VNC session is not forwarded. In this case the user of the remote computer needs to establish a reverse connection. Very simple on Windows but unfortunately not built into the Ubuntu remote desktop server Vino. Again a simple fix: After installing X11Vnc from the package repository, a reverse VNC session can be established with a simple command: "x11vnc -connect YOURIPADDRESS". Easy to put in a shell script which is then linked to an icon on the desktop. This way, the remote user doesn't even have to type in anything.

And finally, another very important thing Remmina and X11Vnc do is to adapt to the connection being established over the Internet, i.e. much less bandwidth than in a local network. Compression is automatically activated with a good balance between good looks and speed.

Internet Access in the air is once again in the air, so to speak. A couple of months ago, Lufthansa has restarted their on board Internet access again after a pause of several years. On my way back from New York at the time of this writing, I had the fortune to be one one of the planes with a satellite dish on top. Great stuff and I am posting this from over the Atlantic ocean. Download speeds are in the range of 2.5 MBit/s, although the speed is quite variable. Uplink speed is 500 kbit/s and the round trip delay time is around 700 ms from the position you can see in the picture on the left. Time for some sleep now though, with Internet access or not. Good night.

For the second time in so many days I've seen someone sitting in a New York Starbucks and using his/her iPhone/iPad to make a video call. Videocalling has been with us for many years now and was popular to some extent in some countries, as reported here for example already in 2006. However, on a global scale it was never a big success. So twice in two days over an IP based technology now. Looks like there is potential after all, perhaps due to a different pricing proposition…

There is one thing, all current mobile Voice over IP approaches have in common, be they VoLTE, VoLGA or Over-the-Top VoIP applications such as Skype:

Traditional mobile voice services are an integral part of the baseband radio chip and in the case of Android, for example, the user interface that runs on the application processor as part of the operating system communicates with the baseband radio chip with AT commands to establish and tear down a voice call. In other words there's not much to do for the operating system itself except for issuing a couple of commands. All the rest is done in the baseband chip, including voice processing and handovers between different radio access technologies such as UMTS and GSM.

As soon as any VoIP technology is used, and that's what they have in common, all these things move up from the baseband processor to the application processor and the operating system. What stays in the baseband is the handover management between different cells of the same radio technology and, for some VoIP variants if implemented, the enforcement of quality of service.

This means that there is a fundamental shift in who delivers the software for making voice calls on mobile devices in the future. Today it's the baseband chip vendor. For VoIP, it's going to be a third party from a network operator's point of view. Google, Microsoft and others will push ahead with their own voice services that will run over IP, no matter what kind of transfer network is used. This way, those VoIP services are likely to be implemented tightly into the operating system. For mobile network operator VoIP it's likely to be external companies that will offer plug-ins for popular smartphone operating systems. Easily done with Android, as can be seen for example with GAN clients from Kineto today. But what about smartphones that are not bought via a newtork operator, will they have those "plug-ins' as well? And how about closed operating systems such as those from Apple and Microsoft?

This also means that there is a catch for over the top VoIP solutions that are completely transport network independent: They will topple over as soon as the device has to select a 2G network which can't transport the IP packets anymore. Also, it might take a while for handover procedures between LTE and UMTS to mature and be quick enough to keep the the interruption time in acceptable limits. The only thing that helps is to make LTE (or UMTS) as ubiquitous as GSM. Not impossible but I don't see it happening in the next couple of years.

Network operators supplied VoIP solutions have one big advantage, though: They can interact directly with the network over the network signaling layer. This is coordinated in the baseband chip and the network operator's VoIP server and thus, VoIP calls can be handed over to circuit switched channels once the only option to continue the call is a 2G network. However, that's far from being trivial as it requires a very tight integration of the VoIP service (i.e. the IMS) with the current circuit switched MSC architecture. For details see my post from back in 2008 on IMS Centralized Services.

Also not to be underestimated are the potentially higher power requirements of running everything in software and using a transport network that is optimized for high speed data. I wonder how that compares to processing a voice call in a dedicated hardware unit as it is done today and using a transport network (GSM) that is highly optimized, also from a power consumption point of view, for transporting voice frames. For some users, this is perhaps less of a problem as they are now substituting voice calls for other forms of communication such as instant messaging, Facebook, Twitter, etc. and hence have a reduced need for mobile voice. But the number of voice minutes per person per month doesn't seem to fall, so I wouldn't bet on this issue just going away like this.

All things mentioned are not insurmountable but it will take a lot of dedication and effort to tackle them.

I've already stumbled a couple of times over the term "HetNet", a 3GPP work item in LTE-Advanced and an abbreviation for "Heterogeneous Networks". However, it has so far always remained somewhat of a mystery work item to me and I wasn't really sure what people where after here. But after watching this 4 minute HetNet Intro video from Ericsson it's much clearer now.

In essence, one of the aims of HetNets as explained in the video is to make the best use of the spectrum in areas where macro and pico base stations will be deployed in parallel. When a mobile is close to a pico base station it should use it, obviously, and fall back to the macro network once it leaves the coverage area or once the macro network can serve it better in terms of downlink throughput. However, there is a grey zone in which the downlink is better served from the macro network while the uplink would be better served by the pico base station. This imbalance is caused by the higher transmit power of the base station compared to the mobile and the pico cell. In the uplink, on the other hand, distance matters more due to the limited output power of the mobile device. 

So one of the things required for efficient HetNets is a way to handle the uplink and downlink data transmissions of a mobile device to/from/with different base stations. Quite a tricky thing as close co-operation between the pico and macro layer is required.

And for more information on the topic, I can highly recommend this recent whitepaper from Ericsson on Heterogeneous Networks. Bring some time though to read it, this is not a 5 minute pitch.

A couple of months ago, Eutelsat launched a next generation satellite (KA-SAT) for Internet access in Europe and it seems it has ended up in the right orbit and it will be taken into service shortly. Especially one number is quite interesting: The satellite is said to have a capacity of 70 GBit/s, that's 70.000 MBit/s. If you divide this by the capacity of a big fat LTE base station would have, let's say 70 MBit/s to make the calculation easy, that corresponds to 1.000 base stations.

Obviously a little dish is required to communicate with the satellite so it is for stationary use only. But for rural Internet access at home that doesn't really matter beyond getting it set-up in the first place. 1.000 base stations shot into orbit, an interesting picture to visualize.