Author: Martin

UMTS 900 Would Be Great For The Highlands

A random thought today: UMTS 900, the 3G variant running in the 900 MHz band so far mostly used for GSM is already used in a couple of countries like Finland and France to get 3G coverage to rural areas. Mobile devices for this frequency like from Nokia are also on the market already. The big difficulty with UMTS 900 is to find enough space in the narrow 900 MHz band for the 5 MHz carriers. However, I guess that is mostly an issue in cities and not so much for sparsely populated areas, like for example the Scottish highlands, where only a few GSM carriers are in active use and base stations are spaced 7 km apart or even more.

I know, the UK has so far not allowed the use of 3G in the 900 MHz band due to open market questions, but from a user's point of view I think it would be a great thing. In the mid and long term, however, I think the 900 MHz band will be opened up for other technologies, as even in cities, 3G and also LTE have/will have the big disadvantage compared to GSM of a much inferior in-house coverage. Going from a voice centric to an IP centric wireless network architecture, it seems like a natural evolution of things.

LTE as an HSPA Capacity Extension

Thought of the day: I keep hearing that LTE is great because you can go beyond the capacity of HSPA(+). Well, from an air interface perspective (Bits/s/Hz), that's going to be tough to achieve as HSPA(+) is going in the same direction capacity wise given the same amount of spectrum as LTE.

BUT, and that's how I haven't thought about it yet, LTE can be used in the new 2.6 GHz band, something for which HSPA is not specified and current base stations and many antennas are also not designed for. So once you get to the limit of your HSPA capacitiy, i.e. once you have used all the assigned spectrum in the 2.1 GHz band, you can use LTE to increase capacity with an overlay 2.6 GHz deployment. Where a lot of capacity is needed, range, which is going to decrease with the higher frequency, is also not a big issue.

Maybe you are lucky as an operator at this point and your 2G/3G equipment at this location is end of life and needs to be replaced at the time you run out of capacity anyway. It might then be possible to replace the old base station with a multi-technology, multi-band base station. If you are even luckier you manage to get a backhaul fiber to the site as we are talking triple digit MBit/s that have to be transported.

And at the same time you give your customers an incentive to upgrade to LTE: Higher speeds for them as they don't have to share the network with the masses anymore. At least for a while.

No EDGE in the UK

One thing that surprises me a bit about the UK wireless market is that despite being one of the most competitive in Europe, non of the mobile network operators have Vodafone does not have deployed EDGE in their its GSM/GPRS network. Some might argue that there is no necessity for it as 3G is the playground for mobile broadband these days. Not so fast I say though.

Take bigger cities for example like London. Millions of people must be out and about with their Blackberries, most of them still on GPRS/EDGE and not on 3G. They would surely benefit from an EDGE upgrade. Also, it would significantly increase capacity of the GPRS network as data is transferred more efficiently over the air. But capacity wise it doesn't seem necessary, as I haven't heard complains about slow Blackberry e-mail delivery in London yet.

Personally, I also often lock down my N95 to GSM only as web browsing with Opera Mini is very bandwidth efficient, it increases battery lifetime significantly and minimizes times the mobile looses coverage, e.g. when entering buildings and while I'm traveling by train. I also noticed no slowdowns in GPRS in London, which means that the current Vodafone GSM network capacity seems to cope well with 2G data traffic.

The Scottish highlands are the other extreme. Except in a few cities, there's no 3G coverage, and GSM base stations are spaced wide apart. That makes it a difficult terrain for broadband Internet. Again, Opera Mini performed very well on the GPRS only network but I had really wished for some EDGE so web browsing would have been possible as well.

But for the moment, it seems its not to be had. I wonder if integrated GSM/UTMS/LTE base station with a common backhaul link might change this in the future?

Internet Access on the Flying Scotsman

Despite its name, the Flying Scotsman is not a plane but actually a train with lots of history, running daily between London and Edinburgh. From a wireless perspective, a recent trip with it was interesting because free Internet access is offered to all passengers during the ride. A bit of background research revealed that the service has been realized together with Swedish company Icomera and some very high level information about it can be found here.

It looks like for most of the trip, a satellite based connection is used to backhaul the data. However, compared to the Internet access on Thalys trains between France, Belgium, The Netherlands and Germany, the connection is very slow and I could not get more than a couple of kbit/s over the link at any time. Round trip times varied greatly between a couple of hundred milliseconds to several seconds. Yes, several seconds (!), no idea where those packets went in the meantime…

It seems the connection is pretty much congested all the time, which might be because it is free for all passengers, due to a limited link capacity or a combination of both. So when web browsing, it usually takes quite some time for pages to come up. After a while I adopted a "better than nothing" approch but I wonder if some people would rather be willing to pay extra for the privilege to be "fully" connected and to shorten the wait!?

It would be interesting to know what kind of satellite system they use as I didn't see any dome like structures on top of the train such as those on the Thalys. Also, I wonder if they have similar uplink / downlink capacity on the link. No way of telling from the outside.

To summarize I'd say I got the work done I wanted to do during the trip, which was mainly e-mail, IM and a little bit of research on the web. I'd be quite unhappy to be stuck with such a slow connection for more than a couple of hours but for the train ride it was all right. That doesn't mean, though, that National Express East Coast should sit on their hands and do nothing, the service could be much improved as the Thalys example shows.

Mobile Application Stores Conference At CTIA With A Great Lineup of Speakers

Ajit Jaokar, friend and co-presenter of our LTE course at the University of Oxford has a couple of interesting events coming up over the next couple of months. Needless to say that I am more than happy to help spreading the word:

At the upcoming CTIA, Ajit's company Futuretext is producer of the Mobile Application Stores, Strategy and Deployment conference and is proud to announce an all-star speaker lineup for this unique event. Mobile Application Stores is a partner seminar of International CTIA WIRELESS I.T. and Entertainment October 8th in San Diego.

Mobile Application Stores is the only conference to focus exclusively on the business of mobile applications and will focus on the tremendous opportunities in the mobile apps stores ecosystem. The event is designed to give a complete understanding of how to capitalize on this dynamic market.

Featured speakers for the event include:

  • Dr. Jin-Sung Choi Ph.D, Senior Vice President, Head MC Global
  • Product Planning Team, LG Electronics Korea
  • George Linardos Vice President, Product Management, Media, Nokia
  • Ilja Laurs Founder & CEO, GetJar.
  • Tim Haysom, Chief Marketing Officer,OMTP
  • Mike Merril, CEO-Smart Phone Technologies
  • Ajit Jaokar, President-futuretext
  • Chetan Sharma, CEO, Chetan Sharma Consulting
  • Jouko Ahvenainen, Founder, Grow VC International
  • William Volk, CEO, PlayScreen
  • Sena Gbeckor-Kove, Chief Technology Officer, imKon

The timing is perfect for an event like this. The Apple Appstore announced its billionth download in less that 9 months after opening and the recent launch of LG’’s Applications Store and Windows Marketplace for Mobile as well as Android and the Blackberry App World are making tremendous impact in the mobile marketplace.

Mobile Application Stores is co-located with the largest wireless event in the U.S., International CTIA Wireless I.T. and Entertainment. Registration is only $295 at http://www.mobileappevent.com/

About Mobile Application Stores: The Mobile Application Stores event is produced by futuretext, a London based research, consulting and publishing company. For additional information, please contact Larry Lockhart at NextVision Media at 727-388-9849 or Larry@nextvisionmedia.com or Ajit Jaokar Ajit.jaokar at futuretext.com. The web site again for registration is: http://www.mobileappevent.com/

Still no Cellular in the London Tube

I really like London and do come here often, but as soon as I go down an escalator to take the tube, my cellular signal fades away and I feel like my hands are bound until I surface again at the other end of the trip.

That feeling is of course heightened by having good underground coverage in most other cities I usually travel to and I keep wondering why on earth London, capital of a nation that has fierce competition amongst network operators and good network coverage hasn't come around on this issue yet!?

Even in mobile markets that aren't known for their competitive environment such as France, the metro is fully covered, even between the underground stations. Worries about terrorists using the network for their purposes are in my opinion also no good reason for not going forward. Previous attacks unfortunately worked despite no cellular network being present to trigger anything.

Also, arguments that it's difficult to find space for cables also don't count as Transport of London has just finished deploying their underground Tetra network. Signaling equipment being sensitive to GSM or UMTS? Unlikely if TETRA (probably on 450 MHz) doesn't confuse the equipment…

And finally to those who argue that people using the phone create disturb others, take a Eurostar to Paris and convince yourself of the opposite. Most people in the metro use their phones for texting, emailing and web browsing as it's just too noisy for lengthy phone calls. So no worries here either.

So please, everyone involved, give yourself a push to finally do it and join the rest of the developed world!

Mobile Ticketing – Paper or Plastic – Some Thoughts

Thalys rail is pretty innovative when it comes to onboard Internet in their trains and ticketing. In addition to the standard tickets than can be bought at the railway station or via the Internet and then sent to you, they also offer print-out tickets via the web, they offer using the Paris metro card (Navigo) as a ticket and they also have a completely ticket-less offer in combination with a mobile phone for trip details and last minute updates. Lots of options to choose from.

It might be surprising but so far I haven't touched the ticket-less option yet, I still much prefer something to print out and to take it with me. It's mainly habitual I guess, but there are quite a number of other reasons for that as well:

  • I don't have to register.
  • I usually order my tickets a long time in advance, like for example 6 weeks. A lot can happen in 6 weeks.
  • I usually don't travel alone so buying one ticket for the mobile phone and one on paper makes things difficult.
  • I like having a piece of paper I can use to look up times, train numbers, etc. again.
  • Should I loose the ticket, I can just print it out again. That's much simpler than figuring out what to do should I loose my metro card or, heaven forbid, my mobile phone.

But I guess one of these days I will register and give it a try because there is one important advantage of going ticket-less with Thayls: Their print-out tickets can't be exchanged or returned so the sale is final.  In other words, not all tickets can be printed out. I am not quite sure, but it seems the ticket-less tickets can be modified just like the plain old ones. Well, we shall see.

One way or another, mobile and virtual tickets haven't quite arrived here yet.

Wi-Fi Tracing With Ubuntu and an Acer Aspire

If you are running Linux on a PC, notebook or netbook with a Wi-Fi card it's "relatively" easy to use the system together with Wireshark for WLAN tracing. Since Wireshark version 0.99.5, even WPA decryption is supported so Wireshark also decodes the packets from other devices in your network.

Relative is a relative term though as it seems that depending on the Wi-Fi hardware and the drivers used, there are different ways to set the network card and protocol stack into monitoring mode. This is necessary to send the full 802.11 Wi-Fi frames to Wireshark. On the Asus eeePC 701 running Xandros Linux it works as described in this post.

On my new Acer Aspire One D250 with an Atheros AR242x 802.11abg wireless chip running Ubuntu 9.04, things work a bit differently and it took some experimenting to figure things out:

The first step to install "iw" via the Synaptic package manager. Once installed, setting the Wi-Fi card into monitoring mode is quite straight forward with a couple of commands via a shell:

sudo ifconfig wlan0 down
sudo iw dev wlan0 interface add mon0 type monitor
sudo ifconfig mon0 up

At this point the Wi-Fi card stops working as a normal network interface and Wireshark gets a new network adapter "mon0" that can be used for tracing in promiscuous mode. Unlike with the original eeePC that required the Wi-Fi card to be configured for an unencrypted network before switching to monitor mode to prevent decryption of some packets before they reach Wireshark, this is not necessary on the Acer.

Wireshark-wpa-acer The picture on the left shows how Wireshark needs to be configured via the preferences menu for decoding encrypted packets. Different network cards might need different settings here. Changing the configuration and clicking on "apply" makes Wireshark go through all packets already traced and apply the changes. This way it's not necessary to generate a new trace which testing different settings.  For the WPA decoding to work, it's necessary to know the encryption key to capture the key exchange of the device to monitor. In other words, the Wireshark trace has to be started and only then should the device to be monitored enter the network.

Once done with tracing the network adapter can be set back to normal operation with the following commands:

sudo ifconfig mon0 down
sudo ifconfig wlan0 up

Happy tracing!

Vodafone Websessions Keep Timing-Out

Gateway Timout 2 Sometimes you have to look at the good sides of things going wrong. Every now and then, I use Vodafone's Websession offer in Germany as it is a convenient way to go online occasionally. If it works… Over the summer, unfortunately, I have observed continuous glitches. Everyone has glitches now and then and I wouldn't haven mentioned it at all if it was only a singular occurrence. But this one keeps dragging on.

So here's what's going on: In most failure cases, automatic initial redirect to the payment web portal works, the money is deducted from the account, but anything else either results in nothing or a technical error message on the portal. In most cases, disconnecting and re-connecting a couple of times from the network helps the service to come back to its senses. Not so, however, when I recently needed it. While I was charged and the service kept insisting that it would forward me to the requested page after connecting to the network, it never did no matter how often I tried to re-connect.

So what's the good side of this you might wonder!? Well, the good side is that Wireshark revealed a bit of how the service works and I learnt a couple of things:

First, the services uses a transparent web proxy that redirects all http requests to the landing page with a “moved temporarily” answer to a HTTP GET request for any page until the session is paid for or directly after re-establishing a network connection to display the remaining time of the session.

Second, the web proxy also responds to a request to a web page if there is a problem with the service. In the most recent one, it answered web page requests after a while with a “504 Gateway Timout”. The picture on the left shows how this looks in practice. The server information element of the message is set to “WebProxy/5.0”. From that I assume that each and every requested web page flows through the transparent proxy. This, by the way, is also supported by the network based picture compression that can be deactivated via the Vodafone dashboard software or by including a special http header parameter in every request.

O.k., I've learnt enough this way now, so please Vodafone, fix this service!

Snapshot from Paris Metro Cabling for GSM Coverage

Metro cabelage Here's a rare snapshot (for those of you interested in network details…) of a splitter/combiner for GSM coverage inside the Paris metro. An interesting detail: The component covers all frequency bands between 870 and 2170 MHz, i.e. both GSM bands are supported as well as UMTS. So while I don't know if UMTS capable antennas have been installed underground, at least the cabling and passive components seem to support 3G once they want to upgrade the underground system. So, how about it?