Category: Uncategorized

It is always said that Quality of Service (QoS) mechanisms are important for VoIP, but what does it mean in practice? Well, as long as that Skype connection just works it doesn't really mean a whole lot. It suddenly means a lot though, when the call breaks up and the other end is barely understandable due to congestion that provokes rapid round trip time changes between 300 ms and 1600 ms in the course of just a few seconds.

This happened to me recently and at the time I wished I had some QoS preferring my VoIP packets over whatever else the other 99 participants of the meeting were transferring over that Wi-Fi link connected to a way too slow backhaul link at the time. It suddenly makes you aware of the benefits of network enforced QoS. And it must be the network because otherwise half the participants would immediately tweak their PCs to demand a better QoS for their packets irrespective of the application. Well, that's at least what I would do…

So in the end I resorted to making a call over GSM. Just another way of getting QoS, really, just not on an IP bearer.

Yes, I very much like my wireless mouse but I have just discovered the use for a cable bound mouse these days again: On an airplane! For long haul flights, if you have enough space to use a mouse it comes in very handy as wireless mice are not allowed to be used.

I wonder if that "suddenly" changes again once airlines introduce Internet access on some of their flights again (e.g. Lufthansa via satellite or American carriers via land based systems) but for now, the cabled mouse comes in quite handy.

With the rising use of the mobile Internet, the amount of signaling required to set-up and maintain radio bearers is changing. While in pre-mobile Internet times, radio and core networks were mainly dealing with location updates and signaling due to SMS and voice calls, always-on smartphones are used quite differently.  Lets do a little comparison:

Someone who's only two applications that require network interaction are SMS messages and voice calls might have the following signaling pattern:

• 4 radio bearer setups a day for incoming SMS messages
• 4 radio bearer setups a day for outgoing SMS messages
• 2 outgoing voice calls (some with handovers, which increase signaling load)
• 2 incoming voice calls (some with handovers, which increase signaling load)
• 5 location updates a day (periodic and some triggered because the user as he moves)
• no routing area updates since the mobile is only attached to the circuit switched side of the network
• These numbers are obviously for someone who doesn't move a lot and who is, by today's definition, someone with a low usage. The young generation often sends and receives my more SMS messages a day.

Personally, my CS messaging load is a bit different. I send and receive fewer SMS messages as I mostly use e-mail for text messaging as my friends are distributed throughout the world and these exchanges are usually also not required to be had in real time. But I usually make and receive more than two calls. I try to minimize calls when moving as I find it impolite to talk on the phone while on a public transport and also prefer some privacy when calling.  But for the calls I do make while on public transport I am glad handovers exist.

But now lets go to the packet switched side and see how things are here:

• I am always-on and receive about 4 e-mails per hour. In other words, there are 4 signaling evens per hour or about 4 * 15 hours (per day) = 60 events per day for this application alone. That easily surpasses all my CS signaling
• While on public transportation I often use the time to read my favorite blogs and browse my favorite news web sites. Let's say I browse on 30 pages a day and read each long enough for the radio link to go back to idle. In other words, 30 signaling events.
• While I am moving the radio link has to be maintained and handed over to neighboring cells which creates quite a significant amount of signaling, especially with my 'old' N95 that doesn't have fast dormancy and hence the network needs to work more to maintain the established but not really required radio bearer after background push/pull requests.
• Also during quick breaks I try to catch a news bite or two to know what's going on in the world. Lets say that's an extra 10 signaling events per day.
• No instant messaging or other push applications are running in the background but more and more people are doing that these days, too.

In total that's easily 100 signaling events on the PS side per day. Compared to the 15 signaling events on the CS side for voice and SMS, that's quite a difference, not only for the network but also for the mobile, i.e. the impact on the battery charging interval is significant.

Today I've got something positive to say about network coverage in France: While the country has been slower than most other European countries to deploy 3G in areas other than big cities, it seems coverage has much improved in recent years. Over the weekend I was in a remote village near Nantes and experienced great 3G coverage. Quite unexpected! And then on Sunday, a 6 minute call out of a high speed train darting through the countryside at 300 km/h on GSM without a call drop. Very good! Now some more prepaid love for Internet access and I'm a happy customer!

Inspired by this post over at the 3G4G wireless blog on VoLGA and VoLTE architecture differences, I reflected a bit on why it has become a bit silent around LTE voice recently. From a VoLGA point of view, maybe it is because there is little more it can prove until the time real LTE mobile devices (not USB sticks) come to the market.

Back in February 2010, VoLGA was demonstrated at the Mobile World Congress in Barcelona as fully functional, using live network equipment. It's here and it's working but until real devices become available, there is nothing more to be shown that could go beyond it. And with closely related UMA (Unlicensed Mobile Access) stacks used in practice today on Nokia, RIM and Samsung devices for Voice over Wi-Fi, I have little doubt that this final piece can be implemented very quickly. Same thing for VoLTE and CS Fallback, they are there on paper and are waiting for devices they can be implemented on.

But once the solutions can be demonstrated in practice, I expect that the competition between them will accelerate again. It's going to be interesting to see if the simplicity, full functionality from day one, fast call setup times and a relatively simple but hyper-important in-call handover from LTE to GSM / UMTS of VoLGA will trump over other solutions.

Unlicensed Mobile Access, or UMA for short, is basically GSM and GPRS over Wi-Fi. Used by a number of network operators and supported by some phones from Nokia, RIM and others, it's an interesting technology and the basis for VoLGA, a voice over IP solution for LTE that I am quite passionate about. Recently, I stumbled over this website which explains how to configure Wi-Fi Access Points that run the open DD-WRT operating system for the use with UMA phones. Some tips and tricks are given but basically the message is that the Wi-Fi Quality of Service Extensions (WMM) have to be turned on. That also answers one of the questions I had as to whether UMA in practice only runs with access points offered by network operators.  So if you are into the details the link might provide some interesting information for you, too.

Ajit Jaokar over at the Open Gardens blog has started a blog ring to promote a request from the European Internet Foundation (EIF) to answer an online survey of 20 questions to select those to forward to Neelie Kroes, EU commissioner for the digital agenda. So what's it about?:

On May 19th the European Commission adopted its “Digital Agenda” for Europe, proposing some 100 actions – including 31 legislative actions – read here. The European Parliament has also adopted a Report on the Digital Agenda, which you can find here. The EIF wants you to help them choose the questions they ask Vice-President Kroes on the occasion of the 10th Anniversary of EIF in the European Parliament on the evening of July 13th.  The top questions emerging from this survey will be the ones we ask the Commissioner. Video replies will be available on the EIF website, shortly after the event. 

So if you are interested in taking part, have a look here for the questions.

Now I do get around quite a bit and I am always fascinated at the differences that exist of how prepaid wireless Internet access is offered in different countries. Now here are the two most extreme examples I have encountered so far (except for countries in which no prepaid wireless Internet access is offered):

Austria:

Here, you go to a supermarket, buy a prepaid SIM for mobile Internet for 9.98 euros that already includes 512 MB of Internet traffic that is valid for 12 months. No ID, no activation, it works out of the box in 0 seconds. In case you don't have a 3G USB modem yet, you get it together with the SIM + 3GB of data valid for 12 months for less than 50 euros. Details here. Ah yes, and you can choose between many offers and network operators.

Apart from being dead simple for a user, there is also 0 waiting time for the customer and 0 cost as no special stores and no interaction with special sales personnel is required. Remember, you just buy the SIM in the supermarket like a candy bar.

US:

Here, there seems to be only one network operator offering prepaid Internet access for notebooks on GSM/UMTS. You can buy a prepaid SIM but I am not sure if/how one can buy a 3G modem on the spot that works on 850/1900 MHz 3G without a contract. Fortunately I have one anyway 🙂 You get the same amount of data for $50 but only valid for a month. And the wild thing: You need to register the IMEI of the device before the offer is activated. Now that's a first! Not quite as customer friendly as the example above.

I was quite surprised when I heard that the upcoming Nokia N8 would support 5 UMTS bands in a single device. I was skeptical at first but both Wikipedia and Nokia confirm it here and here. In other words, it seems there won't be several hardware versions of the N8 for different parts of the world as was the case for many other devices before. Instead, a single device can be sold and used everywhere. Let's have a look at the bands:

• Band I (UMTS 2100, Europe's main 3G band)
• Band II (UMTS 1900, US band)
• Band IV (UMTS 1700/2100, US band)
• Band V (UMTS 850, US band)
• Band VIII (UMTS 900, Europe and used e.g. in France and Finland in rural areas)

Great stuff which will hopefully find many followers to enable truly global roaming!

A quick one today: Here's a link to a post I stumbled over recently that describes the new features currently discussed for LTE-Advanced in 3GPP Release 10. I haven't yet ventured out too far into the LTE-Advanced land, being quite busy with LTE Release 8 so the article helped me a lot to quickly learn a couple of important things about the different Coordinated Multipoint (COMP) modes and other things in LTE-Advanced. Enjoy!