Prepaid 3G Internet Access In Switzerland

Switzerland is the latest country for which I have bought a local SIM card for prepaid 3G Internet access while traveling there. Getting the SIM was quick and I was online in less than 5 minutes.

Zurich airport seems to also be a big shopping mall these days and all mobile network operators have a store there. Swisscom has an offer for prepaid 3G Internet access, which, even if it was unintended, is especially interesting for travelers. With the introduction of the iPhone by Swisscom, they also launched a new prepaid tariff which caps Internet charges at 5 Swiss Francs a day. While that is quite a bit if you use it every day, it looks like an acceptable price for occasional use, at least to me. The SIM card is also available separately and can be used with any other device as well.

So after getting into the store, it took only about 5 minutes to get the prepaid SIM. The shop assistant was aware of the Internet tariff and actually what it could be used for. Congrats, I am not quite used to that. Many shop assistants have no clue and will even give out false information such as "it will only work with our phones"…

Their provisioning system is also quick, the SIM card was activated instantly and the tariff option also worked right away. That's how it should be and not like in other countries where activation of an option takes half a day. Kudos to Swisscom, I had a very good customer experience.

Here's a link to the prepaid 3G Internet access Wiki with more details of how to configure your 3G device for the SIM card. Enjoy!

The 2.1 GHz situation in Vienna

Back in April I ran some tests in London to see how many 3G frequencies were used by the carriers there to get a feeling of how much capacity is offered today. To my great surprise, only one of the network operators had deployed more than one 5 MHz carrier frequency. Recently, I was in Vienna and since the country has many affordable 3G Internet offers that lots of people already use, I was wondering if the situation was different.

It turned out that the situation was pretty similar. Except for T-Mobile, who had two 3G carriers deployed in the center of Vienna, all other operators only used one carrier frequency. Network throughput during the day and in the evening in the A1 network were always good (above 1.5 MBit/s) so the current low capacity build-out from an available carrier perspective can handle the traffic well. To me, that sounds like good news!

Nokia N97 Review Part 5: Nokia Maps and the FM Transmitter

I've used Nokia Maps in the past a lot for car navigation with my N95 so obviously it is a must work application on the N97 as well. So when I recently drove from southern Germany to Vienna I used the N97 to guide me. While a beta of Nokia maps 3 is already available for some time now, I preferred using the installed Nokia maps 2 to test the stability of the N97. No issues, the GPS works well, a first fix only takes a couple of seconds due to A-GPS support and the route planning and execution works flawlessly. Great!

I like listening to podcasts while I'm driving and in the past this has always been an issue as the built in speakers of my N95 aren't loud enough to overcome the background noise while driving. The N97 has an FM transmitter to send the audio signal to a radio which could be a great solution to the problem.

In practice it's a bit difficult to use as the transmission power seems to be very low. To make the radio detect it I had to hold it very close to the radio. Once detected, the N97 can be removed a bit and the audio signal is still o.k. for an audio (voice) podcast. For music however, there's a bit too much static. I changed the length of the external car antenna a bit which improved the sound quality a bit but still, there is some static in the background. While driving I lost the signal after an hour or so, probably because a radio station came into range which used a nearby frequency. While driving, it's impossible to re-tune the FM transmitter and radio due to the proximity required for the radio to find the N97. This makes the whole thing a bit impractical.

So if possible from a technical and regulatory point of view, the FM transmitter should have a higher power output, the current level is just too low.

How the LTE Core Network talks to UMTS and GSM

An important functionality that has to be in place when LTE networks are launched from day one is the ability for mobiles to roam from LTE to other types of radio access networks. In most parts of the world except for the US and Canada, that is UMTS and GSM. While doing some research on this topic as to how that works from a network point of view, all books I have come across so far point to the new S3, S4 and S12 interfaces between the 2G and 3G network nodes (the SGSN and RNC) and the LTE core network nodes (or the Evolved Packet Core (EPC) to be precise), i.e. the Mobility Management Entity (MME) and the Serving Gateway (S-GW).

One might be happy with this answer from a theoretical point of view but in practice this approach might be a bit problematic. As the functionality has to be there from day one, using the new interfaces means that the software of the 2G/3G SGSNs and RNCs need to be modified. Now one thing you don't want to do when introducing a new system is to fiddle with the system that is already in place as you've already go enough work at hand. So I was wondering if there was an alternative to introducing new interface, even if only for Inter-RAT (Inter Radio Access Technology) cell reselection triggered by measurements on the mobile side.

It turned out that there is. After some digging, annex D in 3GPP TS 23.401 provided the answer (sometimes I wonder what is more important, the specification text or the annexes…). Here, a network setup is described where the 2G and 3G SGSN is connected to the LTE world via the standard Gn interface (Gp in the roaming case) to the MME and the PDN-Gateway. To the SGSN, the MME looks like an SGSN and the PDN-Gatweay looks like the GGSN. No modifications are required on the 2G/3G side. On the LTE side, this means that both the MME and the PDN-Gateway have to implement the Gn / Gp interface. But that's something that has to be done on the new network nodes which means its not a problem from an real-live network introduction point of view. With the Gn / Gp interface support in place, the introduction of LTE and roaming between different radio access networks could be introduced as follows:

Cell Reselection Only at First

To make things simple, LTE networks are likely to be launched with only cell reselection mechanisms to 2G and 3G networks instead of full network controlled handover. That means that the mobile is responsible to monitor signal strengths of other radio networks when connected to LTE and autonomously decide to switch to GSM or UMTS when leaving the coverage area of the LTE network. When using the GSM or UMTS network the mobile also searches for neighboring LTE cells and switches back to the faster network once the opportunity presents itself (e.g. while no data is transmitted).

Handovers Follow Later

The advantage of cell reselection between different types of access networks is that they are simple and no additional functionality is required in the network. The downside is that when a network change is necessary while a data transfer is ongoing the mobile will either not attempt the change at all or the change results in an temporary interruption of the ongoing data transfer. The answer to the downside is to perform a network controlled handover between the different radio systems. This makes the change between access networks a lot smoother but requires changes in both the new and the old radio networks. On the GSM/UMTS side, the software of the base stations and radio network controllers have to be upgraded to instruct the mobile to also search for LTE cells while the mobile is active and to take the results into account in their existing handover mechanisms. As far as I can tell, no modifications are required in the SGSN, as transparent containers are used to transfer non-compatible radio network parameters between the different networks.

Packet Handovers Today

At this point I think it is interesting to note that packet handovers are already specified today for GPRS/EDGE to UMTS and vice versa. However, I haven't come across a network yet that has implemented this functionality. Maybe it is the speed difference between the two radio access networks that makes the effort undesirable. Between UMTS and LTE, however, such packet handovers might finally make sense as in many scenarios, the speed difference might not be that great.

The GGSN Oddity

One last thought: In annex D, the 2G/3G GGSN functionality is always taken over by the PDN-GW. That means that an LTE capable mobile should never use a 2G/3G only GGSN when first activating a PDP context in GPRS/EDGE or UMTS. If this was done I don't see how it would be possible to reselect to the LTE network later. This is due to the fact that the GGSN is the anchor point and can't change during the lifetime of the connection. If an "old" GGSN would be the anchor point, then the MME and S-GW would have to talk to the "old" GGSN after a cell reselection or handover from GPRS/EDGE or UMTS to LTE instead of a real PDN-GW. That's a bit odd and I don't see this described in the standards.

There are several ways how that could be achieved. Using a special APN for example that triggers the use of a combined GGSN/PDN-GW when the connection is established could be a possibility or the analysis of the IMEI (the equipment ID). While the first idea wouldn't require new software in the SGSN, the second one probably would and then there is always the chance that you miss some IMEI blocks in the list on the SGSN, especially for roamers, so it's probably not such a good idea after all. Another option would be to replace the GGSNs in the network or upgrade their software so they become combined GGSNs/PDN-GWs. However, there some risk involved in that so some network operators might be reluctant to do that at the beginning.

If you know more about this or have some other comments or questions in general, please leave a comment below.

LTE and the SMS Question

As standardized today, LTE does not have built in SMS capabilities. In a recent webinar on VOLGA (Voice over LTE via GAN), Franz Seiser of Deutsche Telekom (formerly T-Mobile International) argued that this might be a significant issue in the future for a number of reasons.

First, he said, there are a lot of systems in the network that rely on SMS such as SIM card provisioning, for updating the roaming operator list and other data on the SIM card for example, SMS subscription to activate/deactivate add-ons, etc.

Second is the EU mandated SMS user interaction while roaming. Introduced during the first wave of roaming regulation, operators are obliged to inform their subscribers by SMS about roaming costs when they start using a network abroad. In the future, notification to prevent "bill shock" (e.g. when using mobile data abroad) might also be based on SMS.

While the roaming tariff SMS announcements for voice and SMS are probably meaningless for LTE networks that do not support voice and SMS, the notification about bill shock might very well apply to LTE as well. Unless of course, the same tariff applies abroad like at home. Unlikely I would say…

So I quite agree with Franz, if a network allows VOLGA roaming in the future, the SMS solution already comes included at no extra price.

Another option is using SMS as part of the CS fallback (CSFB) feature that is already standardized. However, if the roaming country does not support CSFB and the mobile device is mostly data centric, then the SMS can't be delivered. While it's pretty obvious that a USB data dongle is a data centric device, I wonder what an iPhone or an N97 qualifies as.

And then there is SMS over IMS. However, I doubt we will see IMS and mobile IMS clients anytime soon.

My Netbook…. 15 Years Ago

Netbook 15 years ago Here's a picture of my new netbook, a 10.1" Acer Aspire One D250 side by side with my first notebook I bought 15 years ago. Sizes are quite similar but the interior is quite different. 1 GB of RAM vs. 8 MB, 160 GB hard drive vs. 20 MB, 386 processor running at a couple of MHz against an Intel Atom running at over 1 GHz. About two orders of magnitude apart from each other. Of course, 15 years ago it wasn't called a netbook, even though my 14.4 kbit/s Modem (external) was start of the art then. Surprisingly, the 15 year old notebook still works. MS-DOS and Windows 3.1 boot in a matter of seconds, out of the 8 MB of memory, 5 MB are free once the OS is loaded and Microsoft Word loads faster than anything I have seen in the past decade. Sounds all nice but I don't want to go back. It's just a bit more comfortable today and I am not sure the old Compaq could handle a 6 MBit/s DSL line. After all, at that speed the hard drive would be full in less than a minute 🙂

First Vodafone Femtocell User Review

Vodafone UK has recently launched their first Femtocell product which they call the 'Vodafone Access Gateway'. Andrew Grill over at 'London Calling' is probably one of the first in the UK to get one to test and use at home.
An interesting report about clueless shop managers, setup procedure,
femto features and performance at home. Thanks Andrew, very insightful

Nokia N97 Review Part 4 – eMail

One of the most important applications on my mobile device is e-mail. The built in Nokia e-mail client is a bit to light weight for my purposes so I've been using Profimail the past couple of years. In this part of the review, I'll have a quick look at both.

The Natvie e-Mail Client

For the newcomer, the functionality and usability of the built in e-mail client might just be ok so I concentrated on how easy it is to create a new e-mail account with the creation wizard. It turns out that just a couple of steps are necessary to get an Ovi mail account (name@ovi.com), assuming general access to the Internet has been set-up already. The account creation wizard asks for your name and a new password, makes a couple of suggestions for how the e-mail address can look like and then sets-up the account and configures the phone. Nicely done even if the web based wizard was not yet optimized for the screen size of the N97.

My first attempts to send an e-mail to the newly created account failed but after half an hour or so the server configuration seemed to be working and e-mails were delivered promptly afterwards. Another plus is that e-mail attachments are not automatically downloaded as that is  mostly unnecessary anyway. New e-mails are notified by an audio alert, by vibration and by changing the blinking of the light behind the menu button.  The blinking, however, is hardly noticeable, I would have wished they would have done something more visible. There's a small white LED next to the USB / power port which which could be put to good use. Next software version, maybe? Downloading and opening a PDF attachment worked fine while doing the same with a word document repeatedly resulted in a "server error" and a subsequent automatic closing of the e-mail client.

Profimail

Now over to Profimail. I've been using it for a number of years now and I am a huge fan. With it's own UI layout it's more efficient in displaying information and it's also more customizable. So no doubt I want it on the N97, too. The installation worked flawlessly and the program has even been adapted for touch input. The style and size of the menu and the soft keys are just the right size for me, not too big to take too much of the visible space and not too small for touch input. Scrolling through the e-mails with a finger on the touch display also works great and the big screen of the N97 makes e-mail reading even better than before. All the rest works as on the non-touch N95 so definitely two thumbs up for the N97 implementation. What I found a bit more difficult is writing an e-mail. The QUERTY keypad of the N97 is good for short replies but for longer texts I reverted to the on-screen T9 input. While typing works ok, the very limited space available for showing the text in this mode is not as comfortable as on the N95 where all of the screen is used for showing the text. Also, for some strange reason, typing a space character sometimes resulted in a new line. So the learning curve for typing text is not as smooth as I hoped for.

In summary, the e-mail experience on the N97 with Profimail works for me and I guess that with a bit of practice, I could manage to work with the different text input modes that are available. Well done Nokia and Profimail!

LTE and HSPA Uplink Power Control in Comparison

And here's my LTE thought of the day:

One of the fascinating things about the 3G/WCDMA/HSPA uplink is the 1500 power control commands per second to ensure all devices transmitting at the same time are received with a similar power level. This is necessary as only this way the base stations can retrieve the individual data streams that are stacked on each other in the code/power domain. 

With LTE, however, such a fast power control is no longer required as each mobile sends at a different time or uses different subcarriers (i.e. different time / frequency domains). While it is still necessary that all transmitting devices are received by the base station with "more or less" the same power in order not to overload the A/D converters it is by no means as essential as before. A lot less work and signaling involved that way.

VOLGA Forum Publishes Stage 2 Specification For Voice Over LTE

Regular readers of this blog probably remember that I'm a fan of Voice over LTE via GAN (VOLGA). For those who don't, have a look here on more details on why I think it has a good chance of becoming THE voice solution for LTE. It's amazing how fast the Volga-Forum is pushing out the specifications. In May, they published the stage 1 specification document, which contains a high level architecture and the requirements. Now only a month later, a first version of the stage 2 specification is available. Stage 2 specifications as per 3GPP contain a detailed architecture description and all procedures required from connecting to the network, originating and terminating calls, doing handovers, etc.

While their speed is incredible, maybe it should not be that surprising, because VOLGA is based on the already existing 3GPP GAN (Generic Access Network, i.e. GSM over Wi-Fi) specification. That's a good thing because that means that VOLGA could thus be developed quite quickly as it's likely that existing products can be modified instead of being designed from scratch. In addition, this should also mean that the first version of the standard is already quite mature as many areas were already verified during implementation and rollout of GAN in current networks.

I did a quick comparison between the two stage 2 specs and as I expected, many parts are very similar. While the GAN stage 2 specification has 126 pages, the current VOLGA stage 2 specification has 87 pages. This is probably because VOLGA is simpler than GAN. There are fewer handover procedures and most of the handover details are part of the 3GPP Single Radio Voice Call Continuity (SR-VCC) specification (for IMS) so they don't have to be included in the VOLGA spec. In addition to fewer handover scenarios, handovers are a bit more simple with LTE from a VOLGA perspective, as the network takes care of it unlike with GAN, where the mobile has to force the network into a handover. Also, there's no need to support the packet switched part of the network which also significantly lowers the complexity.

Well done, I am looking forward to the stage 3 specification which will contain the details on all messages and information elements used.