Category: Uncategorized

Here's a quick tip today to myself for the future which might be helpful to some of you as well: When I switch from one phone to another it takes ages to transfer all the calendar entries as I have well over a thousand on my Nokia Symbian OS phone. Most of them are years old and not very useful anymore. Deleting them one by one is not really an option. But I just found out that it's possible to batch delete them from a certain date backwards. Go to calendar – month view – options – delete entries – select date. It even figures out to leave the yearly recurring ones in. Very nice and smooth!

One of the things that will make it tough for future IMS deployments is the need to hand-over a connection to a circuit switched 2G carrier when running out of coverage of a network technology such as UMTS or LTE that can support the required packet switched quality of service and speeds. Yes, there is SR-VCC (Single Radio Voice Call Continuity) and soon even Reverse SR-VCC (see here) but it's still a long way from theory to practice.

Recently, it appeared to me that a network operator that doesn't have that sort of problem is NTT DoCoMo. They are fully relying on their 3G network for everything including voice calls (which is still handled by the MSC) so there is no need to fall back to 2G. In other words, they are in an ideal position to introduce IMS, perhaps with LTE once they feel coverage is sufficient and then seamlessly hand-over the packet switched IMS voice call to a packet switched UMTS bearer.

So as you can't get it any easier, I wonder if they will be one of the first to deploy IMS?

Back in 2007, Metageek sent me one of their Layer-1 2.4 GHz probes to play around with. So far I mostly used it for Wi-Fi network analysis. But the 2.4 GHz band is also used by other technologies such as Bluetooth. Unlike Wi-Fi with its 20/40 MHz channels, Bluetooth only uses 1 MHz chunks and performs frequency hopping over the full 80 MHz of the band to keep interference with Wi-Fi and other technologies using the band to a minimum. So far the theory. How it looks like in practice can be seen on the screenshot on the left (click opn the picture to enlarge). Thanks to Metageek, your hardware and software keeps coming in handy!

In theory, Bluetooth is a great technology, but in practice, I find Bluetooth implementations on many operating systems and drivers for many sticks immature, unstable, not very well integrated into the OS and cumbersome to use. For example, I find the standard Bluetooth integration in Ubuntu 10.04 too rudimentary to be of much use. But then I stumbled over this web page which describes how to easily integrate the Blueman project in Ubuntu for using a mobile phone as a 3G gateway to the Internet over Bluetooth (dial-up functionality). Yes, Bluetooth is too slow these days to make full use of 3G speeds beyond but in most cases, the 2-3 MBit/s that can be squeezed over the Bluetooth link are sufficient. Also, Blueman makes file transfers from and to a mobile phone a quick and easy thing and the integration into the native file browser is great. So here's the short version of how to make it work:

• Install Blueman: sudo apt-get install blueman
• Hide the default Bluetooth manager icon in the tray by deactivating it in "System -> Preferences -> Bluetooth Manager"
• Plug in a Bluetooth dongle and the Blueman icon will appear in the tray. The rest is pretty much self explaining

Yes, I'm admittedly a long standing Symbian fan boy who appreciates a flexible and mobile optimized operating system, fine grained network access control to keep my data roaming charges under control and who's manufacturing company is not spying on me and also not telling me what I can and can't do with my mobile device. Uh, long sentence. For a number of weeks the N8 has now become my everyday device and quite admittedly it's a huge leap beyond the Nokia N95 I hung on to as all Nseries devices that followed were just not what I was looking for. Fortunately this has changed with the N8 and I've even adapted to the touchscreen, although it is still something of a let-down not to have a real keyboard anymore.

Lots of reviews are out there saying good and bad things about the N8 and Symbian^3 and the one which reflects my impressions best is over at AllAboutSymbian in 6 parts. So I won't start raving about the great camera, the cool multitasking, etc., etc. but I'd rather like to write down a list of improvements I noticed in usability that have gone into Symbian since the N95. Most of them are just small things but they have a huge impact on usability:

• RAM plenty: The N95 was one of the few devices with ample RAM for running programs. Later models have had less leading to frequent complaints in the blogosphere. The N8 again has plenty of RAM and despite heavy multitasking I haven't had a single out of memory error yet. 

• Remote Phone Lock: A bit hidden and not advertised at all, but there's now a remote phone lock via SMS functionality with an SMS reply when the phone has been locked. Gives me a lot of peace of mind because I hate typing in an unlock code every 5 minutes.

• Timed Profile: An expiry time can be set when switching to the 'meeting' , 'silent' or any other profile. It frequently happened to me so far that I forgot to switch my phone back to normal mode once a meeting was over and frequently had missed incoming calls afterward. 

• Date and Profile always shown: One of the few things I always disliked on the N95 was that I couldn't see the date when I was in any other profile than the standard one. That's fixed now!

• Alarm clock easily reachable from home screen: A tap on the time display and I'm in the alarm clock feature right from the front screen. I use it a lot so that's very helpful.

• HDMI TV out: Like the N95, the TV output is great for showing pictures and videos.

• Bluetooth Headset range: The Bluetooth chip and antenna in the N95 had a very limited range and I found it to be pretty much unusable when the phone was in a pocket. The N8 now has a really good implementation and streams music to a headset even at a significant distance through an office space. Incredible!

• FM transmitter: Every now and then I take the car to work and listening to podcasts and music stored on the mobile phone is now so easy. Just switch on the radio, tune to the frequency set in the FM transmitter settings on the phone and there you go. No fiddling with a cable, plugging the phone into something, etc. etc. The transmitter is even strong enough to blast over a radio station on the given frequency.

• Clock on the standby screen: The N8 is the first phone I've used that shows the date and time in big numbers on the screen when the device is locked and the screen is off. Great stuff!

• Bluetooth mouse and keyboard support: For long emails and other things a full QUERTY keyboard can't be replaced by anything that attached to a mobile device. I've had a Bluetooth keyboard for years which is again supported by the N8. And on top, even Bluetooth mice are supported.

• Ovi Maps improvements: As I travel abroad a lot I very much like the downloadable maps as there are no data charges except for retrieving the ephemeris data for the GPS receiver. Getting a first fix only takes a few seconds and scrolling through the maps is much faster now than on the N95. Very smooth and both search and navigation work like a charm.

• Profimail touch: For many years I've used Profimail as my mail client as it is highly customizable, knows how to partially download emails (again, good to keep roaming charges down) and is very stable and mature. I've heard that Mail for Ovi has matured to a good state by now but I see no reason for switching. For Symbian touched based devices, there are a number of slick features in Profimail now, one of them being a circle that pops up when one keeps the finger on an email or inside an email on the display for a bit with a number of options what to do next distributed around on the circle.

• A native Opera Mini: Forget the build in browser, I need speed no matter where I am and what network is available at the time. Opera Mini uses a network based compression and is ultra fast and now also available as a native application on the N8. Ueber-cool!

• Touch phone and one hand use: And the last one today, but most important, is that the form factor of the device and the OS enable me to use the phone with one hand, despite the lack of a hardware keyboard. A must have for me!

Great work, thanks a lot to the Nokia and Symbian teams!

P.S.: Oh yes, and there is Angry Birds… 😉

Recently I was on the road again for a couple of days and as always had my 3G/Wi-Fi router with me to connect several devices to the net with a single 3G connection. After a while I was a bit surprised that despite my mobile phone and the 3G/Wi-Fi box showing very good coverage (5 signal bars) transmission speeds were consistently below 500 kbit/s. Network overload? So I got out my little analyzer and saw that in the spot I placed the 3G router, the signal level was strong (-72 dbm) but there was high interference as two cells were received with an equally strong signal level. The result was an EcNo (signal to noise ratio) of -12db for both cells (for details see here). So despite the 5 signal bars, not an ideal place to put the 3G router.

So I walked around a bit to find a better spot and in most other places I encountered a similar situation. But in a few places I could consistently receive one cell much stronger than the other one, with the serving cell having a much better EcNo of -6 db while the first neighboring cell continued to have -12db. The signal level was a bit weaker (-78 dbm) but the result was quite stunning. Instead of a throughput below 500 kbit/s I persistently got well over 2 MBit/s.

In other words, the signal bars shown on mobile devices today are clearly optimized for showing the user the quality of the network for voice calls but not for finding good spots for placing a 3G router. On the one hand, I don't think it will help to put RSSI and EcNo values in front of the average user as that might be too complicated. On the other hand, though, I think that for data centric products device manufacturers should think about a more meaningful indicator. It's not an easy task though as the signal to noise ratio of the serving cell can vary widely and quickly depending on the activity of other users. But I am sure some middle ground can be found.

A number of network operators are already selling femtocells today to their subscribers to improve their 3G network coverage at home these days. All of them so far offer it as a standalone box with its own power supply and its own space requirements. A shortcoming of this is that when connected via Ethernet to a DSL or cable modem not supplied by the same network operator, it's usually not possible to prefer IP packets to and from the femto box to ensure quality of service.

But things are evolving and Lightreading now reports that fixed/mobile network operator SFR will shortly launch a new home gateway (combination of DSL/Wi-Fi/TV/fixed line phone box) that has a slot that can hold a femto card. I've been waiting to see news of this approach making it to the market for quite some time now and I think it will help to bring femto deployment to a whole new level. No additional box, no 'visible' extra transmitter, no 'visible' additioanl power requirements, easier installation, QoS can be ensured as the femto is now part of the access device at home.

Here's a question that's been on my mind for quite a number of years know which I've finally had the time to figure out: When a 3G or LTE Voice over IP user (think IMS One Voice or VOLGA) roams in a network in another country, how can the local resources be used?

The question might seem a bit strange at first but today, GPRS and 3G connections abroad are usually connected back to the GGSN (or the LTE PDN-GW) in the home network. This has a number of advantages. For the user, such a setup is good as no configuration changes are necessary to allow packet switched roaming. Also, the additional latency incurred is often not very high when the roaming and home networks are not too far away from each other or if the servers the user accesses are in his home country anyway. For the network operator, this home routing has the advantage that the connection remains under his control and he can collect billing information and meet the traffic policy as per the contract with the subscriber.

So far, so good. But for voice over ip, the issue is that a call to someone in the visited country first goes back to the home network and then has to come back to the visited network. If one roaming subscriber calls another roaming subscriber both in the same country, the speech packets travel backwards and forwards several times. Also, its difficult to establish local emergency calls this way as the voice infrastructure of the home country is used that knows nothing about emergency numbers in foreign countries.

For this reason, the GPRS standards that govern 2G, 3G and LTE have always included a sort of "local breakout" option with which the GGSN (or LTE PDN-GW) in the visited country can be used. This is good for network operator based VoIP as this allows the use of the visited network voice infrastructure. The disadvantage is, of course, that the home network operator has little to no control over the connection and can't do the billing for it.

So much for the foreplay. How does it work in practice. There are two interesting documents that describe the details. First, there is 3GPP TS 23.060 which describes the protocol theory and then there is the GSMA IR.33 GPRS Roaming Guidelines which describes how things can work in practice which is linked at the end of this post over at LinkedIn. In short, the two documents describe the process as follows:

The subscribers record in the HLR contains a VPLMN (Visited Network) Address Allowed flag in the GPRS permissions. If set to 'no', and that's the default that is used today, all GPRS PDP context activations have to go back to a home GGSN. This is done by appending the Operator ID to the APN sent by the mobile device. A subsequent DNS query with that extended APN then results in the IP address of the GGSN in the home network to which a connection is then established.

If the VPLMN Address Allowed flag is set to 'yes', a GPRS connection can remain in the visited network, i.e. a GGSN in the visited network can be used if (!) the Access Point Name specified by the mobile device is known in the visited network. In other words, there needs to be some sort of information exchange between home and visited network on the APNs that can be used locally. In this scenario, it's the Operator ID of the visited network operator and not that of the home network operator that is attached to the APN sent by the mobile device before the DNS query for the IP address of the GGSN is made. If the APN is unknown, as far as I understand the documents (and I'm not quite sure about this), a GGSN in the home network is established in case the APN is known there.

There we go, that's the process for a "local breakout" in the visited network.

Back in 2006, it was Nokia with its N80 phone that introduced Wi-Fi in a mobile phone to me. What is so  normal now was revolutionary and daring then and I wondered at the time if we would see software for such devices that turned the phone into a Wi-Fi access point. Pretty much unthinkable only five years ago as mobile devices and operating systems were pretty much closed to the outside world and Symbian was pretty much alone at the time (perhaps acompanied by Windows Mobile?) with multitasking capabilities for third party applications and a native program runtime environment.

In 2007, first things about Android were heard and I was once again speculating about the Wi-Fi chip being used as an access point. Here, my hopes were even higher as Android is even more open so more chances for third parties to do this, at least in theory.

Fast forward to 2010 and we now have Wi-Fi AP functionality in both Android and Symbian but not quite in the way I was imagining then. On Symbian it's a third party application while on Android, the functionality is directly built in by Google. That might have something to do with apps on Android running in a virtual machine which probably makes it a bit more difficult to get to lower layer functionality.

About two years ago, I reviewed the Nokia 5000, a sub 100 euro phone to see how well Opera Mini would run on such a comparatively cheap device. I came away quite impressed at the time but since then the world has moved on. Recently I noticed that the Samsung released the Android based Galaxy 550 which is currently available for 169 euros without a contract. Albeit it costs 70 to 80 euros more, it runs Android 2.1, has a touch screen, Wi-Fi, a memory card slot, a 2 Megapixel camera, FM radio, supports 3G HSDPA and has a GPS unit built in. Incredible at this price point and according to this test report (in German, sorry), the phone including the web browser works quite well. Give it another two years and I guess Android phones with this feature set will be in a price range of the Nokia 5000 I reviewed two years ago. In other words its going to get very tough as we move forward to sell non-smartphones for more than 30 to 40 euros in the foreseeable future.