UMTS 900 in London – A Tough Decision

Recent press reports (e.g. here and here) revealed that O2 UK has expanded their 3G service to the 900 MHz band in London and other big cities in the UK. Quite a surprising move for me since the common perception is that there is not enough bandwidth in the 900 MHz range to allow operators to remove a 5 MHz chunk from GSM services in busy cities and use it for UMTS in this band. So how is this possible in the UK from a technical point of view?

After some digging I have found the two references (here and in particular here) that suggest that in the UK, the 2×35 MHz bandwidth in the 900 MHz band is only shared between two network operators. That makes things very easy from a technical point of view as each operator has much more spectrum compared to countries in which up to four network operators share the resource.

In a first instance, this is very good for customers since 3G indoor coverage should be considerably enhanced by this. Personally, I can't wait to come to London again to get some first hand experience.

From a competitive point of view the move by Ofcom to allow the incumbent two operators to keep all the spectrum and to use it for more than just GSM (refarming) must have been a very difficult one as it puts the other operators at a disadvantage in the short and medium term. Until they can get similar spectrum, e.g. in the 800 MHz band, until manage to deploy a network and until they can get devices, a significant amount of time will pass.

And here's why: The bandwidth auctions for the 800 MHz band in the UK is set for 2Q2012 and there are still some question marks attached. And once that spectrum is allocated it is most likely going to be used for LTE. That's good for high speed Internet access with 3G dongles and embedded 3G/LTE modules but that still leaves the LTE voice problem to be solved. Here's a post of mine from back in 2008 describing the issue. It's 2011 now and I don't see that the industry has moved an inch closer to a solution (dual radio mobiles don't count).

It's not the additional 5 MHz that is the business advantage, it's the indoor coverage. And smartphone owner don't care only for 2G indoor coverage they want fast Internet access as well. According to this report (again, but see (*) below) the 900 MHz operators have to pay a yearly fee to compensate for the fact that 2100 MHz 3G operators would have to build three times more base stations in order to reach a similar coverage. But that's easier said than done, just imagine how an operator could triple the number of base stations in London. I wonder if that yearly fee (how much is it by the way?), which in theory should make tariffs more expensive with the 900 MHz operators, will be enough to ensure ongoing competition between four network operators. I am a bit skeptical.

Would it have been better to give some of the 900 MHz spectrum to other network operators? Difficult question. Perhaps it would have been a bit more fair in that band but it would also have meant that, according to current wisdom, there would have been no 900 MHz 3G in the UK, just like in other countries. That leaves the 800 MHz digital dividend band for fast Internet services with good indoor coverage in cities and economical rural coverage like in other countries. Unfortunately, the bandwidth of 30 MHz there is not enough for four operators, three is the best you can reasonable do here.

Tough choices!

(*) P.S.: The article states that EE uses 1800 MHz for 3G services. That is unlikely as there are no 1800 MHz 3G devices on the market today.

doesBenefitFromBatteryConsumptionOptimisation

A bit of a strange post title today but fitting the tech deep dive. When recently looking for something in the UTMS RRC Specification Document (3GPP TS 25.331) I noticed a parameter introduced in Release 6 of the specification which is called "deviceType". The parameter is included for example in the ue-radioAccessCapabilities Information element in the RRC Connection Setup Complete message. By default its value is "doesBenefitFromBatteryConsumptionOptimisation" but can be set to the device to "doesNotBenefitFromBatteryConsumptionOptimisation". No further explanation is given in the spec. I have to say I'm intrigued as to me it looks like something that could be used on top of the Fast Dormancy and Continuous Packet Connectivity extensions. So far the world has mostly looked at these two and I think the combination of the two of them makes a good package indeed as I described here.

A combination of FD and CPC makes a lot of sense for battery driven devices. But what about devices that do not require an optimization to conserve battery power? UMTS Modules in netbooks for example do not have the same battery capacity restrictions and here it might be better, both for the user and the network, to keep the device in Cell-DCH state (with CPC on top) for a much longer time if the user is actively using an application that requires frequent exchanges with a server on the Internet. For the network, fewer state changes would be required while on the UE side, no state changes mean that data can be delivered more quickly after the user has, for example, clicked on a link.

One could even imagine that the parameter could be used to configure CPC in a different way depending on the type of device. For battery constrained devices, CPC could be configured with larger transmission/reception gaps to conserve energy, while for other devices, shorter gaps could be configured for faster reaction times.

But o.k., let's first let the industry figure out how to do FD (Release 8) and CPC well before going to the next level of optimization…

 

What Happened To 2D Bar Codes?

For many years I've had a 2D bar code at the side of my blog to help people to get to my blog more easily on their mobile device when they discover it on their notebook or desktop PC. But these days I wonder if it is really still necessary!? While seeming to be very popular in Japan, bar codes to get further information haven't really caught on anywhere else. Every now and then I see a 2D bar code on a poster but if I'm really interested I'd rather type in the name of the product and let Google or Bing guide me to the website. And for me it's even more convenient, as making a search query with a single term even with a virtual keyboard is still easier than trying to remember where to find and how to use the 2D bar code reader application on my mobile device. What do you think, where will the 2D bar code story go?

Spectrum Usage Comparisons

How much spectrum is used in the US today for GSM/CDMA/UMTS today vs. in a typical country in Europe? Here's a couple of thoughts on this:

In the US there are mainly two bands used today:

850 MHz US (vs. 900 in Europe)

First, there's the 850 MHz band, used for GSM, CDMA and UMTS services. The bandwidth is 25 MHz according to this link. From my point of view that pretty much compares with the usage of the 900 MHz band in Europe which has a bandwidth of 35 MHz. Here, however, it is used for GSM only in the majority of cases and only few countries such as Finland and France also use it for UMTS in rural areas. In practice I guess it is quite tough for US carriers to squeeze both voice and broadband data services in a 25 MHz band.

1900 MHz Us (vs. 1800 in Europe)

The second major band used in the US is the 1900 MHz band with a bandwidth of 60 MHz. Again, this compares to the 1800 MHz band in Europe, which is 75 MHz wide. How much of these bands is used on each side of the Atlantic I am not quite sure but I would assume that in the US quite heavy use is made as based on it's width it must be the main band for data services. In Europe on the other hand, the 1800 MHz band is mostly used for voice services and quite a bit is still unused today. That might change though as a number of carriers have announced that they will start using the 1800 MHz resources for LTE.

1700/2100 MHz

And then there is this third band, in the 1700 MHz area for uplink transmissions and in the 2100 MHz area for downlink transmissions with a width of 45 MHz. Today, as far as I know, only T-Mobile uses it for UMTS services but other major carriers have significant (unused) holdings as well as discussed in a previous post. As only one network operator uses it, I don't think it can be compared today to the 2100 MHz band in Europe which has a width of 60 MHz and is used intensively by 3 to 4 network operators per country for UMTS services.

Other bands and the future

Yes, other bands should not be forgotten but from what I can tell they are not playing an important role just yet. There's around 30 MHz of spectrum in the 700 MHz range in the US that Verizon has just started to use 10 MHz for its LTE services. And then there is the 2500 MHz band used by Clearwire for WiMAX. The former compares to the 800 MHz digital dividend band in Europe that has just started to see intensive usage by a number of operators. A definite advantage on the European side is that the 30 MHz are all in one chunk while the 700 MHz resources in the US are cut into several chunks with uplink and downlink turned bottom up on one chunk, probably to protect TV transmissions. That probably complicates transceiver design for devices aiming to support more than just one chunk compared to the straight forward approach of the 800 MHz digital dividend band. And then on the European side of course, there's the 2600 MHz "LTE" band with a total of 70 MHz of bandwidth.

No doubt, this view is a bit "Europe biased" but when looking at it I can't help the impression that things are a bit smoother and broader outside the US!?

 

Malta: Antennas in a Ruin

Ruin1 Here are a couple of pictures from a somewhat special antenna placement on Malta. In the midst of a ruin, one of the Maltese network operators has installed, rather ad-hoc, a base station. At first I thought that a ruin might not be the best place for a BTS but on the other hand, I don't think that ruin is going anywhere in the next decade and is unlikely to be demolished either. And the rent for the network operator is probably quite cheap as well. The second picture shows how well the antenna is hidden. The black color makes the antenna blend in with the black background perfectly so most people will likely never notice it despite it being only a meter or so away. On the third picture I used a different setting on the camera and the support of the flash to make the antenna more visible. That's how you see it once you've become aware of it. An interesting installation and probably one of the reasons why both 2G and 3G coverage is excellent on the island. 

Ruin2 Ruin3

Who Owns and Uses AWS Spectrum

While doing a bit of background research on the amount of wireless spectrum available and used in the US today (more on that in a future post) I had a closer look at the AWS band. The AWS band is mostly used in North America today and encompasses a bandwidth of 45 MHz in the 1700 MHz frequency range for uplink transmission and another 45 MHz for downlink transmission in the 2100 MHz range.

Here's a link that shows who owns how much of that spectrum in the US. T-Mobile US seems to be the only active user today for its UMTS services but pretty much every one else including Verizon and I suppose AT&T (through Cingular) have a chunk as well and might use it in the future for UMTS or LTE services.

But like T-Mobile US, whoever starts using that band will require specific devices supporting that band. For T-Mobile US things have improved a bit in the last year or so with quite a few devices supporting the band now, including all new Symbian3 devices that are even pentaband UMTS capable, i.e. supporting all three US bands and the two major bands used in the rest of the world.

So in other words, most parts of the AWS band is still unused in the US at the moment.

Malta – Go Mobile and Internet Access – A Near Miss

This week I was in Malta for a couple of days and as usual I was looking for some affordable local tariffs for wireless Internet access with one of the 3G operators on the island.

Offers from both Vodafone and Go Mobile sounded promising and reception in the hotel room was equally good so I let chance decide which one to take. Vodafone SIMs were sold out in two tourist shops I tried but I was able to get a Go Mobile SIM card with the second one. No registration, they are just sold over the counter for 10 euros and an extra 10 euros for some credit to activate their internet offer for 4 euros for 10 days, 350 MB max. This should do for the vacation. So far so good. Activation of the SIM card was straight forward by just calling a short code and activation of the Internet offer was done quickly as well by sending an SMS with the name of the offer which was confirmed within the minute. What didn't quite work as expected was that the line was not provisioned for packet access, i.e. the GPRS attach was always rejected. Strange, you can book an Internet offer but GPRS services are not activated at the same time?

So I first called the customer help and top-up line (123), or at least tried to, as whenever I pressed the option in the voice based menu for a customer representative the call was released. Real good customer service… After the third time I gave the leaflet that came with the SIM card a closer look and found another direct number for the customer help line. Fortunately there was an English help-desk so I explained the issue without getting too technical. The support person insisted to send me an SMS to configure my phone despite me explaining several times that it's not the phone but the network that needs to be configured. I gave up in the end hoping that the SMS configuration would perhaps also trigger the corresponding network parameters for my line to be set up. Unfortunately it didn't. I was almost prepared to give up and search for a Vodafone SIM but wasting 20 Euros is a bit much. So I decided to give them a final call. I ended up with the same support person as earlier, explained to him the issue again and this time gave him the full technical issue –> "Configure my line in the HLR for GPRS services". I was put on hold for a couple of minutes so I guess he spoke to a network technician. When he came back he told me that things should be working now so I restarted the phone and indeed, the GPRS attach went through this time.

Fine, I had Internet access now but this raised a number of questions:

  • Why were packet services not activated in the first place?
  • Why weren't they activated when I bought the Internet bundle via SMS?
  • Why was the call to the help line not working via the general number?
  • Why did it take two calls to get things working despite a precise error description?

Without technical background knowledge I don't think I would have gotten it to work. Also I was quite glad I had a Symbian phone with me because here one can see on the idle screen why things weren't working (the GPRS attach already failed). On other devices based on Android, for example, this information can't be seen at all.

So, Go Mobile, if you read this, have a look at your back-end procedures to see how they can be streamlined to make things a bit smoother. Oh and yes, by the way, make the default APN work so people don't have to guess the APN for general Internet access after the GPRS attach works (which is 'rtgsurfing' by the way).

 

My Mobile Devices 10 Years Ago

2001 Have a look at the picture on the left that I recently re-discovered. It's back from 2001 and shows the mobile devices I was using at the time. A Siemens S25 GSM mobile, no GPRS yet and a Palm III. Internet connectivity for email and some very very basic black and white web browsing over and infrared link and a circuit switched data connection (9.6 or 14.4 kbit/s) to an analog fixed line modem of an internet service provider. And that was only 10 years ago! Interesting to compare that to the gigahertz powered processors we have in mobile devices now, gigabytes of Flash RAM and display resolutions equaling that of desktop PCs of the time.

This might help to understand how people where once excited about 384 kbit/s wireless connections over the future UMTS system. Look at it also from this angle next time somebody says that UMTS was a mis-design before HSDPA was put on top of it.

Exploring Android – Part 5 – Wi-Fi Offloading

Next in line on my Android exploration path is how Wi-Fi is integrated into the system and how the OS switches between 3G and Wi-Fi use automatically. The implementation in fact is straight forward. If a Wi-Fi network is detected for which security details are available, Android automatically changes from 3G to Wi-Fi use. For running applications that means that their current TCP/UDP context is broken and that they have to reestablish contact with the server. For my most often used applications, Opera Mini and Profimail, that works quite well as most of the time they don't transfer data and therefore the switch usually happens when they can live with an interruption anyway. If I remember well, I was once told that the iPhone performs a 3G/Wi-Fi switch in the same way.

But what happens when there is an ongoing data transmission while the bearer is switched? I gave it a try with a podcast application that can also stream a podcast from a server. As expected the OS did not care that there was an ongoing transmission and the stream download was interrupted. The streaming application presented an error and had to be restarted manually. Not so nice.

Symbian on the other hand uses a different algorithm that prevents such behavior. Different networks can be grouped and priorities can be given for each network in the group. Individual applications can then either use the networks of the default group or can be assigned another group. For my podcasting application for example, I use a "home" group that only contains my private Wi-Fi network. This ensures that I don't use the 3G connection for large downloads by accident. I've also configured the SIP telephony client to the "home" group so it automatically starts up once the home Wi-Fi is detected. Changes between the networks in a group are not allowed while at least one application is running that uses the network group. This way the loss of TCP/UDP contexts is prevented.

In practice I think few people will use all the possibilities offered by the more complex Symbian implementation. They will most likely only have a single group with all known networks part of it. To prevent TCP/UDP context loss, Wi-Fi is only used when all applications are closed. That might have been o.k. a couple of years ago when applications were closed after use but with email programs and web browsers running in the background all the time now, it's not ideal anymore. But neither is a drop of the TCP/UDP context as in the Android implementation.

There is of course a remedy by using one form or another of mobile-IP to rescue the IP address when switching between access networks. There are several different ways to do this, unfortunately, which is likely going to hinder implementation and use in the foreseeable future. But sometimes a simple implementation trumps over more complicated ones if the drawbacks are acceptable.