8 SIM Cards and 3 Operators

In the days of prepaid SIMs and multiple phones many people carry, counting the Average Revenue Per User (ARPU) based on SIM cards has pretty much become irrelevant. I am the best example that this approach doesn't work anymore. Let's make it simple and only take a look at how I use mobile networks in a single country, Germany:

  • The 'currently used prepaid SIM card' in my primary phone which has good rates for telephony and small screen mobile Internet access. Network: T-Mobile, MVNO: Congstar.
  • My 'I always stay the same' prepaid SIM who's phone number is known by all my friends and via
    which they can reach me no matter in which country I am at the moment.
    When I am in Germany, I forward all incoming calls to the currently used SIM card since the price for Internet access is too high. Network: T-Mobile, MVNO: Simplytel.
  • My business SIM card, the only one that is postpaid. Network: T-Mobile
  • The prepaid SIM card in my car. I have a block heater which is connected to a GSM module. In the morning and evening, I call the car to switch on the heater so my windows are de-frosted and the interior is warm by the time I arrive. Network: T-Mobile, MVNO: Simplytel.
  • The prepaid SIM for notebook Internet access. I can activate 200 MB for 10 euros or 5 GB for 20 euros. Network: O2/Telefonica.
  • Two prepaid SIMs for notebook Internet access in Germany (€4.95 a day) or when I travel abroad and no local offer is available (€14.95 a day). Network: Vodafone. I have two so I can lend one to guests or colleagues traveling abroad.
  • One prepaid SIM to use in the mobile phone abroad for small screen web browsing and mobile e-mail in countries where I don't have a local SIM card. 19 cents for 100 kB is not exactly cheap but does the job well for mobile only use. Network: E-Plus, MVNO: Alditalk.

Altogether that's 8 SIMs and 3 mobile operators. Have fun calculating the ARPU! From a technical point of view all this is quite uneccessary, one sim card for the mobile phone, one sim card for the 3G USB notebook dongle, and one for the block heater in the car is all I would need.

3G Coverage on a Train Ride to Vienna

A1-on train
Recently I took the train from Linz to Vienna and I was quite surprised that Mobilkom Austria (A1) must have put a more or less dedicated 3G coverage alongside the railway track even in very rural areas. I've had 3G coverage for most parts of the trip and in the few places 3G coverage was lost, their EDGE network kicked in. I've reported on my experiences with non-optimized 3G HSDPA coverage on board of trains before (here and here), but this time, the experience was even better. The connection I established was maintained throughout the trip and high speed data transfers taking several minutes were performing very well as shown on the image on the left. I even dared to launch my IM client as connectivity was simply always there. I stepped out of the train very impressed by what is possible when operators decide to do a proper network planing and deployment.

Samsung D880 – Two SIM Cards Simultaneously

I've heard about dual-SIM phones before but only from not very well known Chinese manufacturers so my interest in them was not very high. Also, I assumed that while those phones could hold two SIMs, only one would be active at a time. While browsing the phones available at a mobile phone shop recently, I noticed that I've been wrong on both accounts.

Samsung has released two dual-SIM (GSM only) phones, the D880 at the end of 2007 and the D780 in the middle of this year, both capable of having both SIMs active simultaneously. Kudos for their courage, I am sure network operators are not very keen to see these phones.

For details see GSMArena:

Here are some technical details from the reviews above which hints how the dual-SIM functionality is implemented:

  • A master SIM card has to be declared which can be used in 900/1800 and 1900 MHz. This SIM is also used for GPRS/EDGE.
  • The secondary SIM card can be used for incoming and outgoing calls and SMS messages but only 900 and 1800 MHz.

To me this seems to indicate that each SIM card has its own GSM module and the second one is only dual band capable. Unfortunately, the review doesn't mention if an SMS can be received via the secondary SIM card while being in a voice call with the first SIM card. This would certainly prove it.

With the D880 available for around 200 euros and the D780 for even less, I can quite imagine that I will pick one up and give it a try myself. After all, it could reduce the number of phones I have to carry around with me these days by at least one. Not sure if they are a hit in sales statistics since I can't imagine network operators selling or even advertising them directly. In many countries, however, like in Italy and Germany for example, these phones can be bought from independent stores. If I were Samsung, I'd opt for a viral marketing strategy for those phones.

The LTE Frequency Gamble

A friend of mine pointed me to this document which gives an overview of which portions of frequencies have been allocated to which mobile operators in Europe. I've been looking for such a document for quite a while now as it can give interesting insights into which options mobile operators in Europe have when it comes to frequency bands in Europe. Here's what I think:

The 900 MHz band

In total, there are 35 MHz available in this band, which are typically shared for GSM today by two to four operators. Even if only two operators use this band, each operator has typically less than 10 MHz of consecutive bandwidth available here. For LTE that means that the best that an operator can do in this band is to deploy a 5 MHz LTE carrier. For most operators, that's unlikely though as the remaining 900 MHz chunks they already own are probably not enough to ensure GSM in-house coverage with enough capacity. So, most operators could only deploy a 1.25 MHz LTE carrier in this band. I wonder if that's attractive as the achievable bandwidth is severely limited. But maybe for deep in-house coverage, it's better than nothing!? Also, there's no possibility to buy additional chunks in this "prime" band, it's all allocated.

The 1800 MHz band

This game is a bit different as in total, 75 MHz were assigned to GSM here and many "second wave" GSM operators in Europe got assigned chunks of more than 10 MHz. Also, in many countries, not all of the 75 MHz have been sold so some operators might be thinking of acquiring some of the so far unused chunks to start with a 5 MHz or 10 MHz LTE carrier here.

The 2100 MHz band

This is the 3G UMTS band in Europe with a total of 60 MHz. In most countries, each operator has a 10 MHz chunk and probably only uses 5 MHz of that for a single 3G carrier. Also, there is some of that bandwidth still available, e.g. due to alternative 3G carriers having given up after they paid a bit too much for the licenses back in the year 2000. So scenarios for this band could be that some operators will start with a 5 MHz carrier in this band or try to by additional spectrum to be able to operate a 10 MHz carrier. Since there is not enough bandwidth left for all, let's see if a price fight breaks out again like in the early 3G days. Doubtful but I see more interested parties then available chunks.

The 2600 MHz band

In most countries, this part of the spectrum is still up for grabs. The issue here is that in-house coverage would be even more difficult to achieve than with the 2100 MHz band. Lots of space for 10 MHz+ carriers.

Do 5 MHz carriers make sense?

This is the big question. With MIMO, the performance of LTE with a 5 MHz carrier is similar as HSPA+ with MIMO. Even if operators do not choose to upgrade their HSPA networks to MIMO, I wonder if the speed difference is big enough to justify the expense to go to LTE compared to upgrading their already existing HSPA base station with a second carrier.

Multiband Devices

So there are four frequency options for LTE in Europe: 900, 1800, 2100 and 2600, each with benefits and drawbacks. Different operators will surely have different strategies, including using several bands at once, so it's likely that single band LTE devices are likely not to be a winner. Supporting all four frequency bands with MIMO, which requires at least two antennas per band in a single device, however, is going to be difficult to achieve. And on top of that we haven't even talked yet about the 700, 850, 1900 MHz band in the US.

I guess both first movers and followers in this space will have difficult choices to make when it comes to frequency bands. As always, comments are welcome.

3G Connection Sharing – Part 3: The D100

D100
While the software on the Fritzbox for 3G connection sharing over Wi-Fi is still an early beta, I have recently also tested the Huawei D100, a box dedicated for 3G connection sharing. So far, I've seen it advertised by 3 in the UK (with contract only) or by 3 in Austria, here unlocked for 99 euros. Needless to say I preferred the Austrian variant and went into a shop while in Austria recently to buy one. I have now used it for several days with a E220 3G USB stick in the Mobilkom A1network and I have to say I am very impressed by stability of both the Wi-Fi and the 3G connection and the ease of use of the box.

Once power is switched on and the power on button has been pressed, the box automatically attaches to the 3G network and establishes an Internet connection. What I've found a bit odd is that the power button has to be pressed for the box to start. This is a bit inconvenient after a power outage for example. Should the 3G connection drop while being online, the box is smart enough to figure out something is wrong and automatically re-establishes the connection within a couple of seconds. It happened two or three times in the course of a couple of days but it's hard to say if that was due to the D100, the 3G stick or the network.

The Austrian D100 comes preconfigured for all Austrian networks, but it's also possible to add configurations for SIM cards of other operators and countries. The page for this is a bit hidden but one found, it's pretty much straight forward.

While most people will probably use it for Internet connection sharing, Dean Bubley recently had a number of other interesting ideas of how to use what he calls 'the dongle dock'. Have a look here, especially the last paragraph. Now I need to get a femto to test his idea 🙂

HSPA State Change Measurements

A1-state-changes Last week I did some measurements to get an idea of the time required when switching between different HSPA air interface states. While data is transferred, the mobile is usually in Cell-DCH state on a High Speed Shared Channel. When only little or no data is transferred, the connection transferred to the Forward Access Channel, which is slow but has little overhead for both the network and the mobile device in terms of control measurements and power adjustments commands. If no data is transmitted for a longer duration (e.g. 30 seconds) the connection is put into Idle state. While the IP address is retained, the physical connection between the mobile and the network is severed.

As can be seen in the picture on the left, the round trip time to the first hop in the network of a ping packet is around 100 to 120 milliseconds while the mobile is using a high speed shared channel. While on the slower forward access channel, round trip time increases to 240 to 260 milliseconds. Moving from the high speed shared channel to the forward access channel is relatively quick, it takes around 550 to 600 ms (minus the actual round trip time of the packet itself). Going back to the high speed shared channel takes a little bit more time, around 1000 to 1500 milliseconds.

When using a 3G dongle with a notebook, a connection is rarely set into idle state as there is always one program or another such as an instant messenger, VoIP client, etc., that feels it needs to send a keep alive message to a server in the network before the idle time can expire. Therefore I haven't measured it this time. In the past, I've seen values around 2500 to 2800 milliseconds.

Some say that the effect of this state switching is that web browsing feels a bit more sluggish over HSPA than over a DSL line, which always offers Internet connectivity at full speed without the need of state switching. I use 3G connectivity a lot and quite frankly, while I can feel a difference, it's absolutely no problem to work and live with it.

And here's a quick overview of the test setup: Mobilkom Austria 3.5G HSPA network, a notebook connected via Wi-Fi to a D100 Wi-Fi/3G gateway, connected to a Huawei E220 3G USB stick, HSDPA category 6, no HSUPA.

Europe-wide Prepaid Data Roaming

Here's news on an interesting offer recently started by German MVNOs using the e-Plus network (Simyo, Blau, Alditalk): Since October 1st, their prepaid SIM cards are now activated for data roaming in the EU and a number of other countries. Price per 100kb block is 0.19 euros. While not exactly cheap, it's a 10th of their previous price and a 10th of the price of most other operators around Europe.

I wouldn't use it with a notebook but for small screen web browsing and mobile e-mail reception it sound quite affordable. In the countries they support data roaming outside the EU (btw. Switzerland is part of that list…) the price per 100 kb block is 49 cents. For details, see the Prepaid Wireless Internet Access Wiki.

Recently, I tried the offer with my Alditalk prepaid SIM while in France. The first time I tried, right after the start of their offer, 49 cents per 100 kb block were charged. I sent an eMail to their hotline, asking what was going on and they admited that they have a problem with their billing system and returned the money that they overchaged. When I tried again last week, the billing system was fixed and the proper amount was charged.

Uplink Downlink Ratios Revisited

Ul-dl-ratio
I've been traveling for two weeks now in Austria and Italy and have been online throughout that time 'only' via 3G to do my daily business thanks to prepaid 3G Internet access. Wherever I went, 3G HSPA access has been available so using the Internet with a 2 MBit/s downlink on average didn't feel much different from using DSL at home. I've reset the data counters on my N95, which I used as my 3G modem during the trip, to get an idea on how much data I exchanged. In the past seven days, I used about 750 MB in total for e-mail, web browsing, company Intranet access, VoIP, IM, etc.

As can be seen on the picture on the left, my uplink to downlink ratio is around 1:2 and not 1:10 as I observed during a previous trip. That's probably got something to do with the fact that this time, I received and sent many e-mails with massive file attachments (those 5 MB PDF or PPT files everybody likes…) and have been using VoIP extensively for lengthy conference calls. With VoIP, the uplink / downlink ratio is 1:1 and generates around 20 MB per hour in each direction.

From a network point of view a 1:2 ratio means that I used about as much resources in the uplink as I did in downlink, since uplink transmissions are less efficient than those in downlink due to the smaller antenna and little transmission power compared to a base station. While in most situations, I could get uplink speeds of around 400 kbit/s, which is almost as fast as the uplink of my DSL line at home, I nevertheless wished I would have had a High-Speed Uplink Packet Access (HSUPA) capable device and network. Those 5 MB Power Point presentations do take quite a while to get transmitted.

Yes, one can never have enough bandwidth 🙂

3G Connection Sharing – Part 2: My Fritzbox DSL/Wi-Fi box speaks 3G now!

Fritzbox 3G
Recently, AVM, manufacturer of the 'famous' Fritzbox ADSL2+/Draft-N Wifi router, released a beta software that adds Internet connectivity via 3G USB keys to their router software. I really like this box as it's crammed full of features such as a DECT base station, SIP capabilities, meaningful status reports, Wi-Fi interference monitor, DSL line visualization, etc., and now also 3G capabilities with an external 3G modem.

While it wouldn't work with a Huawei E160 3G USB stick, I managed to get it working with a somewhat older E220. The software is still quite an early beta and the GSM/UMTS configuration page in the router is not updated correctly once the connection is established as it remains in the "trying state". Nevertheless the connection is established and the main configuration screen properly shows the IP address and connectivity state. The throughput is the same as if the stick was connected directly to the PC.

Kind of an inverse 3G femto cell and great for traveling when more than one person or device needs Internet access or in areas without DSL coverage. For traveling, however, a somewhat smaller configuration, e.g. a 3G stick in combination with a D100 is probably preferable. For most users, such a setup is probably a lot more practical than the 3G Internet connection sharing via a PC, as I described a long time ago in this post.