Category: Uncategorized

When watching the Sol 4 press conference for the Mars Science Laboratory (MSL) mission, better known for the Curiosity rover, the person responsible for the on-board computers was saying that the on-board computer was less powerful than an iPhone. One reporter in the audience was totally baffled by this and asked how it was possible to fly to Mars with something that had less power than the smartphone in his pocket.

A very revealing question as it shows that the general public has no idea of how much processing power is required if no screen is attached to a device and software is highly optimized for a specific purpose. It would probably be even more incomprehensible to him that when flying to the moon, the Apollo Guidance Computer did not run at 1 GHz like his iPhone, but at a mere 2 MHz (500 times slower clock speed), and instead of Gbytes of RAM and flash it contained the equivalent of a meager 4 kbytes of RAM and 64 kbytes of ROM. For the details see here and for the details on the bit level have a look at this excellent book which I just recently finished reading. In other words, the specs are similar to those of a 1980's Commodore 64, even though it's difficult to compare those two computers due to their very different purposes.

But anyway, this made me wonder how many times you could store a C64 game that filled the better part of a 5.25" disc or tape in the days of the C64 on an iPhone with 16 GB of flash today. Let's take the original Giana Sisters game on the C64 for the calculation. The disk image has a size of 174 kbytes to play it in a C64 simulator today. And that's already quite big as the C64 only had 64k of RAM so perhaps it was compressed in some form or shape in memory. But anyway, 174 kbytes it is, more than the ROM of the Apollo Guidance computer could have held only a decade and a half earlier. For the comparison let's take an iPhone with 16 GB of flash, which is roughly 16 000 MB or roughly 16 000 000 kb. The game would fit into the flash memory 91 954 times!

Stunning!

An annoyance when working on the settings of a network is that the PC used for the task becomes part of that network and depending on the job, looses Internet connectivity. Even if a 3G stick or second network adapter is used, DHCP settings, which are part of the setup mingle with the PCs settings and again cut the Internet connection. A hassle I have now found a remedy for: Wi-Fi in a Virtual Machine.

A few weeks ago I had a post on how to do 3G testing in a virtual machine but this did not extend to working in wired or Wi-Fi network. But by simply getting a USB Wi-Fi stick and making it available to the guest operating system running in the virtual machine, working on a network is completely isolated from the host computer. The picture on the left shows how this looks in practice. The host operating system uses the built in Wi-Fi chip while the guest operating system (Windows XP in the window) uses a USB Wi-Fi stick and connects to the network to be configured. No matter what is done there and how that affects the client operating system, the host operating system (Ubuntu in my case) is entirely unaffected from the changes as it uses a different network and Internet connectivity remains in place.

And if you have enough RAM you can even launch two or three virtual machines simultaneously, each using a different Wi-Fi or 3G dongle connecting to different networks. Great for testing VPN solutions, NATing, etc. etc. The more I play with Virtual machines, the more uses I find for them.

Now here's the perfect gift for a telecoms man who doesn't really have all that many wishes for someone to fulfill easily. Every now and then when tracing signaling messages, being able to spot or decipher numbers in binary is essential. But when not doing it regularly, the process is a  bit cumbersome. But here's the solution: Train you binary skills with a watch that displays the time of day in binary. After two days I was fluent again 🙂 Priceless…

An unexpected result: Chip, a popular computer magazine in Germany, noticed when doing their yearly cellular network measurement campaign, that LTE coverage from one of the leading network operators was present on 95% of their route all across Germany. For the details see here (sorry, in German, but Google can help with the translation…). And for comparison, here are last year's results.

And two other especially noteworthy data points:

1. Call setup success rates >99%, drop rates of ongoing calls <2%. Values customers in other countries can only dream of…
2. Wireless Internet connectivity of the leading operators is still as good or even slightly better than last year. The number of smartphones and data usage is rising but the numbers show that even without LTE taken into the equation, well designed networks are capable of dealing with the load.

In other words: It can be done, don't let those who can't, make you believe otherwise!

P.S.: Always looking for links to similar tests done in other countries!

One of the things a well configured GSM, UMTS or LTE network does is to give the mobile device clear and precise instructions of when it should select another cell or even performs a handover to a better suited cell during an active communication session. There are plenty of standardized parameters and algorithms based on the signal strength of the current cell, the neighboring cells, offsets before a lower speed technology network is selected, interference, etc. etc. When a mobile ends up on the Wi-Fi layer, this kind of sophistication abruptly ends as I recently experienced.

On the Wi-Fi layer it's completely up to the device to decide when it is time to reselect from one Wi-Fi access point to something else. The device I played around with clung to the Wi-Fi access point right down to the last dbm where communication was hardly possible anymore, despite an excellent other Wi-Fi network with a different known SSID in range. I manually had to reselect to the other Wi-Fi to continue working. Also, reselection from Wi-Fi to the cellular layer is probably also only done once connectivity with the Wi-Fi network is lost, which often happens much later than moving out of the "usable range" of the network where data rates are still acceptable.

Sure, Wi-Fi was never designed to include that kind of functionality and 99% of home users would likely be unable to make the required settings. Also, the break incurred in terms of IP connectivity and a different pricing between cheap home Wi-Fi and a more expensive cellular layer makes the decision to move from Wi-Fi to cellular as late as possible understandable. Nevertheless from a usability point of view it's far from ideal. In other words, the user has to make sure the Wi-Fi signal is strong enough everywhere in the house or appartment so devices never leave the usable range.

When living and traveling in big cities it's easy to forget that network coverage in the countryside is a different thing. Some places are covered by one network while other places have better coverage of a different network. Too bad if you are expecting phone calls as you never know whether you will have coverage or not.

My solution: Have an extra phone and a prepaid SIM card of another network and set a "call forwarding when not reachable" from my main contract SIM to the phone with the prepaid SIM on another network. One of them will have coverage and calls are seamlessly forwarded to the second phone if the main phone lacks coverage. Perfect!

And for Internet access the second mobile with the prepaid SIM could be used, too. With an Android phone and Wi-Fi tethering, the main smartphone and tablet have a quick alternative should they run out of cellular coverage. Agreed, not a straight forward approach but when the network is not there, one has to improvise… 🙂

I've recently come across a new pricing scheme in which unlimited voice telephony and Internet access are included in the flat rate while SMS messaging is priced at an expensive 19 cents per message. Is this incredibly clever or stupid? I am not sure.

Anyone even remotely intelligent would try to avoid sending SMS messaging as much as possible and use WhatsApp, iMessage, Google Talk, etc. instead. And to avoid the 19 cents per message to those who still only have a dumb phone one can use Skype with the built-in SMS option that circumvents the operator's SMS service center. It's even possible to register the mobile's phone number with Skype so SMS messages will look like they were sent the traditional way and can be responded to by the recipient. Sure, sending SMS messages via Skype costs something as well but it is way cheaper (in the order of 10 cents per SMS).

In other words, does such a pricing scheme drive people even faster away from your own services towards Internet based services or was the thinking here that this has happened already anyway and let's try to monetize the exceptions as much as possible? Others seem to think so as I just noticed that another network operator in the country bundles flatrate Internet access with 1000 SMS messages per month.

What do you think?

So there we go, first mobile network operators in the US and Korea have officially announced that they will start VoLTE (Voice over LTE) service with the Samsung Galaxy III shortly. Sounds interesting, but I've been using Skype on 3G for years now which is also Voice over IP and it has worked quite well. So what's so special when mobile network operators are doing it, too now? Some thoughts:

The QoS question: For Skype calls Quality of Service mechanisms in the radio network can't be used because Skype has way of interacting with the RAN. Network operator deployed VoLTE on the other hand can instruct the radio network to prioritize those packets and to not repeat data packets over the air interface for the voice data flow because the repeated packets would come too late anyway. This is all not necessary when radio conditions are good but could enhance the experience in border areas between cells where capacity is at a premium.

But that's pretty much it. Perhaps the client is more fully integrated into the overall phone functionality of the phone compared to Skype but that remains to be seen once the phone is launched.

And here are some thoughts on things that might not be so well early on: I wonder how call drop rates and call setup success rates will compare to the current voice service. Both values are extremely good in well designed networks and I wonder if VoLTE in early years with networks still in deployment and likely being deployed without fallback to a 2G network will come anywhere close.

Higher power consumption? Current voice telephony is handled entirely in the baseband and is optimized for power. VoLTE will likely use both the baseband and the application processor and includes the overhead for the full IP stack. In other words, it's likely that the phone will get warm and the battery empty quite quickly. Perhaps I'm the pessimist here, but that remains to be seen as well.

And finally it's going to be interesting to hear how good the sound quality is, but please not only tests while the mobile is stationary to compare the soft client's voice optimization to hardware background noise cancellation and other tricks today performed for circuit switched calls. The other really interesting thing to observe is what happens with voice quality during handovers between cells when the data flow is interrupted for a short while. Again, current circuit switched voice technology has been optimized for years to make this experience as seamless as possible, e.g. with soft handovers in 3G that totally eliminate delays and interruptions.

I hope some serious tests will follow these announcements soon to see where we really are with VoLTE and how that compares to other mobile voice solutions available for a while now.

And a final non-technical thought: I wonder what kind of discussions VoLTE will bring about when network operators that block other VoIP services on their mobile network today will launch their own service. Will that be the end of third party VoIP blocking?

When I recently bought a SIM card for the first mobile phone of my 10 year old nephew I was positively surprised that unlike most other prepaid offers I have seen for a long time, packet switched network access is enabled by default but all attempts to browse the web are redirected to a landing page from which a tarrif has to be selected before Internet access is granted and the prepaid account is charged. This is great as even if he should accidentally activate Internet access while browsing through the menu structure and playing with the device it will still be free of charge until an option from the landing page has been selected. No accidental activation and subsequent charing, I hope that is something I will see more often in the future on prepaid offers!

Yes, I know NTT-DoCoMo has long shut down their 2G network but that was a special case as it was their proprietary technology little used anywhere else. Since then there have been rumors, speculations and analysis when network operators in other countries in the world might switch-off their more popular and wide spread 2G GSM networks. Now AT&T has given a date for their US GSM network shutdown, it's envisaged for 2017 as reported by the Wall Street Journal.

2017, that's 5 years from now. I've noticed AT&T making a lot of progress of deploying UMTS in remote areas and 5 years is enough time to continue the process in addition to rolling out LTE. Also, when I was recently in Canada, I was positively surprised about the 3G coverage along highways in sparsely populated areas between cities. On 850 MHz, the coverage area of a UMTS cell is similar to that of a GSM cell and for carriers that quit CDMA in the past to go to UMTS it obviously did not make sense to deploy GSM alongside.

5 Years ago, back in 2007 I had a post on this blog about when GSM will be switched-off. Let's take a look what I thought at that time and how that matches today's situation and AT&T's announcement:

"So what are we going to see in Europe by 2012 then? In five years from now [i.e. 2012] I expect the majority of subscribers in Europe to have a 3G compatible phone that is backwards compatible to 2G. "

[Yes, right on the mark, more than half of the phones sold today are smartphones and even feature phones have 3G included now, too. There are few models now to be found in shops that are only GSM.]

In urban areas, operators might decide do downscale their GSM deployment a bit as most people now use the 3G instead of the 2G network for voice calls. Cities will still be covered by GSM but maybe with fewer number of available channels / bandwidth.

[Mostly on the mark: While for many years people have switched off 3G in their phones for fear of higher battery power consumption and thus made most of their voice calls on 2G, that's a thing of the past in 2012. Accessing services on the Internet from smartphones has become a mass market trend. As a consequence, most voice calls from such phones are now established over 3G networks. In the UK, O2 has deployed UMTS 900 in London. It's still a bit of an exception in Europe. O2 in the UK is in the fortunate position of owning half of the 900 MHz band so it could easily carve out 5 MHz and put a UMTS channel there. There are no announcements of similar intentions by other European network operators for the moment. However, with voice calls migrating to 3G due to the use of smartphones I think this will not remain the only major urban deployment of UMTS 900 in Europe.]

"Such a scenario could come in combination with yet another equipment refresh which some operators require by then for both their 2G and 3G networks. At that time, base station equipment that integrates 2G, 3G and beyond 3G radios such as LTE could become very attractive. The motto of the hour could be "Replace your aging 2G and 3G equipment with a new base station that can do both plus LTE on top!"

[Yes, that's what we see today when new network equipment is being rolled out. Huawei, for example, calls it Single RAN and NSN's Flexi concept goes in the same direction]

"I wonder if it is possible by then to only use one set of antennas for all three radio technologies!? If not, adding yet another set of antennas on top of an already crowded mast is not simple from both a technological and psychological point of view."

[Today, at least GSM and UMTS use the same antenna but I haven't yet seen what kind of antennas are used at base station sites at which GSM, UMTS and LTE are deployed, all in very different frequency bands. Single antenna solutions exist, even in variants that have several antennas in a single casing, as for example demonstrated by Kathrein at the Mobile World Congress in 2011].

When looking at all of these developments I think it is very likely that we will see a lot of movement around what kind of technology is used in the 900 MHz band in Europe. In many countries, licenses for the 900 MHz spectrum will be renewed, reassigned or re-auctioned in this time frame and in many countries auctions for the 800 MHz digital dividend band and the 2600 MHz band for LTE have not yet been undertaken. All of this will have a significant impact on what network operators will do with their 900 MHz spectrum assets. My prediction is that GSM will still be around in Europe in 2017 but the debate on when to switch it off will be in full swing. I've described how such a phaseout could look like in a post on 'GSM Phaseout Scenarios'. Despite written in 2008 I think it still applies from today's perspective.