Is (Mobile) VoIP Driving Down Voice Prices?

In a discussion around VoIP someone recently said to me that he thinks that "non-network operator supplied" VoIP is having a big impact on voice prices, both in fixed and mobile networks. I am not quite sure this is yet the case, however. When looking at prices for fixed and mobile voice calls, it can be observed in most countries where telecommunication was liberalized a decade or so ago, that prices are falling. This has consistently been happening over that time, long before VoIP came up.

From my point of view, falling fixed and mobile voice prices are more a result of competition between incumbent and startup telecom companies, who are offering voice services over circuit switched technology.

Technology has advanced, so in many cases, voice calls are transmitted over IP in the backbone networks of network operators and also internationally, but that's still virtual circuit switching and not 'end to end' VoIP over the Internet. Sure, there are services such as Skype, which are free while the call stays between two users of the same service but all people I know use it as additionally to circuit switched services rather than a replacement.

So why are VoIP services still lacking popularity today? I think it's quality of service and ease of use, in which end-to-end VoIP is still very much behind traditional circuit switched voice. That doesn't mean VoIP isn't catching up, but in my opinion we are not yet at a point where VoIP is a serious threat to circuit switched fixed and wireless voice.

As always, comments are welcome.

LTE Test Network with 20 Base Stations in Austria

Heise news reports today about an LTE field trial T-Mobile is performing right now in Innsbruck, Austria and lists some interesting details about it:

  • Base stations: The outdoor test network consists of 20 base stations with three sectors each, supplied by Huawei.

    Note: That's a good network setup to test the impact of neighbor cell interference, a major factor that limits throughput in live networks. If the network vendor has implemented a test mode in the base stations, it might even be possible to simulate neighbor cell interference as there are probably not enough mobiles yet to generate meaningful load in all cells of the setup.

  • Backhaul: Fiber backhaul (200 MBit/s) is used. Looks like Innsbruck has good network infrastructure in place!
  • Frequency band: The 2.6 GHz frequency band is used.
  • Throughput: Downlink up to 35 MBit/s, uplink up to 31 MBit/s with a 20 MHz carrier.

    Note1: That sounds quite realistic as there's probably not much interference from neighboring cells yet due to the limited number of mobile devices used in the trial.

    Note 2: Broken down to a 5 MHz carrier for easy comparison with HSPA, the speed would have been 8.75 MBit/s (disregarding statistical multiplexing gains of a broader channel). I wonder what the speed would be today with HSPA+, 64QAM (no MIMO) and suitable devices. I suppose it would not be much less. Happy to hear your thoughts on this!

  • Round trip delay times: 21 ms. Very nice, current HSPA technology in live networks have a round trip time of around 100-110 ms.
  • Mobile device used: No names given but the picture in the original post is interesting!

    Note: Looks like the devices they used are still early proof of concepts. Side note: The LG dongle sized LTE mobile I've seen at the Mobile World Congress in Barcelona this year was already a lot smaller.

MIMO Testing Challenges

Over at Betavine Witherwire there's an interesting post on the challenges of consistently testing multi-antenna devices which will shortly appear on the market. The author of the post mentions that even without MIMO, 3G network capacity could increase by 50% if all devices are equipped with multiple receive antennas and sophisticated noise cancellation algorithms. Obviously that also translates in higher throughput per device. Consequently, network operators are likely to be very interested in these developments and accurate testing of the performance enhancements is a must.

While many tests with mobile devices today are performed with the air interface simulated over a cable, that won't work that easily anymore for MIMO and receive diversity as the antennas in the device are effectively bypassed. It's the antennas and their location and shape inside the device, however, that will make the big difference. More details in the post linked to above.

So I wonder if it's possible to model the impact of the antennas by simulating their characteristics in addition to the signal path with a simulator box that sits on the cable between a real base station and the mobile device)!?

A formidable challenge and I look forward to what the guys in 3GPP RAN4 come up with.

Apartment Hunting, The Internet and Mobile Technology

Looking for an apartment is a tough job as you can probably imagine, especially if you are looking far away from your home town. Here are some reflections from an Internet and mobility point of view from such an undertaking.

Preparation

No idea how apartment hunting worked in the days before the Internet and mobile phones, but I am sure the experience must have been tough. The non wireless part of the search from a technology point of view is of course the Internet and good web portals with apartment offers. For Germany, Immobilienscout24 is a good place to start. From there, I assembled a list of apartments I wanted to see and contacted the real-estate agents for appointments a couple of days before traveling to my new hometown. Already here, mobile technology helped a lot as most agents are not really sitting around in their office waiting for their desk phones to ring.

Navigation

Once on the ground, the mobile phone on my end came into the game. Most agents called me a day or a couple of hours before the meeting to make sure I hadn't lost interest. I big time saver for them. A big time saver on my end was Nokia maps on my N95 as navigating through an unknown city is much easier that way. When new to a town, for example, it's often confusing when one should get out of the bus or tram unless of course there is some mobile GPS help in your phone and you can see the destination in the maps application and your location relative to it in real time.

Netbook Help

After having seen some apartments and getting a first feeling for the city and the different neighborhoods,  I decided that some parts of town I hadn't considered so far would also be a good place to live.  The netbook I recently bought and a wireless Internet connection were quite helpful while still out and about to find some more interesting places to see. This worked well and the mobile phone was very useful to contact agents and arrange for a meeting immediately or the next day.  That saved a lot of time as well as it's not necessary to wait until you are back home in the evening. Instead, it can be done between two appointments.

Remove all the technology invented in the past 20 years from this experience and it would have looked entirely different.

The Future

I can't remember exactly where I've seen it before but I can imagine that augmented reality could help to make the process even smoother in the future. Hold your GPS and compass enabled camera phone into the direction of a street you think would be nice to live in and your location and direction will be sent to a server on the net (just like my apartment search portal I used manually). The server then queries the database, returns the available apartments close by that fit my preferences and the phone shows them as an overlay to the image I see on the screen. Yes, I can well imagine that and it would have been great to have it as I often thought that a street looked particularly nice and that it would be great to find something here. Well, still in the future today, but I wonder if 20 years from now people will wonder how they could have ever found an apartment without this technology!?

Solar Powered GSM in the Dominican Republic

Flexenclosure In the past two years I've seen a number of companies at the Mobile World Congress working on solar and wind powered GSM base station solutions targeted at countries where the power grid is unreliable and many base stations are powered by diesel generators. Looks like the industry is now slowly moving from the concept phase to practice.

Apart from environmental issues, diesel generators need fuel which is sometimes very difficult and expensive to get to rural areas. So if solar or wind power can partly or fully supply a GSM base station with power, that's good for the bottom line and for the environment as well.

Here's a link to a press release over at TeleGeography that Orange Dominicana has started rolling out solar powered base stations. The article concedes at the end that its only 30 base stations for now, but it's a start.

The press release doesn't mention which solution is being used. At the World Congress, I've seen VNL for example, that develops very low power GSM base stations with limited range and Flexenclosure who work together with, among others, Ericsson (see picture on the left).

Relative Cost of Voice over GSM, UMTS and LTE

The other day, a reader asked whether it is true that a voice call over a UMTS circuit switched bearer is less expensive than over a packet switched UMTS bearer. Good question and I guess very difficult to answer as there are many parameters. But nevertheless, let's expand the question and put GSM and LTE on top.

GSM

In the GSM world things were simple at first. There's a 200 kHz carrier and you can squeeze 8 timeslots into it. On the main carrier of a cell 6 out of those 8 timeslots can be used for voice, on all others, all timeslots can carry one voice call. Further, the adjacent carrier can't be used due to overlap, so the carriers bandwith is effectively 400 kHz. To increase the number of calls, the network operator can use AMR half rate, theoretically doubling voice capacity. Here it starts to get difficult as a half rate channel should not be used under weak signal conditions, i.e. some calls should fall back to a full rate channel so more redundancy and error correction information can be added to prevent the call from dropping. Anyway, a full rate channel voice coded streams at 12 kbit/s in each direction. Add error detection and correction bits and you end up with around 28 kbit/s.

UMTS Circuit Switched

In terms of resource use, things are similar as in GSM. The AMR full rate codec streams at around 12 kbit/s and redundancy information is added. I'd say resource use is similar as in GSM.

UMTS / HSPA Packet Switched

Packet switched means Voice over IP. Here, things start to get difficult because what is VoIP in practice? There's no standard solution as in the wireless circuit switched domain so there are different possibilities.

Let's look at standard SIP first that uses the 64 kbit/s uncompressed PCM codec. Add IP overhead and you stream at 80 kbit/s in each direction. Quite a difference to the 12 kbit/s used in the circuit switched wireless network. But wait, it's 28 kbit/s due to error detection and correction. However, that has to be added to the 80 kbit/s as well but how much, that's difficult to say. That depends how far the user is away from the base station, i.e. which modulation and coding is used. So to get realistic values, you have to calculate with a traffic mix. But no matter how you calculate it, there's no way to bring the 80 kbit/s down to the circuit switched value.

Some SIP implementations also use AMR if they detect that both ends support it. That brings down the data rate to 12 kbit/s + IP overhead to a total of 32 kbit/s. For details see this post. Still three times more than 'native' AMR. For users very close to the base station not a lot of redundancy needs to be added so I think we could come pretty close to GSM or be even better. But then, you switch-on half rate AMR and GSM is doing better once again. You could do that in VoIP as well but the IP overhead won't go down and it's already 2/3rds of the total bandwidth for full rate AMR.

Better spectral efficiency could also help to some extent to compensate for higher VoIP data rates as mobiles close to the base station do not only require less error detection and correction bits in the stream but can also use a higher order modulation, thus making the transmission more efficient than GSM circuit switched. But again, that's only for some but not all mobile devices.

Something that works against VoIP efficiency over wireless networks are channel assignments. While circuit switched timeslots are only assigned at the beginning of the call, bandwidth for VoIP calls over HSPA needs to be frequently re-assigned. There were some efforts in 3GPP to reduce the need by using static assignments but it starts getting messy quite quickly here (HS-SCCH-less operation).

But wait, there's IP header compression in UTMS, at least in theory. In practice, however, it's not used as far as I know, so I won't put that into the equation.

Over the top VoIP such as Skype uses pretty bandwidth efficient codecs that are in a similar bandwidth requirement range as AMR. There are lots of VoIP systems that could be used over wireless as well but I don't know what kind of bandwidth needs they have so I won't discuss them here.

LTE

There's a real pressure with LTE to switch to VoIP and similar dependencies on features such as modulation and coding, signaling overhead, etc. as in UMTS will have an impact. Robust header compression will probably make it into LTE much faster than in UMTS, be it for IMS, for VOLGA, or for any other network operator voice solution that will be used.

The Calculations

The book from Hari Holma and Antti Toskala on UMTS/HSPA has some interesting calculation on VoIP capacity. Their conclusion is that UMTS packet switched voice capacity can easily exceed that of GSM – if, and that's the big if, all optimizations are present and switched-on. For over the top VOIP, however, it's unlikely that these conditions will be met.

Summary

So as you have seen VoIP over UMTS or LTE can be more or less efficient than circuit switched voice over GSM depending on how you look at it. So maybe the question for the future will not be on efficiency but if mobile network operators will in the future continue to be the main provider of wireless voice calls or if over the top voice providers will take a bigger share of the market for which radio network optimizations are not working as efficiently.

3G Sticks Everywhere These Days

This is probably not big news to most but I just realized recently when walking through a German city how many people sit in cafes and restaurants with a notebook and a 3G USB dongle these days. I could swear it was still much different last year. Most people I saw were (still) using notebooks instead of the smaller netbooks, so I guess that trend is not yet as pronounced. I didn't talk to the people I saw so I don't know if they are using prepaid daily, hourly or monthly options or if they have a postpaid contract. Both are available in Germany. Also, it would be interesting if the connectivity is provided by the company they work for or if they are paying themselves. Would be quite interesting to find out.

LTE and UMTS Air Interface Comparison

There's a very interesting blog entry over at the 3G and 4G Wireless Blog by Devendra Sharma on the differences between the LTE and UMTS air interface beyond just the physical layer. By and large he comes to the conclusion that the LTE air interface and its management is a lot simpler. I quite agree and hope that this translates into a significantly more efficient power management on the mobile side (see here) and improved handling of small bursts of data of background IP applications (see here and here). I guess only first implementations will tell how much it is really worth. I am looking forward to it.

Symbian vs. Memo? – Some Thoughts

This week, the Financial Times Deutschland ran an article that Nokia is about to "change its strategy" ("Strategiewende") concerning their use of smartphone operating systems, that "they are loosing faith" in Symbian ("verliert Vertrauen") and are about to "abolish" ("verwerfen") Symbian in favor of Maemo.

Tough words which are immediately followed by the statement that in the future, Nokia will equip "many" of its new phones with Maemo. To me that doesn't quite sound like abolishment or loosing faith but more like continuing the path of working on more than one operating system.

The article only cites internal sources so it's difficult to verify the claim or the spin of the article. Other news websites have picked up the story (e.g. here, here and here) but I don't quite believe it yet.

Here's how I see things:

Something is going on behind the scenes at Nokia concerning their smartphones and I am not quite sure what it is. The innovation in the smartphone sector Nokia has so long driven with their Nseries range has notably slowed down. I have my Nokia N95 for almost 18 months now, and I am still waiting for a successor. Neither an iPhone nor the N97, that has just started shipping recently, are what I'm looking for. From that point of view, the speculation is understandable.

But the latest Maemo device, the N810, was released in the same timeframe as the N95, back in 2007. So Nokia has definitely not really pushed that OS with new hardware either. There are rumors of a new Maemo device to be released shortly, but I don't think that this is a change of strategy or loosing faith in Symbian.

The FTD article says Symbian is old, has 20 million lines of code by now and is difficult to extend. I would hold against it that Maemo, which is based on Linux, has probably similar complexity and Linux itself is not much younger either. But it's open source and well known by programmers which are two formidable advantages over Symbian. Symbian is going open source, too. How much that will draw programmers to it, however, still remains to be seen.

An advantage of Symbian over Maemo is it's integration of 2G and 3G network stacks, something Maemo does't have for any hardware with which it was released so far. On the other hand that seems to be something that can be overcome, as shown by Google's Android, which is based on Linux as well. 

Also, a change from Symbian to Maemo would not solve Nokia's challenges concerning platform popularity and an encompassing ecosystem such as a popular web store, synchronization to web services or to a PC, etc. These aspects have nothing to do with the operating system running on the mobile device itself.

The article further says that Nokia is loosing smartphone market share. After many years with little competition, I'd say this is not really surprising with strong competition coming from several directions now such as RIM, Apple and Google. That's not something that could be fixed by changing to another operating system.

But market share is not everything. I'd rather have a smaller market share of a big market than a big market share of a small market. I don't have the numbers here, so maybe someone can help me out with this, but I think there's a fair chance that with all the attention of companies with good products other than Nokia on the smartphone sector, the number of smartphones sold are probably increasing.

So without further facts I can't quite go along with the message of the FTD article that Symbian is going to be ditched. What do you think?

Vodafone and Petabytes

Another interesting number popped up on the Internet recently. Here, Teltarif quotes Georg Benzer, Chief Network Officer for Vodafone/Arcor in Germany, saying that Vodafone/Arcor (I assume he means both their DSL and mobile network Germany) transport 1.5 petabyte a day. No more details were given and there is only one more source on the net reporting the same number. But nevertheless, let's play around with this number a bit.

The 3UK CTO recently reported that at the end of 2008, they transferred around 1.000 terabytes (=1 petabyte) a month through their wireless network in the UK. Let's say most of that traffic was generated by 3G dongles. The exact 3G dongle subscriber number of 3UK is not known, I estimate it at around half a million at the end of 2008. That means every subscriber consumed about 1.000 terabytes / 500.000 subscribers = 2 GB of data a month.

Now lets say the 1.5 petabyte a day or 45 petabyte a month in the Arcor/Vodafone network were consumed by both fixed and mobile subscribers. Let's say Vodafone Germany has 2 million 3G dongle users (just an assumption, approximated from the 3UK number, no source for this) then out of the 45 petabyte, 4 petabyte would come from mobile subscribers. That means 41 petabytes are used by fixed DSL subscribers.

The number of fixed DSL subscribers of Vodafone/Arcor Germany is reported to be around 3 million. That makes 41 petabytes / 3 million subscribers = 13.6 gigabytes per subscriber per month on average. Note that both the 2GB above and the 13.6 GB are average values and there's no telling from those numbers how many users are at both ends of that figure (i.e. how many use much less and how many use much more).

Many of Arcor/Vodafone's DSL subscribers also use their DSL line for
VoIP (with a POTS to VoIP converter at home). That traffic should not
be counted either as it doesn't leave the network, at least not as IP packets. Let's say the average subscribers uses the fixed line phone
for 5 hours a month. VoIP produces 2*80 kbit/s (uplink + downlink) = 160 kbit/s of data
traffic = 72 MB per hour or 360 MB for 5 hours. Not very much compared to the 13.6 GB per month which are just reduced down to 13.3 GB per month.

A raw comparison of the two numbers would indicate that DSL subscribers are transferring 7 times more data through their connection than wireless subscribers. But I think that is a bit too simple a view. Most wireless subscribers are likely to also have a DSL line at home and fixed and mobile use might be different. Further, DSL lines at home are often shared with family members and several devices while a 3G dongle is mostly used by a single person with only one device at a time. Also, since most wireless offers have bandwidth caps, heavy users are much more likely to use a DSL line rather than a wireless modem, thus further distorting the direct comparison.

So despite the two numbers not being directly comparable they nevertheless give an interesting indication that mobile use is is not that far away from fixed line use.