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Ever since Skype has entered the VoIP sphere, I prefer using it over other VoIP or conventional phone networks for a
single reason: For Skype to Skype calls, voice quality is much better than what
other systems offer today. The secret is
a new voice codec which is much better than the standard G.711 PCM (Pulse Code
Modulation) codec which was invented several decades ago. For mobile networks a
new codec called Adaptive Multi Rate Wideband (AMR-WB) will do a similar thing
in the not too distant future.

Higher Sampling Rate

The
difference of AMR-WB compared to G.711 used in mobile core networks and fixed
line phone networks around the world, and the Enhanced Full Rate (EFR) and conventional
AMR coders used in the access part of mobile networks today is the much higher
sampling rate. While G.711, EFR and AMR use a sampling rate of 8 kHz to
digitize an audio signal in the range of 200 to 3400 Hz, AMR-WB uses an overall
sampling rate of 16 kHz to include audible frequencies between 50 Hz and 7000
Hz. In practice, this doubles the frequency range that is digitized and also
includes lower frequencies than before which are also very important for a
natural voice reproduction at the receiver side.

Standards and Interoperability

Initially,
AMR-WB was standardized by 3GPP and an overview with references to
detailed standards documents can be found in TS 26.171 [1]. Later on, the ITU-T
also adopted the codec in its G.722.2 specification [2]. This could one day
lead to the adoption of this codec for fixed line networks as well. In
addition, a new wideband speech codec was also specified by the 3GPP2 for the
CDMA world which shares some of the AMR-WB modes. Therefore, if both originator
and terminator of a voice call as well as the originating and terminating
network support AMR-WB it is possible to establish wideband speech calls across
network boundaries.

Variable Bit Rates and Audio Quality

The AMR-WB
standard specifies 9 different codec rates. These are 6.6 kbit/s, 8.85, 12.65,
14.25, 15.85, 18.25, 19.85, 23.05 and 23.85 kbit/s. For circuit switched GSM
and UMTS connections, only the first three codecs are
used. In UMTS networks, it is also possible to use the 15.85 kbit/s codec.
According to [3] and [4], AMR-WB offers superior audio quality to AMR starting
with the 12.65 kbit/s codec while the 6.6 and 8.85 kbit/s should only be used
during bad radio conditions. EFR and AMR use similar bandwidths in the radio
network. Consequently, AMR-WB offers better audio quality with the same
bandwidth requirements. This is important for backwards compatibility as will
be shown below.

Codec Introduction

AMR-WB uses
the ACELP (Algebraic Code Excitation Linear Predication) codec which is also
used by EFR and AMR. The frequency band of 50 – 7000 Hz is split in to parts in
order to achieve the best possible compression. The main frequency band covers
50-6400 Hz. As it is narrower, an internal sampling rate of only 12.8 kHz is
required. The band between 6400 and 7000 Hz is treated separately. Also, fewer
sample bits are assigned to the higher band as the lower band is more
important. For lower bit rates only the main frequency band is transmitted and
the receiver synthesizes the higher band out of the information of the main
band. At a frame duration of 20 ms, the sampling frequency of 12.8 kHz produces
256 samples (12800 Hz * 0.02 s = 256). This is convenient as this allows
efficient software and hardware implementation of bit level operations. For
silence periods during the conversation, AMR-WB also supports Voice Activity
Detection (VAD) and Discontinuous Transmission (DTX) which are also used by EFR
and AMR. During times of no voice activity, Silence Descriptor (SID) frames are
sent only once every 160 milliseconds with which the receiver can recreate the
sender’s background noise in order to avoid a “dead channel” . This
results in an average bandwidth requirement of only 1.75 kbit/s. A detailed
codec description can be found in [4].

Network Issues: Getting Rid of Tandems and
Transcoders

The main
issue with the introduction of AMR-WB in operational networks are the
transcoding units. These are used to convert the EFR or AMR speech codecs used
in the radio network to the standard 64 kbit/s PCM codec which uses a sampling rate of 8 kHz per second. Therefore, it is necessary to
enhance networks as well so that they detect that both sender and receiver are
AMR-WB capable. In such a case, transcoders in the network have to be
deactivated to create a transparent connection. This is called Transcoder Free
Operation (TrFO) in UMTS and Tandem Free Operation (TFO) in GSM. For details on
TrFO and TFO take a look at this blog entry.

Availability

Even though
AMR-WB has already been standardized a couple of years now, it’s not out there yet. There are some indications though that
things are moving forward, like for example a recent AMR-WB test of T-Mobile Germany and
Ericsson in Germany.
Take a look at the press report here.

 

References

[1] 3GPP TS
26.171, Adaptive Multi-Rate – Wideband (AMR-WB) speech codec; General
description

[2] ITU-T G.722.2

[3] Pasi
Ojala, et al., “The Adaptive Multirate Wideband Speech Codec: System
Characteristics, Quality Advances, and Deployment Strategies”, IEEE
Communications Magazine, May 2006

[4] B.
Bessette et al., “The AMR-WB codec”, IEEE transactions, vol. 10, no. 8,
November 2002

Rudy De Waele of m-trends.org has written a very comprehensive article on Mobile 2.0 which is now featured on Read/WriteWeb. Lot’s of information about Mobile 2.0 is already out there in the web and this article combines and summarizes the current discussion and contains a lot of links for further reading. Highly recommended!

Next Tuesday, December 12th 2006, the bidding for WiMAX licenses in Germany will finally commence. Updates throughout the bidding process will be published life on the Internet at the Website of the Bundesnetzagentur. Here are some facts behind the auction:

Technology Neutrality

The licenses being auctioned are not reserved for a special technology. Thus, the title of this entry is not quite correct. However, it is expected that WiMAX will be the technology used by companies interested in this spectrum to provide broadband wireless access.

Bidders

It’s not quite clear yet who is going to bid for the licenses, it seems to be a well kept secret by the Bundesnetzagentur until Tuesday morning. The Deutsche Breitband Dienste GmbH, also known as DSLonAir, has publicly stated that they will participate, so at least one contender is known. They’ve also publicly stated that they are interested in getting a nationwide license.

Regional Licenses and Coverage Commitments

In total, four licenses will be auctioned for 28 regions. In order to provide nationwide service a company needs to get a license in all regions. The starting price for a region depends on the population density and prices vary from 300.000 euros to about 1.8 million euros per region. To get a license for all regions the starting price of the auction is about 16 million euros. As there are four licenses per region, the minimal revenue for the state, should all licenses in all regions be taken, is 64 million euros. Licensees are required to cover at least 15% of the towns in each region by the end of 2009 and 25% of the towns at the end of 2012.

Frequency Bands Being Auctioned

Each license covers a paired 21 MHz channel, i.e. two 21 MHz channels with a duplex distance of 100 MHz between 3410 – 3494 MHz and 3510 – 3594 MHz. It is left to the digression of the company using the frequencies to use frequency division duplexing (FDD) systems which requires paired spectrum or if time division duplexing (TDD) is used which does not require paired channels. According to a recent Intel Whitepaper (page 8), WiMAX 802.16e will use TDD in this frequency band. The white paper also states that in this frequency band channel bandwidths of 5 and 10 MHz are specified. This means that a licensee can operate four independent channels with one license.

Auction Result Depends on Competition

As except for one company the names of the bidders are not yet known it remains to be seen how many of the interested parties will go for a full nationwide coverage and which are only interested to cover certain regions. As there are four licenses per region at least five of the six companies would have to bid in each region in order to significantly increase the minimal price. So what would be a price for the licenses which would still be realistic? Well, let’s make a quick and dirty calculation here: Let’s assume all four licenses are awarded in all regions and the companies are able to get 10% of the population of Germany, which would be 8 million people, to subscribe to services over a period of 15 years. Let’s further say that licenses should cost no more than 1 euro per subscriber per month. Let’s also leave all other complicated stuff like interest, network ramp up, etc. out of the equation for the moment. Thus, the maximum sum bidders would be prepared to pay equals 8 million subscribers * 1 euro * 12 months * 15 years = 1.4 billion euros. This would be 360 million euros per licensee. Sounds like a huge sum, but compared to the 50 billion euros spent for UMTS licenses it would still be a bargain.

Of course the three big unknowns in the equation are if there is enough competition to get such a sum, if companies are willing to shed such a lot of money up front and of course if WiMAX networks will be attractive enough to get a penetration of 10% of the population. Much depends on how these networks will offer their services. For more on this, take a look on my entry on "WiMAX Culture: Hotspot or 3G".

Quite a number of 3G UMTS networks have been upgraded over the past year to HSDPA (High Speed Downlink Packet Access) which boosts data transmission rates from about 384 kbit/s to over 1 MBit/s in a first step. The second step of HSDPA, with data rates of over 3 MBit/s, has also gone life in some of networks already. So far, there were only PC data cards which were HSDPA capable. But now it looks like the first HSDPA handsets are close to market readiness.

In Europe and Asia, the Nokia N95 for example will surely take full advantage of HSDPA with it’s built in multimedia and Internet applications. For the US, where different frequencies are used, it looks like Samsung will take the lead with a new HSDPA smartphone called "Blackjack" which will be available from Cingular. The video below from Mobilytsite compares download speeds of HSDPA (Cingular), EVDO (Sprint) and EDGE (Cingular).

As you can see in the video, the download speed is faster than what I can get over my 1 MBit/s ADSL line at home. Amazing! The other plus of the device is the built in EDGE (Enhanced Data Rates for GSM Evolution) support so the smartphone is also usable in areas with no 3.5G coverage without being crippled by low GPRS speeds. With these and other phones surely in the pipeline of Samsung and other companies, it looks like we could soon see some real traffic in the UMTS networks in the US which so far have not been used much due to a lack of market adapted handsets. Great! Now let’s work on dual frequency UMTS handsets for international roaming!

Background for the story via the 3G Portal, Moveable Beast and Mobilitysite

It was back in February this year when I first met Stuart Mudie, co-author together with Derek Torres of  The Unofficial Guide to Windows Vista in Barcelona during the 3GSMWorldCongress. Since then, we’ve met a couple of times again in Paris and it was quite interesting to exchange thoughts on how our book projects were advancing. So it looks like his book will be available shortly and I have gladly agreed to host the Unofficial Guide to Windows Vista blog tour for an entry on Vista’s Wifi capabilities. Over to Derek:

First, I’d like to thank Martin for being a gracious host  and letting me spend some time discussing Wi-Fi capabilities in the new Windows Vista. Let’s take a look at the basics!
   

It’s easy to make the case that Windows Vista is all about  wireless. Instead of having to waste time with Network Connections like in  Windows XP, you can handle most of your Wi-Fi configuration through the new Network Center in Windows Vista.

Let’s be honest; during the Beta phase of Windows Vista,  Wi-Fi was absolutely atrocious. Neither Stuart or I were able to connect over a  wireless connection and were confined to the length of our network cables. That’s  not totally unexpected, after all, this was Beta. By the later stages of Vista  development, Microsoft was on the right path.   Using a USB wireless adapter (Netgear WG111T), Windows Vista immediately  recognized the software and installed all the necessary drivers without me  having to insert an installation CD. I was online in a matter of minutes.

What’s particularly interesting about Wi-Fi in Windows Vista is that it goes well beyond using your computer around the house or in the garden;  in fact, what’s most interesting about Wi-Fi is not how your computer can use  it, but what other components can use it!

If you’ve got an Xbox 360 or a digital media receiver, you can use those with Windows Vista over a wireless (or wired if need be)  connection. Instead of enjoying your laptop anywhere in your house, you can use  your Xbox 360 to broadcast media – including music, movies, and pictures – from  your computer to another room in the house. You can also use it to enjoy  digital music across the house using Windows Vista’s Wi-Fi capabilities.

Windows Vista certainly helped up the ante in terms of Wi-Fi  capabilities; not only is Wi-Fi more and more exciting, but it’s definitely more useful!

Derek Torres, co-author of the Unofficial Guide  to Windows Vista
   

 

One of the many new things I relish about the Nokia N93 is that it let’s me download podcasts with the podcast catcher application directly to the phone via Wifi. Previously I had to download podcasts to the PC first and then had to sideload them to the phone either via the USB cable or by putting the phone’s memory card into the card reader on my PC.

Things are much simpler now: New podcast feeds can be discovered in the application via the search function, no PC needed. Should you stumble over a good podcast feed on the PC, you can also type in the feed’s URL in the unlikely case the search on the phone doesn’t find it. With a push of a button the application updates all bookmarked feeds and new podcasts can be selected and downloaded afterwards. I’ve got a 1 MBit/s DSL line at home and I was quite astonished that the phone is easily able to fully use the bandwidth.

While I’ve set applications like the web browser to always ask which network connection to use, I’ve set the podcast catcher to always use the Wireless LAN connection without asking. Downloading a 50 MB video podcast via 3G is of course possible, but somewhat expensive.

Here is my current list of podcasts I’ve subscribed to:

• The All About Symbian Podcast
• The All About Symbian Video Podcast
• The Smartphone Show
• Computer Club 2 (A German tech magazine!)
• The Voice of S60
• The French Pod Class (vraiment encroyable…)

Know of similar ones? Please let me know!

P.S.: Steven Stewart, product manager for the application recently gave an
interview to Phil of the Voice of S60. Here’s the link to the
podcast. Very insightful.

The recent Nokia World had a couple of very interesting keynote speeches which Jyri Engeström has summarized very nicely on his blog. Videos of the keynotes can be found here and the Nokia World blog can be found here.

Nokia’s Anssi Vanjoki has always interesting stories to tell. Some might think he’s talking about tomorrow when describing mobile usage scenarios. But in fact, it’s all possible today. Take my day as an example:

I got up, updated my private eMails on my N93 over Wifi at home, downloaded some podcasts to the phone to have something to listen to while on the way to the airport in the afternoon, side loaded some mobile transcoded TV shows I like from the PC to the phone to additionally have something to watch. Finally before leaving the house I updated my weather forecast widget and my blog roll on the phone over Wifi and my DSL line. On the way I "consumed" most of the content while sitting in a train and also jumped right into very interesting articles in my blogroll while listening to some music from my collection on the phone. Every now and then, I followed a link in one of the blog entries with the phones web browser over the 3G network to get some background information on a topic. While waiting at the airport I also checked some news web sites to see what’s going on outside the cyber space. After so much consumption it’s good to be a bit productive as well and so I answered some of those eMails which have accumulated over the week. A foldable keyboard for quick typing is a real helper for this. Arriving in Paris I checked my eMails again over the wireless network while sitting in the suburban train and arriving at my destination I downloaded the latest news videocast of my favourite TV station over Wifi to the phone to watch the news while having dinner.

And then there’s the new bed I ordered online at Ikea tonight. But I have to admit that I didn’t do that on the phone but used the PC for a change…

P.S.: And yes, I made two phone calls with the phone multimedia computer while traveling. When arriving at my destination in Paris I used a dedicated wireless VoIP SIP phone to call back to Germany. The N93 has a SIP stack but as of yet no SIP client that makes use of it. Hello Nokia, here’s your chance to complete my experience.

And here’s a flash message on very short notice: It looks like December 4th will see the first Mobile Monday in Germany. The inaugural session will take place in Düsseldorf. One of the founders seems to be Russell Buckley who writes over at Mobhappy. Strange, I read nothing about it on his blog or elsewhere until I stumbled over it today. They’ve got a very interesting speaker lineup for the first session including Russell and Ajit Jaokar, fellow book author and blogger over at the OpenGardens blog. So spread the word and go if you can still do it on such short notice, it is going to be great! Unfortunately for me, I’ll be in Paris on Monday and won’t be able to come.

Got an N93 or other N-series phone and like to convert your videos and TV recordings for mobile viewing? It seems it is simpler than I initially thought. Take a look at the free MediaCoder for Windows which converts just about any video format into what’s required for mobile. Converting a file is as simple as selecting the input file and hitting the start button in the application.

Converting videos for the N93 works just perfectly with the default settings in the program for the iPod video format. The N70 has it’s own setting as it doesn’t seem to support the 25 frames per second and high encoding rate of the N93 and iPod.

I made a first test by converting a WMV coded one hour TV show I recorded via an online video recorder into mpeg4. Input file size: 387MB. Output file size: about 200MB. Good that I’ve got that 2GB flash card in my phone… Video quality on the N93 is excellent, even the smallest details and texts can still be read on the screen. Conversion time for the one hour show was about thirty minutes on my 1.9 GHz Centrino notebook. Final test step: I’ve played the recording on the N93 and detected no problems, no glitches, no crashed. Excellent!

Several years after the start of 3G and some operators still
struggle with their 3G network engineering. Unbelievable but true.

Latest
example: Wind in Milano, Italy. I’ve been using the Wind network already last
year in Roma for several weeks and enjoyed great 3G coverage and performance. A year
later, I am in Milano, a city in Northern Italy, and the situation is
completely different. Last week when I was here the 3G network was completely
unusable, due to packet drop rates of 30% or more. This week the situation has
improved but it still is nowhere where it should be.

Over the weekend I had some time to take a closer look what was
going on. While at first I suspected that they had some timer and threshold
problems that makes the connection switch between dedicated and common
channels, I quickly saw that this was not the case. Instead, there is frequent
measurement control messaging, traffic channel reconfiguration and active
setup updates. Every time the channel is reconfigured, packets are either lost
or delayed for a second or two which slows down the connection considerably.
After a while this starts a chain reaction as sometimes web page downloads
become so slow that the network decides to switch the connection onto a common
channel. This again provokes packet delays. It doesn’t seem to be a single
mobile issue as it happens with three different phones. Very strange as I am in
a place with excellent network coverage. So Wind, please get out there and fix
this!

But then, Wind’s also got EDGE coverage in Milano, which
works very well… Shame I have to fall back on 2.5G because their 3G network
engineering is flawed…