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Here's an interesting link to a report on Light Reading on how AT&T sees their backhaul networks for fixed and wireless networks combining and evolving as we head into the future. Perfect opportunities for converged fixed/wireless network operators to reduce cost while at the same time increasing available bandwidth. An interesting and multi-faceted read.

As some of you might remember I am running Ubuntu on my netbook (see here, here and here). One of the few disadvantages is that natively, only few 3G sticks were supported in Ubuntu 9.04 Jaunty, which I installed last year. Only one of four USB sticks I tried was supported at the time. But now with Ubuntu 10.04 Lucid, all those four sticks I tried (three from Huawei, one from ZTE) are supported without any additional drivers. Also, the PIN entry works flawlessly now so it looks like in the past 12 months, they've quite done some work on their wireless broadband implementation. Well done, thanks!

In most countries around the world there is only one or at most two 3G bands in use. In Europe, Africa and Asia, 2100 MHz is the prime band (not counting China) and a few countries such as France and Finland also use the 900 MHz band for 3G. But there is also regions where 3G is used in three bands: In North America it is 850, 1900 MHz and 1700/2100 MHz. And in Australia it is 850, 900 and 2100 MHz. Any country you can think of in which more than 3 frequencies are used for UMTS?

A couple of days ago I wrote the "LTE Voice Takes a Break" post musing on the fact that for some time there hasn't been a lot of news on any of the proposed voice over LTE solutions, potentially because everyone is waiting for devices with which they can demonstrate their solution. But it seems the VOLGA-Forum has pressed ahead internally and continued working on its specs. The latest update now includes SIM-less emergency calling over VOLGA, making the solution even more robust by not even requiring a circuit switched network for such emergency situations. Also, they've introduced means to use the VOLGA architecture over HSPA, introduced optimized voice bearer routing (have to take a closer look as to exactly what that is, or maybe someone can leave a comment below) and have defined some APIs for LTE handsets (also not sure yet what they will be used for). So its good to see these incremental additions coming while everyone is waiting for LTE handsets.

What do you do as a network operator in places where hundreds and hundreds of people waiting in line and potentially tens of thousands on people visiting that place every day? Right, you make sure you have excellent network coverage in that spot to keep your customers happy while they are standing in line. There's your chance, the people are bored while waiting in line so it's a good opportunity to sell some voice minutes or some bits of data when your subscribers make good use of the idle time. Maybe they even take a picture and send it to mom via MMS!? But in some places of the world, clocks are ticking differently.

Recently I was up the Empire State Building in New York, which exactly resembles this scenario, except…, well, there's no network coverage up there from any GSM operator. And it's not that you are just there for a couple of minutes. If you come at the wrong time you probably have to wait more than an hour in a no network coverage area. I am stunned, really! Ah hold on yes, there was some sort of coverage, AT&T UMTS coverage was indicated on the iPhone of my neighbor. Very good reception was indicated but each time he wanted to use the phone the bars went away. Not sure what that was but a coverage that is not working is even worse than no coverage at all. Yes, I am not amused.

Just went through the specs on EPS trusted non-3GPP networks to find some details on CDMA to LTE interworking when I suddenly wondered if there is anyone at the moment besides Verizon who will need this kind of interworking!? While lots of network operators require GSM/UMTS/LTE interworking (handover, cell reselection, voice handovers, etc) there seem to be only few CDMA operators who might require the functionality. Any others come to your mind besides Verizon?

When talking about signal strengths, values are usually expressed in dBm, which is, according to Wikipedia 'an abbreviation for the power ratio in decibels  (dB) of the measured power referenced to one milliwatt (mW)'. In other words, dBm is a value for the power or signal strength on a logarithmic scale.

In practice, signal strengths between -60 and -90 dBm are encountered at the receive antenna of a mobile device. So how much is that actually? On the high end of the scale, -60 dBm equals 0.000000001 Watts, while – 90 dBm are 0.000000000001 Watts.

I find two things quite remarkable in these numbers: First, both values are very small, definitely not enough to power anything and its amazing that receivers can pick up such small signals. And secondly, the wide range a receiver has to adapt to as the weakest signal compared to the strongest signal in this example is 1000 times weaker.

Interesting news from mobile network operator "3" in Austria: Heise reports in this article that their monthly data volume is now at 700 Terabytes per month. According to Wikipedia they currently have about 1 million subscribers which makes this number even more interesting, as on average that would be 700 MB  per subscriber per month. Of course many of their subscribers only use the network for voice calls and SMS so imagine what the number must be for the typical mobile Internet user in their network. With Austria being a super competitive mobile network country and usage numbers way ahead of those in other countries it's a good indicator of what is possible and of things to come.

One cool feature of UMTS compared to GSM is that you can't hear the interaction with the network when the mobile device is close to a radio or telephone conference equipment. This is because while GSM transmits bursts whose transmit on/off changes can be picked up by such equipment, UMTS transmits continuously in the uplink direction and as a consequence no annoying clicking sounds can be heard. With the introduction of Continued Packet Connectivity (CPC), however, this will change to conserve power. So I am wondering if CPC devices will again produce some sort of a clicking noise in other audio equipment!? I hope not… And in case it does it would be nice if CPC could be deactivated in the device. I know, highly unlikely that such an option will be put into devices but then one never knows. If a 'sexy' name can be attached to it someone might just do it. How about 'stealth mode' or 'undisturbed meeting mode'. I am sure marketing departments can come up with something better.

I was in New York for a couple of days recently and as my N95-8GB (yes, I am a traditionalist) can only do UMTS 2100 MHz my voice calls and small screen Internet connectivity had to be content with the GSM network layer. But there are interesting things to discover here as well.

It looks like AT&T consistently uses AMR Half-Rate in the center of the city to double their voice capacity. All calls I established were always set-up with this codec. Also, AT&T uses both the 850 and 1900 MHz bands and if the mobile detects both, the network always handed the voice call over to a 1900 MHz carrier, even when the signal in the 850 MHz band was 30 db stronger. That could have many reasons, maybe they use the 1900 MHz band as a capacity layer and reserve the 850 MHz carriers for difficult terrain and indoor connections.

Speaking of difficult terrain: AT&T when you have a minute, have a radio team look at your coverage in Penn Station. Even when standing still, my calls in the underground station frequently dropped. Despite a high signal level, audio quality was horrible, which points to interference, and every couple of seconds, the call was handed over between the 850 and 1900 MHz layer and the traffic channel bounced between AMR Full-Rate and Half-Rate. Quite a frustrating experience.