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Interesting to see how the bottleneck of my Internet connection at home has been shifting recently. With my new 25 MBit/s VDSL connection I am having difficulties shuffling peak data rates over my Wi-Fi network. So far with a 6 MBit/s ADSL connection that was no problem even for my notebook with a 802.11g adapter and a throughput of 21 MBit/s under the best of conditions.

For a 25 MBit/s downlink and 5 MBit/s uplink, however, that's not enough anymore. I've upgraded to 802.11n but even so I find it difficult to really squeeze the 25 MBit/s out of the wireless link. The 2.4 GHz band is quite crowded and the Wi-Fi access point is in another room so I don't get the signal conditions necessary for the highest transmission rates. I've tried the 5 GHz band that both the access point and the notebook support but the attenuation of the walls between my office and the router make the throughput even worse.

On the other hand, you first need to find a host on the Internet that delivers data at such high speed. In practice to really saturate the line several things need to go on in parallel. Not too difficult with kids using the connection, too I suppose…

Even when a mobile device just sits there and seemingly doesn't doesn't do a whole lot it is nevertheless quite busy every now and then internally to check the signal strength and quality of the current cell and those around it to make sure it never looses contact to the network even if the user roams around. I've recently came across a good description of which values are actually measured in this book and thought I'd put together an ultra brief summary:

GSM

Here, the world is still quite simple. Once the mobile has found a cell it keeps monitoring it's received signal power and computes the Received Signal Strength Indicator (RSSI) over the complete carrier frequency (200 kHz). Neighboring cells use different frequencies and the same value is calculated for those as well.

UMTS

Here, things get a bit more complicated as all cells use the same frequency. As a result not only the received signal strength is important but also the general noise level on the carrier. In the end, what good does it do to you when the overall signal level is strong but most of it is interference? That's why there are three values: 

• RSCP: The Received Signal Code Power: That's the power level the pilot channel of a cell is received with and usually expressed in dBm (mW on a logarithmic scale). With this parameter, different cells using the same carrier can be compared and handover or cell reselection decisions can be taken.

• RSSI: In UMTS that's the signal power over the complete 5 MHz carrier which includes all components received, including the signals from the current and neighboring cells on the same frequency.

• EcNo: That's the received energy per chip (Ec) of the pilot channel divided by the total noise power density (No). In other words the EcNo is the RSCP divided by the RSSI. And again in other words: The better this value the better can a signal of a cell be distinguished from the overall noise. The EcNo is usually expressed in dB as it's a relative value. The value is negative as the RSCP is smaller than the total received power. As the RSCP this value can be used to compare different cells on the same carrier and handover or cell reselection decisions can be taken.

LTE

LTE networks also use the same carrier frequency in neighboring cells so again the signal level and interference are important:

• RSRP: That's the Received Power of the Reference Signal.

• RSSI: That's the total received power including Interference from neighboring cells and other sources.

• RSRQ: That's the Reference Signal Received Quality and equals the RSRP divided by the RSSI. The better this value the better can the signal of the cell be received against the interference generated by other cells.

Quite a lot of similarities between UMTS and LTE from a high level point of view even though the values are measured in quite a different way due to the different air interface natures (WCDMA vs. OFDMA).

This is the strangest setup of a conference call I have been in for a while: A Skype video session with high quality audio over speakers and a third person, also on the other end, part of the conversation over a mobile phone as part of the call via loudspeaker/hands-free mode. The person on the other end of the line didn't even realize I was not in the room but a thousand kilometers away. On my end, the speech quality of the hands-free mode on the other end was also pretty much the same as if the phone was on my end. Speaks for Skype's audio codec and the echo cancellation of all devices.

Observation of the day:

In the past, I 'had to' do many things at home because I could not do them while commuting, because I couldn't take a sufficiently small computer with me and had no Internet connection.

Today, I 'don't do' the same things at home because I can as well do them while commuting with a netbook and a 3G Internet connection.

In other words a total reversal of thinking and behavior. And to the better I think!

And here a quick not to myself and to all of those who sometimes need an overview of all the functionalities that have been changed and added in the different 3GPP Releases since Release 99. Here's a link to one document per Release which contains a 'short' one page description of each new work item and the updated TS and TR documents behind it. I know, there are also whitepapers available on the net describing the different 3GPP releases and they are probably much easier to read. However, they usually don't contain references to the specification documents and they don't contain all the features.

An electronic payment story today: The credit card industry has been through quite some pain in Germany the past couple of weeks with a year 2010 bug hampering transactions at teller machines and in shops. But here's some good news I wanted to post long before but forgot:

For many years electronic payment in France was a pain for me as the chip on my German EC/maestro card didn't work there. I always had to tell shop assistants not to use the chip but to swipe the card through to read the magnetic stripe. I got so frustrated that I reverted to paying with cash or with a credit card that did not yet have a chip.

So after another little glitch late last year when credit card information was supposedly stolen in Spain, credit card companies around the world replaced affected cards in a hurry. Probably due to having been at the Mobile World Congress in Barcelona I was one those customers getting a replacement card. This time it contained a chip and this one now works in France as well. Great, at least from this perspective the credit card industry finally gets their act together. Now I can blend in again…

Let's hope the 2010 bug doesn't ruin it again… Just makes me wonder where we are with mobile payment in Europe these days. Probably still nowhere.

I'm back at home after a short visit to Norway this week to give a talk at the 2nd anniversary meeting of MoMo Oslo on Monday. It's been a great trip and a great MoMo with about 150-200 people showing up for the event. With Steinar Svalesen, Ajit Jaokar, Tomi Ahonen, Andrew Grill and Karine Storaker Braaten I think we offered a diverse program and despite the long program of over 3 hours the hall was still packed at the end. Thanks very much to Shaun Thanki for making it happen! Thanks also to all the people taking the time to talk to me after the presentation I learnt a lot about life and mobile in Norway!

No need to take it from me though, all presentations, the video and pictures can be found online:

• The pictures
• The videos
• Steinar's presentation on innovation in telecom & media
• My presentation on the future of fixed and mobile networks
• Ajit's presentation on understanding the impact of open mobile
• Tomi's presentation on mobile social media & networking
• Andrew's presentation on key trends in mobile marketing
• Karine's presentation of MoMo Norway online community

I'd say that's excellent online coverage of the event!

And I learnt a couple of mobile things while walking a bit through Oslo: Two things are hard to find: Mobile phone stores from network operators and base station antennas. Both are very well hidden and you have to look closely 🙂 Also, I didn't see or hear anything of the LTE network supposedly running in Oslo!?

Picture above courtesy of MoMo Norways Flickr stream.

In my latest book I have not only described how IMS works in mobile networks in Chapter 4 but I also gave a short introduction to the fixed line counterpart which was initially specified by TISPAN before the activities were merged in 3GPP. I've been wondering a bit lately if it's going to be easier to implement IMS in fixed line networks compared to mobile networks. Here's what I think is much easier:

• Legacy Device Reuse: In mobile networks, IMS requires mobile phones with IMS clients and a sophisticated packet switched radio network. In fixed line, things are much simpler. Customers just keep the analog phones they have today and either plug them into an analog to SIP converter that is part of their DSL or cable modem at home. If the analog to SIP converter is in the next street cabinet, the user doesn't have to do anything. To him IMS will be completely transparent.

• No interworking with a legacy network from a user point of view: Once a line is physically connected to the IMS system, it's just using that system. Period. In wireless, mobile phones often fall back to GSM where IMS is not available. In that case the legacy circuit switched system has to be used or at least a circuit bearer next to the IMS packet switched signaling. Not pretty and very complicated.

• No handovers to CS: A fixed line is a fixed line, no handover of an ongoing call to a circuit switched channel is required as a fixed line device never leaves it's place and network of origin. Compare that to wireless IMS where a mobile can leave the UMTS or LTE coverage area and has to be switched to a circuit switched bearer before contact is lost. A nightmare in practice.

• Different Mindset: In wireless, IMS is the IP MULTIMEDIA subsystem and many see voice telephony as just one service to run over it. In the fixed line world, I have the impression that for most people the IMS is there to put voice calls on an IP bearer (PSTN and ISDN emulation service) but that's pretty much it. No big dreams of IMS as the universal service platform for everyone and everything. 

Thoughts, anyone?

Tomorrow's going to be an interesting day for me as I'll be in Oslo at the Mobile Monday focusing this time on Mobile Social Media and Telecoms 2.0. Among others, Tomi Ahonen, Ajit Jaokar and Andrew Grill will also be there, so it's going to be an interesting mix of thoughts flowing in from all over the mobile space. Very much looking forward to it, thanks to Shaun Thanki for organizing the event! If you are in or around Oslo tomorrow, I'd be happy to meet up!

These days I see a lot of talk in the press about rising wireless data consumption. To make things more spectacular, things don't double, no they rise by 100% (or by 200% or by 400% [insert your own % here]). Sounds much more dramatic, no? But what's even worse is that without a base from which the rise is calculated, it's completely meaningless. And usually that base is not given.

Here's an example: Let's say network use was 1%. Doubling that brings the network use to 2%. That's a lot isn't it? 100% more but the network is still sitting around doing pretty much nothing. But 100% more…(Note: Agreed, I've selected the other extreme for my example here…)

Also, such numbers kind of suggest that things will continue to grow at the same rate or even faster and the numbers are set in a light that suggests operators are in real trouble in the very near future. But that's also a wrong assumption. At some point everybody has 5 phones, several 3G dongles, etc. and bandwidth needs will mainly grow with more use from the same number of people and devices. And how much growth that requires is a different story again.

But one thing is clear, mobile operators need to increase the capacity of their networks over time to keep up with the demand. But then that's not much different from what fixed line operators do to keep up with the demand for high speed Internet connections. Maybe they have to do even more with digging up roads, putting new fibers in, etc. From a different point of view they are even doing the ground work for wireless network capacity extensions as they will also benefit from the fibers in the ground.