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When I was recently in a Starbucks and wanted to get some work done over a coffee I was quite surprised that despite good cellular network coverage, the Internet connection from my smartphone to the PC via Wi-Fi tethering was behaving very strangely. Needless to say that I started to investigate…

As I wanted to download a firmware image of a couple of hundred megabits I counted on the LTE network to give me adequate speed. But all I got was half a megabit per second and very erratic round trip delay times. Moving the smartphone sometimes helped for a second or two but then data rates were done and delay was up once again. O.K. so perhaps an LTE problem I thought, let's switch to UMTS. Strangely enough I encountered exactly the same problem there!? O.k. so perhaps the phone has a problem, lets restart it. But no, again the same problem afterward!?

Now I was a bit at a loss for a moment, what else could it be? Then I realized that there is one more wireless link, i.e. the  Wi-Fi connection between the smartphone and the PC. Perhaps something strange is going on there!? So I disabled auto-channel selection in the tethering configuration and manually set a channel. And voila, LTE became lightning fast, the download of the firmware image I needed started to run at 20 Mbit/s and everything was o.k. Interesting, something must have interfered on the 2.4 GHz channel the smartphone started the tethering hotspot on. Something to remember.

Some interesting statistics for this blog today. Here's a screenshot showing the top ten countries from where my blog is read. Unsurprisingly the US is due to its size and the language of the blog number one and the UK is number three. But apart from that the list is full of surprises. India is on number two of the list, and I can imagine it's due to the IT and telecoms industry there so I can understand that. But look at Sweden and Finland in place 4 and 5 respectively. With around 10 and 5 million people living in these countries it's quite surprising that they appear in the list. Ericsson and Nokia perhaps? Korea takes 10th place in the list, hello Samsung and LG I would imagine. China is completely missing and although I am not quite sure I think that's probably the great firewall blocking Typepad content…

Faintly similing as usual with a bit of sarcasm over the worthless Wi-Fi Internet access in Thalys trains I noticed that French and Belgian network operators have made their homework in recent years and have  installed 3G network coverage along the high speed train line. So I turned off the lousy on-board Wi-Fi and switched over to 3G to see how it fares at speeds of 300 km/h.

To my surprise it did really well. In most places between Paris and Brussels, I could get speeds of around half a megabit per second and web surfing and emailing felt hyper-fast. Only a slight hassle: At this speed you don't see the border sign between France and Belgium, i.e. you don't quite know when to reselect to another network.

There are two take aways from this: The first one is that this proves that UMTS works well at 300 km/h. And the second: Where there is a will, there's a way (and coverage)!

Once upon a time, not too long ago,
actually, perhaps 12 years ago or so, I got my first 1 Mbit/s ADSL
line at home. 1 Mbit/s in the downlink direction, mind you, and a
few hundred kilobit/s in the uplink direction. But it was fast,
really fast, compared to my previous modem and ISDN connections and
besides email, accessing information on the web designed for modem
speeds was the main use.

Fast forward to today and I argue that
especially for a family that same speed of 1 Mbit/s I had then in the
downlink direction is by far insufficient in the uplink direction
today. A single Skype video connection already saturates a 1 Mbit/s
uplink easily leaving little room for uplink communication of other
family members without compromsing video quality. Accessing files
stored at home remotely is also very limited with such an uplink. In
other words, I am quite happy that I have a VDSL line at home with a
5 Mbit/s uplink that I could easily upgrade to 10 Mbit/s if I wanted
to. However, I am still amazed that in some places, people get 20
Mbit/s ADSL lines with just 1 Mbit/s in the uplink direction.

At first I thought this was network
operator policy driven (yes, always assume the worst) but the ADSL
entry in Wikipedia reveals that even for ADSL2+ (without the Annex M
published in 2008), only 1 MBit/s uplink speeds were defined. And
even with Annex M, uplink speeds only reach 3.3 Mbit/s at best. In
other words, many will feel the consequences in the next couple of
years as their offspring uses the network ever more. Welcome to the
uplink bottleneck!

Being on the road quite a bit I have the need every now and then to use a printer or scanner at a friends place. When it comes to Windows, this is usually a bit of a dangerous thing to do if you are like me and like to keep the PC clean and fast. In the best case, the manufacturers CD is not needed and Windows finds a default printer driver after a
couple of endless minutes of hard drive activities and online driver
downloads. In the worst case, one has to resort to the original software of the manufacturer, which means installing hundreds of megabytes
of printer drivers and utilities of doubtful quality. Fortunately, I use Ubuntu Linux (12.04) on my PC and I was quite surprised at how simple and fast this has become. Read on for the details.

In the first instance I had to connect to to a simple HP color printer over USB. I can't remember the model anymore, probably because it was rather a non-installation as Ubuntu discovered the printer when I plugged it in and automatically installed the correct printer driver. I was quite surprised when I went to the printer settings to find that it was already installed. I guess it can't get any better than that…

A couple of weeks later I was faced with a brand new Canon Pixma MG2255, a printer, scanner and copier combination. Ubunutu's Canon support for this particular device was not as good as for the HP above as drivers were not installed automatically. When trying manually I managed to get a driver installed from the default list that would print a page or two but then stop working. A quick check on the net revealed that this is a common problem with an easy fix by getting the Linux drivers from Canon. Instead of downloading several hundred megabytes the drivers , it's size was only around 2 megabytes and installation took about a minute by double clicking on the included installation script.

When it came to the scanner part of the device I was a bit disappointed that it wouldn't work with xsane like my HP scanner at home. But Canon at least supplies its own Linux based scanner program (scangearmp), again via an easy installation archive. It's a bit of a basic scanning program that works quite well to scan single pages into png or pdf format but not much else. There's no option to collate several pages into a single PDF file and for each page a file name has to be given separately. Hm, would that really have been much extra work? Anyway, for manual multi-page scans a simple Linux shell command converts all PNG output files in a directory into a single PDF file with a good picture quality and reasonable file size (around 1.5 – 2 Mbytes per page):

convert *.png -resize 1020×1320 -units PixelsPerInch -density 120×120 scan.pdf

Agreed, a bit of tinkering is involved, but I much prefer that to my PC accumulating unused Windows printer utilities from different vendors that are difficult to impossible to get rid of again completely once not used anymore.

Back in 2009 I published the first edition of my Beyond 3G book giving an introduction to the technology of wireless networks, capacity forecasting, mobile voice, mobile device hardware and also the software running on them. It's been a tremendous success so I decided to update it and publish a second edition with a slightly changed title to address the launch of LTE networks: "3G, 4G and Beyond – Bringing Networks, Devices and the Web Together".

It is quite amazing what has changed since 2009. Many of the predictions I have made at the time have become a reality and new challenges and opportunities have arisen. While LTE was only on the distant horizon when the first edition was published, it is a reality today and HSPA networks have undergone a significant evolution as well. New spectrum bands have been assigned and auctioned in the meantime and many network operators around the globe have since made use of them to increase the coverage and capacity of their networks.

Perhaps the biggest evolution over the past five years has been on the mobile device side. Mobile operating systems dominating the market only a few years ago have almost vanished and new entrants such as Android and iOS have taken the mobile world by storm. On the web and application programming side, significant advances triggered an update of this chapter as well and I've even included a section that introduces Android programming to the reader.

As a consequence, about half the content of the previous edition of this book was updated or entirely rewritten to reflect the current state of the art and to give an outlook of what is to come in the next five years.

It's been fun and, needless to say, a tremendous amount of work to radically update the book this way. But besides staying up to date in all the different areas discussed in the book it's been an interesting way to experience the change of 3 years in one effort. As always, comments are very welcome and I am looking forward to the changes coming in the next couple of years.

Before the German LTE spectrum auctions almost exactly three years ago, pretty much everyone I talked to agreed that the 2600 MHz range is the beachfront property for LTE due to the large 20 MHz channels it was offering. Yes, 800 MHz spectrum was interesting as well but not very much loved due to the obligations to deploy on the countryside first. Few people spoke of the 1800 MHz band and actually saw it as a side show. Fast forward to 2013 with three LTE networks now deployed in Cologne where I live. Two of the three networks run on 10 MHz channels in the 800 MHz band because countryside coverage obligations have been met. And the third one is using a 20 MHz channel with twice the speed in the initially little observed 1800 MHz band which has drawn a lot of attention in the meantime all over Europe. And what about the 2600 MHz beachfront property? Nowhere to be seen for the moment. An interesting change of tides.

Telegeography has recently published an update of their zoomable submarine cable map with chronological information and overall lit capacity. Especially interesting for me is the the graph at the bottom which shows a sudden strong increase of used (lit) capacity in 2007 and onwards compared to previous years. To get political for a moment, I also found it quite interesting that the name of the state of Isreal is missing on the map while even small countries such as Luxembourg have their name on the map!? I wonder if that has something to do with the sponsor? Back to technology: For more detailed information on individual cables I can also recommend Greg's cable map and for some technical nuggets have a look at my post from back in January 2012.

One of the limitations of Solid State Drives is that the Flash cells can’t be rewritten indefinitely. The cells on the SSD drive I recently bought can only be rewritten around 1000 times. That doesn’t sound like much but wear leveling ensures that desktop users with normal use don’t have to worry about it. AnandTech has a good analysis on how wear leveling works and how long I should be able to use my SSD here. According to these calculations, my 500 GB version should be good for at least 14 years, based on a daily write amount of 10 GB and and a write amplification factor of 10. So while I believe those numbers I was wondering how how much data I actually write to disk on average per day. As I use Ubuntu Linux I found a couple of interesting counters that shed some more light on this:

The first one is /proc/diskstats. It lists all block devices and lots of counters for them. For my SDD which is the ‘sda’ device in the list, field 7 contains the number of sectors written since boot time. A sector is 512 bytes so one can easily calculate the number of bytes written since power on.

The second is /sys/fs/ext4/sda1/lifetime_write_kbytes. As the name suggests this counter contains the overall total and is only available for ext4 formated volumes. Since I only use one volume and no swap partition (due to my 8 GBs of RAM) these two counters should actually increase by the same value over time.

Here’s a command line displays both counters and strips away all other information the commands also output:

date; awk '/sda/ {print $3"\t"$10 / 2 / 1024}' /proc/diskstats; cat /sys/fs/ext4/sda1/lifetime_write_kbytes

The result: I am using this computer for about half a year now and the total lifetime writes give me 922 GB. Divided by approx. 180 days, that’s approx. 5 GB of data written to the drive per day on average. The data written since power on gives me a similar value, around 4 GB per day. Comparing that to the 10 GB a day used in the AnandTech post for estimating my SSD lifetime, I should be good for twice their calculated amount, i.e. no write issues due to wear out of the flash cells due to writing for the next 30 years. A comforting result.

So while it is comforting that my average daily use is less than what was used in AnandTech’s caclulations, I’d still like to understand a bit better why my daily average is around 5 GB of data written to the drive as it seems to be quite a lot and I am not using the drive (or the sda1 volume queried) for memory swapping at all.

This post over at the radio access blog has made me think a bit of how many users in Cell-DCH state could be supported simultaneously on HSDPA. As the post analyzes correctly, each user requires a Dedicated Physical Control Channel in the downlink direction with a spreading factor of 256. That means that there are a maximum number of 256 such channels that could be used but unfortunately that wouldn't leave spreading codes for any other use, including the high speed data channels themselves. So in practice there must be significantly fewer users to still have enough codes for other purposes such as the HS channels and also for voice calls. So we end up with quite a small number and it will be more and more difficult to serve the 2000 subscribers with 3 sector base stations if there can only be a fraction of them active at the same time. So fast forward to the fractional DPCCH feature also described in the blog post above that bundles 10 control channels on a single spreading code and it's quite obvious how significant this feature will become in the future as smartphones and connected apps spread ever further.