WirelessMoves

One year after the first version of my experimental Android Program – Cell Logger – I have published version 2.0 with one major addition: It now uses the GPS receiver to also track the location of signal strength and cell changes. You might remember this and this blog post where I ran some tests with it in Germany and Korea.

If you are interested, you can download the APK for a direct install on the device via this link. The source code is available via this link. In Google Play, you'll find the app by searching for "Cell Logger 2".

Independently from installing directly or via Google play, it's a good idea to download the source zip file from this page as well as there's an extra folder inside that contains some useful information on how to use the generated KML/XML file for offline analysis with Google Maps or Openstreetmap.

And after the jump, some more detailed info. Agreed, as always with experimental projects, documentation etc. could be better 🙂 Nevertheless, enjoy.

License

Cell Logger is available as Open Source Android app using the GPL 2 or later version license. For details see the source code.

What does it do?

Cell Logger records date and time of signal strength changes, the cell's Location Area ID, Cell-ID and, if available, the GPS coordinates where a cell change from one cell to a new cell that has never been observed occurs. GPS coordinates will not be recorded for cell changes between cells that have already been observed to prevent ping-pong handovers in certain situations to be counted as real cell changes. On the display of the device all this information is shown real time including counters on the number of cell changes and the number of unique cell changes (i.e. without ping-pong).

Whenever a cell change occurs data is written to a file in the main directory on the mass storage partition of the device. The file name used for this is “cell-log-data.txt” and data is appended until the file is removed. The file output is buffered in memory until 2k of data have accumulated to prevent frequent write access to Flash memory. The file buffer is also written to the file when the app is moved to the background.

This document is accompanied by an Excel file that gives a description on the fields of the .txt file described above. For analysis it often makes sense to copy and past the data contained in the text file into the Excel spreadsheet.  Auto filters for each column have also been added for easy data evaluation.

When a unique cell change occurs and GPS information is available, the event will be logged into a separate file, “cell-change-log.kml”. The format is text/xml and can be used for import to Google maps (http://maps.google.com). A Google account is needed to use the “import” functionality on the website. As the app has no control when logging starts and stops, the XML header and footer need to be inserted after copying the file to a PC before data is imported to Google maps. The file “header-footer.kml” that accompanies this document contains the required XML structures for easy copy/paste to the KML file that is used for the maps import.

The Network Type that is recorded in each line is a number as given by Google's API. Here are some numbers and their meanings:

2 = GSM/GPRS/EDGE
3 = UMTS
8 and 15 = HSPA (some networks switch between 3 (idle) and 8/15 (DCH)
13 = LTE

The KML file uses three different styles to indicate the use of different network types. The numbers given by the Google IP are mapped as follows:

1,2=GSM is mapped to STYLE 2 and is then mapped to blue ballons in the KML header file.

3=LTE is mapped to STYLE3 and is then mapped to yellow balloons in the KML header file.

Everything else is mapped to STYLE 1 and is then mapped to red balloons in the KML header file

It is important to let the app run in the foreground at all times. It prevents the device to go to sleep mode, i.e. the display is always on to ensure it is supplied with location and cell information from the baseband processor. If put to the background (e.g. when going to the idle screen), GPS location tracking is disabled by the app and no cell information is recorded. Recording continues once the application is brought back to the foreground again.

After many years of using a 3G stick for my notebook on my daily commute I've finally made the switch to Wi-Fi tethering, either to an Android smartphone or an Android tablet, whatever I carry on a particular day. For the moment, it seems more convenient as that 3G stick requires some extra space which is at a premium in trains.

That makes me wonder if 3G sticks will have a future or if their will be completely replaced by Wi-Fi tethering, even more so because a 3G stick needs a separate SIM card which is usually a hassle and which often costs extra money. The few megabytes I use during my daily commute can easily be absorbed by my smartphone plan that does not exclude tethering use.

Speed wise I have not seen a difference between a 3G stick and smartphone tethering. Over both connections I can easily reach speeds well over 6 MBit/s, depending of course on cellular signal quality. Sure, dual-carrier sticks can go far beyond this speed but LTE smartphones with tethering capabilities are now on the market, taking away this advantage as well.

I've also noticed interesting Wi-Fi power saving mechanisms. While the ping round trip delay times are quite normal when tethering to my smartphone, they are around 300ms when tethering to the tablet. However, when I transfer more data over the tablet than just the ping packets, round trip delay times are down to the usual 60 ms again during the transfer and return immediately to 300 ms afterwards. This rules out cellular power saving schemes like Cell-FACH and Cell-PCH which take a much longer time to get activated. No disadvantage but I was a bit surprised when I saw the 300ms for the first time and initially thought something was wrong.

One thing that is an advantage as much as a disadvantage is that the smartphone or tablet runs on a battery vs. the 3G stick that takes the power from the notebook. On the positive side my PC runs a lot longer on a charge. My Lenovo Thinkpad requires about 12 Watts without the stick and an additional 3-4 Watts with the stick (depending on the type of 3G stick). This cuts the operation time by at least one and a half hours.

On the negative side I have to remember to activate/deactivate the Wi-Fi hotspot option on my smartphone once I arrive at work or at home. I wonder when we'll see an option to switch off the Wi-Fi hotspot functionality after a configurable time when no clients are active anymore.I faintly remember of already having seen such an option in a device but it deactivated the hotspot immediately after the last client had left. Not good for my train scenario in which every now and then suspend the notebook for a minute by closing the lid to answer a call or to show my ticket.

But even when switching off the Wi-Fi hotspot functionality after use the smartphone probably doesn't last a full day when using it for other tings, too, as a Wi-Fi/3G bridge for an hour a day with frequent data transfers requires quite some power. The tablet's got an advantage here due to its much bigger battery.

Another downside of the tethering solution is that in other scenarios such as libraries or at Starbucks two power sockets are required, one for the PC and one for the smartphone/tablet. Usually one is lucky if there is even one socket available.

But tethering is often cheaper than having an extra SIM for a 3G dongle which is why I think most people will not mind the drawbacks in some situations.

When it comes to cellular networks, Austria is one of the most advanced countries concerning network ubiquity, speed and low prices. To see how things evolve, a German mobile communication magazine together with a test house does an anual in-depth test of networks in Germany, Austria and Switzerland. Their reports of these activities are usually quite insightful. Here's a link to the ENGLISH version of the 2012 report for Austria. An interesting read that shows what's possible, even in a country where for around 20 euros a month there's so many voice minutes included and so much data that it's hard to hit the limit (read: usage is high).

The Internet is great for freedom of choice, freedom of use, freedom of expression, freedom of speech. I really like that I'm able to post things on my blog that can be read anywhere in the world where the open Internet is available. I equally like that there are search engines that let me find documents and information no matter where they are stored and I like small companies that are offering videos, podcasts and other content on niche topics that would never make it to the mainstream media.

So all of these things are great and do not match the title of this post at all. However, the Internet is now more and more also used to restrict the freedom we used to have. Here are some examples: Companies such as Apple, Google, Microsoft and Amazon have great products that are used and enjoyed by people around the world including the author of this post. But more and more these companies are trying to build silos by offering software and hardware that is tightly controlled by them. Third parties offering services and content independently are unwanted. A few examples: Apps can only be downloaded to the iPhone from the Apple store, Amazon's kindle only accept apps from Amazon's store and also Microsoft wants to go down that road with Windows 8, as metro apps can only be installed from Microsoft's web store.

Why such limitations and why now? The second part is answered easily, it's because it's possible to do it now. 10 years ago, restricting devices to a particular web store was not feasible as many PCs were not yet connected to the Internet and hence, installation of new programs from disks and CDs was the norm rather than the exception. Nobody would have accepted to only be able to install programs that had a Microsoft certificate. This has significantly changed as most devices are now connected to the Internet and the ease of use of exclusive web stores make many people blind to the fact that they are giving up a freedom they used to have. Giving up this freedom means that those who do are subjecting themselves to the values that a company thinks are the right ones rather than your own.

The first question of why this limit is imposed is often answered by saying that this protects users from badly designed or even malicious programs and that it's in the user's own good. To a certain extent that is of course true as programs go through a centralized audit. But I am a grown up and responsible person and I want to decide for my own. Someone else deciding what is good for me or not, no, thanks, I like my freedom. Google is using a somewhat different approach for Android. By default, downloading and installing apps from third party sources, e.g. from this web site or via sideloading from an SD card is blocked. However, the user is informed that if he really wishes to do that, it can be enabled in the settings. From my point of view that is a fair middle ground. It protects users from accidental installs of malware but still allows to open the door to freedom for those who want it. Also it is an incentive for users to buy software and content from the company that built the device or the operating system which is, by the way, the main reason for companies going down that road. Company interets and freedom do not have to be at odds with each other if done the right way.

One should also keep in mind that malicious programs are not the only way for a device to get infected by malware. Zero day exploits in web browsers that can inject malicous code that downloads keyloggers, scareware and other nasty programs are still frequently found. Web browser plugins such as Flash and Java leave the barn door wide open as well. Also, documents in email attachments that exploit weaknesses in office programs and files looking like documents but being executables are also able to infect systems and are very common today. A centralized and exclusive app store does not help against any of that. So the security argument might even backfire as it creates a false sense of safety.

Unfortunately, the anti-freedom effect the Internet has these days doesn't stop here. More and more, ubiquitous Internet access is also used for location and usage tracking, and only media pressure has so far prevented some excessive forms from becoming the norm. Anyone remember the "Carrier IQ" row from only last year? Yes, people forget quickly… Oblivion is the enemy of freedom.

Let also think about cloud services, freedom and privacy for a moment. Have a look at the terms and conditions of your favorite cloud service company. Is the data you store there, be it emails, documents, pictures, etc. really still yours or have you, by uploading them to that cloud service given the owner of the cloud service usage and redistribution rights to your data? You don't know? Well better check it out and ask yourself if this is acceptable to you or not. Note that I am not saying that all cloud services are bad. I use cloud storage for example but only with encrypted containers and the key is under my control and never ends up in the cloud. I also use email, obviously, one of the first cloud services and I am quite aware that I have no control over who sees what on the way from me to the recipient. And I act accordingly.

No, not everything is bad and if one is aware of these things one can act accordingly. My desktop is free, I am using a Linux distribution and I can install whatever software I like. Yes, it's not the only choice for a free desktop today, but companies are working hard to make it the only choice in the future. I use a VPN solution to protect my Internet connectivity when I travel and to prevent unwanted interference with the data I exchange such as unwanted network side compression or VoIP blocking. On the mobile side I use an operating system that lets me install any third party software I want and I only use cloud services to store unencrypted data I don't consider private, personal or my own. All of that takes effort, another enemy of freedom.

Freedom is not given it has to be struggled for.

For years, I've been collecting information from all around the web about which mobile network operator has how much bandwidth in which bands. Such information is quite helpful when it comes to understanding strategies and arguments in debates. No need to do that anymore as CEPT has just released a very comprehensive document giving an overview of spectrum owners for all European countries for the 800 MHz digital dividend band, the 900 MHz GSM/UMTS band, the 1800 MHz GSM/LTE band, the 2100 MHz UMTS band and the 2600 MHz LTE band. Here's the link to the page and here a link directly to the document ('ECO Report 03'), enjoy!

I recently noticed how relative time can be. Take 5 minutes for example, is that a long or a short time? I'd say it depends. Here are three examples

• Waiting 5 minutes in a call center queue seems like ages.
• Waiting for 5 minutes for a file download to finish because the server is on the other side of the world and has a slow link feels sluggish at best. 

• But: Waiting for 5 minutes in a doctor's waiting room before it's your turn feels very short.

Now how do the extra 6 seconds required to establish a voice call between two LTE mobiles due to Circuit-switched Fallback (CSFB) feel?

With mobile network operators using more and more radio systems (GSM, UMTS and LTE) simultaneous and on many different frequency bands, it's getting a bit difficult with traditional network coverage maps to find out where what kind of mobile device can be used. Some network operators have therefore now begun to diversify their maps with options to show different technologies and different frequency bands different colors.

Two interesting examples:

Elisa from Finland shows GSM, UMTS 900 and UMTS 2100 and LTE (1800???) coverage and dual carrier operation in separate colors

T-Mobile Germany that shows GSM, UMTS, LTE 800 and LTE 1800 in different colors (especially for devices that are not LTE 800 capable…)

In both cases, GSM coverage is still wider than the combined UMTS and LTE coverage. Such maps are also interesting to deduct what kind of network strategy the operator follows.

Quadrature Amplitude Modulation, or QAM for short, is a modulation technique used by systems such as UMTS, LTE and also by microwave backhaul systems. UMTS and LTE use QAM, 16QAM and 64QAM to encode 2, 4 or 6 bits per transmission step. And 64QAM already pushes the limits quite hard and is only used when a user is very close to the base station.

The highest modulation technique I have heard about for microwave Ethernet backhaul systems to transfer data back and forth from and to the cellular base stations so far is 256QAM, i.e. 8 bits per transmission step. This is possible due to the very directional focus of the radio beam versus sectorized transmission in cellular systems.

Now Dragonwave is saying that their latest system is capable of 2048QAM, i.e. 11 bits per transmission step. Further numbers cited in the article match that claim. A peak throughput of 550 Mbit/s over the channel mentioned in the article would mean that a 50 MHz channel is used for data transmission. Quite a fat pipe but not unheard of for microwave backhaul (see also link above).

An incredible number from today's perspective despite the directional nature of the transmission and pushes the state of the art quite a bit.

P.S. The latest version of Wi-Fi, 802.11ac uses 256QAM for very good signal conditions.

I've come to like tablets for purposes such as eBook reading or the occasional web search or Youtube video on the couch. However, I can't imagine just taking a pad with me instead of a small notebook computer when I travel, it's just too restrictive in terms of multitasking especially when it comes to creative tasks from email to word processing. But I think we are getting closer with Canonical just having announced that they've created an easy installer to get the current Ubuntu version running on a Google Nexus 7 tablet.

It's just experimental at this point but if there is enough processing power in that ARM based CPU then it will hopefully mature quite quickly. With one gigabyte of RAM it is on par with my 3 year old first generation Intel Atom based netbook that I've used intensively as my private PC when traveling during that time.

And who knows, perhaps in a year from now together with a thin or foldable Bluetooth keyboard for productivity, a pad running a decent Ubuntu version might finally be an alternative for a notebook. Kudos to all working on this!

When mobile networks are discussed, it's usually about the air interface, i.e. the last few meters between the base station antenna and people's mobile devices. What gets little attention in the press, however, is how the data is transported between the base stations, the radio network controlers (in case of UMTS) and the core network. This is what's called the 'backhaul' network. On a very high level it's clear that UMTS and LTE networks today due to their broadband transmission speeds can no longer use 2 MBit/s E-1 connections but have to use something else. In practice that something else is either Fiber, copper cable or microwave. But which technologies are actually used over that medium in different parts of the backhaul network? This is what 'Mobile Backhaul' by Juha Salmelin and Esa Metsala gives an in-depth answer to. While reading the book I've learned a lot about how pervasive Ethernet technologies have become in recent years over any kind of medium. I've gained a much better understanding of how Ethernet protocol extensions for use in the WAN work and how MPLS plays into the game. In short, a very recommended read!