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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!

When you perform a manual network search in the UK today, you'll see 5 networks on the display. They are in no particular order:

• O2
• Vodafone
• T-Mobile
• Three
• Orange

But in fact with the recent decision of the UK regulator to allow network sharing between Vodafone and O2, there are a mere two mobile networks left in the UK. And non of the above mentioned 5 companies are actually operate one of those networks anymore. And here's why:

T-Mobile and Orange have merged and are soon going to be re-branded Everything Everywhere (EE) for consumers as well. From what's in the press they have already begun to put their network together, which reduces the number of companies to 4.

And then there's the UMTS network sharing deal between EE (form the T-Mobile side) and Three UK in a common company called MBNL (Mobile Broadband Network Limited). On their web page they write:

"Having successfully delivered the consolidation project, MBNL is now responsible for managing the consolidated network of sites including the 2G and consolidated 3G radio access networks for Three UK and Everything Everywhere. We are also responsible for the delivery of all site upgrades to continuously improve the consolidated network."

So we are down to three, i.e. MBNL, Vodafone and O2. But now Vodafone and O2 have been allowed to share their network as well, perhaps to 'compensate' the two companies for EE's early LTE start in the 1800 MHz band? As part of the network sharing agreement, Vodafone and O2 will establish a new network operator called "Cornerstone" that will manage and operate their consolidated network.

In other words, in the future there will only be two networks left in the UK:

• MBNL
• Cornerstone

I really wonder how under such circumstances competition will continue to flourish!?

In effect, Vodafone will be unable to differentiate from O2 and EE has no real means to differentiate from Three. They all claim that using their own spectrum will keep competition alive but I strongly doubt that. After all, everything is shared, from the antennas, to the base station to the backhaul. Only core networks will remain in the hands of the 4 'hollow operators'. So what for example if one gets a capacity issue in some locations? If the company had its own base station it could simply add a carrier. But that won't work so easily now because the base station and backhaul is shared. Is there enough capacity and room left for another carrier? Also, putting another base station into place close by will be difficult as the partner that shares the network might not want to do that. Perhaps putting micro base stations somewhere under direct control of the parent? Again difficult because neighbor cell relationships and handovers need to be coordinated. No, probably not possible with a shared network either. And even without that the bill is likely to come later when 'real' network operator asks for more money after the contract expires.

So it's down to two networks in the UK and it's going to be difficult to impossible to revert that trend if things don't work out for the consumer. A hazardous and unnecessary experiment…

Recently I read that one of the 4 big network operators in the US supposedly has 37.000 base stations in the country. Sounds like a lot, doesn't it?

Well perhaps, but only until you compare it to other places in the world. Take Vodafone Germany for example. Back in 2009 they said that they have 20.000 GSM base stations, so about half of that number above. But, it's for a population of 82 million compared to almost 314 million in the US and a landmass that is significantly smaller than the US. From that point of view 37.000 base stations is not very much and explains a lot…

Back in 2009 I reported on 3GPP standardizing a feature for mobile devices and SIM cards referred to as 'In Case of Emergency' or ICE. The idea behind it was, and still is, to offer a standardized way to store emergency contacts and information and to give access to the information to first responders such as medics, doctors and hospital personnel. Standardized is the important word here because it should be easy for first responders to find and access the information. Unfortunately the idea never really took off, and I think that's a real shame for the mobile industry as a lot could be achieved to help in medical emergencies with little effort. But at least some parts of the idea seem to have made it into some mobile devices. Take a look at the picture of a recent Android device I saw in Korea that has a default 'ICE' group in the phone book. I don't know how much this will help in practice as I had no time to see if the information is accessible from the password screen. Without that the information would inaccessible to first responders as most people lock their devices these days. However, it's a first step and perhaps the idea will spread and be developed some more.

And here's the post I hinted at earlier on cellular network coverage in the popular district I've been reporting about with an antenna on everything that does not move. Think I exaggerate? Then have a look at the screenshot on the left, produced with output from my Cell Logger App. Each red dot is the location at which a change to a new, so far, useen cell has occured (i.e. cell ping-pongs already removed!). The cell density is incredible, about one cell every 50 meters (have a look at the map resolution). And that is only SK's network which uses 3 carriers in this area. Signal levels are also way higher than in most other places I have performed measurements so. Signal strenghts up to -40 dbm are not unusal there. And no, I am not kidding, it is really -40 dbm. The meter never went far below -65 dbm in that area. In that 600 x 400 m area (0.25 km²) I walked up and down there were no less than 15 individual cells! Compare that to, lets say, busy areas in Cologne were cells are typically spaced apart 300 meters.

In a previous post I had a couple of nice pictures on wired and wireless chaos in a popular Seoul district. One might wonder if there are any cables that are deployed underground? To my surprise there are! Here's a picture of a KT crew deploying a new cable on a Sunday. I had a look down into the cable duct and there were lots of others already there, pretty much in the same chaos as those on the poles. The cable was manufactured… by Samsung 🙂 Is there anything that this company does not manufacture?