Wireless Waffle - A whole spectrum of radio related rubbish
All Are Bored with On-Train Wifisignal strength
Thursday 5 June, 2014, 09:23 - Spectrum Management, Much Ado About Nothing
Posted by Administrator
bbc watchdog presentersLast night’s BBC Watchdog programme discussed the issue of the apparently poor WiFi connectivity available on a number of inter-city train routes across the UK. The programme conducted a survey of the paid-for WiFi service of three long-distance train operators. They measured the percentage of the journey for which a connection was available, and the time it took to download a short file. The average results, together with the current tariffs for WiFi on the three train companies surveyed are shown below.

Train OperatorConnection AvailableTime To Download A FilePrice
Cross-Country96.7%39 seconds£2 for 1 hour, £8 for 24 hours
East Coast79.4%13 seconds£4.95 for 1 hour, £9.95 for 24 hours
Virgin Trains82.2%112 seconds£4 for 1 hour, £8 for 24 hours

WiFi services on trains are provided by using antennas on the roof of the trains to connect to mobile networks. These mobile internet connections are then shared amongst all the WiFi users on a train. Companies such as Icomera and Nomad Digital provide boxes that enable multiple mobile internet connections to be combined together to increase the speed of the connection as a single 3G or 4G connection is not going to cut it when shared between multiple WiFi users.

icomera rail solution

In the programme, self-proclaimed IT Guru Adrian Mars then goes on to explain that the problem with the East Coast and Virgin services is that they make use of the signal from just one mobile operator and share that amongst all the WiFi users on the train, whereas Cross-Country use connections from multiple operators. This would explain why the time for which a connection was available on Cross-Country’s WiFi service was so much higher than on the other two, as they can make use of the overlapping coverage provided by multiple operators.

wifi on board trainIt is also true to say that many of the UK’s inter-city train routes pass through very sparsely populated areas, as well as tunnels and deep cuttings, where there is unlikely to be much in the way of a mobile signal. Given the different routes taken by Cross-Country, East Coast and Virgin Trains it is therefore unfair to directly compare them as each route will have a different proportion of these hard-to-get-at areas. 3G and 4G mobile networks also don’t work as well at high speed and (usually) trains travel at speeds that are fast enough to begin to affect performance.

Where the Watchdog’s IT guru did go astray was to suggest that it might be better for train passengers to rely on the connection to their own mobile phone for internet rather than the on-train WiFi. Why is this wrong? There are two main reasons. Firstly, the antennas used by the on-train WiFi systems are mounted on the train roof, whereas your phone will be lower down, inside the carriage. A previous Wireless Waffle article highlighted the need to get high to improve reception and the signal on the roof of the train will be bigger than that inside by dint of this fact alone.

But there is a much bigger problem… trains are typically constructed of metal. Some, including Virgin Trains’ Pendolino trains, have metallised windows. Passengers are thus enclosed in a Faraday cage which will do a grand job of stopping any signals on the outside of the carriages from making their way into the carriages. According to a paper written by consultants Mott MacDonald for Ofcom:
In modern trains the attenaution[sic] can be up to -30dB.

This means that of the signal presented to the outside of the carriage, only one thousandth of it makes it inside the carriage. Add this immense loss to the difference in height between the roof-mounted antenna and you sat in the carriage and it becomes apparent why using your own phone is highly unlikely to yield a better connection than that available through the on-train WiFi.

sandwiches or wifi trainThe Watchdog team suggested that due to the poor quality of the on-board WiFi it should be offered for free instead of making passengers pay. Many fare-paying train passengers would no doubt express a lot of sympathy with this suggestion. The cost to the rail companies of doing this is not trivial. East Coast, it was claimed, are upgrading their on-board WiFi to the tune of £2 million which compared to the paltry £7m profit they made in 2012/13 is quite a bite. But given the choice of free sandwiches (whose quality is as notoriously dubious as that of the WiFi connection) or free WiFi, most would surely prefer to enhance their digital diet instead of their gastronomic girth.
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H comes after E, E comes after G...signal strength
Friday 4 April, 2014, 09:57 - Much Ado About Nothing
Posted by Administrator
ww explains it allWhen using your mobile phone, smart phone or tablet have you ever noticed that next to the signal strength bars (usually found at the top of the screen), there is often a letter (or two) that seem to change almost at random as you move around, and even sometimes when you aren't moving at all? Have you ever wondered what these letters are there for and what the implications of them changing from one letter to another are? Well wonder no more because the answers are about to follow, as Wireless Waffle explains it all...

Letter(s)MeaningTypical Connection SpeedExplanation
G or GPRSGPRS10-20 kbpssignal bars gThis is a 2G service and is the slowest connection you can get. It's often achingly bad.
E or EDGEEDGE50-60 kbpsThis is also 2G and the second slowest connection - theoretically up to 384 kbps but almost never this fast. Think 'dial-up' internet (if you can remember back that far).
3G3G80-100 kbpsThis is the original 3G mobile system and is good (compared to GSM) but still not brilliant.
HHSPA0.5-2 MbpsA truly broadband wireless connection with good real-life connection speeds.
H+Evolved HSPA (or HSPA+)2-8 Mbpssignal bars h+An even faster connection, might even be termed 'zippy'.
4GLTE5-20 MbpsThe fastest connections available today.
RRoaming-Beware - this means you are connected to a network outside your home country and data costs could be astronomical! The R is sometimes shown in a triangle.
XNo signal-On some phones, an X appears above the signal bars if there is no signal at all.

Note that the typical connection speeds given above are those that are generally achieved in real-life. Though in theory the technologies used can offer faster connections, much depends on how many users are in a cell and what they are doing, how close to the centre of the cell you are, whether you are stationary or on the move, and a whole host of other factors.

Arrows (sometimes coloured, and sometimes integrated into the signal bars) pointing up and down are also illuminated. This just shows whether you are downloading (the downward arrow) or uploading (the upward arrow) data to the mobile network.

youtube bufferingIn addition, the number of bars shown on your signal meter will also affect how good your connection is. So a '3G' connection with all signal bars lit might be better than a 'H+' connection with only one bar lit. However a full strength signal may not necessarily mean a fast connection as most phones show the 'strength' of a signal and not the 'quality' It's quite possible to have a full strength signal that's suffering lots of interference and thus is bad quality.

What does any of this matter? It doesn't really, but if you are wanting to view a YouTube video and your phone is showing 'G' or 'E', the chances of you getting a fast enough connection are virtually nil.
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Marconiji and Elastic-Magneto Wavessignal strength
Tuesday 1 April, 2014, 08:04 - Much Ado About Nothing
Posted by Administrator
gujarat science 4 bookIt has been widely reported with great delight across India and in the world-wide media that the Level 8 Social Science school text books being given to children in the Indian state of Gujarat contain many inaccuracies. Examples of these heinous inaccuracies include 'factlets' such as these gems:
  • It was Japan that dropped a nuclear bomb on America during World War II (and not vice versa).
  • Carbon Trioxide (CO3) has increased due to the cutting of trees (CO3 is highly unstable but can be made by blowing ozone at dry ice).
  • That after the partition of India in 1947, a new nation called 'Islamic Islamabad' was formed whose capital was Khyber Ghat (and not that Pakistan was formed with a capital Islamabad).
Wireless Waffle has managed, through a contact living in the state, to get hold of a copy of the Level 4 Physics book used in classrooms across Gujurat. Like its social science bretheren, it is also chock-full of errors and mistakes. For example, it claims that:
  • marconijiIndian inventor Guglielmo Marconiji (pictured right) discovered the elastic-magneto wave and his brother, Luigi, is the source of the character in the SuperMario game.
  • Elastic-magneto waves travel at the speed of steam, which is generally taken to be 100 km per hour.
  • The first radio station in India went on-air in 1748 and was called 'Bhapa Stesana Bharati' (Indian Steam Radio), as it used steam engines to generate the elastic-magneto waves. The signals from this station will not reach the moon until a week next Tuesday, if the timetable doesn't change.
  • Phones work by transferring ear molecules between those speaking. Conference calls are a modern invention because of the need to clone ear molecules to be heard in several places at once.
Laughable as these 'factlets' may seem, there are many, much worse, part-truths that are espoused by those who ought to know better... Here's looking at you, ITU!
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The full Gravity of the situationsignal strength
Friday 14 March, 2014, 14:28 - Spectrum Management, Much Ado About Nothing
Posted by Administrator
For those who have not yet seen the Oscar winning film, Gravity, please note that although there are no spoilers (in the traditional sense) in the ensuing text, for those who are regular readers of Wireless Waffle, reading what is to follow before seeing the film may leave you with the same level of bemused bewilderment that it did us, and may spoil your enjoyment of the film! So a spoiler that's not a spoiler.

The movie begins with a few astronauts on a space-walk (a.k.a EVA) to add some new equipment to the Hubble space telescope. They are communicating with each other using radios built into their space suits and also, at the same time, are able to communicate seamlessly with ground control in Houston.

Following the 'disaster' around which the film's premise is based, the astronauts lose communication with Houston, and, for that matter, any ground based people. According to the film, this has been caused by the loss of the communication satellites that were handling the signals. In addition, their space suit radios seem incapable of communicating with each other over ranges of just a few hundred metres.

Let's first examine the space suit radios themselves. According to a document provided by NASA the range of the communication system between suits is just 80 metres in the worst case (though could be much greater). Given that this system took US$20 million to develop and operates in a 'free space' environment, the poor coverage performance is lamentable. However, it appears that this element of the story might just be feasible. Note that the Russians use a much more off-the-shelf technology for EVA voice communication that has a much greater range!

Could a ground station communicate directly with a space-suit. Based on NASA's paper, and on typical UHF communication systems, no. But with a little ingenuity, for example the use of a high power transmitter and high gain antenna on the ground, it is not beyond the wit of man.

space shuttle legoAs for a loss of Earth-space communication being caused by the loss of a communications satellite, there are satellites used to relay data from space to Earth (for example, the TDRSS), however full data communications with a space shuttle could also be accomplished directly from the shuttle to a network of ground stations at S-band frequencies around 2.2 GHz (and voice-only communication at VHF and UHF frequencies). Although in theory, these ground stations could be connected back to Houston via satellite, the chances are that there would be a terrestrial, fibre-based connection that could do the job just as well. So whilst passing over such a ground station, there is no reason why Earth-space communication could not have been re-established. Of course a space vehicle (such as the shuttle) is then needed to relay these signals to any astronauts on EVA.

tdrss space links

There is then a moment when one of the astronauts finally receives a signal from the ground but it appears to be from a Chinese man whose dogs and baby can be heard to be barking and crying (respectively) over the air. Whilst tuning into these transmissions, the astronaut in question says 'you're coming in on an AM frequency'. What is an AM frequency when it's at home? AM is a modulation scheme and not a frequency. And why would someone sitting at home in China be using any kind of frequency that is shared with Earth-space communications? And the communication seems to be full duplex as the astronaut can communicate with the man on the ground concurrently with listening to his transmissions. None of this makes much sense.

landing module re entryAnd lastly, communication with the ground is finally re-established when a landing module descends into the atmosphere. The range of the types of frequencies used for Earth-space communications at atmospheric altitudes is limited by the curvature of the earth, (e.g. at 30,000 feet, the range of communications is roughly 300 km). This would mean that those on the ground would have needed to be aware of the location where the landing module was coming down (odd that they could do this if they had had no communication with the landing module until that point) and thus be in the neighbourhood for communications to be possible.

Whilst the film may have excelled for its special effects, the way in which the radio communications were portrayed will be a real 'spoiler' for anyone who knows anything about the radio technologies or radio propagation. Still, science-fiction, by its definition, doesn't need to be scientifically accurate!
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