Wireless Waffle - A whole spectrum of radio related rubbish
LEO: Roaring in the wrong direction?signal strength
Wednesday 23 September, 2015, 12:36 - Satellites
Posted by Administrator
wireless waffle ferretOn several previous occasions, Wireless Waffle has discussed some of the problems, both technical and economic that the raft of companies planning to launch new constellations of high throughput, broadband delivering, satellites may face in making their services a success. Whilst ferreting around the internet, it was interesting to discover a paper entitled 'LEO: Roar or Whimper' which discussed many of the same issues on which Wireless Waffle has opined in the past.

The paper, however, takes a more sideways approach and compares the situation facing new operators such as WorldVu and SpaceX who are intending to launch literally thousands of satellites to provide broadband services, with satellite broadband networks that were planned to do just the same thing in the 1990s (such as Teledesic and Skybridge) but which never got off the ground (so to speak).

leo roar or whimperIt turns out that many of the potential hazards facing today's planned satellite networks have changed little since the 1990s and in some cases the situation may have gotten worse. Take for example the amount of space debris now hanging around at various orbits which is much greater than it was 20 years ago. And though the technology has moved on, the costs of implementing complex satellite earth stations that can track the satellites are no less soluble today than they where when the Spice Girls were topping the charts, even with the advent of leading-edge technologies such as meta-materials. There are a range of other issues discussed in the paper which seems to consider the landscape for the LEO networks to be relatively bleak and foreboding despite many big name investors backing these projects.

For what it's worth, the Wireless Waffle answer to the question posed in the paper's title, 'LEO: Roar or Whimper', is that it seems that the LEOs will roar, but quite possibly directing their volume at people who are wearing noise cancelling headphones and thus won't hear their bellowing cry. Metaphorically speaking!
add comment ( 27 views )   |  0 trackbacks   |  permalink   |   ( 2.9 / 56 )

Is WiFi hazardous to health?signal strength
Monday 31 August, 2015, 14:13 - Spectrum Management
Posted by Administrator
A number of people claim that they have had adverse medical and psychological responses to the presence of WiFi signals. But can WiFi actually constitute a health hazard? Wireless Waffle investigates...

Let's begin by considering the international rules which establish the limits for which exposure to radio signals is deemed to be detrimental to health as defined by the International Commission on Non-Ionising Radiation Protection (ICNIRP for short). ICNIRP has established a set of limits for the general public which are designed to stop the temperature of an average human body rising by more than 1 degree Centigrade over a roughly 24 hour period. This level of exposure is 50 times below that at which any measurable biological effects on humans have been identified.

These limits, measured in terms of the measured electrical field strength in Volts per metre, are shown below over a range of different frequencies.

icnirp general public

But what do they mean in practice and how does this help calculate whether WiFi could be dangerous. A WiFi transmitter, operating at full power (100 milliWatts, or 0.1 Watts) that is 2 metres (or 6 feet) away, produces an electrical field strength of just over 1 Volt per metre. The threshold of danger at the frequency that WiFi operates - 2450 MHz - is 61 Volts per metre and so at just 2 metres distant, the signal from a WiFi device is 61 times below the safety limit.

laws of physicsThere is another, and maybe more straightforward, way to calculate whether or not a radio transmission is likely to be dangerous. According to the laws of physics (which as everyone knows, canna be changed) 1 Watt of power (equivalent to 1 Joule per second) will raise the temperature of 1 gram (or 1 ml) of water by 1 degree Centigrade in 1 second assuming that all of the power can be focussed into the water. This is effectively how microwave ovens work: radio energy is focussed into the water in whatever is being cooked, heating it up.

If, for the sake of argument, we make the assumption that an 'average' human being weighs 50 kg (110 lb), and that it is made largely of water, it would take 50,000 Watts (or 50 kW) of energy to raise their temperature by 1 degree Centigrade in 1 second. To do the same job over the 24 hour period defined by ICNIRP would require 86,400 times less (60 x 60 x 24) meaning that if our average human absorbed around 0.6 Watts of energy for a 24 hour period, this would be deemed to be unsafe. WiFi transmitters have a maximum transmitter power (limited by law) of 0.1 Watts, which is below this limit. So even if ALL of the power transmitted by a WiFi device were absorbed by a human for 24 hours, it would still be a factor of 6 times lower than the ICNIRP safety limit.

In reality, it would be impossible to absorb all of the power from a WiFi transmitter unless that transmitter was inside the human body. Even if the antenna was placed directly on the skin, as signals from a WiFi transmitter are sent out equally in all directions at least half of the power would radiate away from the body, further reducing the impact on the human concerned.

swallow antennaIf the WiFi transmitter is 2 metres away, the signal from the WiFi antenna will have spread out so much that far less than a tenth of the original signal would wash over the body of a human, putting the exposure at a factor 60 times below the ICNIRP limit - gratifyingly the same as the level of exposure calculated using the graph above.

It is also worth noting that WiFi transmitters do not transmit constantly. At their busiest, they transmit around 50% of the time (they spend the other 50% of the time listening for incoming transmissions). Any exposure will therefore be another factor of 2 times smaller than above.

So what is the conclusion? As long as you don't swallow 6 transmitting WiFi antennas that continue to transmit on full power for a 24 hour period, any radiation from WiFi transmitters is far, far (far) below the established safety limits.
add comment ( 460 views )   |  0 trackbacks   |  permalink   |   ( 2.9 / 119 )

ITU roll the dice on the use of C-bandsignal strength
Wednesday 8 July, 2015, 15:43 - Spectrum Management, Satellites
Posted by Administrator
The bedrock of the recommendations posited by many consulting companies involved in radio spectrum management is the cost-benefit analysis. The principal of such an analysis is quite straightforward - you calculate the cost of doing something and then evaluate the benefits of the same thing and compare one with the other. If the benefits outweight the costs, then it should be worth doing. If the costs outweigh the benefits then it is not worth doing.

motorway farm landBut many such analyses are incomplete. As an example, consider the case of building a new motorway over some existing farmland. A typical analysis would look at the costs in terms of the need to find alternative employment for the farmers whose land will be compulsorily purchased to turn into the motorway. The benefits would be calculated to drivers, whose journeys would be shortened and therefore who would save time and money (for fuel). This is not the whole picture: it misses a whole set of costs and a whole set of benefits. It does not take into account the cost of building the motorway, and it fails to consider the benefits being generated from the farmland (e.g. the value of the business being conducted by the farmers). The table below illustrates what a full analysis might look like.

FarmersMoving farm to new location or finding alternative employmentRevenue generated from existing farming business
DriversBuilding a new motorway and modifications to existing roadsShorter and faster journeys, savings in fuel consumption

It might also be informative to consider other ways that the same benefits might be delivered, for example by re-engineering existing roads, or by using more fuel efficient cars.

None of this is rocket science and even those studying economics at school ought to be able to identify all of the costs and benefits. It is surprising, therefore, that some otherwise well-respected economists continue to write reports that miss out parts of the analysis. Plum Consulting (no stranger to Wireless Waffle) have recently published a report entitled 'Use of C-Band for mobile broadband in Hungary, Italy, Sweden and the UK'. In it they conduct a cost-benefit analysis of migrating existing spectrum users out of the C-Band (3400 - 4200 MHz) and using it for mobile broadband services. But as with the example above, they fail to consider all the cost and all the benefits. They consider the costs to existing users, and benefits to the new users, but not the benefits to existing users or costs to the new users. The table below summarises their analysis.

Existing Users
(Satellite and Fixed Links)
Modifying equipment to allow access by mobile or using alternative frequencies.Not considered
New Users
(Mobile Broadband)
Not consideredHigher speed connections in hotspot areas.

In addition to missing a large chunk of the necessary analysis, they also do not assess alternative methods to achieve the same outcome. For example, no consideration is given to whether the improved spectrum efficiency of 5G networks (which will presumably have started being rolled-out in the timescales considered in the report) would be more cost effective for the mobile broadband operators than using older technology in a new band. The fact that the costs to the mobile operators are not evaluated serves to hide alternative solutions such as this.

ssi c band useOf course the report has been paid for by Ericsson, Huawei and Qualcomm and so it would be expected that the results would show in favour of the mobile industry, and so missing out various parts of the analysis which might make the results less favourable is perhaps no surprise. It is also the case that, for example, evaluating the value of the spectrum to the existing users is a complicated task due to the very wide range of types of users that would have to be considered, from the oil and gas industry to banks, and from broadcasting to humanitarian relief. The Satellite Spectrum Initiative have published a helpful factsheet which identifies and, to some extent, quantifies, the value of the use of C-band to various users. To actually value the C-band properly is a big task which it seems that even the satellite operators who stand to lose most if the spectrum is re-farmed for mobile services, are unwilling to cough up the funds needed to put a figure on it.

itu c band decision makingUntil such time as someone does pay to do the job properly, it seems that all discussions on the value of C-band spectrum to satellite operators or to mobile operators will be conducted without all the facts being on the table. With C-band being a hotly contended issue at the forthcoming World Radiocommunication Conference (WRC) (which will take place at the ITU in November in Geneva) any decisions taken will be rather uninformed. Such important decisions, with billions of pounds of mobile and satellite money involved, should not be taken so lightly. Maybe those users who rely on C-band for their businesses today could club together and raise enough money for decent economics experts to actually work out a realistic value of today's C-band use, and equally the mobile industry could do a full analysis of the costs and benefits of the use of the band, and of other alternatives so that all concerned could be comfortable that they are taking any decisions on a realistic basis.
add comment ( 337 views )   |  0 trackbacks   |  permalink   |   ( 3 / 266 )

So farewell, then, analogue TVsignal strength
Monday 29 June, 2015, 17:34 - Broadcasting, Licensed, Spectrum Management
Posted by Administrator
A year ago Wireless Waffle posited the notion that we were beginning to see the end for digital terrestrial television. Just over a week ago in Geneva, the ITU celebrated the date on which, in Region 1 (Europe and the Middle East) and Iran, protection of interference for analogue television services ceases, and digital is the only protected broadcasting service. This 'celebration' presented the position from across the region where there is an extremely wide range of 'success' from countries who have already switched off analogue television, to those who are yet to launch any digital services at all. Of the 119 countries that form Region 1, only around 40 have completed switch-over - hardly a 'success' to be 'celebrated'.

digital switch over status

Director of the ITU Radiocommunication Bureau, Franšois Rancy, explains the situation.

Let's stop fooling ourselves - digital terrestrial television (DTT) as a platform for delivery of everyday TV, is already on its last legs in many countries, or at least it has a bad case of arthritis. Like many of today's technologies, it is a fixed point in an evolving market and eventually it will be overtaken. Analogue television had its purpose, but is beginning to be phased out. Digital terrestrial television will do likewise, no matter how strongly bodies such as the EBU argue that it will remain important until 2025 and beyond.

When DTT was launched, its ability to offer dozens of television channels, and use less spectrum and less electricity made great strides forwards. But the digital world is moving ever faster and DTT is beginning to lag behind and will surely, over the next 10 years, become the lame horse of television broadcasting.

Why? Here's 5 good reasons:
  • Televisions are getting bigger and resolution is improving. When DTT launched, standard definition television was the norm. The norm now is becoming High Definition television, which requires double the bandwidth of standard definition, meaning that the DTT platform can now carry only half as many channels. With the move to Ultra High Definition, or 4K, each television transmitter will, at best, be able to carry 2 (and in the future, as video compression improves, maybe as many as 3) channels. Thus the wide range of content currently available on DTT will slowly wane such that even with a half-dozen multiplexes, the DTT platform will only carry 15 to 18 TV channels. Compare this with the hundreds that cable, satellite and even the internet will offer.
  • What's more, the availability of these alternative delivery platforms is increasing. Satellite, of course, provides near universal coverage already, and though it would be fair to say that the coverage of cable TV networks is not growing significantly, the delivery of television over IP networks (IPTV) such as BT Vision in the UK is only dependent on the availability of a broadband internet connection and most countries are investing heavily to make these as ubiquitous as possible.
  • Whilst household screens are getting bigger, not all viewing is on such big screens. Watching TV on tablets and smartphones is becoming commonplace and although DTT proponents argue that DTT receivers could be built into such devices to allow them to view their transmissions, the manufacturers of such devices appear reluctant to do so. The connection to such devices is WiFi, 3G, 4G or even 5G but not DTT.
  • Although national television broadcasters (such as the BBC, ARD or France Televisions) still account for a very high proportion of viewing, an increasing amount of this viewing is non-linear, that is to say that it is not live, but catch-up through platforms such as the BBC's iPlayer. Certain content will always remain linear due to its immediacy, such as sports events and communal television such as talent shows and soap operas where the ability of all to share a common experience is important. But the use of non-linear television for other programmes such as factual programmes or dramas to allow them to be watched at the convenience of viewers will surely become the standard.
  • Finally, the take-up of over-the-top services which do not rely on standard broadcast content but which have a catalogue of material which viewers can watch at their discretion (e.g. Netflix or Hulu) are starting to become the preferred way to relax and watch a programme. Watch what you want, when you want, without being beholden a particular broadcaster's choice of schedule of what you should watch at a particular time of day.
dtt rabbit earsProponents of DTT argue that:
  • it can continue to operate in disaster situations (but no-one will have any power to watch TV, though they may well have batteries in their radios);
  • that it is the cheapest way of delivering mass TV (this is singularly dependent on the number of viewers that use the platform - fewer viewers = higher cost per viewer);
  • that it is the only platform under national control (e.g. that it is not owned by nasty foreigners that might turn the service off, such as the normally docile Luxembourgeous that own the Astra satellites);
  • and so forth...
All these arguments do hold water, but so does a colander, for a short time.

Is it really likely that, in ten years from now, we will all still be sitting down at 10pm to watch the news over terrestrial television, or that at 10:17 after we have finished watching the ninth season of House Of Cards on Netflix, we launch our custom news channel which provides a set of news reports tailored to our interests. As E. J. Thribb would no doubt have it:
tv service goneSo. Farewell then
Terrestrial Television

Your days were

With ones and naughts

And now you
but naught

At one
your analogue

add comment ( 69 views )   |  0 trackbacks   |  permalink   |   ( 3 / 831 )

| 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | Next> Last>>