The Wireless

Mum would always describe the radio as ‘the wireless‘ , yet today we accept the term in all manner of devices and controllers, from switching on your TV to making a phone call from your mobile.

But push through the broad term, and you enter the invisible world of frequencies and channels, white space and bands, many of which have a direct influence on the functionality of your mobile phone.

So ‘What is a frequency?’

Up and Down

Your mobile communicates using Radio waves.

A radio wave goes up(peak) and down(trough) and up again and so on in cycles.

The time taken between the two peaks(cycle) is the frequency.

Frequency is described in Hertz – the number of cycles per second.

1000 Kilohertz(kHz) = 1 MegaHertz

1000 MHz = 1 GigaHertz(GHz)

Radio communications used by our mobile phones use the range 3 kHz to 300 Ghz.

Traditionally the higher the frequency the more data it can transmit; the lower the frequency the more the signal can penetrate trees, walls etc.

The only variable is power. A dedicated device(rather than say a shared mobile phone), can be allocated greater power.

Crowded Skies

In the UK Ofcom regulates the use of radio frequencies amongst a wide range of broadcasters.

  • Radio Broadcasters – Analogue, Digital and Community
  • TV Broadcasters – Analogue Digital and Special services
  • Radio Communications – Amateur, Business, Shipping, Aeronautical, Short Range, Fixed wireless, Mobile, Military and Satcom.

In short, lots of folks competing for a fixed amount of frequencies. They are all assigned a specific frequency range(band) within which their equipment must operate at. Whilst the International  Standards Group usually ensure that equipment types operate at the same frequencies, some countries may offer different frequency allocations.

White Space

When you set up a new digital TV, it will automatically search for Channels, namely a specific frequency or frequency band in which a digital TV signal is being transmitted.

To stop interference between Channels, so called White Space is created. White Space is a no-go frequency band  which acts as a buffer between Channels to avoid Interference.

Technology

Radio is a classic example of how technology uses frequencies.

Mums’ old analogue radio gave you a set for frequencies to tune to.

Name Frequency
Long Wave 153 to 279 kHz
Medium Wave 531 to 1620 kHz
Short Wave 2310 tp 2580 kHz
FM 87.5 to 108 MHz

 

I often had to retune between 606 and 909 MW for BBC Radio Five as I drove up the motorway.

In DAB (digital broadcasting) up to 10 individual radio stations(channels) can be grouped(multiplexed) into one stream, which your DAB radio picks up, interprets, and then you select which of them you want to listen to.  So the BBC can broadcast nationally up to 10 channels all on the single 225.648 MHz frequency.

Hence when Ofcom finally switches off analogue radio, a heap of frequencies can be used for other means of communication.

Mobile Usage

On our phones today we can expect a mobile service(2G, 3G and in the future LTE/4G), a Wifi interface, a Bluetooth interface and on more expensive mobiles a NFC(Near Field Communications) interface.

2G services in the UK run in the frequency band 900-1800MHz

3G services operate in the 2100MHz band.

For 4G the UK is utilising the frequency from the now defunct Analogue TV service of 800Mhz plus an additional frequency range at 2.6GHz .

For Wifi they use the 2.4, 3.6 and 5GHz band under the 802.11 Wireless Local Area Network(WLAN) standards.

Not to be outdone Bluetooth also uses the 2.4GHz range, specifically 2400-2480Mhz for short range communications.

NFC, is also a short range(4-20 centimetres) wireless transmitter using 13.50MHz range.

Future

The 4G standards are designed to bring together various communication methods into one integrated mobile platform.

That includes the addition of Wimax, which  whilst lacking any defined spectrum does, via the Wimax forum, have initial standardisation on the 2.3, 2.5 and 3.5GHz frequency bands.

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