Sunday 5 February 2012

Contents of module

Management of the Spectrum

Radio Services

In the parlance of the World Radio Conference (WRC) the uses of radio are typically divided into:

  1. radio services
  2. the spectrum used is divided into frequency bands
  3. administrations allocate frequency bands to different categories of services
  4. often with a licensing process for different types of transmission by service providers who use the frequencies assigned to them by the administration.

Public and private service requirements are two distinct areas. The spectrum required for government and public services, for example the emergency services, national defence, public service, broadcasting, and so forth, has traditionally been determined by administrative means, which raises some problems.

On the one hand, it is necessary to reserve spectrum for these services because a market mechanism would almost certainly result in the relevant spectrum being used for other, more commercial purposes. On the other hand, political and security concerns may well result in an over-allocation of spectrum to these services, and the use of the spectrum by public service operators may become very wasteful if there is no mechanism to enforce the most efficient use of frequencies.

Spectrum allocated to private services, and frequencies assigned to private service providers, may confer either property rights or rights of usage, which can raise difficult questions of whether spectrum should be tradable, of the dangers of monopoly, and what, if any, regulations or obligations should be imposed upon the assignment of frequencies.

A further question concerns the re-assignment of frequencies that may become necessary, and whether the holders of the frequencies are under an obligation to return them before the expiry of their licences. And in the absence of strict regulations governing the use and non-use of frequencies, private operators may be tempted to ‘bank’ licences, being motivated by the prospect of a future sale, or simply by the desire to keep the frequency out of the hands of a competitor.

For all these reasons the allocation of spectrum and the assignment of frequencies needs close co-ordination between the technical, engineering side of the regulator’s office to monitor the efficient use of spectrum, and the economic, policy side to monitor the market and possible abuses of market power.

Frequency Bands

Nothing illustrates better the explosive growth in the demand for radio spectrum than the upper limits of the ITU’s frequency tables.

  • Pre-1947 = 200 MHz
  • 1947 = 10.5 GHz
  • 1959 = 40 GHz
  • 1971 = 275 GHz

By the time of WRC 1997 most of the bands below 25GHz were in use, and although the higher bands have less utilization, additional applications, such as fixed wireless, have encroached above 25 GHz. A growing interest in space exploration and in broadcasting satellite services have also created a demand for the higher end of the spectrum. The frequency bands are shown below.

Frequency
band		 Band number Symbol
3 – 30 kHz 4 VLF – Very Low Frequency
30 – 300 kHz 5 LF – Low Frequency
300 – 3000 kHz 6 MF – Medium Frequency
3 – 30 MHz 7 HF – High Frequency
30 – 300 MHz 8 VHF – Very High Frequency
300 – 3000 MHz 9 UHF – Ultra High Frequency
3 – 30 GHz 10 SHF – Super High Frequency
30 – 300 GHz 11 EHF – Extremely High Frequency

Note: The upper limit of the ITU’s frequency tables was lifted from 200 MHz to 10.5 GHz in 1947, to 40 GHz in 1959, and to 275 GHz in 1971. Micowave and millimeter wave frequencies have no specific definition, but often refer to frequencies 1 – 20 GHz and above 10 GHz.

WARC and subsequent WRC recommendations have given the guidelines to the allocation of these frequency bands by national administrations.

WRC Regional Frequency Allocations

As far as possible the ITU tries to achieve harmonization of frequency allocations intra-regionally and inter-regionally. In some cases frequency allocations are specific to a particular service; in other cases a group of services can share a band and it is left up to the local administration to assign frequencies according to local requirements.

For example, in some areas the demand for cellular mobile telecommunications services will be far greater than in others. Climatic variations and signal propagation characteristics may also be important considerations.

Sharing frequency bands obviously raises problems of potential interference and regulators have to consider safeguards such as constraints on usage, for example restrictions on power levels, on the direction of antenna, on day time or night time transmission, on the use of guardbands, and so on.

Interference may be impossible to eliminate altogether, in which case acceptable levels have to be imposed.

  1. Primary and Secondary Allocations
    The mechanisms for doing this vary from the carefully calibrated use of algorithms to simple trial and error, but in the allocation of frequency bands the ITU recommendations include primary and secondary allocations. Primary allocations are indicated by upper case in frequency tables, such as FIXED or MOBILE, whereas only the first letter is capitalized in secondary allocations, for example Fixed or Amateur. In the event of interference, operators with secondary assignments are required to accommodate the requirements of those with primary assignments.
  2. Frequency Table
    The WRC frequency tables contain over thirty footnotes (treated as paragraphs in the ITU’s Radio Regulations or RR) which specify a variety of addenda, such as primary and secondary allocations, jurisdictions where exceptions apply, and so on. They also cover the allocation of radio bands for technical, scientific and medical equipment and apparatus which use radio frequency (RF) and from which there is a danger of radiation which could prove either hazardous or an interference.
Service category Service type
Fixed service (FS) Radio links between stations at specified terrestrial locations
Fixed satellite services (FSS) provide satellite links between stations at specified terrestrial locations.
FSS also includes satellite feeder links between other services provided by terrestrially-located stations, such as mobile-satellite and broadcast-satellite.
Broadcasting service (BS) Terrestrial transmitters and their emissions for direct reception by the general public
Broadcasting satellite service (BSS) emissions for distribution for general public reception.
Mobile service (MS) Radio stations on land vehicles, aircraft, ships or handheld, stations at fixed locations that communicate directly with them, and the radio links used between any of them.
Mobile satellite service (MSS) links with mobile radio stations or the stations at fixed locations that communicate directly with them.
Maritime mobile service (MMS) and Maritime mobile-satellite service (MMSS) – two special categories are port operations service and ship movement service.

Aeronautical mobile service (AMS) and Aeronautical mobile-satellite service (AMSS) - includes civil air ‘Route’ (R) and non-civil air ‘Off-Route’ (OR) frequencies for traffic control AMS(R) and AMS(OR) and safety messages AMS (R)S and AMS(OR)S

Land mobile service (LMS) and Land mobile-satellite service (LMSS)

All separately identified for frequency band allocation.
Amateur service (AmS) Amateur service (AmS) and Amateur-satellite service (AmSS)
Technical and Scientific services Space research service (SR), Earth exploration-satellite service (EES), Meteorological-satellite service (MetS), Meteorological aids service (MetA), Radio astronomy service (RAS), the Standard frequency and time signal service (TFS), the Standard frequency and time signal-satellite service (TFSS), and the Space operation service (SO) for telemetry purposes.
Radiodetermination service (RDS), Radiodetermination satellite service (RDSS) – radio waves are used for measuring the distance or location or relative movement of objects or other physcial characteristics – includes Radionavigation service (RNS) for ship and aircraft navigation, which is subdivided into the Maritime radionavigation service (MRNS) and the Aeronautical radionavigation service (ARNS), and the Radiolocation service (RLS) for other RDS systems. The RDSS is similarly sub-divided into the MRNSS, ARNSS, and the RLSS.
Inter-satellite service (ISS) Direct links between satellites where the frequency bands allocated in most cases can be used regardless of the service.
Note: International frequency tables normally specify the satellite uplink and downlink frequency bands and direction of transmission.

Source: David Withers, 1999, Radio Spectrum Management: Management of the spectrum and regulation of radio services, 2nd edition, The Institute Institution of Electrical Engineers, Stevenage, UK. Note: no standard terminology exists but the above is widely used.