A look at some Spectrum – Part 1

  Jan 22, 2015 9:16:37 AM

Spectrum or electromagnetic spectrum is the range of all possible frequencies of electromagnetic radiation. The spectrum is divided into ranges of frequencies called chunks suitable for different purposes like mobile communication, TV broadcasting, radio, etc. The definition of ranges of frequencies & allocation is carried out by ITU-T.  This blog explains about the spectrum space and spectrum bands. Spectrum allocation policy for different usages is defined per region. Spectrum bands allocation for different purposes in US is available in the chart linked below.

http://www.ntia.doc.gov/files/ntia/publications/spectrum_wall_chart_aug2011.pdf

There are three regions defined by ITU-T, and countries fall in any one region.
Region 1 : Europe, Middle East, Africa, Countries belonging to former Soviet Union, Mongolia and Siberia
Region 2: North and South America
Region 3: Asia and Australia

Spectrum space is controlled by respective Governments, through some Authoritative body. In US, it is FCC and NTIA and in India it is Wireless Planning & Co-ordination wing along with TRAI.

Spectrum bands are licensed through allocation/auction by respective Governments. In addition, Government may limit the usage to certain areas within the country. Examples of licensed bands are 900 MHz, 1800 MHz, etc for Mobile communications.
Unlicensed low power transmitters can be used with restrictions on the output power and modulation schemes at various frequency bands.  In some frequency bands like Radio Astronomy, Mobile distress calling, unlicensed low power transmitters are not allowed. ISM bands like 2.4 GHz, 5 GHz are popular as FCC allows much higher output power in these bands.

Of course, unlicensed does not mean Authorization is not necessary, all low power equipments have to be certified by authoritative bodies such as FCC.  Link below provides more details.

http://transition.fcc.gov/Bureaus/Engineering_Technology/Documents/bulletins/oet63/oet63rev.pdf

Sasken has extensive experience in WiFi and other wireless technologies like BT, Zigbee. Sasken closely keeps track of changes and introduction of wireless technologies. Sasken is member of various wireless technology forums. As part of this, Sasken is analyzing some spectrum bands that have received active interest  where work is going on and which could lead to disruptive results. Some of these works have been going on for some years, but are in the process of getting mainstreamed. The following will be covered in the upcoming posts.

TV White Space Spectrum
Unlicensed 60 GHz space
Li-Fi/Visible Light Communications

Author: Jayasimha Holkal - Sr. Architect,  ERnD Practice

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