Description: This Document will
help you in understanding the Radio Frequencies with its classification and
uses of Frequency Band in Wireless and in others applications.
About Radio Frequency (RF)
Radio
frequency (RF) is any form of the electromagnetic wave frequencies that lie in
the range extending from around 3 kHz to
300 GHz which is used for wireless communications or radar signals and many
others purposes as Signal Broadcasting, military operations [1].
Band name
|
Frequency and wavelength in air
|
Uses
|
Extremely low frequency (ELF)
|
3–30 Hz
100000 km-10000 km |
Communication with submarines
|
Super low frequency(SLF)
|
30–300 Hz
10,000 km – 1000 km |
Communication with submarines
|
Ultra-low frequency (ULF)
|
300–3000 Hz
1000 km – 100 km |
Submarine communication, communication within mines
|
Very low frequency (VLF)
|
3–30 kHz
100 km – 10 km |
Navigation, time signals, submarine communication,
wireless heart rate monitors, geophysics
|
Low frequency (LF)
|
30–300 kHz
10 km – 1 km |
Navigation, clock time signals, AM longwave broadcasting, RFID, amateur
radio
|
Medium frequency (MF)
|
300–3000 kHz
1 km – 100 m |
AM (medium-wave) broadcasts, amateur radio
|
High frequency (HF)
|
3–30 MHz
100 m – 10 m |
Shortwave broadcasts, citizens' band radio,
amateur radio and over-the-horizon aviation communications, RFID, automatic
link establishment (ALE), marine and mobile radio telephony
|
Very high frequency (VHF)
|
30–300 MHz
10 m – 1 m |
FM, television broadcasts and line-of-sight
ground-to-aircraft and aircraft-to-aircraft communications, land mobile and
maritime mobile communication, weather radio
|
Ultra-high frequency (UHF)
|
300–3000 MHz
1 m – 100 mm |
Television broadcasts, microwave oven, microwave devices/communications, radio
astronomy, mobile phones, wireless LAN, Bluetooth
|
Super high frequency (SHF)
|
3–30 GHz
100 mm – 10 mm |
Radio astronomy, microwave devices/communications,
wireless LAN, most modern radars, communications satellites, cable
and satellite television broadcasting
|
Extremely high frequency (EHF)
|
30–300 GHz
10 mm – 1 mm |
Radio astronomy, high-frequency microwave radio relay,
microwave remote sensing, amateur radio, directed-energy weapon, millimeter
wave scanner
|
Tremendously
high frequency (THF or
THz)
|
300 GHz – 3 THz
1 mm – 0.1 mm
|
Experimental medical imaging to
replace X-rays, ultrafast molecular dynamics, terahertz time-domain.
|
What is ISM Band?
The industrial, scientific and medical (ISM)
radio bands are radio bands (portions of the radio spectrum) reserved
internationally for the use of radio frequency (RF) energy for industrial,
scientific and medical purposes other than telecommunications [2].
Wi-Fi
is aimed to use frequencies which are within unlicensed spectrum. This enables
users to access the radio spectrum without the need for the regulations and
restrictions that might be applicable elsewhere.
ISM bands
are also called unlicensed bands. Unlicensed bands that can be used for
any purpose without a license in most countries.
The Unlicensed ISM Band categorized into
following three (3) range of Frequency Range in which 5 GHz Frequency Range are
further divided into 3 levels of band as classified by the Unlicensed National
Information Infrastructure (UNII).
ISM Frequency Band
(unlicensed bands)
|
Brief Description
|
902 to 928 MHz
|
The 33-centimeter or 900 MHz band is a portion
of the Ultra high frequency (UHF) radio spectrum
internationally allocated to amateur radio on a secondary basis. It ranges
from 902 to 928 MHz.
|
2.4 GHz
(2400 MHz to 2483 MHz)
|
Generally referred to as the 2.4 GHz band,
this spectrum is the most widely used among all the bands available for
Wi-Fi. Used by 802.11b, g, & n standards. It can carry a maximum of 3
non-overlapping channels.
|
5 GHz
Band A (Lower) UNII-1
(5180 MHz to 5240 MHz)
Band A (Middle) UNII-2
(5260 MHz to 5320 MHz)
Band B (Extended)
UNII-2
(5500 MHz to 5700 MHz)
Band C (Extended) UNII-3
(5745 MHz to 5805 MHz)
|
The 5 GHz spectrum are broken into four bands
according to the Unlicensed National Information Infrastructure (UNII) providing
a 555 MHz of spectrum, with total 27 channels in which 23 are non-overlapping
channels and remaining 4 are overlapping with other channels.
This 5 GHz band provides additional bandwidth,
and being at a higher frequency, equipment costs are slightly higher and
because of this its usage is low, and hence interference is less. Used in
802.11a & n standard. It can carry up to 23 non-overlapping channels, but
gives a shorter range than 2.4 GHz.
|
Brief introduction about Wireless IEEE 802.11 standards
IEEE
802.11 is a set of media access control (MAC) and physical layer (PHY)
specifications for implementing wireless local area network (WLAN) computer communication
in the 900 MHz and 24GHz, 3.6GHz, 5GHz, and 60 GHz frequency bands. These standards are
created and maintained by the Institute
of Electrical and Electronics Engineers (IEEE) LAN/MAN Standards Committee
(IEEE 802) [3].
Following
are the ISM frequency bands with corresponding IEEE Standards -
IEEE 802.11 Standards
|
ISM Frequency Bands
|
Description
|
Equipment that operate on
RF Range
|
802.11y
|
3.6 GHz
|
Standard for WLAN and operates in the
3650-3700 MHz
(introduced
in 2005 )
|
Operates at much higher powered Wi-Fi equipment
than traditional Wi-Fi equipment (coverage up to 3 miles or more)
|
802.11b
|
2.4 GHz
|
Max raw data rate of
11 Mbps
(introduced in 2000)
|
Wireless Devices such
as Mobile Phones, Laptops, Bluetooth devices, cordless telephones, and some
radio equipment.
|
802.11g
|
2.4 GHz
|
Max raw data rate of 56
Mbps (introduced in 2003)
|
|
802.11n
|
2.4 GHz & 5 GHz
(Dual Band)
|
Operates on both 2.4
GHz and 5 GHz bands with max. data rate at 450 Mbps
(introduce in 2007)
|
|
802.11a
|
5 GHz
|
Data rates are within
the range of 1.5 to 54 Mbps with error correction.
(introduced in 1999)
|
Wireless devices
|
802.11ac
|
5 GHz
|
Also Known as "Wireless AC" capable of 1300
Mbps which is 3x faster than 802.11n
(introduced in 2013)
|
For faster Wi-Fi
performance, 802.11ac standards is mostly used because it operates on data
rate from 433 Mbps to 1.3Gbps.
|
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