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DTUS065 rev A.7 – June 27, 2014
XII
APPENDIX – RADIO CHANNELS LIST
XII.1
11b/g (2.4GHz)
These networks use the ISM (Industrial Scientific and Medical) radio band
on the [2.3995-2.4965] spectrum.
Channel
(25 MHz)
Central frequency
(GHz)
Allowed by
1
2,412
Asia MKK, Europe ETSI, US FCC
2
2,417
Asia MKK, Europe ETSI, US FCC
3
2,422
Asia MKK, Europe ETSI, US FCC
4
2,427
Asia MKK, Europe ETSI, US FCC
5
2,432
Asia MKK, Europe ETSI, US FCC
6
2,437
Asia MKK, Europe ETSI, US FCC
7
2,442
Asia MKK, Europe ETSI, US FCC
8
2,447
Asia MKK, Europe ETSI, US FCC
9
2,452
Asia MKK, Europe ETSI, US FCC
10
2,457
Asia MKK, Europe ETSI, US FCC
11
2,462
Asia MKK, Europe ETSI, US FCC
12
2,467
Asia MKK, Europe ETSI
13
2,472
Asia MKK, Europe ETSI
14
2,484
Asia MKK
Besides specifying the center frequency of each channel, 802.11 also
specifies (in Clause 17) a spectral mask defining the permitted distribution
of power across each channel. The mask requires that the signal be
attenuated by at least 30 dB from its peak energy at ± 11 MHz from the
center frequency, so that the channels are effectively 22 MHz wide. One
consequence is that stations can only use every fifth channel without
overlap, typically 1, 6 and 11 in the Americas, 1-13 in Europe, etc. Another
is that channels 1-13 effectively require the band 2401-2483 MHz, the actual
allocations being for example 2400-2483.5 in the UK, 2402-2483.5 in the
US, etc.
Since the spectral mask only defines power output restrictions up to ± 22
MHz from the center frequency to be attenuated by 50 dB, it is often
assumed that the energy of the channel extends no further than these limits.
It is more correct to say that, given the separation between channels 1, 6, and
11, the signal on any channel should be sufficiently attenuated to minimally
interfere with a transmitter on any other channel. Due to the near-far
problem, a transmitter can impact a receiver on a “non-overlapping”
channel, but only if it is close to the victim receiver (within a meter) or
operating above allowed power levels.
