Case Study: Measurements of Radio Frequency Exposure from Wi-Fi Devices

Annex A – Wi-Fi Standards, Spectral Allocations and Emissions

The common Wi-Fi standards are summarized in Table A.1.

Table A.1 – 802.11 Network standards
802.11 Protocol Release date Frequency (GHz) Channel bandwidth (MHz) Channel number Data rate per stream (Mbits/s) Allowable MIMO streams Modulation
- June 1997 2.4 20 1-14 (2.4 GHz) 1, 2 1 DSSS, FHSS
a Sept. 1999 3.7/5 20 131-138 (3.7 GHz) 34-165 (5 GHz) 6, 9, 12, 18, 24, 36, 48, 54 1 OFDM
b Sept. 1999 2.4 20 1-14 (2.4 GHz) 5.5, 11 1 DSSS
g June 2003 2.4 20 1-14 (2.4 GHz) 7.2, 14.4, 21.7, 28.9, 43.3, 57.8, 65, 72.2 1 OFDM, DSSS
n Oct.2009 2.4/5 40 1-14 (2.4 GHz) 34-165 (5 GHz) 15, 30, 45, 60, 90, 120, 135, 150 4 OFDM

Abbreviations: DSSS, direct sequence spread spectrum; FHSS, frequency hopping spread spectrum; MIMO, multiple input multiple output; OFDM, orthogonal frequency division multiplexing.

The following figures and tables show the spectral emission and channel allocation for 2.4-GHz Wi-Fi (Figure A.1, Figure A.2 and Table A.2) and for 5-GHz Wi-Fi (Figure A.3, Table A.3, Table A.4 and Table A.5).

Figure A.1 – 2.4-GHz spectral emission

Figure A.2 – Spectral emission of Wi-Fi AP2

Table A.2 – Wi-Fi channels in the 2400-2483.5 MHz band (RSS-210, Annex 8)
Channel Frequency (MHz)
1 2412
2 2417
3 2422
4 2427
5 2432
6 2437
7 2442
8 2447
9 2452
10 2457
11 2462
12 2467
13 2472
14 2484

Figure A.3 – Spectral emission of Wi-Fi AP1

Table A.3 – Wi-Fi channels in the 5150-5350 MHz band (RSS-210 Annex 9)
Channel Frequency (MHz)
34 5170
36 5180
38 5190
40 5200
42 5210
44 5220
46 5230
48 5240
52 5260
56 5280
60 5300
64 5320

Table A.4 ­ Wi-Fi channels in the 5825 MHz band (RSS-210, Annex 9)
Channel Frequency (MHz)
100 5500
104 5520
108 5540
112 5560
116 5580
120 5600
124 5620
128 5640
132 5660
136 5680
140 5700
149 5745
153 5765
157 5785
161 5805
165 5825

Table A.5 – Wi-Fi channels in the 5725-5875 MHz band (RSS-210, Annex 8)
Channel Frequency (MHz)
149 5745
153 5765
157 5785
161 5805
165 5825

Annex B – Near-Field and Far-Field Zones

An antenna whose largest dimension is no greater than the wavelength of its operating frequency is referred to as an electrically small antenna.20 The reactive near field of these antennas extend up to the distance given below:

Rrnf = λ/2π

where:

Rrnf is

the reactive near field, and
λ is the wavelength of the operating frequency

Rrnf at 2.437 GHz = 0.123/2p = 0.020 m (or 2 cm)
Rrnf at 5.18 GHz = 0.058/2p = 0.009 m (or 0.9 cm)

An antenna whose largest dimension is greater than the wavelength of its operating frequency is referred to as an electrically large antenna.21 The far-field region of this type of antenna extends from 2D2/λ to infinity, where D is the largest dimension of the antenna. In SC6, however, the transition region and the far-field region are considered to be the same, and the far-field region is therefore considered to extend from 0.5 D2/ λ to infinity.

Rff = 0.5D2

where:

Rff is the distance from the antenna to the boundary between the near field and far field in metres
λ is the wavelength of the operating frequency
D is an electrical dimension in metres

All measurement locations were in the far-field zone of both AP1 and AP2 (except for the measurement at 20 cm from AP1).

Annex C – Uncertainty due to Measurement Equipment

Table C.1 and Table C.2 list the expanded uncertainty of the measurement system (consisting of the Narda SRM 3006 and its electric field antennas) over its usable frequency range, with a confidence level of 95%.

Table C.1 – Expanded measurement uncertainty for three-axis E-field antenna 3501/02 from 75 MHz to 3 GHz (in conjunction with SRM basic unit and 1.5-m RF cable)
Frequency range (MHz) Single axis (dB) Isotropic measurement (dB)
75-900 +2.4 / –3.4 +2.4 / –3.3
>900-1400 +2.3 / –3.1 +2.4 / –3.3
>1400-1600 +2.2 / –3.1 +2.6 / –3.7
>1600-1800 +1.8 / –2.2 +2.2 / –3.0
>1800-2200 +1.8 / –2.2 +2.4 / –3.3
>2200-2700 +1.8 / –2.3 +2.6 / –3.6
>2700-3000 +1.9 / –2.4 +3.2 / –5.3

Table C.2 – Expanded measurement uncertainty for three-axis E-field antenna 3502/01 from 420 MHz to 6 GHz (in conjunction with SRM basic unit and 1.5-m RF cable)
Frequency range (MHz) Single axis (dB) Isotropic measurement (dB)
420-750 +2.1 / –2.9 +2.6 / –3.8
>750-1600 +2.0 / –2.7 +2.2 / –2.9
>1600-2000 +1.7 / –2.2 +1.9 / –2.4
>2000-4000 +1.7 / –2.2 +2.0 / –2.6
>4000-4500 +1.8 / –2.3 +2.2 / –3.0
>4500-5000 +1.9 / –2.5 +2.2 / –3.0
>5000-5000 +1.9 / –2.5 +2.5 / –3.5
>5000-6000 +1.9 / –2.5 +2.9 / –4.3

Annex D – Health Canada's Safety Code 6 Limits for Uncontrolled Environment

Industry Canada has adopted Health Canada's RF exposure guideline, Safety Code 6, in its regulation for the protection of the general public. The SC6 limits for uncontrolled environments are listed in Table D.1.

Table D.1 – Safety Code 6 limits for uncontrolled environments
Frequency
(MHz)
Electric field strength, rms
(V/m)
Magnetic field strength, rms
(A/m)
Power density
(W/m2)
Averaging time
(min)
0.003-1 280 2.19   6
1-10 280/f 2.19/f   6
10-30 28 2.19/f   6
30-300 28 0.073 2a 6
300-1500 1.585f0.5 0.0042 f0.5 f/150 6
1500-15,000 61.4 0.163 10 6
15,000-150,000 61.4 0.163 10 616,000/f1.2
150,000-300,000 0.158 f0.5 4.21 × 10–4f0.5 6.67 × 10–5f 616,000/f1.2

a Power density limit is applicable at frequencies greater than 100 MHz.

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