Wireless Channels


IEEE 802.11g/b wireless nodes communicate with each other using radio frequency signals in the ISM (Industrial, Scientific, and Medical) band between 2.4 GHz and 2.5 GHz. Neighboring channels are 5 MHz apart. However, due to spread spectrum effect of the signals, a node sending signals using a particular channel will utilize frequency spectrum 12.5 MHz above and below the center channel frequency. As a result, two separate wireless networks using neighboring channels (for example, channel 1 and channel 2) in the same general vicinity will interfere with each other. Applying two channels that allow the maximum channel separation will decrease the amount of channel cross-talk, and provide a noticeable performance increase over networks with minimal channel separation.
The wireless frequencies used by 802.11a and 802.11b/g networks are different. These channel frequency options are discussed below.

802.11b/g Wireless Channels

IEEE 802.11b/g wireless nodes communicate with each other using radio frequency signals in the ISM (Industrial, Scientific, and Medical) band between 2.4 GHz and 2.5 GHz. Neighboring channels are 5 MHz apart. However, due to spread spectrum effect of the signals, a node sending signals using a particular channel will utilize frequency spectrum 12.5 MHz above and below the center channel frequency. As a result, two separate wireless networks using neighboring channels (for example, channel 1 and channel 2) in the same general vicinity will interfere with each other. Applying two channels that allow the maximum channel separation will decrease the amount of channel cross-talk, and provide a noticeable performance increase over networks with minimal channel separation.
The radio frequency channels used in 802.11b/g networks are listed in Table B-1:
Table B-1: 802.11b/g Radio Frequency Channels
Channel
Center Frequency
Frequency Spread
1
2412 MHz
2399.5 MHz - 2424.5 MHz
2
2417 MHz
2404.5 MHz - 2429.5 MHz
3
2422 MHz
2409.5 MHz - 2434.5 MHz
4
2427 MHz
2414.5 MHz - 2439.5 MHz
5
2432 MHz
2419.5 MHz - 2444.5 MHz
6
2437 MHz
2424.5 MHz - 2449.5 MHz
7
2442 MHz
2429.5 MHz - 2454.5 MHz
8
2447 MHz
2434.5 MHz - 2459.5 MHz
9
2452 MHz
2439.5 MHz - 2464.5 MHz
10
2457 MHz
2444.5 MHz - 2469.5 MHz
11
2462 MHz
2449.5 MHz - 2474.5 MHz
12
2467 MHz
2454.5 MHz - 2479.5 MHz
13
2472 MHz
2459.5 MHz - 2484.5 MHz
Note: The available channels supported by the wireless products in various countries are different. For example, Channels 1 to 11 are supported in the U.S. and Canada, and Channels 1 to 13 are supported in Europe and Australia.
The preferred channel separation between the channels in neighboring wireless networks is 25 MHz (5 channels). This means that you can apply up to three different channels within your wireless network. There are only 11 usable wireless channels in the United States. It is recommended that you start using channel 1 and grow to use channel 6, and 11 when necessary, as these three channels do not overlap.

802.11a Legal Power Output and Wireless Channels

IEEE 802.11a utilizes 300 MHz of bandwidth in the 5 GHz Unlicensed National Information Infrastructure (U-NII) band. Though the lower 200 MHz is physically contiguous, the FCC has divided the total 300 MHz into three distinct domains, each with a different legal maximum power output. Below is a table of summary for different regulatory domains.
Table B-2:
U-NII Band
Low
Middle
High
Frequency (GHz)
5.15 - 5.25
5.25 - 5.35
5.725 - 5.825
Max. Power Output
· 50 mW for US
· 200 mW for Canada, Europe, and Australia
· 250 mW for US
· 200 mW for Europe and Australia
· 1 W for Canada
· 1 W for US and Australia
· 4 W for Canada
· 25 mW for Europe
802.11a Radio Frequency Channels
Note: Please check your local Authority for updated information on the available frequency and maximum power output.
IEEE 802.11a uses Orthogonal Frequency Division Multiplexing (OFDM), a new encoding scheme that offers certain benefits over a spread spectrum in channel availability and data rate. The 802.11a uses OFDM to define a total of 8 non-overlapping 200 MHz channels across the 2 lower bands; each of these is divided into 52 sub carriers and each carrier is approximately 300 KHz wide.
Figure B-1: IEEE 802.11a Channel Allocations
The WG511U user can use thirteen channels in non-turbo mode.
Table B-3: 802.11a Turbo Mode Off Radio Frequency Channels
Turbo Mode OFF
Channel
Frequency
36
5.180 GHz
40
5.200 GHz
44
5.220 GHz
48
5.240 GHz
52
5.260 GHz
56
5.280 GHz
60
5.300 GHz
64
5.320 GHz
149
5.745 GHz
153
5.765 GHz
157
5.785 GHz
161
5.805 GHz
165
5.825 GHz
The WG511U user can use five channels in turbo mode.
Turbo Mode ON
Channel
Frequency
42
5.21 GHz
50
5.25 GHz
58
5.29 GHz
152
5.76 GHz
160
5.8 GHz
The available channels supported by the wireless products in various countries are different.

NETGEAR, Inc.
http://www.netgear.com