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Building Wireless Community Networks, Second Edition by Rob Flickenger

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Interference

This device complies with part 15 of the FCC Rules. Operation is subject to the following two conditions: (1) This device may not cause harmful interference, and (2) this device must accept any interference received, including interference that may cause undesired operation.

[Labeling requirement in Part 15.19]

Description

Of course, interference is typically the state of the signal you are interested in while it’s being destructively overpowered by a signal you are not interested in.

The FCC has a specific definition of "harmful interference”:

Part 2.1(c) Harmful interference - Interference which endangers the functioning of a radio-navigation service or of other safety services or seriously degrades, obstructs, or repeatedly interrupts a radio-communication service operating in accordance with these [International Radio] Regulations.

In Part 15 it is repeated as:

Part 15.3(m) Harmful interference.

Any emission, radiation or induction that endangers the functioning of a radio navigation service or of other safety services or seriously degrades, obstructs or repeatedly interrupts a radio communications service operating in accordance with this chapter.

Interference will be a factor in your deployment. The 2.4GHz band is a bit more congested than the 5.8GHz band, but both have co-users that you must consider (see Table A-1).

Table A-1. Spectrum allocations for 802.11b and co-users

Part / Use

Start GHz

End GHz

Part 87

0.4700

10.5000

Part 97

2.3900

2.4500

Part 15

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