Sunday, March 1, 2009

Defining the "Harm" in "Harmful Interference"

Here's a post from CommLawBlog which readers might find both interesting and informative when it comes to radio and wireless communications system interference....

"The concept of “harmful interference” is central to FCC spectrum policy. (It might surprise you however, that) the FCC has never said just what the term means. Oddly, though, that might be a good thing.

Nearly every band of the radio spectrum is shared among two or more categories of users. If we think of the spectrum as being spread out horizontally, the users of each band are stacked vertically. To see how this looks, click here.

Each band has a predetermined pecking order among its users: primary, secondary, and unlicensed. The relationships among all of these turn on harmful interference. Specifically:
  • “Primary” users are protected against harmful interference from all other users.

  • “Co-primary” users – services in the same band jointly designated as primary – may not cause harmful interference to each other.

  • "Secondary” users may not cause harmful interference to primary users, and must accept harmful interference from primary users.

  • Unlicensed users may not cause harmful interference to primary or secondary users, and must accept harmful interference from everybody.

The notion of harmful interference being key to the whole enterprise, we might expect to find a crisp and objective definition in the FCC rules. But when we look, we find something else. " (End excerpt)

Take a few minutes to learn more about the often mis-understood element of "harmful interference" - which is found in all radio and wireless communications systems - and the criteria that the FCC uses to help define it, here:

It's actually a pretty tough job these days, especially when spectrum matters....

See for more insight.


1 comment:

MJM said...

I have also written on this topic,

But I feel that the current vagueness of the definition favors the spectrum "haves" who have the potential to lobby FCC to keep the "have nots" out.

In any case, the lack of transparency on what is meant discourages capital formation for innovative radio technologies that will need a harmful interference finding from FCC.

Finally, the harmful interference problem will be key if Congress orders a spectrum inventory, see

Even if we know the location and technical details of all transmitters in the US, we may never agree on what is available for use. For example, while it is clear that AWS-3 band (2155-2175 MHz) is empty, there is a huge controversy about whether its use will lead to harmful interference to its neighbors - who happen to be using filters for the European band plan not the US one.

Imagine how many similar arguments will follow the spectrum inventory!