> For a radio receiver it is irrelevant how many interfering signals exist.

> The only things that matter are the radiant intensity (i.e. power per solid angle) of the interfering transmitter and the percentage of the time when that transmitter is active.

And if a transmitter isn't pointed at you, then it isn't an interfering transmitter. This is a crucial factor in the math.

Or for a more realistic analysis of directionality, the radiant intensity is only high for a small fraction of observers, and is very low for the rest of them.

In the first scenario I talked about, total interference is probably the same.

In the second, total interference is almost always much less.

> A single interfering transmitter with high radiant intensity (a.k.a. EIRP) will blind the radio receiver for all the time when it is active.

If a moderate boost blinds the receiver, then the alternative is being almost blind for much longer (because there are more interfering transmitters), so I'm not convinced that's a problem.

> Doing discovery at a low bit rate is fine, but that means that your fancy phased array antenna cannot achieve any higher distance for communication than an omnidirectional antenna, but it can only increase the achieved bit rate at a given distance.

I don't understand what you mean.

If you don't care about speed, the maximum distance is the same for both antennas, and is defined by obstacles alone.

You can always slow down to compensate for a lack of gain. And it's a proportional slowdown, not very expensive. Especially when you only need to send a beacon that's a few bytes long to initiate contact.

Just some example numbers: Your functional requirements are 1Mbps of bandwidth with pretty tight focus. You send the few bytes of initial omnidirectional contact at 1Kbps. Your slow omnidirectional signal actually reaches further than your fast focused signal.

> Limiting EIRP is the right thing to do in order to limit the interference that you can cause to your neighbors.

If your only concern is the worst case of everyone being pointed at the same spot, yes. In normal situations the average level of interference matters more.

> The law does not stop you to use a phased array antenna or any other kind of directive antenna, with the purpose of lowering the power consumption of your transmitter, while maintaining the same quality for your communication and the same interference for your neighbors.

The law says that I can maintain quality and decrease interference, but I don't gain any real benefit because I'm only saving half a watt. So I'm not very motivated to do so. I'd prefer if it was legal to split the difference between increased signal quality and somewhat decreased interference.

> What you want to do, i.e. increase the interference for your neighbors, is the wrong thing to desire.

Where do you think I said that?

Edit:

> your neighbors would also

Here, I'll elaborate on a scenario.

Originally, me and my 6 neighbors are all transmitting omnidirectionally and causing 1 unit of interference to each other person. Everyone gets 6 units of interference.

I want to lower my transmit power but double my EIRP. I am entirely selfishly motivated, and just want a better signal to my devices. As a consequence I will now cause 2 units of interference to a single neighbor, and 0.1 units of interference to all other neighbors.

What happens when everyone thinks this way and does the same thing? Well now the neighborhood receives 2.5 units of interference on average instead of 6. Even with a bit of variance as devices move around, everyone is better off now. I love that my neighbors did the same thing I did.