Some More INSTEON Questions

[upstatemike]

I know this has been covered but I still don't quite understand...

1- If every INSTEON device repeats every signal, how are collisions prevented once you start scaling up to large numbers of devices (say 100+)?

2- I have a "high density" area in my current X-10 setup. It is an L shaped room with 15 switches and modules installed along the outside walls. The outside wall is a single AC circuit and represents a total wire run of about 45 feet. The inside wall of the L has 5 devices on a second circuit so this one room contains 20 devices (not counting boosterlinks and filters) or about 20% of my total X-10 implementation. It works because only 2 devices are transmitters and I have a boosterlink on the circuit and filters on some loads to help out. If I convert these all to INSTEON will it work? Or will 15 transmitters in such close proximity on one circuit load the line to the point where repeating the signal doesn't help due to low impedance dampening eveything down to zero?

 

[AccessX10]

1- If every INSTEON device repeats every signal, how are collisions prevented once you start scaling up to large numbers of devices (say 100+)?

A quote from the INSTEON whitepaper:

Most networking protocols for shared physical media prohibit multiple devices from simultaneously transmitting within the same band by adopting complex routing algorithms. In contrast, INSTEON turns what is usually a problem into a benefit by ensuring that devices transmitting simultaneously will be sending the same messages in synchrony with each other.

Have you downloaded the whitepaper yet? If not, it should answer all of your questions.

To download:

http://www.accessha.com/forums/showthread.php?t=530

 

[upstatemike]

Thanks for the reminder, I had forgotten about the whitepaper! The technology appears sound. The price point is realistic. The light bar and LED color change kits give a nice WOW factor, and the shallow form factor puts them at the top of the list for ease of installation. I feel I am being drawn irrevocably into the INSTEON camp!

 

[electron]

btw, the INSTEON keyword links to the whitepaper, and other useful INSTEON information as well.

 

[PeterW]

Insteon's combination of timeslice hopping and simulcasting does seem to work really well here in practice. It's left the X10 (lack of) reliability in the dust.

Summary of the whitepaper.. Each packet has a 'hops left' count. If it is greater than 0, then each device subtracts 1 from the value simulcasts it on the next timeslice. What this usually means is that a packet will "echo" 2 or 3 times, but the duplicate packets are handled correctly.

What I mean by echo is.. suppose you have nodes

A - B - C - D

and they are a long way apart, and each device can ONLY hear its neighbor. In a large house, this kind of situation isn't out of the question.

A transmits with hopcount of 3. B hears it.

B transmits with hopcount of 2. A and C hear it.

A and C transmits with hopcount of 1. B (again) and D (finally!) hear it.

B and D transmit with a hopcount of 0. A and C hear it.. again!

ie: "A" heard its "echo" twice and squelched it. One caveat (not that it matters for the example): I'm not sure if repeaters will re-repeat a packet they've already repeated. I just don't recall.

With multiple devices, they just re-transmit over the top of each other. Suppose 'B' is actually a cluster of 4 devices in a large J-box. In this case, all of the 'B' devices recieve the same packet, and they all blast it out simultaniously onto the wire as a group. This is necessary in order to "overcome" the fact that they are each sucking each other's signal, but even then it is still an overall positive.

This is why adding more devices generally makes the network better. They all reinforce the signal as they go to make up for the fact that they are absorbing each other's signal and reducing the individual range of each device on its own. X10 on the other hand just sucks more and more signal away.

It would have been really cool if Smarthome had figured out a way to repeat X10 somehow. As I mentioned in the previous paragraph, adding devices reduces each device's range.. and since they use the same transmitter circuit, that means the "reach" of X10 part of the system is reduced while the Insteon reach goes up. Of course, adding non-Insteon X10 transmitters has exactly the same effect...

 

[rocco]

It would have been really cool if Smarthome had figured out a way to repeat X10 somehow.

Actually, that is what BoosterLinc is. I think they could have added it to their Insteno devices, but chose not to.