I just read in a post by Jeff Liebermann that ad-hoc mode only supports
9 nodes at time.
Why is this?
I would like to create an ad-hoc network that allows an essentially unlimited number of nodes present.
What low-level exchanges are involved in an ad-hoc network. I would also like to know what configuration of the transceivers would allow the *absolute miminum* delay between the time N nodes present themselves into a space and the time that they can start sending data frames between each other.
Note that I am only interested in what happens at the link-layer and below. Above the link-layer, I am not concerned.
There's no real limitation in the 802.11 spec to the number of nodes. There may be some limit to bridging table sizes, but nothing inherent in the specification. Microsoft recommends 9 clients maximum, but I've connected many more without much difficulty. |
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Ad Hoc is sometimes called peer to peer mode or Independent Basic Service Set (IBSS). If you don't mind having your brain turned to mush, read IEEE 802.11-1999. |
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Unlimited is a very large number. Please note that wireless mesh networks are essentially a collection of ad-hoc networks.
The IBSS protocol is defined in IEEE 802.11-1999.
That's going to be a difficult. Optimimum timing for large systems is usually provided by synchronous intelligent polling. However, the FCC clearly specifies that there is to be no synchronization between Part
15.247 radios. That's to insure that one system does not hog all the airtime in an area. That also means you're going to have collisions and timing issues no matter what you do.
Hint: Search Google for "queueing model 802.11 ad hoc". There has been quite a bit of research on optimizing wireless systems.
Also, you might want to look at:
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has a large number of wireless mobile ad-hoc papers.
Great info. :) I've visited the Monarch site a few times over the years.
I started reading that each night before bed time. I searched the doc for ad-hoc and came up with some links that did not say what was involved. I tried to cheat by reading the overview only (Chapter 5) and again, the information was light in nature. The only thing I am concerned with is the necessary minimum exchange required before two ad-hoc nodes can send frames to/from each other.
I would also like to know, aside from RSSI, what harware indicators there are to support notification of a (perceived) change in PHY state.
I'm still going to read the 802.11 spec, but in truth, these are the only two pieces of information that I need to determine whether what I am trying to do will work.
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