[e2e] Collaboration on Future Internet Architectures

David P. Reed dpreed at reed.com
Thu May 3 07:18:47 PDT 2007

Jon Crowcroft wrote:
> 1/ some people have claimed that one can build many-to-many multihop radio
> systems that offer more capacity as the number of nodes join. If this is true,
> this can operate within quite a narrow band (e.g. ISM) and should be sufficient
> for a very long time. If we can show its true in that band, other bands can
> follow - within regions we still need to multipelx spectrum in some hard non
> liquid (dave reed) way just til some of the technology is better  the identifiers
> and management of this could be done through Virtual Private Wireless Channel
> Idenfiers which might use some name space we have seen before
A linear growth in capacity as nodes join probably does not provide more 
capacity per node.   The simple model one might imagine achieving is:  
Cap[System] = o(M*W*log(S/N)) where M is the number of nodes, W is the 
bandwidth, and S is signal power per station.   It is actually unknown 
whether this is an upper bound, if only because the standard analysis 
presumes that the noise process is independent at each receiver, an 
overly non-physical and way-too-conservative-assumption by a factor 
likely o(M^k) where k is >= 1.  

The per-node capacity in this hypothetical conservative model is thus 
Cap[node] = o(W*log(S/N)), and as you can see from that the English 
language translation would be "narrow band radio sucks!" or "narrow band 
radio is good for cooking!"  W is a limit, unless you want to fry any 
biological organisms in the field who respond not o(log(S)) but o(S).   
In other words, the reason for multiplexing a wideband system is that 
everyone can potentially achieve much higher burst rates without turning 
the world into a microwave oven.

This is the same reason that packet systems rather than rate-limited 
systems are better for many applications other than 3 kHz telephony - 
around which one might believe the entire communications incumbency 
rallies every time its government or god granted monopoly is threatened 
by technology change.

But there are still people out there who reason that "no one will ever 
need more bits per second than a human can type or a human can read", 
and US Senators who babble about Internets made of clogged pipes.


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