On Wed, 1 Dec 1999, Nate Bargmann wrote:
> Hmmm, then why not just implement token ring? For one thing, for a
> multi-drop wireless LAN, it would seem to be an interesting solution.
> In fact it seems to me (thinking about it for the past 30 seconds) that
> the radio LAN would serve as a virtual MAU (Media Access Unit). Only
> trouble is that token ring testers and familiarity is much lower than
> Ethernet, but I think Token ring would lend itself well to such an
> application. The transmit and receive pairs are always split as the
> network is always an electrical ring from one station to the next and
> is a logical ring as well.
No. The case where every station on a packet channel hears everybody else
is the exception rather than the rule. On an uplink frequency it is
pretty much a requirement that the uplink station can communicate with
all users, so centralized media access makes a lot of sense.
On user-to-user frequencies almost no assumptions about who hears
what can be made, so there would have to be some data exchange
protocol. Consider a geography like
a b c d
Let's say two adjacent stations hear each other well but stations
further apart are pretty much out of earshot of each other. That
would mean the links a->b and d->c can be used simultaneously,
and so could b->a and c->d, but any other combination would cause
too much interference.
That means the best idea would be some kind of distributed algorithm
that groups stations accordingly, maybe based on signal strength
measurements. One flaw of such a system would be that "everyone
else" is required to remain silent while the signal of a given
station is being monitored. Propagating the information who
should transmit a test signal at what time is not trivial,
especially if we also consider asymmetric links.
Any ideas anyone?
Kai
