From: Janet Davis (jlnd_at_cs.washington.edu)
Date: Fri Feb 27 2004 - 10:36:46 PST
On Fri, 27 Feb 2004, Tony Offer wrote:
> For question 3 on homework3, I had two questions regarding the fact that
> stations cannot send and receive at the same time:
>
> 1) If a situation occurs in which a station attempts to send and receive
> at the same time, do the send and receive actions both fail, or does one
> "overpower" or take precedence over the other?
You should assume that while a station is sending, it is not able to
receive. The send operation may still be successful (see below).
> 2) Does the physical location in which a station cannot simultaneously
> send and receive encompass just the station itself or the station combined
> with the entire length of the link? For example, if a base station sends
> to the satellite at the same time the satellite broadcasts to the base
> stations, is there a send and receive conflict, even though the actual
> data being sent is physically separated by the distance between the base
> station and the satellite? Or can the two transmissions pass through each
> other in mid-air and successfully reach their destinations?
The latter: two transmissions can cross and successfully reach their
destinations. (The high delay would make life very difficult otherwise --
think about this.) There is a collision only if two transmissions arrive
at the same time, or if you do not receive another's transmission because
you are sending when it arrives.
Cheers,
Janet
-- Janet Davis jlnd_at_cs.washington.edu http://www.cs.washington.edu/homes/jlnd/ _______________________________________________ Cse461 mailing list Cse461_at_cs.washington.edu http://mailman.cs.washington.edu/mailman/listinfo/cse461
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