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To: cs551@merlot.usc.edu
Subject: Re: Lecture 24 
Date: Fri, 04 May 2007 22:31:33 -0700
From: william@bourbon.usc.edu

Someone wrote:

  > I have a doubt regarding your previous reply,
  > 
  > I believe Collision is very much different from the case of
  > "Hidden terminal" Coz in collison B cannot hear from either of
  > the two sources but in "hidden terminal" A is already sending
  > some byte stream to B when C tries to send to B.
  > 
  > This is further exemplified in paper [MACAW]  section 2.2 second
  > paragraph.
  > 
  > Please correct If I am wrong

Section 2.2 of the MACAW paper did say that "this produces a
collision at B" (in the last paragraph on the 2nd page of the
paper).  The reason for the collision is "hidden terminal".

In your original e-mail, you used the word "intervene" and
it's not a technically word in this context.

For the exams, if you use a word that does not have the right
meaning, you won't get credit for it.  You cannot argue that
you mean the right thing but just put down the wrong word.
To be fair to all, I can only grade what you wrote and not
what's in your mind!
--
Bill Cheng // bill.cheng@usc.edu <URL:http://merlot.usc.edu/william/usc/>




  ----- Original Message -----
  From: william@bourbon.usc.edu
  Date: Friday, May 4, 2007 8:21 pm
  Subject: Re: Lecture 24
  To: cs551@merlot.usc.edu
  
  > Someone wrote:
  >
  >  > 1) In lecture 24 slide 20 The "hidden terminal"  Problem means A
  >  > sending to B while C interveans.
  >  > Correct??
  >
  > Well, you should get the terminology correct.  If you go to the
  > previous page, this is "collision".
  >
  >  > 2) Also just wanted to confirm that . All the CTS packets are
  >  > sent to all members in the Cell.
  >  > Correct??
  >
  > I wouldn't say "send to".  "Send to" sounds like the case
  > that if you have N other nodes, you send N packets.
  >
  > These nodes are using wireless radios.  One node puts out a
  > signal.  Any node that's in range can hear it.
  >
  >  > 3)Can it be interpretted that the CTS packets are multicasted
  >  > ones??
  >
  > Multicast is basically a mode of "addressing".  It's more like
  > broadcast for wireless.  Only nodes within range can hear the
  > broadcast.
  > --
  > Bill Cheng // bill.cheng@usc.edu
  > <URL:http://merlot.usc.edu/william/usc/>