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Homework Help: Multi-path propagation

  1. Feb 12, 2009 #1
    1. The problem statement, all variables and given/known data


    Consider the multi-path propagation phenomenon discussed in class. Assume the signal from a sender takes 4 paths to arrive at the receiver, and the delay along each path is 3, 6, 9, 21 (in micro-seconds), respectively. Each symbol is 1 bit long. Two symbols can be successfully received/detected at the receiver if their received impulses are at least 1 micro-second apart. What is the maximum allowed transmission rate from the sender to the receiver?

    2. Relevant equations

    delay along each path is 3, 6, 9, 21 (in micro-seconds)


    3. The attempt at a solution

    no idea
     
  2. jcsd
  3. Feb 12, 2009 #2

    Delphi51

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    You could send at the maximum 1 bit per microsecond . . . for 3 microseconds. Then you are going to get interference from the path with delay 6. How long must you wait before things quiet down?
     
  4. Feb 13, 2009 #3
    3+6=9 microseconds?? is it?
     
  5. Feb 13, 2009 #4

    Delphi51

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    The 2nd path message arrives 3 microseconds later.
    You only get that long before you have to stop and wait.
     
  6. Feb 16, 2009 #5
    there are four paths with delay 3, 6, 9, 21 (in micro-seconds)
    for the first path require 3
    first to second path require 3
    second to third require 3
    third to forth require 21-9=12
    therefore 3+3+3+12 in total is it?
    maximum allowed transmission rate from the sender to the receiver is 21?
     
  7. Feb 16, 2009 #6

    Delphi51

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    I don't understand your total.
    I should say I don't know much about this - just interested!
    I am thinking like this:
    SEND time 0 to 2: Receive on path 1 from time 3 to 5 -> 3 bits delivered
    Interference 6 to 8, 9 to 11 and 21 to 23

    SEND time 9 to 11: Receive on path 1 from 12 to 14 - 3 bits delivered
    Interference 15 to 17, 18 to 20, 30 to 32

    So far 6 bits in 14 us. If you kept up the chart for a while, say 60 us, you would have a pretty good idea of the delivered bit rate.
     
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