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Compen/EE 362
Asst. 4 Solution
Spring 2009
Problem 1.
Text Problem 230.Was previously assigned in error, same solution as before.
Problem 2.
Text problem 232:
“How many frames will be inspected on average to
resynchronize with probability < .001 of being wrong” modified to state: “How many frames will
have to be inspected, on average, such that the probability is .001 that the number is not
sufficient?” (A T1 carrier system slips and loses track of where it is. It tries to resynchronize
using the first bit in each frame.)
Solution. The search must continue until all 192 false places fail the test. The probability a
particular wrong place is eliminated after n tests is 1(½) . The probability all the false
n
places are eliminated after n tests is
n
p must be greater than .999. The smallest value of n that ensures this is n = 18
.
The following is not expected for the student to find:
Ignoring any bit errors, after any number of tests, the searcher is either certain because
only one position matches the pattern, or has a probability
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 Spring '09
 JOHNMETZNER

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