Exam Questions Papers - Engineering

Q1:

Consider a Binary Symmetric Channel (BSC) with probability of error being p. To transmit a bit, say 1, we transmit a sequence of three 1 s. The receiver will interpret the received sequence to represent 1 if at least two bits are 1. The probability that the transmitted bit will be received in error is

A p3 + 3p2 (1 - p)

B p3

C (1 - p)3

D p3 + p2 (1 -p)

ANS:A - p3 + 3p2 (1 - p)

Probability of error = P Thus probability of no error = (1 - P) Now probability that transmitted bit, received in error = all bits are with error + one bit is with error = P3 + 3C1P2 (1 - P) = P3 + 3P2 (1 - P).