QUESTION

(a) Consider the following digital bit stream 01001100 is to be encoded in:

i. NRZ-I
ii. Pseudoternary
iii. Manchester
iv. Differential Manchester

Show the waveforms for each of the above-mentioned codes showing clearly the bit durations, signal levels and transitions where necessary.

(Assumptions: The signal level for NRZ-I for most recent preceding mark was positive; the signal level of the most recent preceding space was negative for Pseudoternary).

(b) A frame transmitter is using the generator polynomial x⁴ + x + 1 and that the header contains the above bit pattern: 10100110. Derive the transmitted CRC header checksum.

(c) Show how you could use a (11,7) block code to correct and detect a 1-bit error if say, the subsequent 1011000 bit pattern is received, while the original 1001000 bit pattern was transmitted.