04122012 2nd Midterm The following Kxy table is given for 8B10B coding Current

# 04122012 2nd midterm the following kxy table is given

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04.12.2012 2nd Midterm The following K.x.y table is given for 8B10B coding. Current running disparity is given to be -1. What would be the coded output nibbles for the inputs “100”, “011” and “111”? y -D +D 000 0100 1011 001 1001 010 0101 011 0011 1100 100 0010 1101 101 1010 110 0110 111 0001 or 1000 1110 or 0111 Solution Since we are to select output nibbles that correct/compensate (or just preserve) running disparity, we need to select codes with higher number of 1’s than 0’s. For 100 we select 1101 for 011 we select either 0011 or 1100 for 111 we select either 1110 or 0111 so that the disparity either becomes 0 or +1 or stays at least the same.
151227621 DIGITAL COMMUNICATIONS 60 104.04.01.2013 Final Exam For the given parity bit equations, complete the table for single bit errors in information bits. Error in bit Syndrome vector 1 110 2 101 3 011 4 111 Solution Writing syndrome vector equations from above parity bit equations 1 1 2 4 5 s r r r r 2 1 3 4 6 s r r r r 3 2 3 4 7 s r r r r we calculate syndrome vectors for single bit errors in information bits using code vectors of “1000000”, “0100000”, “0010000” and “0001000”. 1 2 3 1 0 0 0 1, 0 1 0 0 1, 0 0 0 0 0 s s s   => s=110 1 2 3 0 1 0 0 1, 0 0 0 0 0, 1 0 0 0 0 s s s   => s=101 1 2 3 0 0 0 0 0, 0 1 0 0 1, 0 1 0 0 1 s s s     => s=011 1 2 3 0 0 1 0 1, 0 0 1 0 1, 0 0 1 0 1 s s s       => s=111 105. 04.01.2013 Final Exam A 3B4B minimum disparity code will be designed. Complete the following conversion table by selecting 4-bit correspondences to 3-bit inputs. Note that positive running disparity means there were more 1’s than 0’s in the previously transmitted data. Solution A solution is given below input output running disparity is + running disparity is - 000 0100 1011 001 1001 010 0101 011 0011 1100 100 0010 1101 101 1010 110 0110 111 0001 or 1000 1110 or 0111 5 1 2 4 c c c c 6 1 3 4 c c c c 7 2 3 4 c c c c
151227621 DIGITAL COMMUNICATIONS 61 Since the objective is to correct disparity or at least not to unbalance furthermore, many other code choices are also valid. Another example is given below. input output running disparity is + running disparity is - 000 0001 1110 001 0010 1101 010 0100 1011 011 0011 1100 100 0111 1000 101 1010 110 0110 111 1001 106. 04.01.2013 Final Exam Draw the rate 1/3 convolutional encoder given with 0 11111 O , 1 11011 O and 2 10101 O . Solution 107. 04.01.2013 Final Exam A ∆-Modulator (1 bit differential encoder) has the following input signal. Assuming the ∆ is the same as the distance between horizontal grids and sample/measurement points are at the vertical grid lines; a) Draw accumulator values on the same graph (first sample point is shown by a short line at the lower-left) b) Generate binary output D in D out
151227621 DIGITAL COMMUNICATIONS 62 Solution After drawing the accumulator value for 1 step per sample increment/decrements we generate the binary stream using increments=1 and decrements=0 assignments and get “…1010101111110000…”

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• Fall '18
• Mr. Bhullar
• Hamming Code, Error detection and correction, Parity bit

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