1. Differential Coding and Scrambling Six Meeting

2. Channel coding for error correction

3. Channel coding by scrambling

4. Differential coding

5. Differential Coding Example 1 1 1 0 0 1 0 Last Output: 0 0 1 1 1 1 1 1 0 0 0

6. Differential Coding Example 2 1 1 0 1 Last Output: 0 0 0 0 1 1 0 0 0 0 1

7. Scrambling: Shift Register

8. Self-synchronizing Scrambler An n-stage descrambler An n-stage scrambler

9. Scrambler: Example 0 0 0 0 0 0111001110Initial code 0 0 0 0 0 Stage 12345 0

10. Scrambler: Example 0 0 0 0 0 0111001110Initial code 0 0 0 1 1 Stage 12345 1

11. Self-synchronizing Descrambler + +

12. Tap Polynomial Self-synchronizing. scramblers do not need the frame synchronization, The x in the polynomial can be interpreted as a shift operator Pseudo-random binary sequences (PRBS) Put the shift register stages into a known start-up condition

13. Set–reset scrambling Sending Combining the input data with a PRBS in an exclusive-OR gate. Receiving Combining, in an exclusive-OR gate, the coded data with the identical pseudo-random sequence used at the transmitter, synchronization. Frame alignment must take place

14. Error Detection: Cyclic Redundancy Checks Original message = X X = 7654321. Divide this message number by G, G = 99 X = 7654321 = 77316 × 99 + 37 Reminder = 37 Sent message = Y Y = 765432137

15. Modulo-2 Cyclic Redundancy Checks Orig. Message: 11100110 Sent Message:111001100110

16. Org = 0110 Div = 01 1110 10 | 01100000 10 111 10 010 10 000 00

17. CRC With Shift Register (Nice View)