A. B. M. Nasiruzzaman Dept. of EEE, RUET 4B/5B Coding In 4B/5B, the 5 bit output that replaces the 4 bit input has no more than one leading zero and two trailing zeros. So when different groups are combined to make a new sequence there are never more than three consecutive 0s Some unused groups are used for control purposes Some are not used at all ; they provide a kind of error detection

A. B. M. Nasiruzzaman Dept. of EEE, RUET Table 4.2 4B/5B mapping codes

A. B. M. Nasiruzzaman Dept. of EEE, RUET Figure 4.16 Substitution in 4B/5B block coding

A. B. M. Nasiruzzaman Dept. of EEE, RUET We need to send data at a 1-Mbps rate. What is the minimum required bandwidth, using a combination of 4B/5B and NRZ-I or Manchester coding? Solution First 4B/5B block coding increases the bit rate to 1.25 Mbps. The minimum bandwidth using NRZ-I is N/2 or 625 kHz. The Manchester scheme needs a minimum bandwidth of 1 MHz. The first choice needs a lower bandwidth, but has a DC component problem; the second choice needs a higher bandwidth, but does not have a DC component problem. Example 4.5

A. B. M. Nasiruzzaman Dept. of EEE, RUET Figure B/10B block encoding

A. B. M. Nasiruzzaman Dept. of EEE, RUET Figure 4.18 AMI used with scrambling

A. B. M. Nasiruzzaman Dept. of EEE, RUET B8ZS (Bipolar with 8 Zero Substitution) substitutes eight consecutive zeros with 000VB0VB. violation; V denotes violation; this is a nonzero voltage that breaks an AMI rule bipolar; B denotes bipolar; this is a nonzero voltage in accordance with the AMI rule Note

A. B. M. Nasiruzzaman Dept. of EEE, RUET Figure 4.19 Two cases of B8ZS scrambling technique

A. B. M. Nasiruzzaman Dept. of EEE, RUET HDB3 (High-density bipolar 3-zero) substitutes four consecutive zeros with 000V or B00V depending on the number of nonzero pulses after the last substitution. Note

A. B. M. Nasiruzzaman Dept. of EEE, RUET 1. If the number of nonzero pulses after the last substitution is odd, the substitution pattern will be 000V Rule

A. B. M. Nasiruzzaman Dept. of EEE, RUET 2. If the number of nonzero pulses after the last substitution is even, the substitution pattern will be B00V Rule

A. B. M. Nasiruzzaman Dept. of EEE, RUET Figure 4.20 Different situations in HDB3 scrambling technique

A. B. M. Nasiruzzaman Dept. of EEE, RUET 4-2 ANALOG-TO-DIGITAL CONVERSION Pulse Code Modulation (PCM)

A. B. M. Nasiruzzaman Dept. of EEE, RUET Figure 4.21 Components of PCM encoder

A. B. M. Nasiruzzaman Dept. of EEE, RUET Figure 4.22 Three different sampling methods for PCM