1. Introduction
1.1. Transmission of binary data in a format bit is usually used for short-range communication (ie.,data transmission within computer system.
1.2. Binary bits trasnmitted through wires, optical cable or RF must be encoded, so that high and low bit can be easily detected at the reciever.
1.3. Channel coding is performed at baseband digital signals by clock cycle.
2. Advantages of PCM
2.1. Uniform transmission quality
2.2. Compatibility of different classes of Traffic of the network
2.3. Low manufacturing cost
2.4. Integrated utilization of existing circuit
2.5. Good performance over very poor Transmission path
3. Disadvantages of PCM
3.1. Large Bandwidth required for transmission
3.2. Noise and crosstalk leaves low but rises attenuation
3.3. An integrated digital network can only be realized be a gradual extension of noise
4. Types of Encoding
4.1. number of channel code formats commonly use in PCM systems
4.2. 1. Non-return-to-zero (NRZ) 2. Return-to-zero (RZ) 3. Phase encoded and Delay Modulation
5. Non-return-to-zero (NRZ)
5.1. NRZ code format is a simple code
5.2. 1. Non-return-Zero-Level (NRZ-L)
5.2.1. Bit 1: high level
5.2.2. Bit0 : low level
5.3. 2. Non-return-to-zero-Mark (NRZ-M)
5.3.1. Bit 1 : level changes at the beginning of every bit
5.3.2. Bit 0 : no level change
5.4. 3. Non-return-to-zero-Space (NRZ-S)
5.4.1. Bit 1 : no change
5.4.2. Bit 0 : level change at the beginning of every bit
6. Return-to-Zero (RZ)
6.1. RZ code format goes to 0 for each clock cycle
6.2. 1. Return-to-zero unipolar (RZU)
6.2.1. Bit 1 : +ve pulse return to 0 before the end of bit
6.2.2. Bit 0 : no pulse
6.3. 2. Return-to-zero bipolar (RZB)
6.3.1. Bit 1 : +ve pulse return to 0 before the end of bit
6.3.2. Bit 0 : -ve pulse return to 0 before the end of bit
6.4. 3. Return-to-zero Alternate Mark Inversion (RZ-AMI)
6.4.1. Bit 1 : +ve & -ve pulse of equal amplitude are used alternatively
6.4.2. Bit 0 : No pulse
7. Phase Encoded and Delay Modulation
7.1. 1. Bi-Phase mark (Bi-Phase M)
7.1.1. Bit 1 : level changes at beginning until midway of bit
7.1.2. Bit 0 : no changes at midway
7.2. 2. Bi-Phase level (Bi-Phase L/Manchester)
7.2.1. Bit 1 : level change from high to low midway and return to 0
7.2.2. Bit 1 : level change from low to high midway and return to 0
7.3. 3. Bi-Phase space (Bi-Phase S)
7.3.1. Bit 1 : No changes at midway
7.3.2. Bit 0 : level changes at midway
7.4. 4. Differential Manchester
7.4.1. Bit 1 : Level changes at midway
7.4.2. Bit 0 : level change at the beginning
7.5. 5.Miller/Modulation Delay
7.5.1. Bit 1 : Level changes at midway
7.5.2. Bit 0 : No level change unless next bit is 0