Chapter 5 - Signal Encoding Techniques Part 2

5.2/ Digital Data, Analog Signals
A modem (modulator-demodulator) is used to modulate, encode, digital data into an analog signal and vice versa.

Basic techniques to convert digital data into analog signals:

1. ASK (Amplitude Shift Keying) - represents digital data as different amplitudes in a carrier signal. For a binary data, zero amplitude can represent a binary 0 and another amplitude will represent a binary 1.
2. FSK (Frequency Shift Keying) - represents digital data as different frequencies in a carrier wave. BFSK is binary FSK.
   
3. PSK (Phase Shift Keying) - represents digital data as different phases in a carrier signal. BPSK is binary PSK.
   

5.3/ Analog Data, Digital Signals
digitization - conversion of analog to digital.
A codec (coder-decoder) is a device used to digitize (encode) or decode data.

Basic techniques to convert analog data into digital signals:

1. PCM (Pulse Code Modulation) - the sampling of analog data at a minimum rate (twice the frequency) and the conversion of the samples to a digital (usually binary) code.
2. DM (Delta Modulation) - the differential of the sampling of analog data is converted to a digital code.
   

5.4/Analog Data, Analog Signals

Basic techniques to convert analog data into analog signals:

1. AM (Amplitude Modulation) - involves modification of the amplitude of the transmitted signal to represent data.
   
2. PM (Phase Modulation) - involves using the phase to represent data.
3. FM (Frequency Modulation) - involves modification of the frequency of the transmitted signal to represent data.

The information above is based on the textbook Data and Computer Communications by William Stallings.