Multi level Digital Modulation
Multi-level digital modulation schemes are used to increase bit rate in data communications. Ordinary modulation techniques such as ASK, FSK and PSK are 2-level modulation schemes. They can transmit only 1- bit/sec.
To increase the bit rate (or data rate), we should be able to transmit more than 1-bit per second. This can be achieved by using multi-level modulation techniques. BAUD RATE is an important term related to multi-level modulation.
Baud rate: is defined as number of symbols per sec. Example of one symbol of carrier waveform is shown below:
Generally in 2-level modulations, only 1-bit can be transmitted in one cycle or symbol. In multi-level modulation, we can transmit more than one bit per symbol.
2 level modulation ----- 2 = 21 ----- 1 bit per symbol is transmitted 4 level modulation ----- 4 = 22 ----- 2 bits per symbol is transmitted 8 level modulation ----- 8 = 23 ----- 3 bits per symbol is transmitted etc.
