More Complicated Signals Sets

• Using difference in phase, we can construct signal sets with more than two signals.
• The signal set below uses four sinusoids with different phases.
• This signal set is called quarternary phase shift keying or QPSK.
• It is very popular in practice.
• With this signal set, 2 bits can be transmitted simultaneously.

  

Figure 2.28: Signal Set with four sinusoids of different phase.