1. EE 445S Real-Time Digital Signal Processing Lab Fall 2013
Additional recitation slides for Lab 6 Quadrature Amplitude Modulation (QAM)
Debarati Kundu

2. Additional Constellation diagrams
Quadrature Phase Shift-Keying (QPSK)
Phase Shift Keying:
8-state Phase Shift-Keying (8-PSK)
16-state Phase Shift-Keying (16-PSK)
32-state Phase Shift-Keying (32-PSK)

3. QPSK Constellation points: Subset of 16-QAM constellation.
Not a unique representation,
but popular.
Constellation points lie in a
circle. (“Constant envelope”).
Gray coding employed.
Bandwidth unchanged
compared to BPSK.
Constellation diagram for QPSK

4. 8-PSK Three bits per symbol. Constellation points lie on a circle.
More data packed in at the same bandwidth, hence, more spectral efficiency.
Constellation diagram for 8-PSK

5. Even more spectral efficiency
Constellation diagram for 16-PSK
Constellation diagram for 32-PSK

6. An engineering tradeoff
Higher constellation indicates higher data rate.
But the points to come closer to each other.
At the receiver, higher SNR required at the same error performance.
Tradeoff between spectral efficiency and signal quality.