Quadriphase Phase Shift Keying - QPSK
Proposed as physical layer standard for CATV reverse channel modulation in use with Cable Modem by SA
Power efficient digital data modulation technique
2 bits/Hz efficience in spectrum use cf BPSK
Practical for use in burst mode
Satellite and Digital Video cable systems employ QPSK in burst mode
Ease of implementation and excellent performance for even low C/N ratios
Framing Issues
Guard band
Preamble
Sync Word
Data Field
Reed-Solomon Parity