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MCQ Practice Question
Communication SystemsError Performance

Which digital modulation among coherent BPSK and coherent QPSK has the same theoretical BER versus Eb/N0 in ideal AWGN when Gray mapping and coherent detection are used?

  • AQPSK can have the same BER as BPSK
  • BQPSK must always have twice the BER
  • CBPSK always has zero BER
  • DNeither can operate in AWGN
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Correct Answer: A. QPSK can have the same BER as BPSK
Explanation: Coherent Gray-coded QPSK can be viewed as two orthogonal BPSK channels, giving the same theoretical bit-error performance versus Eb/N0 in ideal AWGN.
Reference: Standard communication systems: error performance
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