Limits of Coding: Nyquist's Theorem

• Says that you cannot stretch bandwidth to get higher and higher data rates indefinitely. There is a limit, called the Nyquist limit (Nyquist, 1924)

• If bandwidth = H; signaling scheme has V discrete levels, then:

  • Maximum Date Rate = 2 H log2 V bits/sec

• Implication 1: A noiseless 3 kHz channel cannot transmit binary signals at a rate exceeding 6000 bps

• Implication 2: This means that binary-coded signal can be completely reconstructed taking only 2 H samples per second

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