The Shannon limit defines the maximum achievable data rate for reliable communication over a noisy channel given what factor?

• A. The maximum theoretical data rate for reliable communication given the channel noise level
• B. The minimum energy per bit required for reliable reception
• C. The maximum bandwidth available for the channel
• D. The optimal modulation order for a given SNR

Answer: (A)

Shannon capacity tells us the highest data rate at which information can be sent over a noisy channel with arbitrarily small error, given the amount of noise in the channel. The defining relationship is C = B log2(1 + SNR), which shows that capacity depends on both the available bandwidth and the signal-to-noise ratio (the noise level). Since the question asks for the factor that sets this limit, the essential factor is the channel noise level (SNR). With more noise (lower SNR), the maximum reliable rate drops; with less noise (higher SNR), the rate can be higher. Modulation order or energy per bit influence practical performance, but the fundamental limit is governed by the noise level.