Shannon Channel Capacity

Shannon channel capacity gives the theoretical upper limit on how fast information can be sent over a noisy communication link if the only impairments are bandwidth limitation and additive white Gaussian noise. It comes from information theory: as bandwidth increases or the signal-to-noise ratio improves, the number of reliably distinguishable signal states per second rises, so the maximum error-free rate increases logarithmically rather than linearly. In practice, this is an ideal benchmark, not a guarantee, because real systems also suffer from coding losses, interference, fading, and hardware imperfections.

Use this formula when estimating the absolute data-rate limit of a communications channel, such as a radio link, fiber segment, or modem link, from its bandwidth and SNR. It is especially useful for comparing whether a target throughput is theoretically feasible before accounting for protocol overhead and implementation losses.

• Using SNR in dB directly instead of converting to a linear ratio first
• Forgetting that bandwidth B must be in hertz, not kHz or MHz, unless converted consistently
• Treating Shannon capacity as a guaranteed real-world throughput instead of a theoretical maximum