The
rate at which data can be transmitted over a given communication channel, under
given conditions, is referred as the channel capacity.
There
exist two formulas for calculate theoretical maximum data rate. Nyquist bit
rate for noiseless channel and Shannon
capacity for noisy channel.
Nyquist Bit Rate
The
Nyquist bit rate formula is use to calculate the theoretical maximum bit rate.
Bit
rate=2*bandwidth*log2L
Where
bandwidth is the bandwidth of the channel, ‘L’ is the signal level used to
represent data.
Signal-to-Noise Ratio (SNR)
To
calculate theoretical bit rate for noisy channel we need to consider signal to
noise ratio of that channel. The signal to noise ratio is defined as
SNR=average
signal power/average noise power
A
high SNR means the signal is less corrupted by noise and a low SNR means the
signal is more corrupted. Because the signal to noise ratio is the ratio of two
powers, usually the SNR is described in decibel unit.
SNRdb=10log10SNR
Shannon Capacity
To
determine the theoretical highest data rate for a noisy channel, we can use Shannon capacity.
Capacity=
bandwidth * log2(1+SNR)
When
SNR is very high, we can use the following formula for calculate highest data
rate,
Capacity
= bacdwidth * SNRdb/3
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