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Spectral efficiency, spectrum efficiency or bandwidth efficiency refers to the information rate that can be transmitted over a given bandwidth in a specific communication system. It is a measure of how efficiently a limited frequency spectrum is utilized by the physical layer protocol, and sometimes by the medium access control (the channel ...
where is the pulse frequency (in pulses per second) and is the bandwidth (in hertz). The quantity later came to be called the Nyquist rate, and transmitting at the limiting pulse rate of pulses per second as signalling at the Nyquist rate. Nyquist published his results in 1928 as part of his paper "Certain topics in Telegraph Transmission Theory".
the maximum modulation frequency (or range of modulation frequencies) of an optical modulator; the range of frequencies in which some measurement apparatus (e.g., a power meter) can operate; the data rate (e.g., in Gbit/s) achieved in an optical communication system; see bandwidth (computing).
When instead, the frequency range is (A, A+B), for some A > B, it is called bandpass, and a common desire (for various reasons) is to convert it to baseband. One way to do that is frequency-mixing the bandpass function down to the frequency range (0, B). One of the possible reasons is to reduce the Nyquist rate for more efficient storage.
Bandwidth (computing), the maximum rate of data transfer across a given path Channel capacity , an information-theoretic upper bound on the rate at which data can be reliably transmitted, given noise on a channel
The consumed bandwidth in bit/s, corresponds to achieved throughput or goodput, i.e., the average rate of successful data transfer through a communication path.The consumed bandwidth can be affected by technologies such as bandwidth shaping, bandwidth management, bandwidth throttling, bandwidth cap, bandwidth allocation (for example bandwidth allocation protocol and dynamic bandwidth ...
Early uses of the term Nyquist frequency, such as those cited above, are all consistent with the definition presented in this article.Some later publications, including some respectable textbooks, call twice the signal bandwidth the Nyquist frequency; [6] [7] this is a distinctly minority usage, and the frequency at twice the signal bandwidth is otherwise commonly referred to as the Nyquist rate.
This is called the bandwidth-limited regime. When the SNR is small (SNR ≪ 0 dB), the capacity ¯ is linear in power but insensitive to bandwidth. This is called the power-limited regime. The bandwidth-limited regime and power-limited regime are illustrated in the figure.