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The feedback capacity is known as a closed-form expression only for several examples such as the trapdoor channel, [14] Ising channel, [15] [16]. For some other channels, it is characterized through constant-size optimization problems such as the binary erasure channel with a no-consecutive-ones input constraint [ 17 ] , NOST channel [ 18 ] .
As an example of how the 2D spreading on VSF-OFCDM works, if you take the first data symbol, d 0, and a spreading factor in the time domain, SF time, of length 4, and a spreading factor in the frequency domain, SF frequency of 2, then the data symbol, d 0, will be multiplied by the length-2 frequency-domain PN codes and placed on subcarriers 0 ...
Frequency-selective time-varying fading causes a cloudy pattern to appear on a spectrogram. Time is shown on the horizontal axis, frequency on the vertical axis and signal strength as grey-scale intensity. In wireless communications, fading is the variation of signal attenuation over
Frequency diversity: The signal is transmitted using several frequency channels or spread over a wide spectrum that is affected by frequency-selective fading. Later examples include: Later examples include:
Techniques known since the 1940s and used in military communication systems since the 1950s "spread" a radio signal over a wide frequency range several magnitudes higher than minimum requirement. The core principle of spread spectrum is the use of noise-like carrier waves, and, as the name implies, bandwidths much wider than that required for ...
The following channels are the principal multi-terminal channels first introduced in the field of information theory [citation needed]: A point-to-multipoint channel , also known as broadcasting medium (not to be confused with broadcasting channel): In this channel, a single sender transmits multiple messages to different destination nodes.
In telecommunications, common-channel signaling (CCS), or common-channel interoffice signaling (CCIS), is the transmission of control information via a separate channel than that used for the messages, [1] [2] The signaling channel usually controls multiple message channels.
Frequency (subcarrier) interleaving increases resistance to frequency-selective channel conditions such as fading. For example, when a part of the channel bandwidth fades, frequency interleaving ensures that the bit errors that would result from those subcarriers in the faded part of the bandwidth are spread out in the bit-stream rather than ...