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In a digitally modulated signal or a line code, symbol rate, modulation rate or baud rate is the number of symbol changes, waveform changes, or signaling events across the transmission medium per unit of time. The symbol rate is measured in baud (Bd) or symbols per second. In the case of a line code, the symbol rate is the pulse rate in pulses ...
Digital 16-QAM with example symbols Constellation points for 4-QAM, 16-QAM, 32-QAM, and 64-QAM overlapped As in many digital modulation schemes, the constellation diagram is useful for QAM. In QAM, the constellation points are usually arranged in a square grid with equal vertical and horizontal spacing, although other configurations are ...
In a 6 MHz channel, the data rate is at most 36 Mbit/s (for 64-QAM or 8-VSB); the 8-VSB ATSC achieves a data rate of 19.3926 Mbit/s while the 64-QAM J.83b achieves a data rate of 26.970 Mbit/s. While both systems use concatenated trellis/RS coding, the differences in symbol rate and FEC redundancy account for the differences in rate.
The advantage of APSK over conventional QAM is a lower number of possible amplitude levels and therefore a lower peak-to-average power ratio (PAPR). [2] The resilience of APSK to amplifier and channel non-linearities afforded by its low PAPR have made it especially attractive for satellite communications, including DVB-S2 .
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If the impulse responses of the two filters are chosen as sine and a cosine, the only mathematical difference between QAM and CAP waveforms is that the phase of the carrier is reset at the beginning of each symbol. [1] If the carrier frequency and symbol rates are similar, the main advantage of CAP over QAM is simpler implementation. [1]
DVB-C2 allows bit rates up to 83.1 Mbit/s on an 8 MHz channel bandwidth when using 4096-QAM modulation; future extensions will allow up to 97 Mbit/s and 110.8 Mbit/s per channel using 16384-QAM and 65536-AQAM modulation. [3] Modes and features of DVB-C2 in comparison to DVB-C:
Each symbol is encoded as a different phase shift of the carrier sine wave: 0°, 45°, 90°, 135°, 180°, 225°, 270°, 315°. A constellation diagram is a representation of a signal modulated by a digital modulation scheme such as quadrature amplitude modulation or phase-shift keying . [ 1 ]