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Wireless devices, BPL, and modems may produce a higher line rate or gross bit rate, due to error-correcting codes and other physical layer overhead. It is extremely common for throughput to be far less than half of theoretical maximum, though the more recent technologies (notably BPL) employ preemptive spectrum analysis to avoid this and so ...
The 201A Data-Phone was a synchronous modem using two-bit-per-symbol phase-shift keying (PSK) encoding, achieving 2,000 bit/s half-duplex over normal phone lines. [10] In this system the two tones for any one side of the connection are sent at similar frequencies as in the 300 bit/s systems, but slightly out of phase.
V.91: A digital modem operating at data signalling rates of up to 64 000 bit/s for use on a 4-wire circuit switched connection and on leased point-to-point 4-wire digital circuits, published in 1999 V.92 is an ITU-T recommendation, titled Enhancements to Recommendation V.90 , that establishes a modem standard allowing 56 kbit/s download, 48 ...
The history of modems is the attempt at increasing the bit rate over a fixed bandwidth (and therefore a fixed maximum symbol rate), leading to increasing bits per symbol. For example, ITU-T V.29 specifies 4 bits per symbol, at a symbol rate of 2,400 baud, giving an effective bit rate of 9,600 bits per second.
For example, in a 64QAM modem, M = 64, and so the bit rate is N = log 2 (64) = 6 times the baud rate. In a line code, these may be M different voltage levels. The ratio is not necessarily an integer; in 4B3T coding, the bit rate is 4 / 3 of the baud rate. (A typical basic rate interface with a 160 kbit/s raw data rate operates at 120 kBd.)
14 kbit/s is only 40% of the theoretical maximum bit rate predicted by Shannon's theorem for POTS lines (approximately 35 kbit/s). [1] Ungerboeck's theories demonstrated that there was considerable untapped potential in the system, and by applying the concept to new modem standards, speed rapidly increased to 14.4, 28.8 and ultimately 33.6 kbit/s.
The SupraFAXModem 14400 is a v.32bis modem. When it was launched by Supra, Inc. in January 1992 for US$399 (equivalent to $870 in 2023), [N 1] the 14,400 bit/s model was less expensive than most existing 9600 bit/s models. This price/performance ratio made it a disruptive technology, and its introduction drove modem prices sharply downward ...
The Bell 202 modem was an early (1976) modem standard developed by the Bell System. It specifies audio frequency-shift keying (AFSK) to encode and transfer data at a rate of 1200 bits per second (bit/s), half-duplex. It has separate sets of circuits for 1200 bit/s and 300 bit/s rates. [1]