QAM

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QAM

McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.

QAM

In Q, or basic telecommunication code, it means, “What is the latest met (weather)?”
An Illustrated Dictionary of Aviation Copyright © 2005 by The McGraw-Hill Companies, Inc. All rights reserved

QAM

(1)

QAM

(2)
Quality Assurance Management.
This article is provided by FOLDOC - Free Online Dictionary of Computing (foldoc.org)

QAM

(1) (Quality Assessment Measurement) A system used to measure and analyze voice transmission.

(2) (Quantum Abstract Machine) An interface from Rigetti Computing for running programs in a hybrid classical/quantum computer environment. See QVM and quantum computing.

(3) (Quadrature Amplitude Modulation) A modulation technique that employs both phase modulation (PM) and amplitude modulation (AM). Widely used to transmit digital signals such as digital cable TV and cable Internet service, QAM is also used as the modulation technique in orthogonal frequency division multiplexing (see OFDM). The "quadrature" comes from the fact that the phase modulation states are 90 degrees apart from each other.

Analog QAM
Analog QAM uses two carriers 90 degrees out of phase with each other. Each carrier is modulated by an analog signal, and the resulting modulated waves are combined (see example below).

Digital QAM
In digital QAM, the number of modulation states determines how the digital signal is split up. For example, in 8QAM, each three bits of input alters the phase and amplitude of the carrier to derive eight unique modulation states (see example below).

In 16QAM, 32QAM, 64QAM, 128QAM, 256QAM, 512QAM and 1024QAM, from four to 10 bits generate from 16 to 1,024 modulation states respectively. See modulation and binary values.


Analog QAM
Analog QAM modulates two carriers 90 degrees out of phase with each from two analog input streams. The modulated carriers are combined and transmitted.







Digital QAM (8QAM)
In 8QAM, three input bits generate eight modulation states using four phase angles on 90 degree boundaries and two amplitudes (4 phases X 2 amplitudes = 8 states). Digital modulation greater than 8QAM is difficult to visualize.







Quadrature PSK (QPSK)
QPSK is like 4QAM without amplitude modulation. QPSK uses four phase angles to represent each two bits of input; however, the amplitude remains constant.
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References in periodicals archive ?
The effective throughput range is given by [eta]= {0,1,1.5, 2, 3, 4, 5} bits per symbol (BPS) when there is no-transmission, 4QAM, 8QAM, 16QAM, 32QAM, 64QAM and 256QAM are considered, respectively.
Caption: Figure 17: BER versus electrical received power for QPSK, 16QAM, 32QAM, and OFDM-16QAM at 1.5 m wireless distance.
Through this algorithm, NEC obtained an optimized 32QAM (opt32) constellation that achieves close to Shannon capacity, but more importantly, has a higher nonlinear capacity limit, which is especially more relevant to submarine transmission.
Switching threshold for MQAM without transmission blocking Mode Modulation Thresholds 1 4QAM SNR [less than or equal to] 15.6 dB 2 8QAM 15.6 dB<SNR [less than or equal to] 18.6 dB 3 16QAM 18.6 dB<SNR [less than or equal to] 21.5 dB 4 32QAM 21.5 dB<SNR [less than or equal to] 24.6 dB 5 64QAM SNR>24.6 dB Table 2.
2 represents one symbol, or five bits, in a 32QAM signal.
The value domain of each attribute in the decision table is expressed as follows: 1) Modulation mode ([C.sub.1]) : BPSK, QPSK, 8QAM, 32QAM .
The parameter-adaptation results are SJNR=21.4dBm; modulation-encoding combination is (32QAM, 4/5).
Assume that the SUs cooperate with the corresponding CH using a potential multiple-ary QAM, say 16QAM, 32QAM, 64QAM, 128QAM, or 256QAM.