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


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




Quality Assurance Management.
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(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 ?
Caption: Figure 3: The computational complexity of the proposed detectors with [N.sub.T] = 4, [N.sub.R] = 4, and 64QAM modulation.
For generality, constellations BPSK, 8PSK, 64QAM, and 256QAM are assigned to s, respectively.
Uplink Transmission Scheme PAPR [dB] 4QAM 16QAM 64QAM OFDMA 10.7 10.7 10.7 LFDMA 7.5 8.5 8.7 SLM-LFDMA 5.9 6.6 6.8 PTS-LFDMA 4.7 5.6 5.8
comes with preset support for many common optical modulation formats, including QPSK, 16QAM, and 64QAM. If you are developing or working with nonconventional modulation formats, you can define your own format using Optical LinQ's powerful custom modulation format definition capability."
1 Simulations parameters and their values Parameters Values Digital Modulation QPSK, 8QAM, 16QAM, 64QAM, 265QAM Distance between Source 1Km and Destination, d Number of Relay Nodes, N 1, 4, 8 Channels AWGN, flat Rayleigh fading LDPC Codes WiMAX LDPC codes LDPC Code Rate, r 1/2, 2/3, 3/4, 5/6 Codeword Length, n 2304 bit Encoding Richardson-Urbanke algorithm Decoding Logarithmic BP algorithm Maximum number of iterations 30 Table.
In Figure 13, multiple QAM schemes, that is, 16QAM, 64QAM, and 128QAM, are considered for data modulation.
Modulation QPSK Code rate 1/3 1/2 2//3 3/4 4/5 5/6 SINR [dB] -0.8 1.7 3.7 4.7 5.5 6.0 Spectral 0.41 0.62 0.82 0.93 0.99 1.03 efficiency [bps/HZ] Modulation 16QAM Code rate 1/3 1/2 2//3 3/4 4/5 5/6 SINR [dB] 4.2 7.2 9.9 11.2 12.1 12.7 Spectral 0.81 1.24 1.65 1.86 1.98 2.07 efficiency [bps/HZ] Modulation 64QAM Code rate 1/3 1/2 2//3 3/4 4/5 5/6 SINR [dB] 8.3 12.0 15.6 17.2 18.9 20.0 Spectral 1.24 1.85 2.46 2.76 2.97 3.10 efficiency [bps/HZ]
WRAN mainly uses the constellation points of BPSK, QPSK, 16QAM, and 64QAM. BPSK is mainly used for pilots and preambles.
Within OFDM the number of parallel sub-carriers is the same (52), but the modulation for 6Mbps uses BPSK, while modulation for 54Mbps uses 64QAM. The WMN was fixed to transmit on channel 6 (2437MHz) with transmission power of 20dBm (100mW).
Both of the two techniques supports different modulations, such as QPSK, 16QAM, and 64QAM. In the physical layer design, the two techniques adopt orthogonal frequency division multiplexing access (OFDMA) and discrete Fourier transform spread orthogonal frequency-division multiplexing (DFTS OFDM).