QAM

(redirected from 16QAM)
Also found in: Acronyms.

QAM

QAM

In Q, or basic telecommunication code, it means, “What is the latest met (weather)?”

QAM

(1)

QAM

(2)
Quality Assurance Management.

QAM

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

(2) (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 and 256QAM, four, five, six, seven and eight bits generate 16, 32, 64, 128 and 256 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.
References in periodicals archive ?
Thus, it will double the upload speed, on consolidation with the HSUPA 16QAM technology.
The SoC offers additional advanced features like high-gain soft decision forward error correction (SDFEC), digital transmit filtering supporting flexible grid DWDM, and high-performance carrier recovery that provides the robustness to phase noise that is required with 16QAM modulation.
Fully compliant with DVB-S and DIRECTV specifications, the STV0499 is also able to encode and decode 8PSK and 16QAM with backward compatibility to existing QPSK set-top boxes, smoothing the transition to higher broadcasting performances.
Grad A includes only QPSK modulation, grad B includes both QPSK and 16QAM.
Ciena s WaveLogic 3 Extreme chipset features 16QAM modulation, which doubles system traffic capacity with 200Gb/s per wavelength and allows for a simple-to-deploy dual subcarrier 400G solution.
These include BPSK, QPSK, DQPSK, OQPSK, IC/4 DQPSK, 8PSK, 16PSK, 16QAM, 64QAM, and 256QAM.
11a/g features are supported including data scrambling, forward error-correction via convolutional encoding at rates from 1/2 to 3/4, sub-channel coding of BPSK, QPSK, 16QAM or 64QAM, both short- and long-training sequences, pilot insertion, and the IFFT/FFT required to convert to/from time-domain RF I/Q signals.
Webb proposed an adaptive quadrature amplitude modulation (QAM) scheme, which had about 5dB improvement in the signal-noise-ratio (SNR) over fixed 16QAM [2].
The innovative design of the AEConnect system will allow AquaComms and its customers to take advantage of advanced modulation schemes such as 8QAM and 16QAM that provide greater spectral efficiency and reach.
Spectral efficiency gains in the trial were achieved by using Ciena's WaveLogic 3 based 16QAM coherent modulation, WaveLogic 3 spectral shaping, and Flexible Grid technologies.
This means the network can intelligently scale from 200Gbit/s to 300Gbit/s to 400Gbit/s and from QPSK to 8QAM to 16QAM as required.