# QAM

(redirected from 8QAM)
Also found in: Acronyms.

(communications)

## QAM

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

(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, 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.
References in periodicals archive ?
where, MOD denotes the selected modulation format (it will be replaced by BPSK, QPSK, 8QAM or 16QAM) and [C.sub.EON-MOD] is the corresponding slot capacity.
If we assume that [alpha], [beta], [gamma] and [delta] are coefficients which determine the distribution of the selected modulation formats (BPSK, QPSK, 8QAM and 16QAM) in the network respectively, [alpha][greater than or equal to]0, [beta][greater than or equal to]0, [gamma][greater than or equal to]0, [delta][greater than or equal to]0 and [alpha]+[beta]+[gamma]+[delta]=1.
Proper modulation-encoding combinations NO.1 NO.2 NO.3 NO.4 NO.5 NO.6 Modulation Mode BPSK QPSK QPSK QPSK 8QAM 32QAM LDPC Encoding Rate 1/4 1/4 1/2 4/5 4/5 4/5 Normalized Rate 0.0625 0.125 0.25 0.4 0.6 1.0 Table 2.
Another key benefit of the 150 Gb/s 8QAM technology is the ability to provide high-capacity DCI, which is instrumental in connecting todays app-centric, on-demand society.
Leading programmability/reach powered by Coriant CloudWave Optics, the Coriant Groove G30 DCI Platform supports dynamically adjustable modulation formats (16QAM, 8QAM, QPSK) to deliver cost-optimized optical reach in both metro and long haul applications.
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.
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.
The platform supports 400G in one rack unit with 16QAM now for extended distances with flexible modulation formats available, including QPSK and now, the latest 8QAM capability available via WaveLogic 3 Extreme, for the longest hauls needed.
The ZTE 400G solution features multiple modulations including Nyquist QPSK, 16QAM and 8QAM. It is designed to meet carriers requirements for different network scenarios and transmission reaches.

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