# QAM

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(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 ?
In the mobility testing, it was found that there were numerous regions along the drive route where 256 QAM availability was higher with Ericsson Lean Carrier enabled.
Declining ASPs and channel shipments edged the global CMTS and edge QAM market down for the 3rd consecutive quarter in 4Q12, as revenue fell 1% sequentially, to \$284 million
The discussions then continue by contriving sophisticated iterative coded modulation systems, such as TCM, TTCM, BICM, BICM-ID designed for turbo-detected QAM-based space-time coded OFDM and CDMA systems operating over wireless channels In summary, this volume amalgamates a comprehensive textbook with a deep research monograph on the topic of QAM, ensuring it has a wide-ranging appeal for both senior undergraduate and postgraduate students as well as practicing engineers and researchers.
For the demonstration, held in Zurich, Switzerland, 256 QAM was introduced using software from the recently announced Ericsson Networks Software 16A, which will become commercially available later in 2015.
announces today its latest next generation access solution for its node platform, the RQ4000-series "Remote QAM.
CommScope's wideband edge QAM solution earned both honors in this year's reviews, an impressive accomplishment indeed.
CommScope's LxS-16016 wideband edge QAM will be showcased during the upcoming CableLabs(R) Summer Conference in Keystone, CO, August 8-9, 2011.
a global leader in infrastructure solutions for communications networks, will introduce what it believes to be the cable industry's first all-digital, carrier-grade wideband edge QAM (quadrature amplitude modulation) solution--the LxS-16016--during The Cable Show this week.
By integrating a QAM interface with an EPON optical network unit, or ONU, a cable operator can easily offer digital TV services without building new video distribution networks.
BroadLogic brings unique silicon solutions to a QAM device," said Xu Ming, general manager of ZTE's Fixed Network product line.
Company Expands MSP Product Suite Combining Multi-Service Platform with New Ultra Dense QAM
AT3535G Supports 80-plus QAM Channels and Includes a Pre-Amp, Two Developments Fostering Cable's Evolution toward the Delivery of More Advanced Offerings

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