QAM

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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) (Quantum Abstract Machine) An interface from Rigetti Computing for running programs in a hybrid classical/quantum computer environment. See 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.
References in periodicals archive ?
For example Tx power for 256QAM modulation is +20 dBm using 7/8 GHz; +17 dBm using 10,11,13,15 GHz, +12 dBm using 18,23,26 Ghz, -2 dBm using 24GHz and +10 dBm using 38 GHz frequency bands.
The speed was achieved by aggregating 60MHz of spectrum across three bands and applying 256QAM higher order modulation to deliver another evolution in speed and performance for Qatar's mobile Internet.
Through a series of innovations, it can utilize MBB speed to xGbps level based on existing and future LTE TDD features such as Massive MIMO, 3D Beamforming, 256QAM, and UDC.
The data transmission per symbol for the 4096QAM modulation method is 12 bits/symbol, making it more highly efficient than the 8-bits/symbol of the current widespread 256QAM modulation method.
The corresponding modulations are no modulation, 4QAM, 16QAM, 64QAM, and 256QAM. The noise variance is set to 1.2e-10.
In addition, Anritsu has introduced a single-instrument solution that enables 1-Gb/s IP data communications throughput testing based on its MD8475B signaling tester (Figure 5) that supports 4x4 MIMO with 256QAM high-order modulation and four-component carrier aggregation.
Together with 4CC carrier aggregation, 4x4 MIMO and 256QAM technologies, the trial used a Qualcomm SnapdragonTM X16 LTE mobile test device and Ericsson's micro Radio 2205 for LAA, which is designed for unlicensed spectrum use and provides small dimensions, flexible mounting and superior performance.
Assume that the SUs cooperate with the corresponding CH using a potential multiple-ary QAM, say 16QAM, 32QAM, 64QAM, 128QAM, or 256QAM. Then, the channel bandwidth of the SU-CH link can be written as
The wall-mountable router also features concurrent dual-band wireless operation (600 + 1733 Mbps), data transfer rates of up to 600 Mbps on 2.4GHz (3 spatial streams with 256QAM), data transfer rates of up to 1733 Mbps on 5GHz (4 spatial streams), 4 Removable and adjustable antennas, 4-Port Gigabit Switch/1-Gigabit WAN Port, USB 3.0 / 2.0 / eSATA Ports among others.
Testing 256QAM modulation demands lower EVM within the test system, Asquith said.