QAM

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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, 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 ?
56% de los resultados en uplink tienen un valor superior a los 30 dB que corresponde a la mejor modulacion 64QAM segun las especificaciones del fabricante [6].
4 MHz Number of BS 7 Antenna height of BS 25 (m) Antenna gain 17 dBi Type of antenna Omi directional Transmitted power of BS 40 W Number of recourse block (RBs) 6 Modulation and coding 64QAM code (0.
Axis Network Technology (AxisNT), a supplier of radio remote heads, software defined radios and high efficiency power amplifiers, has introduced a triple mode power amplifier module and IP linearisation solution, offering a 45% final stage efficiency for UMTS ETSI compliant 64QAM systems at 2.
By fixing transistor size and matching circuit, the new transmission amp achieves 64QAM - an efficiency of 1.
The pilot carriers are always BPSK modulated and the data carriers are BPSK, QPSK, 16QAM, or 64QAM.
The platform also dynamically chooses the most appropriate data modulation scheme, from BPSK to 64QAM based on the received signal quality, to provide the maximum possible throughput at all times.
The potentially high interference level makes higher order modulation schemes such as 64QAM impractical.
The live demonstration will show the electrical time domain output waveform with 64Gbaud PAM4 modulated signal, corresponding to an electrical domain signal to convert a 64QAM optical signal in succeeding optical modulators.
16 Release Date 1999/2001 2007 2001 Frequency Range 5855-5875 MHz 5-6GHz 5875-5905 10-66GHz 5905-5925 Channel 20 MHz 5, 10, 20 MHz 20, 25, 28 Mhz Modulation BPSK/QPSK BPSK/QPSK QPSK/16QAM 16QAM/64QAM 16QAM/64QAM 64QAM Data rate 54 Mbps 5.
1 Mbps on the assumption that 15 HS-PDSCH codes and 64QAM are used [22].