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QAM |
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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. Digital QAM In digital QAM, the input stream is divided into groups of bits based on the number of modulation states used. For example, in 8QAM, each three bits of input, which provides eight values (0-7) alters the phase and amplitude of the carrier to derive eight unique modulation states (see example below). In 64QAM, each six bits generates 64 modulation states; in 128QAM, each seven bits generates 128 states, and so on. See modulation.
QAM (communications)
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No references found | The ARRIS D5(TM) Universal Edge QAM is a unique modular edge network device that enables delivery of a wide variety of multimedia services over HFC networks. Our activities in this area focus on enhancing the competitiveness of cable operators who can leverage the established BigBand Networks CMTS and edge QAM platforms in order to economically expand the access speeds they provide to their subscribers, while also opening an upgrade path towards future innovations. Verizon uses QAM to deliver scheduled programming and IP to deliver on-demand video to FiOS TV customers. |
QAM |
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