128QAM

128QAM, or 128-State Quadrature Amplitude Modulation, is a digital modulation scheme used in various communication systems, including digital television broadcasting and wireless communications. It is a form of amplitude and phase modulation, where the amplitude and phase of a carrier wave are varied to encode data. In 128QAM, the amplitude and phase of the carrier wave can take on 128 different combinations, allowing for the transmission of more data per symbol compared to simpler modulation schemes like QPSK or 16QAM.

The 128QAM constellation diagram consists of 128 points, each representing a unique combination of amplitude and phase. These points are arranged in a grid-like pattern, with 16 points along the horizontal axis and 8 points along the vertical axis. The distance between adjacent points is proportional to the signal's amplitude, while the angle between the points represents the phase.

128QAM is more spectrally efficient than lower-order modulation schemes, meaning it can transmit more data within a given bandwidth. However, this increased efficiency comes at the cost of increased sensitivity to noise and interference. As a result, 128QAM is typically used in environments with high signal-to-noise ratios, such as cable television systems or wireless communications with strong line-of-sight links.

The use of 128QAM in digital television broadcasting allows for the transmission of high-definition video and audio signals with minimal interference. In wireless communications, 128QAM is used in various standards, including Wi-Fi (IEEE 802.11ac and later) and 4G LTE, to achieve high data rates and improve spectral efficiency.