Graycodedquadrature

Graycodedquadrature refers to a method used in digital signal processing, particularly in phase-shift keying (PSK) modulation. It involves mapping digital data bits to specific phase shifts of a carrier signal in a way that adjacent phase states differ by only a single bit. This characteristic is known as Gray coding.

In Quadrature Amplitude Modulation (QAM), data is encoded by modulating both the amplitude and phase of a carrier wave. When Gray coding is applied to QAM, it means that the constellation points representing adjacent symbol values in the QAM constellation are designed to differ in only one bit. This has a significant advantage in reducing the bit error rate (BER) of the communication system.

When a signal is corrupted by noise, it may be misinterpreted as a nearby constellation point. If Gray coding is used, and the noise causes the received signal to be closer to an adjacent symbol's constellation point, the decoding error will only result in a single bit flip rather than multiple bit flips. This property makes Gray coded QAM systems more robust to channel impairments, leading to better performance compared to systems that do not use Gray coding. The specific arrangement of constellation points and their corresponding Gray codes depends on the order of QAM being used (e.g., 4-QAM, 16-QAM, 64-QAM).