Wireless Technology Terms, Glossary and Dictionary

16QAM: 16ary Quadrature Amplitude Modulation

16ary Quadrature Amplitude Modulation (16-QAM), one of the forms of QAM, is a modulation scheme. In QAM, the constellation points are usually arranged in a square grid with equal vertical and horizontal spacing, although other configurations are possible. Since in digital telecommunications the data is usually binary, the number of points in the grid is usually a power of 2 (2,4,8...). Since QAM is usually square, the most common forms of QAM are 16-QAM, 64-QAM, 128-QAM and 256-QAM. By moving to a higher-order constellation, it is possible to transmit more bits per symbol. However, if the mean energy of the constellation is to remain the same (by way of making a fair comparison), the points must be closer together and are thus more susceptible to noise and other corruption; this results in a higher bit-error rate and so higher-order QAM can deliver more data less reliably than lower-order QAM.

Related Terms

16QAM: 16ary Quadrature Amplitude Modulation