A decision-directed constant modulus algorithm for higher-order source constellations

This paper discusses methods for calculating and implementing the update error term for the popular blind equalization algorithm known as Godard's (1980) algorithm, or the constant modulus algorithm (CMA), without the use of multipliers so that the chip area and signal latency are both substantially reduced. A decision-directed CMA update term is derived for higher-order (non-constant modulus) source alphabets. The modified update error term can be calculated using a look-up table in place of costly multipliers and adders. Baseband and passband implementations for one-dimensional and two-dimensional signaling are discussed.