Blind channel equalization

Signals that pass through a channel undergo various forms of distortion. One very common type of distortion is intersymbol interference, or ISI. ISI is caused by interference from the symbols that were transmitted before and after the given symbol. ISI-induced errors can cause the receiver to misinterpret the received samples. The equalizer is an important part of a modern digital communications receiver. It filters the received data to minimize the linear distortion induced during the transmission of the signal. (There is no nonlinear distortion.) This distortion occurs when the signal is transmitted through a channel. The channel is the physical medium that connects the transmitter and receiver. For example, the Earth´s atmosphere is the medium in a wireless communications system. By sending the signal through the equalizer, the effects of ISI are counteracted; i.e. the receiver can make accurate symbol decisions based on the equalizer output. This article discusses the constant modulus algorithm, or CMA. This is the most popular algorithm used to blindly update equalizer coefficients