When has a decision-directed equalizer converged?
Rodney A. Kennedy, G.W. Pulford, Brian D. O. Anderson, Robert R. Bitmead · IEEE Transactions on Communications · 1989
Adaptive decision-directed equalizers can become locked for long periods onto incorrect equilibria. A test involving data available at the equalizer output is proposed for determining whether an equilibrium is correct or not, up to a fixed overall delay. If an independent sequence of random variables taking values +or-1 is the input to a finite impulse response filter, and the output of the filter is passed through a slicer, then the slicer output is uncorrelated if and only if it is a delayed version of the filter input. An analogous result for M-ary rather than binary data is outlined.>