Reduction of the error floor of binary FSK by nonlinear frequency discriminators

We consider the error floor of binary FSK due to intersymbol interference in time-dispersive mobile radio channels, with a limiter-discriminator-integrator detector. The errors are caused by bursts in the instantaneous frequency. We propose and verify that a nonlinear frequency discriminator can achieve zero error floor for pure FSK by clipping off these bursts. For filtered FSK, the error floor is not completely removed, but strongly reduced typically by one or two orders of magnitude. The tighter the filtering, the less effective this nonlinearity is. The nonlinear discriminator can be also used in conjunction with adaptive sampling. This work may not be copied or reproduced in whole or in part for any commercial purpose. Permission to copy in whole or in part without payment of fee is granted for nonprofit educational and research purposes provided that all such whole or partial copies include the following: a notice that such copying is by permission of Mitsubishi Electric Information Technology Center America; an acknowledgment of the authors and individual contributions to the work; and all applicable portions of the copyright notice. Copying, reproduction, or republishing for any other purpose shall require a license with payment of fee to Mitsubishi Electric Information Technology Center America. All rights reserved. Copyright c ©Mitsubishi Electric Information Technology Center America, 2003 201 Broadway, Cambridge, Massachusetts 02139 Publication History: 1. First printing, TR-2003-41, May 2003