Published in Ansari, I., & Viswanathan, R. (1994). Performance study of maximum likelihood receivers and transversal filters for the detection of direct sequence spread spectrum signal in narrowband interference. IEEE Transactions on Communications, 42(234, part 3), 1939 - 1946. doi: 10.1109/TCOMM.1994.582904 ©1994 IEEE. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE. This material is presented to ensure timely dissemination of scholarly and technical work. Copyright and all rights therein are retained by authors or by other copyright holders. All persons copying this information are expected to adhere to the terms and constraints invoked by each author's copyright. In most cases, these works may not be reposted without the explicit permission of the copyright holder.


Linear least squares estimation techniques can be used to enhance suppression of narrowband interference in direct sequence spread spectrum systems. Nonlinear techniques for this purpose have also been investigated recently. In this paper, we derive maximum likelihood receivers for direct sequence signal in Gaussian interference with known second order characteristics. It is shown that if the receiver uses samples from outside the bit interval, then the receiver structure is nonlinear. The bit error rate performances of these receivers are compared to those of linear receivers employing one-sided and two-sided least squares estimation filters, for the case of Gaussian autoregressive interference. The results in this paper show that intersymbol interference due to filter taps extending beyond the bit interval cannot be ignored for small processing gains. In some cases, not accounting for intersymbol interference yields too optimistic error estimates, very much away from the true error rates.