James P. LeBlanc

CMA fractionally spaced equalizers: Stationary points and stability under i.i.d. and temporally correlated sources

A common assumption in blind equalization schemes using the Constant Modulus Algorithm (CMA) is that the source sequence is an independent identically distributed (i.i.d.) sequence with equiprobabl ...

Enhanced RAM-based equalizers for nonlinear channels

We present a detection method for nonlinear channels with memory. This method uses a linear feedforward equalizer in conjunction with a random access memory (RAM) based (nonlinear) equalizer. The design criterion for the feedforward equalizer is non-traditional, with the intent to improve the performance of the RAM-based equalizer. Development of the design criterion and a training-mode based adaptive implementation along with examples of this equalizer with a pre-cursor enhanced RAM-DFE canceller are included.

Model order selection for multidimensional innovations based detection in airborne radar

This paper investigates the model order selection problem for use with the multidimensional autoregressive (MAR) process in airborne radar detection processing which uses an innovations based detection algorithm (IBDA). Results indicate that a low order model should be used to accurately portray the return signal spectrum. Specifically, this paper investigates the use of the Akaike (1971) information criterion for model order selection. Examples are included for physically modeled data sets as well as actual radar data sets.

Minimum mean square error channel truncation for magnetic channels

Basic Idea To achieve higher data densities while maintaining a low hit error probability, many systems incorporate an equalizer. We present a non-traditional design criterion for use in a magnetic data recording system. This criterion is different from the standard minimum mean square error (MMSE), zero-forcing (ZF), or target-based (such as EPR4 targets) designs that have appeared in the literature. The critical idea is to relax traditional constraints and allow any intersymhol interference (ISI) within a certain timewindow. The resulting equalizer has less noise gain leading to a lower hit error rate for a given signal-tenoise ratio than the traditional equalizers when each is used with a companion sequence detector.

Convergence properties of the CDMA multidimensional adaptive linear receiver

In this paper we find the theoretical slowest convergence mode for the Multidimensional Adaptive Linear Receiver (MALR) with a received signal consisting of additive white Gaussian noise, multi-access interference, and spatially diverse multitone interference. This convergence mode is used in a decaying exponential that approximates the MSE transient which is directly related to the net effective interference suppression capability of the MALR. We show here that the slowest mode of convergence is related to the AWGN variance.

Multidimensional extension of MMSE linear adaptive receiver for DSSS systems

We extend the single channel adaptive linear receiver (ALR) to the multidimensional case. The extension is used for the cancellation of strong spatially-distributed narrowband interference in direct sequence spread spectrum communications. Simulations show a gain of 8 dB for the case of two interferences occupying 30% of the bandwidth of the spread spectrum signal.

A multidimensional adaptive linear receiver for CDMA transmission corrupted by SD-MTI

This paper presents an extension of the single antenna adaptive linear receiver (ALR) for CDMA transmission. We call the proposed multiuser receiver: the multidimensional adaptive linear receiver (MALR). Specifically, we investigate the spatially-diverse multi-tone interference (SD-MTI) excision performance of the MALR. We quantify the BER performance enhancement achieved by the MALR relative to the ALR for the case of relatively large frequency MTI occupation.