Christopher H. Strolle

Low-complexity and low-latency implementation of the Godard/CMA update

This paper discusses methods for calculating and implementing the update error term for the popular blind equalization algorithm known as Godards (1980) algorithm, or the constant modulus algorithm (CMA), without the use of multipliers so that chip area and signal latency are both substantially reduced. One approach uses a decision-directed CMA update term, and another uses region-based quantization. The quantized error term can be calculated using a look-up table in place of costly multipliers and adders. Baseband and passband implementations are discussed, and computer simulations verify our methods.

Differential carrier loop estimation for digital vestigial side band modulation

In this paper we address the problem of phase recovery for a digital VSB modulation. Two criteria, a Constant Modulus and MSE, which exploit the properties of VSB signaling in the presence of noise are proposed and analyzed. The extrema of the objective functions and their domains of attraction are derived. Under mild conditions on the statistics of the input sequence, it is shown that the derivative of these functions can be used as a new phase detector in a Phase Locked Loop (PLL) implementation. An effective semi-blind solution which consists of a combination of the MSE and CM phase detectors is introduced and analyzed.

Closed form expression of EMSE for Bussgang equalization with spatio-temporal diversity

Bussgang algorithms are a class of simple stochastic gradient type solutions for blind channel equalization. We investigate the degradation of performance in the source estimation resulting from the stochastic jitter around stationary points of Bussgang algorithms (which correspond to the equalizers of the channel). More precisely, we derive a closed form approximation of the excess mean square error (EMSE) defined as the variance of the jitter which depends on the effects of the channel characteristics, the source distribution and the non-linearity used in the update equation. The analysis is performed in a context of spatiotemporal channel diversity involving a single-input/multiple outputs data model.

A decision-directed constant modulus algorithm for higher-order source constellations

This paper discusses methods for calculating and implementing the update error term for the popular blind equalization algorithm known as Godards (1980) algorithm, or the constant modulus algorithm (CMA), without the use of multipliers so that the chip area and signal latency are both substantially reduced. A decision-directed CMA update term is derived for higher-order (non-constant modulus) source alphabets. The modified update error term can be calculated using a look-up table in place of costly multipliers and adders. Baseband and passband implementations for one-dimensional and two-dimensional signaling are discussed.