This paper discusses methods for calculating and implementing the update error term for the popular blind equalization algorithm known as Godard's (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.

This paper discusses methods for calculating and implementing the update error term for the popular blind equalization algorithm known as Godard's (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.

One of the most popular blind equalization techniques is the constant modulus algorithm (CMA), and it has gained popularity in the literature and in practice because of its LMS-like complexity and its robustness to non-ideal, but practical, conditions. Although the CMA has been well-studied in the literature, these analyses have typically implemented the algorithm using "infinite" precision arithmetic. The motivation for this paper is a VLSI implementation of a high data rate, fractionally spaced, linear forward equalizer whose taps are adjusted using the CMA. We examine how implementing the CMA using finite bit precision affects the algorithm's performance.

A common technique in a blind equalization communication system is to use the constant modulus algorithm (CMA) to open the channel eye and then to switch to decision-directed LMS once the error rate has dropped to a sufficiently low level. The propose a new algorithm, blended CMA, which dynamically selects to use either the CMA or DD-LMS update term when adapting the equalizer taps. The decision rule governing this selection is also adaptive. Simulation results presented in this paper demonstrate how the algorithm performs when equalizing 64-QAM over real-world channels and highlights the performance gain over using traditional transfer methods.

Transmission aspects of the advanced digital high definition television (AD-HDTV) system, for terrestrial simulcast delivery of HDTV are described. In AD-HDTV, two quadrature-amplitude-modulated (QAM) carriers, with different power spectral densities, are employed in a frequency division multiplex (FDM) mode within the standard 6-MHz channel. The resulting spectral shaping allows a larger power to be transmitted, compared to that for a single QAM carrier, for the same level of perceptual interference into cochannel NTSC. The coded video data are split into high-priority (HP) data and standard-priority (SP) data, and the vital information is sent on the appropriate QAM carrier, resulting in a robust audio and video transmission system. The availability is higher in scenarios where the carrier-to-noise ratio (CNR) is above the threshold for HP reception but below the threshold for SP reception; this is important in fringe areas. The NTSC planning factors, suitably modified for HDTV delivery, are used to estimate the coverage area for AD-HDTV. The calculated AD-HDTV coverage area of 54.5 miles is comparable to that for NTSC transmission.>