Rapid advancements in adaptive sonar beamforming algorithms have greatly increased the computation and communication demands on beamforming arrays, particularly for applications that require in-array autonomous operation. By coupling each transducer node in a distributed array with a microprocessor, and networking them together, embedded parallel processing for adaptive beamformers can significantly reduce execution time, power consumption and cost, and increase scalability and dependability. In this paper, the basic narrowband Minimum Variance Distortionless Response (MVDR) beamformer is enhanced by incorporating broadband processing, a technique to enhance the robustness of the algorithm, and speedup of the matrix inversion task using sequential regression. Using this Robust Broadband MVDR (RB-MVDR) algorithm as a sequential baseline, two novel parallel algorithms are developed and analyzed. Performance results are included, among them execution time, scaled speedup, parallel efficiency, result latency and memory utilization. The testbed used is a distributed system comprised of a cluster of personal computers connected by a conventional network. 69 J. Comp. Acous. 2002.10:69-96. Downloaded from www.worldscientific.com by UNIVERSITY OF CALIFORNIA @ SAN DIEGO on 04/12/15. For personal use only. 70 P. Sinha, A. D. George & K. Kim other sources and sensor noise and isolate the true source directions accurately. There are various ABF algorithms proposed in the literature. 3-7 Castedo et al. 4proposed a method based on gradient-based iterative search that makes use of properties of cyclostationary signals. Krolik et al. 5 defined a steered covariance matrix as an efficient space-time statistic for high-resolution bearing estimation in broadband settings. The algorithm considered here is the MVDR algorithm described by Cox et al. 6 MVDR is an optimal technique that selects the weights in such a way that the output power is minimized, subject to the constraint that the gain in the steering direction being considered is unity. This optimization of the weights leads to effective interference-rejection capabilities, as nulls are steered in directions of strong interference. Wax and Anu 8 presented an analysis of the signal-to-interferenceplus-noise ratio (SINR) at the output of the minimum variance beamformer. Raghunath and Reddy 9 analyzed the finite-data performance of the MVDR beamformer. Zoltowski 10 developed expressions that describe the output of the MVDR beamformer in the presence of multiple correlated interfering signals. Harmanci et al. 11 derived a maximum likelihood spatial estimation method that is closely related to minimum variance beamforming.However, classical MVDR beamforming techniques suffer from problems of signal suppression in the presence of errors such as uncertainty in the look direction and array perturbations. To mitigate such problems, various constrained MVDR beamforming schemes have been proposed in the literature. These schemes enhance the robustness of the MVDR algorithm. White noise inj...