Fault-tolerant rank order filtering for image enhancement

This paper presents an approach for the fault-tolerant computation of the rank order filtering on a SIMD (single instruction multiple data) mesh processor. The proposed approach improves over a previous approach in two respects: by changing the data dependency in the execution of the rank order filtering, a new algorithm with constant execution time complexity can be designed; and by introducing a dependency for the rank values of faulty processing elements (PEs) as computed by neighboring (fault free) PEs, a lower distortion can be achieved for the image enhancement. An algorithm is presented; this algorithm is based on a two-phase technique in which the rank corresponding to each faulty PE is computed by a selected fault free PE. The effect of the rank computation for a faulty PE is restricted within a window of the image, such that no significant overhead is accounted for in execution complexity. This results in a considerable improvement in speed-up ratio, fault-tolerance as well as a lower distortion in the reconstructed image. The proposed approach is also evaluated using experimental results. As the proposed algorithm is directly compatible with a SIMD mesh execution, a discussion of the communication constructs and switching architecture to support array processing is also presented.