Fault-tolerant FFT networks

Two concurrent error detection (CED) schemes are proposed for N-point fast Fourier transform (FFT) networks that consists of log/sub 2/N stages with N/2 two-point butterfly modules for each stage. The method assumes that failures are confined to a single complex multiplier or adder or to one input or output set of lines. Such a fault model covers a broad class of faults. It is shown that only a small overhead ratio, O(2/log/sub 2/N) of hardware, is required for the networks to obtain fault-secure results in the first scheme. A novel data retry technique is used to locate the faulty modules. Large roundoff errors can be detected and treated in the same manner as functional errors. The retry technique can also distinguish between the roundoff errors and functional errors that are caused by some physical failures. In the second scheme, a time-redundancy method is used to achieve both error detection and location. It is sown that only negligible hardware overhead is required. However, the throughput is reduced to half that of the original system, without both error detection and location, because of the nature of time-redundancy methods.<
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