Digital filters are widely used in signal processing and communication systems. In some cases, the reliability of those systems is critical, and fault tolerant filter implementations are needed. Over the years, many techniques that exploit the filters’ structure and properties to achieve fault tolerance have been proposed. As technology scales, it enables more complex systems that incorporate many filters. In those complex systems, it is common that some of the filters operate in parallel, for example, by applying the same filter to different input signals. Recently, a simple technique that exploits the presence of parallel filters to achieve fault tolerance has been presented. In this brief, that idea is generalized to show that parallel filters can be protected using error correction codes (ECCs) in which each filter is the equivalent of a bit in a traditional ECC. This new scheme allows more efficient protection when the number of parallel filters is large. The technique is evaluated using a case study of parallel finite impulse response filters showing the effectiveness in terms of protection and implementation cost.
Existing Method:
Electronic circuits are increasingly present in automotive , medical, and space applications where reliability is critical. In those applications, the circuits have to provide some degree of fault tolerance. This need is further increased by the intrinsic reliability challenges of advanced CMOS technologies that include, e.g., manufacturing variations and soft errors. A number of techniques can be used to protect a circuit from errors. Those range from modifications in the manufacturing process of the circuits to reduce the number of errors to adding redundancy at the logic or system level to ensure that errors do not affect the system functionality. To add redundancy, a general technique known as triple modular redundancy (TMR) can be used. The TMR, which triplicates the design and adds voting logic to correct errors, is commonly used. However, it more than triples the area and power of the circuit, something that may not be acceptable in some applications. When the circuit to be protected has algorithmic or structural properties, a better option can be to exploit those properties to implement fault tolerance.
Proposed Method:
Digital filters are one of the most commonly used signal processing circuits and several techniques have been proposed to protect them from errors. Most of them have focused on finite-impulse response (FIR) filters. For example, the use of reduced precision replicas was proposed to reduce the cost of implementing modular redundancy in FIR filters. a relationship between the memory elements of an FIR filter and the input sequence was used to detect errors. Other schemes have exploited the FIR properties at a word level to also achieve fault tolerance. The use of residue number systems and arithmetic codes has also been proposed to protect filters. In this brief, a general scheme to protect parallel filters is presented. Parallel filters with the same response that process different input signals are considered. The new approach is based on the application of error correction codes (ECCs) using each of the filter outputs as the equivalent of a bit in and ECC codeword. This is a generalization of the scheme presented and enables more efficient implementations when the number of parallel filters is large. The scheme can also be used to provide more powerful protection using advanced ECCs that can correct failures in multiples modules.