Low-voltage CMOS circuits for analog iterative decoders

Iterative decoders, including Turbo decoders, provide near-optimal error protection for various communication channels and storage media. CMOS analog implementations of these decoders offer dramatic savings in complexity and power consumption, compared to digital architectures. Conventional CMOS analog decoders must have supply voltage greater than 1 V. A new low-voltage architecture is proposed which reduces the required supply voltage by at least 0.4 V. It is shown that the low-voltage architecture can be used to implement the general sum-product algorithm. The low-voltage analog architecture is then useful for implementing Turbo and low-density parity check decoders. The low-voltage architecture introduces new requirements for signal normalization, which are discussed. Measured results for two fabricated low-voltage analog decoders are also presented.