Adaptive iterative detection for expediting the convergence of a serially concatenated Unary Error Correction decoder, turbo decoder and an iterative demodulator

Abstract

Abstract-Unary Error Correction (UEC) codes constitute a recently proposed Joint Source and Channel Code (JSCC) family, conceived for alphabets having an infinite cardinality, whilst out-performing previously used Separate Source and Channel Codes (SSCCs). UEC based schemes rely on an iterative decoding process, which involves three decoding blocks when concatenated with a turbo code. Owing to this, following the activation of one of the three blocks, the next block to be activated must be chosen from the other two decoding block options. Furthermore, the UEC decoder offers a number of decoding options, allowing its complexity and error correction capability to be dynamically adjusted. It has been shown that iterative decoding convergence can be expedited by activating the specific decoding option that offers the highest Mutual Information (MI) improvement to computational complexity ratio. This paper introduces an iterative demodulator, which is shown to improve the associated error correction performance, while reducing the overall iterative decoding complexity. The challenge is that the iterative demodulator has to forward its soft-information to the other two iterative decoding blocks, and hence the corresponding MI improvements cannot be compared on a like-for-like basis. Additionally, we also propose a method of eliminating the logarithmic calculations from the adaptive iterative decoding algorithm, hence further reducing its implementational complexity without impacting its error correcting performance.

Flexible iterative receiver architecture for wireless sensor networks: a joint source and channel coding design example

“…Hence, this ASIC is particularly suitable for WSN applications, where having a low energy consumption and a low chip area are more important than achieving a high throughput. We characterise the proposed architecture using an application example that iteratively activates a quadrature phase shift keying (QPSK) demodulator [12], a turbo decoder and a UEC based joint source and channel decoder [20]. In contrast to the family of source codes [21, 22] previously designed for WSN applications, the UEC improves the error correction capability and it is designed to have a low complexity.…”