A lifting wavelet based lossless and lossy ECG compression processor for wireless sensors

This work presents an electrocardiogram (ECG) compression processor for wireless sensors with configurable data lossless and lossy compression. Lifting wavelet transforms of 9/7-M and 5/3 are employed for signal decomposition instead of traditional wavelet. A hybrid encoding scheme improves compression efficiency by encoding the higher scales of decomposed coefficients with modified embedded zero-tree wavelet (EZW) and the lowest scale with Huffman encoding. Besides, a transposable register matrix for coefficients buffering during EZW encoding lowers the processing frequency without extra register resource. Implemented in SMIC 40nm CMOS process, the processor only takes a total gate count of 10.8K with 92nW power consumption under 0.5V voltage and achieves a compression ratio of 2.71 for lossless compression and 14.9 for lossy compression with PRD of 0.39%.