The booming of Internet-of-Things (IoT) is expected to provide more intelligent and reliable communication services for higher network coverage, massive connectivity, and low-cost solutions for 6G services. However, frequent charging and battery replacement of these massive IoT devices brings a series of challenges. Zero energy devices, which rely on energy-harvesting technologies and can operate without battery replacement or charging, play a pivotal role in facilitating the massive use of IoT devices. In order to enable reliable communications of such low-power devices, Manchester-coded on-off keying (OOK) modulation and non-coherent detections are attractive techniques due to their energy efficiency, robustness in noisy environments, and simplicity in receiver design. Moreover, to extend their communication range, employing channel coding along with enhanced detection schemes is crucial. In this paper, a novel soft-decision decoder is designed for OOK-based low-power receivers to enhance their detection performance. In addition, exact closed-form expressions and two simplified approximations are derived for the log-likelihood ratio (LLR), an essential metric for soft decoding. Numerical results demonstrate the significant coverage gain achieved through soft decoding for convolutional code.

翻译：物联网的蓬勃发展有望为6G服务提供更智能、更可靠的通信方案，以满足更广的网络覆盖、海量连接和低成本需求。然而，海量物联网设备的频繁充电和电池更换带来了一系列挑战。零能耗设备采用能量采集技术，无需更换电池或充电即可运行，在促进物联网设备大规模应用中发挥关键作用。为实现此类低功耗设备的可靠通信，曼彻斯特编码的开关键控调制和非相干检测技术因其能效高、在噪声环境中鲁棒性强及接收机设计简单等优势而备受关注。此外，为了扩展通信范围，采用信道编码和增强型检测方案至关重要。本文针对基于OOK的低功耗接收机设计了一种新型软判决译码器以提升检测性能。同时推导了软译码关键度量——对数似然比（LLR）的精确闭式表达式及两种简化近似公式。数值结果表明，通过卷积码的软译码可显著获得覆盖增益。