一种基于TinyOS的自适应双环调度策略

针对传感器网络操作系统TinyOS无法保证任务实时性的缺陷,提出一种自适应双环调度(ADRS)策略,并在TinyOS上加以实现。自适应双环调度策略将先到先服务(FCFS)调度策略下的单循环队列改为具有不同优先级别的双循环队列,同时原来的多个任务共享同一堆栈空间修改为不同任务分级占用两个堆栈,并根据队列中任务时限的变化动态调整两队列间的任务切换以最大程度地保证任务完成.仿真试验表明,自适应双环调度策略在不影响TinyOS原有性能的情况下,极大改善了传感器网络承担实时性任务的运行效果.

Spatial Distribution of Surface Soil Moisture in a Small Forested Catchment

Predicting the spatial distribution of soil moisture is an important hydrological question. We measured the spatial distribution of surface soil moisture (upper 6 cm) using an Amplitude Domain Reflectometry sensor at the plot scale (2 × 2 m) and small catchment scale (0.84 ha) in a temperate forest. The spatial variation of soil water content was higher during dry conditions than that during wet conditions. Results indicated 3.1 samples at the plot scale were sufficient to estimate mean soil water content when the precision was 0.1. Soil water content increased with increasing topographic index (TI) and soil-topographic index (STI) at the small catchment scale. The correlation between soil water content and TI was higher than that between soil water content and STI. This suggests that topography is more important for estimating surface soil moisture than soil depth as formation of surface soil moisture occurs at ≤6 cm.

基于LoRaWAN自适应数据速率的地下无线传感网络性能评估

随着城镇化进程的不断加快和物联网技术的迅速进步,地下复杂土壤介质中的无线传感网络正成为新的研究热点。在此背景下,首先概述了基于LoRaWAN的地下无线传感网络基本架构和研究现状,接着搭建了网络仿真器并实现了自适应数据速率(ADR)调节机制在传感器节点端和网络服务端的2个优化算法,最后依据网络整体数据接收率和网络能耗等性能指标,分别从传感器节点的地下部署环境(土壤含水量和传感器埋藏深度)和LoRa物理层参数两方面进行了网络性能定量评估。结果表明,针对土壤这一复杂介质,ADR调节机制对LoRaWAN中的物理层参数具有较好的调节能力,该机制可为地下无线网络性能优化提供有利手段,有望大幅降低网络能耗。