應用NB-IoT對配水網路進行可調節資料嚴密性與節能監測

Abstract

在配水網路中佈置感測器，定時蒐集水壓資料，有助於改善嚴重的漏水問題。然而，建置、維護地下無線感測器網路的成本不貲，如何延長無線感測網路壽命是相當重要的議題。Narrow Band Internet of Things (NB-IoT) 是一種新型無線電技術，具有低耗電、低資料量、大範圍覆蓋、低成本的特性，適合應用於位在地底的水壓監控系統。此外，電信商不須大幅更改現行的4G LTE電信網路架構，就能快速部署，因而備受各國電信商所支持。在本篇論文中，我們提出了一套演算法，依照感測器節點之間的距離分配回報資料的優先順序，結合不連續接收(eDRX)的機制分配不同長短的休眠週期，以滿足感測器網路能在限定時間內回覆需求，且提供可靠、可調變的感測覆蓋範圍。接著，我們利用半馬可夫過程分析休眠週期如何影響網路表現。在模擬結果中，討論了不同的時間參數對省電效率及反應延遲的影響，另外，顯示出演算法相較於其他方法能更有效地平衡不同節點的剩餘電量，改善整體的網路壽命，並且說明網路壽命如何影響資料準確性。

For monitoring on water distribution networks, the sensor network lifetime is important to be as long as possible due to the high cost to replace dead nodes underground. Narrow Band Internet of Things (NB-IoT) is a novel radio technology that well suits the features of public civil resource monitoring systems, such as massive amount of devices, low transmission data rates, and the needs of low energy consumption and good penetration to indoor or underground. Using NB-IoT as the wireless communication intermediary in our monitoring system, an operational strategy is proposed to prolong the sensor network lifetime. Our strategy can be divided into two phases. First, a k-extended-cover algorithm is designed to adjust the data resolution and prioritize the reporting of the data according to the distance between the sensor nodes. Second, an eDRX assignment policy is presented to balance power consumption and wake-up latency tradeoff, by using the result of the k-extended-cover algorithm. Next, a semi-Markov process is modeled to numerically analyze the system performance and to obtain the power saving factor and wake-up latency. Finally, the system performance is discussed with the simulation results.