基於802.11標準下設計開發負載平衡的無線感知網路

Abstract

隨著物聯網之盛行，無線感知網路也扮演了一個重要的角色。無線感知網路是一種透過佈設許多感測器所形成的一種可以自動蒐集、計算、傳遞資訊的感測網路，它已成為近年來資訊網路發展之重要趨勢。它可以應用在環境與氣候監測、公共設施維護、交通運輸、大型倉儲、農業與畜牧等領域。而實際上，無線感知網路的傳輸規範(802.15.4)已制定，但在相關的產品上並沒有太多的選擇，市面較容易購得的只有XBee系列產品，但價位較貴。而無線感知網路往往需要數以萬計的節點來做應用，並且大多數的節點會直接分散在戶外空間中，節點若損壞或是能源用盡是不太可能靠人工去回收的，所以低廉的節點成本是非常重要一個因素。另一點則是省電性，就如同上述，由於系統可能使用電池來做為電力的供應，若節點耗電，只要系統在運作頻繁，所消耗的電量一定比不常運作的系統高，如此造成系統的存活時間會相對縮短。關於這些問題，目前似乎沒有完善的解決方法。 因此，我們在考量了以上的問題後，設計了一套基於802.11標準的無線感知網路系統。首先802.11標準已經相當成熟且器材便宜，並且容易取得。我們使用市面常見的ESP8266做為節點與Raspberry Pi做為資料收集站，設計並實現一套負載平衡的方法來降低耗電量，而建立一個低耗能的無線感知網路系統。

Nowadays Internet of Things (IoT) advances quickly, and Wireless Sensor Network (WSN) plays an important role in IoT. WSN is a type of network that automatically collects data, process data, and transfer data by laying a variety of sensor nodes that formed the network. WSN is becoming one of the ICT development trends in recent years, it can be applied in the fields including environment and climate monitoring, public facilities, transportation, warehouse, agriculture, etc. In fact, the protocol specification of wireless sensor network (802.15.4) has been developed but it is expensive. WSN usually need tens of thousands of node to build its application, and both power outage and node failure won’t be recovered thru human resources. With the battery as the sole power source, power efficiency is one of the most important factors in WSN operation. In order to dealing with the above issues, we designed a system of Wireless Sensor Network based on 802.11 standards, by using the off-the-shelf products ESP8266 as node and Raspberry Pi as the data collection station (base station), we designed a load balancing mechanism to minimize the power consumption for extending the WSN lifetime.