| 摘要: | 無線感測網路(Wireless sensor networks, WSNs)是指由數個感測器(Sensor nodes)與一個控制中心(Sink node)，配置在特定區域內所形成的無線網路系統，感測器在遠端收集感測數據，如溫度、濕度、壓力等，並回傳至控制中心，控制中心會將收集到的訊息透過運算、分析以利適當的應用。感測器是以電池為電源，因此有限的電池電量是一個重要的參數，要如何透過省電機制以延長整體網路的壽命，將是本文所要探討的方向。
冕狀無線感測網路(Corona-Based WSNs)將網路範圍切成多個冕圈，每個相鄰冕圈的寬度為一致，外圈的感測器會透過相鄰冕圈內的感測器將資料往內圈傳遞，因此最內圈的感測器會承載太多流量，導致其壽命會提早結束，造成外圈的感測器的資料無法傳回控制中心，即使外圈的感測器仍然有足夠的剩餘能量，整個網路可能提早無法運行，這情況將形成能量漏洞(Energy-Hole)的問題，對於網路效率造成很大的影響。
因此，本論文提出一個將藍牙低功耗(Bluetooth Low Energy, BLE)技術應用在無線感測網路上並優化電源效能的方法。若每個感測器都是使用藍牙低功耗來無線傳輸，透過選擇剩餘電量最多的感測器當作中繼節點(Relay-Node)，直接將感測資料傳送至控制中心，如此可避免內圈的感測器承載過多的流量，盡量平衡內外圈的感測器消耗電量。藉由模擬結果顯示，選擇適合的中繼節點可大大減少內圈的感測器電量，以延長整體網路的生命週期。;A wireless sensor network(WSN) is formed by a number of sensors and a sink node in a specific area. The sensors gather interesting information like temperature, humidity, pressure, etc., and this information will be sent to a sink node. The sink node will calculate and analyze the collected information for proper applications. The power source of sensor is battery, i.e., a limited energy, which is an important parameter in WSNs, showing a research direction about how to design a power-saving mechanism for extending the entire network lifetime of a WSN system.
In a coronal-based wireless sensor network, the network area is cut into multiple concentric corona circles, and the width of each adjacent concentric corona is the same.
The outer corona sensor will transfer data to the inner corona by passing through the sensor in the adjacent corona. The inner corona sensor will carry too much traffic, causing the life of inner nodes ending early, and the data of the outer corona sensor cannot be transmitted back to the sink node. Even though the sensors in the outer corona still have enough residual energy, the entire network may not run. This problem is known as energy holes, which has a great impact on the efficiency of the network.
Therefore, this thesis study proposes a method to apply Bluetooth Low Energy(BLE) technology into wireless sensor networks and optimize energy efficiency. Each sensor uses BLE for wireless transmission. The relay node which is selected by the maximum residual energy will send the data to a sink node directly. Then the inner corona sensor can avoid carrying too much traffic, and the power consumption can be balanced between sensors in inner and outer coronas. The simulation result shows that, selecting an applicable relay node which can mitigate the power consumption of inner corona nodes is able to extend the entire network lifetime of a WSN system. |
