適用於WBAN之高能源效率及可調整之媒體存取控制通訊協定

An Energy-Efficient and Adjustable Communication MAC Protocol for Wireless Body Area Network Applications

季竑丞(CHI, Hung Cheng)

指導教授 ： 馬席彬

國立清華大學/電機資訊學院/通訊工程研究所/碩士(2013年)

摘要

近年來，穿戴式遠端醫療照顧越來越普及。在這種醫療專門的領域，無線感測網路發展出無線近身網路。無線近身網路是一個短距離通訊與低功率損耗的系統，很適合運用在遠端醫療照顧的系統。

在遠端醫療照顧系統中，需要可以多個生理訊號同時傳到一個手持裝置而且可以在裝置上即時的觀測訊號，我們也需要使用很久的時間，這就代表需要很低的功率消耗。根據前面的需求，我們設計了一個低功率消耗，低時間延遲的媒體存取控制位址之協定，藉由這個媒體存取控制位址之協定來提升整體系統的效能。

在此論文中，我們提出以多時分工存取為基礎而去改良整體系統，因為運用多時分工存取可以節省能量，但是還是存在著額外控制封包開支與閒置聆聽的問題，所以我們提出一個低功耗的wakeup radio 連接在感測器之前，加入這個wakeup radio後，它會讓感測器減少處在閒置的狀態然後增加睡眠狀態的時間，這樣可以減少額外控制封包開支與閒置聆聽的問題。使用wakeup radio不但可以減少整體的能量消耗，也可以延長網路的壽命。而在改良傳統多時分工存取中，我們提出一個方法是在當主控者想要接收資料時，才會傳送wakeup radio 給感測器, 當感測器收到wakeup radio才會醒來開始通訊，比起傳統的多時分工存取，我們提出的協定是彈性且可調的。

此論文也會計算我們提出協定中，一個框架的時槽個數與系統的工作週期，接下來再計算我們提出協定的功率消耗與時間延遲，計算過後再與其他媒體存取控制位址之協定比較。在功率消耗的部分，當封包間隔時間為10秒時，系統的功率消耗是WiseMAC的三分之一，在時間延遲的部分，延遲時間為29.76毫秒，而我們提出的協定也不會因為時間延長而延遲越大，可以證明我們提出的協定可以達到低功率耗耗、少延遲與彈性調整，此外也大大的提升整個系統的效能。

關鍵字

無線近身網路 ； 高能源效率 ； 多時分工存取 ； 遠端醫療照顧系統

並列摘要

Nowadays, applications of wearable instruments for remote healthcare have become a highly-valued research and developed the wireless body area network (WBAN). In a remote healthcare system, multiple physiological signals are required to be transmitted simultaneously to a mobile device and be observed in real time. According to the above requirements, we propose a low-power and low time delay MAC protocol.

In this thesis, we improve the time division multiple access (TDMA) system. TDMA is a helpful way to save power, but overhead and idle listening problems still exist. Thus, we propose a low cost wakeup radio to connect to the sensor. Wakeup radio makes sensor nodes to be in sleep state when there is no data to transmit or receive. If the system starts to operate, controller will send message to wakeup radio and then the sensors will start to communicate. Therefore, using wakeup radio can not only reduce the overall power consumption, but it can also prolong the lifetime of the network. In the improvement of traditional TDMA, we propose a method to wake up the sensors through wakeup radio, only when the controller wants them to receive data. After the sensor receives wakeup radio, it soon wakes up and starts to communicate. The proposed protocol is more adjustable than traditional TDMA.

The number of slots at each frame in our proposed protocol is calculated, as well as the power consumption and time delay, which is compared to other MACs. The packet interval time is regarded as the unit of power consumption in the simulation. The comparison shows that the power consumption of the proposed protocol is nearly one third than that of WiseMAC when the packet inter-arrival time is 10 seconds. Besides, the time delay is 29.76 millisecond and does not vary when the operational time becomes longer. Therefore, it is proved that the proposed protocol achieves a low-power consumption, a low time delay and flexibility for utilization. The proposed protocol greatly enhances the overall system performance.

參考文獻

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