在臺大醫院無線感測網路中跨層設計之資料傳輸機制的實作與研究

Abstract

隨著人口高齡化，老人安養問題越來越受到注意，醫療看護人手不足的問題也越顯嚴重，為了有效的照顧老人的安全，我們在北護分院護理之家，佈建了一個無線感測網路系統。在資料傳輸可靠性與即時性的考量下，目前運作的資料傳遞機制是Magnetic Diffusion (MD)。為了減少封包的碰撞，提升資料傳輸可靠性，我們採用以跨層概念設計的Cross-Layer Diffusion (XD)，其特色為在MAC層利用TDMA和CSMA來避開碰撞。我們在testbed和台大北護分院實作XD並分析其表現，和原本的MD做比較。在實作方面，我們發現由於某些硬體上的限制，XD的表現並不像模擬那樣好。且TDMA需要時間同步，在高資料傳輸率的網路中精確的運行頗為困難，所以在北護分院運作的資料傳遞機制目前仍是MD較為適合。

As the elder population grows, elder care becomes a major concern in society and nursing staff shortage also becomes a problem. To solve the problems, we deploy a WSN in the elder care center of National Taiwan University Hospital Beihu Branch. Considering both the reliability and real-time data availability, for now, the data collection protocol in Beihu is Magnetic Diffusion (MD). In order to reduce collisions and achieve high delivery rate, we think about replacing MD with Cross-Layer Diffusion (XD), whose MAC is a hybrid of TDMA and CSMA to avoid collisions. In this work, we implement XD on a 24-node IEEE 802.15.4-based sensor network testbed and on Beihu, where the protocol uses, and analyze its performance and compare it with MD. We find that: (1) limited by the hardware, the performance of XD is not as good as the results in simulation. (2) MD is still more appropriate than XD in the real-time applications in Beihu.