無線感測網路下用以支援多種型態流量之TDMA-over-CSMA鏈結層協定

Abstract

無線感測網路中存在著多種不同類型的流量，因此設計一個滿足各種流量需求的媒介存取控制協定是個具有挑戰性的議題。例如：緊急事件的回報在資訊傳遞的時間上較為緊要，而規律型的回報則是在感測節點上的省電考量較重要。在本論文中，我們提出了一個TDMA-over-CSMA的鏈結層協定，可支援無線感測網路中的資料匯集、緊急事件回報及需求型的流量。我們的主要目標有：使多數的流量可達到較低的傳輸延遲、對於匯集型的流量可達到資料聚集及省電的功效、及降低同一緊急事件區域中同時偵測到資訊之節點的資料冗餘度。另外，我們也提出了一個重複利用時槽的方法以支援需求型的流量。模擬結果呈現出我們的協定具有較佳的或可抗衡現有協定的表現，而這些現有協定可做為處理單一類型流量的代表。我們也在Jennic—以ZigBee協定為基礎的平台上完成實作的部分。

Traffics in wireless sensor networks are typically of multiple types. To design a suitable medium access control (MAC) protocol to satisfy the requirements of all traffic types is a challenging issue. For example, reports of emergency events are more time-critical, while regular reports could be more energy-critical. In this paper, we present a TDMA-over-CSMA link protocol for supporting convergecast, event-reporting, and on-demand traffics in a wireless sensor network. The main goals are to achieve low transmission latency for most types of traffics, to facilitate data aggregation and energy efficiency for convergecast traffics, and to reduce data redundancy in an event area when multiple nodes detect the same event at the same time. In addition, an opportunistic slot reuse scheme is proposed to exploit spatial reuse and to support on-demand traffics. Simulation results show that our protocol performs better than or comparable to existing protocols, which can typically take care of only one type of traffics. Implementation work has also been done on Jennic, a ZigBee-based platform.