設計有效率的機器對機器通訊給智慧型運輸系統

物聯網(IoT)展望連結大量的機器以提供使用者各式各樣的服務。這些機器自動地感測環境、交換局部或全局資訊並一起行動。例如，以IoT為基礎的汽車可以互相通訊並協調以避免碰撞及人員的傷亡。在不遠的將來，這些汽車以及路邊裝置(RSU)一同建立了一個更快、更安全以及更節能的智慧型運輸系統(ITS)。以IoT基礎的ITS的成功依賴有效率的機器對機器(M2M)通訊來散佈感測以及控制訊息。這篇論文的目的即是加強給ITS的M2M通訊的效率。我們把焦點放在兩個ITS的應用包括汽車防撞系統以及汽車遠程信息服務。在汽車防撞系統這方面，汽車週期性地廣播他們的速度、方向、座標給對方。在典型的情況下，汽車只有1.5秒可以發現到對方並避免碰撞。為了加速鄰居發現，一個有合作式轉傳的多頻道鄰居發現被提出了。我們的模擬結果顯示我們的協定勝過單頻道的方案22%。提出的方法也被實作在一個以ZigBee基礎的測試平台上以展示其效果。在汽車遠程信息服務這方面，汽車需要週期性地傳送資料給RSU。RSU再把這些資料傳給伺服器。在這樣的一個兩跳的無線網路下(汽車-RSU-伺服器)，汽車和RSU為了資料傳輸競爭頻道的使用。為了解決頻道競爭的問題，一個分散式且優先化的頻道存取機制被提出。我們也建立了一個數學模型來分析端點至端點的傳輸延遲。不論是數學模型或模擬的結果都顯示與現存的機制相比，端點至端點的傳輸延遲被減少了大約50%。

關鍵字

物聯網；機器對機器通訊；智慧型運輸系統；鄰居發現；加權公平；分析模型

並列摘要

The Internet of Things (IoT) envisions to connect a huge number of machines together to provide users with various applications. These machines sense the environment, exchange local or global information, and jointly take actions in an autonomous manner. For example, IoT-enabled vehicles can communicate and coordinate with each other to avoid collisions and reduce casualties. These vehicles and interconnected roadside units (RSUs) together will construct a faster, safer, and greener Intelligent Transportation System (ITS) in the near future. The success of IoT-based ITS relies on efficient Machine-to-Machine (M2M) communications to disseminate sensing and control data. This thesis aims to improve the efficiency of M2M communication for ITS. We focus on two ITS applications including vehicle crash avoidance and vehicle telematics. In the case of crash avoidance, vehicles periodically broadcast their speed, direction, and geo-coordinates to each other. In typical scenarios, vehicles only have 1.5 sec to discover each other and avoid accidents. To expedite neighbor discovery, a multi-channel neighbor discovery with cooperative relay is proposed. Our simulation results show that our protocol outperforms the single-channel solution by 22%. The proposed protocol is also implemented in a ZigBee-based testbed to demonstrate its practicality. In the case of telematics, vehicles need to periodically transmit data to RSUs. The RSUs then forward the data to the server. In such a two-hop wireless network (i.e., vehicle-RSU-server), vehicles and RSUs contend channel access for data transmission. To resolve channel contention, a distributed and prioritized channel channel access is proposed. A mathematical model is also developed to analyze the end-to-end delay. Both analytical and simulation results show that the end-to-end delay is about 50 less when compared to the existing schemes.

並列關鍵字

Internet of Things (IoT) ； Machine-to-Machine (M2M) communications ； Intelligent Transportation System (ITS) ； neighbor discovery ； weighted fair ； analytical model

參考文獻

Protocol Design for VANET with Adaptive Broadcasting,” Wireless Communications

[2] Qing Xu, T. Mak, Jeff Ko, Raja Sengupta “Medium Access Control Protocol Design

vol. 56, no. 2, pp. 499-518, 2007

[3] Qing Xu, T. Mak, Raja Sengupta “Vehicle-to-vehicle safety messaging in DSRC,”

Proceedings of the 1st ACM international workshop on Vehicular ad hoc networks,

國際替代計量

設計有效率的機器對機器通訊給智慧型運輸系統

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