Self-Adaptable ZigBee Networks & Sensor Applications
|關鍵字:||定址;位址調借;物聯網;微氣候監測;多播;參數選擇;普及運算;自我調適;車載感測網路;無線感測網路;ZigBee;Addressing;Address borrowing;IoT;Micro-climate monitoring;Multicast;Parameter decision;Pervasive computing;Self-Adaptable;Vehicular sensor network;Wireless sensor network;ZigBee|
Recently, many WSN systems have adopted ZigBee as their communication protocol. ZigBee is designed for low cost, low data-rate, and low-power WSN by the ZigBee Alliance. It adopts the physical (PHY) and the medium access control (MAC) layers defined by IEEE 802.15.4 and extends to network, application, and security services. Due to self-adaptable characteristic, WSNs have been widely adopted in surveillance and monitoring applications. In this dissertation, we probe some issues and application in self-adaptable ZigBee networks. In the first work, we are interested in addressing issue in WSNs. Addressing in WSNs is to assign each newly-joining device a unique address. However, to allot the naming space in a large-scale distributed WSNs is not an easy task. ZigBee is a popular communication standard for wireless sensor networks. It suggests a distributed address assignment mechanism. A parent device can calculate network addresses for its child devices without communicating with other devices. However, the parameter configuration of this mechanism strictly restricts the number of children of a device and the depth of the network. ZigBee does not recommend suitable parameters. The improper parameter configuration usually makes many devices isolated from the network which become orphan devices. Two automatic parameter selection schemes are proposed for ZigBee address assignment by probing the network and then selecting parameters in advance to alleviate the orphan problem. They can automatically suggest proper parameters for different network topologies and thus help the original ZigBee address assignment mechanism to effectively reduce orphans. In the second work, we propose a distributed address assignment scheme by allowing a parent to borrow a subtree of address space from a neighbor to alleviate the orphan problem. When a new node tries to associate with a parent router which has no free address, this parent router will inquire its 2-hop neighbors for lending a subtree of free address space. We also propose a light-weight routing to support one-to-one routing in this environment. In the third work, we are interested in the multicast protocol in Internet of Things (IoT). Recently, many Iots or WSN applications adopt ZigBee as their communication protocol. In these applications, messages may need to be disseminated to some specific objects or nodes using multicast transmissions. However, we observe that the original ZigBee multicast protocol causes extremely high packet overhead and energy consumption. In this work, we propose a ZigBee-compatible energy efficient multicast protocol, which allows nodes to execute the designed procedures in a distributed manner. By our scheme, each node uses the designed maintenance module to manage its neighbors. When multicasting, a node utilizes the designed multicasting module to compete for being a relay node by the proposed backoff mechanism. In addition, each node overhears its neighbors' broadcasts to avoid unnecessary transmissions and to ensure that the transmitted multicast packets are successfully received. Our results indicate that the proposed protocol can indeed lengthen network lifetime, reduce redundant packets, and preserve network reliability. The fourth work considers a micro-climate monitoring scenario, which usually requires deploying a large number of sensor nodes to capture the environmental information. By exploiting vehicular sensor networks (VSNs), it is possible to equip fewer nodes on cars to achieve fine-grained monitoring. Specifically, when a car is moving, it could conduct measurements at different locations, thus collecting lots of sensing data. To achieve this goal, this work proposes a VSN architecture to collect and measure air quality for micro-climate monitoring in city areas, where nodes' mobility may be uncontrollable (such as taxis). In the proposed VSN architecture, we address two network-related issues: (1) how to adaptively adjust the reporting rates of mobile nodes to satisfy a target monitoring quality with less communication overhead and (2) how to exploit opportunistic communications to reduce message transmissions. We propose algorithms to solve these two issues and verify their performances by simulations. In addition, we also develop a ZigBee-based prototype to monitor the concentration of carbon dioxide gas in city areas.
|Appears in Collections:||Thesis|