Various types of sensor nodes are deployed in the IoT Each senso

Various types of sensor nodes are deployed in the IoT. Each sensor is an information source and different sensor nodes capture different information content. The sensor data is obtained in real-time. An essential and core technology for the IoT is the Internet. The information is transmitted in real-time through wired and wireless networks. Through RFID and RTLS, the IoT can control objects intelligently with cloud computing [6], pattern recognition [7] and so on. The IoT still has many architecture, technology and business challenges.Sensor nodes in the IoT are often tiny resource-impoverished battery powered devices which have sensing, computation, and communication capabilities. As sensor nodes get energy from a battery source, their energy is limited and should be used judiciously.
When people design protocols for the IoT, energy efficiency is an important consideration. Node discovery (also referred as information discovery or search processing) in the IoT is a widely studied problem in the context of networks [8�C13]. Querying in sensor networks can be classified in the following ways: (a) based on the type of data�Cone-shot information or continuous streams; (b) based on the type of queries�Cpull-based (where the sink node issues the queries for information) or push-based (where the detection of events triggers notification to the sink node), or a hybrid of these two; and (c) based on the query process�Cstructured (using an index or hash table) or unstructured (the search initiator has no clue about the target). Node discovery is a key problem especially in PULL and UNSTRUCTURED networks [14,15].
In PULL networks, the sink node searches for nodes that send emergency data, for example the temperature is too high. In UNSTRUCTURED network, the search initiator (the sink node) doesn’t have any clue about locations of target nodes. Node discovery in networks is a one-shot query, and we mainly do research on the problem based on UNSTRUCTURED networks.Three Anacetrapib important search mechanisms for one-shot queries in UNSTRUCTRED networks are: flooding, controlled flooding (using expanding rings), and random walk. These searching mechanisms have been extensively studied in WSNs [8,16�C20]. The purpose of node discovery is to find nodes that have emergency data. Because the situation is very urgent, the latency of searching mechanism must be very small.
One problem of random selleck compound walk is its high latency and this makes it unsuitable for delay sensitive applications. We mainly consider using flooding mechanism to search emergency nodes, but there are many problems with the basic flooding mechanism. One problem is that when the search initiator sends a query packet to the network, nodes which are not the target forward the query packet to all their neighbors when they receive it. The query packet is transmitted until its Time to Live (TTL) value becomes zero.

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