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Sensor Platforms and Wireless Networks
Published in Kirk A. Phillips, Dirk P. Yamamoto, LeeAnn Racz, Total Exposure Health, 2020
A second wireless topology is a mesh or ad-hoc network. In this wireless topology, all stations can communicate directly with others without the need for a centralized node. This topology can be more efficient and more reliable since there is no single point of failure, but simple mesh networks can only communicate with other nodes within range. More sophisticated mesh networks have derived additional techniques to propagate a packet through the mesh to reach nodes beyond direct radio contact. These techniques fall into two main classes: table-driven methods (where all nodes try to determine and maintain routes to all other nodes), and source-initiated methods (where nodes can dynamically broadcast their desire to route to a particular node in order to determine the route on-the-fly as needed). Both methods have their tradeoffs. Table-driven methods do not scale well as all the wireless bandwidths will eventually get taken up just trying to share/maintain routing information. Source-initiated methods have a latency for the first packet as a route is determined and similarly do not scale well or handle dynamically changing topologies well. For these reasons, the most widely used wireless mesh radio networks do not typically scale beyond 100–300 nodes, although compression of data may extend this bandwidth-scalability tradeoff somewhat.
Wireless Networking Standards (WLAN, WPAN, WMAN, WWAN)
Published in K.R. Rao, Zoran S. Bojkovic, Dragorad A. Milovanovic, Wireless Multimedia Communications, 2018
K.R. Rao, Zoran S. Bojkovic, Dragorad A. Milovanovic
People love the convenience of not being constrained by a wired line. Therefore, we have TV remotes, cordless phones, cellular phones, and so on. In a wireless mesh network, a mobile user can reach the Internet via only a few hops of connections, which is much more reliable and practical than using ad hoc networks. For example, a wireless mesh network can be built on roofs of buildings to provide inexpensive broadband Internet access, while outdoor cellular WiFi cells also form a wireless mesh network. In a wireless mesh network, users can connect to the Internet as long as they are in range of another device that somehow connects to the Internet. A wireless mesh network for vehicles enables people to access traffic information and location-based services.
Field Testing and Instrumentation of Railway Vehicles
Published in Simon Iwnicki, Maksym Spiryagin, Colin Cole, Tim McSweeney, Handbook of Railway Vehicle Dynamics, 2019
The WSNs can be configured using a variety of different arrangements, as shown in Figure 18.19. In a star network, each node sends its data directly to the gateway, whilst, in a cluster tree, data is sent via the higher nodes in the tree until it reaches the gateway. A mesh network aims to achieve better reliability by allowing nodes to connect to a number of other nodes in the network to send data via the most reliable path. Both cluster tree and mesh WSNs have the advantage of extending the range of relatively low-power sensor nodes by allowing them to send their data via other nodes rather than direct to the gateway.
Design of WSN traffic forecasting system with delayed self-sensing
Published in International Journal of Computers and Applications, 2020
With the rapid development and increasing popularization of Wi-Fi technology, Wi-Fi system has been widely used in mobile devices, such as smart phones, computers. At the same time, researchers have been working to improve the network performance of Wi-Fi technology, and enhance network throughput, thus, achieving the maximum throughput 1Gbps specified in IEEE 802.11ac standard [1, 2]. Combined with Wi-Fi technology, the mesh network is also called Wi-Fi mesh network. Compared with traditional wired networks, Wi-Fi mesh network has good performance. In the Wi-Fi mesh network, the source node often transmits the data to the destination node through multiple relay nodes. In the process of data transmission, the key lies in how to establish the route from the source node to the destination node. In order to solve the routing problem in Wi-Fi mesh network, different routing algorithms are proposed. Most of these algorithms are concerned with QoS (Quality of Service) [3] and do not reasonably consider traffic load balancing [4, 5]. As a classical link state algorithm, the Optimized Link State Routing (OLSR) is widely used in wireless networks [6]. OLSR protocol uses HELLO and Topology Control (TC) message to maintain network. HELLO message contains the addresses of all nodes neighboring the sent node and the link state between them, and will not be forwarded by any node, which can be used for neighbor discovery, while TC message contains Advertised Neighbor Sequence Number (ANSN), which contains the serial number of TC messages, used for routing decisions [7, 8].
Wearable electronic textiles
Published in Textile Progress, 2019
David Tyler, Jane Wood, Tasneem Sabir, Chloe McDonnell, Abu Sadat Muhammad Sayem, Nick Whittaker
A Mesh topology proves to be more adaptable in terms of communication. In the case of a Mesh network, nodes are each able to route data around the network between themselves, to reach the final gateway node, which then transmits to the external network. Such networks are often referred to as Peer to Peer (p2p). Individual nodes can decide which route is best, and there are many more connection routes available to permit data transfer. As in a star network, one of the nodes acts as the gateway node and would likely be mains-powered. Mesh networks can self-organise and self-discover, allowing them to discover new routes when a particular route is not available. This allows a method of self-healing to create the most efficient route for data from a particular sensor node to get to the gateway node (Figure 4(c)). A drawback is that a node that is able to route data cannot go to sleep, and hence is likely to consume more power.
An efficient LoRa-based smart agriculture management and monitoring system using wireless sensor networks
Published in International Journal of Ambient Energy, 2022
S. J. Suji Prasad, M. Thangatamilan, M. Suresh, Hitesh Panchal, Christober Asir Rajan, C. Sagana, B. Gunapriya, Aditi Sharma, Tusharkumar Panchal, Kishor Kumar Sadasivuni
An automatic miniaturised greenhouse monitoring system was developed (Ibrahim et al. 2019). This system will monitor constantly and continuously on environmental factors in the orangery, to make sure that it stay in preset levels of temperature and humidity. If the greenhouse surrounding condition is slightly diverge from preset values, and then the monitoring system will automatically turn the sensors in the devices to compensate the preset level conditions. For this monitoring system, four different types of sensors were used for automatic greenhouse monitoring setup implementation. All the data and signals from the sensor are given to the microcontroller which acts as the main control unit. These values are transferred to the user interface or main control unit through the LoRa module. In previous systems, humans manually measured the moisture, temperature, humidity and various factors in the agricultural fields (Raj and Ananthi 2019). Their main aim is to check the condition and alert other farmers for manually alter the field. Some other existing methodologies incorporate Wi-fi and Zigbee technology. For Wi-fi, WSN802G modules are used. Based on this module, wireless sensor nodes are used. The data from these nodes are transmitted wirelessly to the main server, where data gets collected, analysed and displayed based on the farmer needs. Another technique is known as ZigBee, having many advantages like low cost and power. The topology used here is a wireless mesh network, which is a standard used for battery-operated devices particularly in wireless monitoring and control applications. It also provides low-latency communication. The above methods are perfect for smart agriculture. But these methodologies have some of the common disadvantages. Even though the above methods were identified for smart farming, there are some common limitations among them. Direct human involvement increases the errors in the output as the viewing angle and direction differs for different people. The human prediction may lead to half of the error because of climatic predictions by farmers; it varies from time to time. Labour problem is the major limitation in agriculture. Costs for labour is also get increased in recent times. The major limitation is the limited signal range (Butun, Pereira, and Gidlund 2019). The range of Wi-fi can approximately extend up to 50 m. But this range cannot be used in agricultural farms, because of its larger surface area. Data transmission speed in most wireless networks is far slower than the wired networks. Another protocol called Zigbee, also having a limitation of short-range, low complexity, low transmission and low data speed. Maintenance cost is somewhat high that makes it a step back when compared to other protocols.