China
Africa
Explore chapters and articles related to this topic
Wireless Sensor Applications for Building Operation and Management
Published in Barney L. Capehart, Timothy Middelkoop, Paul J. Allen, David C. Green, Handbook of Web Based Energy Information and Control Systems, 2020
Michael R. Brambley, Michael Kintner-Meyer, Srinivas Katipamula, Patrick J. O’Neil
The operating frequency of the wireless network is 902 to 928 MHz, which requires no license per FCC Part 15 Certification [23]. The technology employs spread spectrum frequency hopping techniques to enhance the robustness and reliability of the transmission. The transmitter has an open field range of 2500 feet and is battery-powered with a standard 123 size 3-volt LiMnO2 battery with a nominal capacity of 1400 mAh. The battery life depends on the rate of transmission, which can be specified in the transmitter. The manufacturer estimates a battery life of up to 5 years with a 10-minute time between transmissions. The transmitter has an automatic battery test procedure with a ‘low-battery’ notification via the wireless network. This feature will alert the facility operator through the EMCS that the useful life of the battery in a specific transmitter is approaching its end. The repeaters are powered from ordinary 120 volts alternating current (VAC) wall outlets and have a battery backup. Three repeaters were installed, one on each floor. Because the repeaters are line powered, the repeater operates at high power and provides up to 4 miles of open field range. The receiver and the translator are installed in the mechanical room in the basement. The translator connects the receiver with the Johnson EMCS system.
Introduction to Digital Communication for Building Automation and DDC
Published in John J. “Jack” Mc Gowan, Energy and Analytics, 2020
Repeaters are used to amplify and regenerate signals for the network, and this generally enables the signal to travel longer distances on the path. Boosting the signal through the repeaters is also used at times to increase the number of nodes that the network can support. This is important for nearly all networks, but particularly BAS because of the number of controllers that are being added to networks.
Communication Infrastructure for Smart Microgrids
Published in Sasi K. Kottayil, Smart Microgrids, 2020
Repeater: A repeater is a device that is used to boost the power level of the signal by regenerating it when the signal power level becomes too weak after long distance transmission. It is a two port device that operates in the physical layer and helps to increase the range of the network.
A PSO based optimal repeater insertion technique for carbon nanotube interconnects
Published in International Journal of Electronics Letters, 2022
P. Uma Sathyakam, Shubham Raj, A. Karthikeyan, P. S. Mallick
Recent work in understanding carbon nanotube (CNT) interconnects performance has shown that they face certain issues in realising them as interconnects practically (Sathyakam, Mallick, et al., 2019). One of the reasons for diminished performance of interconnects is due to the lack of signal integrity. Especially in long interconnects, repeaters must be inserted to regenerate the signals before they degrade (Liang et al., 2011; Lu et al., 2016). Lot of work was done in recent years in this regard. While one category of work deals with repeater design for optimising delay or power dissipation, (Karthikeyan & Mallick, 2017; 2019; Khursheed et al., 2019) to name a few, another category deals with optimisation of number of repeaters for reducing delay and power dissipation like (Li et al., 2020; Liu et al., 2020; Zhao et al., 2019)(Li et al., 2020; Liu et al., 2020; Zhao et al., 2019). In the latter category, recent work has used optimisation techniques, such as particle swarm optimisation (PSO), genetic algorithms (GA) and artificial neural networks (ANN), for finding the optimal number of repeaters for lesser delay and power dissipation. Recently, CNTFETs have found their way in nano-electronics applications (Sathyakam et al., 2020).
Low-cost leaky feeder communication for mines rescue
Published in Mining Technology, 2020
Michael D. Bedford, Angel J. A. Rodríguez López, Patrick J. Foster
At frequencies above a threshold, which is referred to as the cut-off frequency, and which depends on the cross-sectional dimensions of the tunnel, radio communication is possible along tunnels via a mechanism referred to as a lossy waveguide mode of propagation – (Emslie et al. 1975; Zhang et al. 2001). In mine galleries, frequencies in the UHF (ultra high frequency, 300 MHz–3 GHz) and SHF (super high frequency, 3–30 GHz) portions of the radio spectrum are suitable, and communication over a range of hundreds of metres or even kilometres has been achieved in transport tunnels, under ideal conditions (Kennedy and Bedford 2014). However, while this method provides a viable solution in perfectly straight tunnels with relatively smooth walls, the loss of a line-of-sight path is problematic. In practice, communication is negatively influenced by a single bend (Jacksha and Zhou 2016) and, at the levels of attenuation quoted in that paper, would typically be lost completely along a path containing two or more bends. This can partially be overcome by installing passive reflectors at each bend (Isberg and Chufo 1978), but these have to be accurately aligned so this wouldn’t be viable for rapid installation during a rescue operation. A much better way of overcoming the problem caused by bends is to place active repeaters at bends (Souryal et al. 2009), indeed a string of such repeaters could be installed temporarily by a rescue team as they progress, even though a large number of repeaters will result in a high degree of latency, i.e. a significant end-to-end delay. Also, since a high density of repeaters might be needed – for example, up to nine repeaters were needed in the highly non line-of-sight test area described in Souryal et al. (2009), despite the area measuring only 57 × 166 m on two levels – this could be an expensive solution, and would require the rescuers to carry a significant amount of equipment into the mine. While still imposing some of these drawbacks, using repeaters to form a mesh network can provide a degree of resilience to equipment failure because signals can be re-routed over a different path if a repeater fails. Equipment using this principle has been produced for mining use. The RESYS system (Buchwald et al. 2017) for example, was designed specifically for rescue communication, while the IWT Sentinel system (Anonymous 2020) is intended for normal operational use but safety is considered a key motivator.