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Wireless Sensing
Published in Mahbub Hassan, Wireless and Mobile Networking, 2022
WiFi sensing refers to systems that try to detect human states from the WiFi signals reflected from the human body. Working principle of WiFi sensing system is illustrated in Fig. 2 where an existing access point (AP) or WiFi router transmits WiFi packets, while a receiver, such as a laptop, extracts specific signal information for sensing. RSS and channel state information (CSI) are dominant signal informations currently used for WiFi sensing.
Detection and analysis of transfer time in urban rail transit system using WIFI data
Published in Transportation Letters, 2023
Li Yan, Nan Si-Rui, Guo Yue, Zhu Cai-Hua, Li Duo
Any network device will constantly broadcast the “probe” information when its WIFI function is enabled, which can be named as “WIFI devices.” A WIFI sensing system is developed to capture this “probe” information, which includes the Media Access Control (MAC) address, the Received Signal Strength Indication (RSSI), and the timestamp. Figure 1 illustrates the probe data format. The WIFI sensing system can be named as “sensing devices,” which is essentially a wireless router without a broadcasting function. It only scans the probe information for every second within its detection range, which can be gained by an antenna. If the sensing devices are installed at the platform level, the arrival time and departure time of detected devices can be obtained by extracting the first and last timestamp of one specific MAC address.
Indoor occupancy detection and counting system based on boosting algorithm using different sensor data
Published in Building Research & Information, 2023
Pushpanjali Kumari, S. R. N. Reddy, Richa Yadav
Different sensors were used to extract features that indicate the occupancy level and the relative changes (PIR motion detectors, CO2 sensors, plug loads, lighting loads, electricity use and Wi-Fi access points), as shown in Figure 3. PIR motion Detectors: Most PIR sensors are utilized in PIR-based motion detectors. Additionally, it is utilized in automatic lighting and security alarm systems. PIR sensors let you detect movement. They are lightweight, affordable, low-power, simple and durable. PIR comprises a pyroelectric sensor that will distinguish among various infrared radiation intensities. Rather than producing any energy, the detector passively collects it. The PIR sensor’'s first slot is broken when an animal or human body passes past. As an outcome, the divergence changes between the two bisects are positive. When someone leaves the identification region, the sensor causes a negative differential shift among the two bisects.CO2 sensors: Carbon dioxide, sometimes called CO2, is a colourless and odourless gas that naturally exists in the environment. Gas is a byproduct of many living things’ cellular respiration and is also created when burning wood, coal, oil, or gas. A room’'s CO2 content rises owing to human breathing when one (or more) people are present. If there is no rapid air exchange, the CO2 concentration might be utilized to determine whether someone is in the room (such as from a ventilation system) to offset the increase in this concentration. When a person leaves a room, the CO2 concentration falls due to infiltration, making it possible to detect their absence.Plug loads (KW): Plug load occupancy sensors are power strips that turn equipment off automatically when workspaces or rooms are unoccupied. They include an occupancy sensor that may be installed above or below a work surface to switch off the equipment when no one is in the space. Energy and financial resources are saved in this way.Lighting loads: Occupancy sensors detect movement inside the intended space. The sensor alerts the control unit when motion is detected. After a user-specified amount of time, the controller determines that the area is empty and then switches off the Light if there hasn’'t been any movement.Electricity use: Energy monitoring sensors enable you to trace energy consumption over time, view detailed real-time energy use and monitor and manage equipment.Wi-Fi access points: A new technology called Wi-Fi Sensing uses existing Wi-Fi signals to provide motion detection, gesture recognition and biometric assessment. It opens up new prospects for service providers in home security, healthcare, business, building automation/management and many other areas.