DIPOL Weekly Review – TV and SAT TV, CCTV, WLAN

Wi-Fi will diagnose respiratory problems.

Researchers at the US National Institute of Standards and Technology (NIST) have invented a method for detecting respiratory disorders using indirect devices that connect to a router via a radio connection. All that is needed for it to work is an ordinary Wi-Fi router that continuously generates radio waves that are received by, for example, smartphones or computers. The radio wave generated by the devices travels, and along the way reflects or partially penetrates obstacles such as walls, furniture or the human body. Movements, including breathing, cause a slight change in the signal path. Researchers have developed a deep learning algorithm, BreatheSmart, that can analyze these minute changes and can determine if someone in the room is having difficulty breathing. Importantly, this can be done based on current Wi-Fi routers and devices.

Sets of CSI (Channel State Information) signals have been used to do this. These represent diagnostic data sent from the client device to the access point to ascertain what conditions currently exist in the transmission channel. This allows, among other things, to determine the optimal power and transmission speed. The transmitted data is subject to a certain scheme and the router always knows what should be included. The solution created by the researchers, also takes advantage of the fact that the CSI signal is disturbed by various obstacles – it can be reflected, it can lose power. The developers have changed the router's software so that it generates 10 such streams per second, allowing for better quality data for analysis. The CSI data streams are small – no more than 1 kB – so they have little impact on transmission quality, which can make a difference when the same router is used to provide an Internet connection.

The researchers set up the training dummy in a reflection-free chamber, where signals are not disturbed by external sources. The dummy is able to simulate both normal breathing and various disturbances, including accelerated breathing, asthma, pneumonia and chronic obstructive pulmonary disease. The body moves differently during these diseases, the movement of the chest changes the signal path. Then the acquired data had to be analyzed and the patterns that indicate diseases identified. Based on that data, the BreatheSmart deep learning algorithm was developed which correctly classifies different breathing patterns simulated with a dummy in 99.54% of cases.

There has been a lot of interest in using Wi-Fi signals for sensing applications. All that is needed to operate is a router and a client device. The researchers have created a framework for building programs that allow easy monitoring of breathing. It was left to programmers to create a suitable algorithm for analyzing the data and extracting the relevant information. This makes it easy to create applications tailored to specific requirements.

Optimization of GSM coverage of premises.

In the case of systems intended to provide GSM signals in multiple rooms (floors), the signal coming from the cell phone amplifier needs to be split and multiple antennas need to be used. A GSM splitter that operates at frequencies from 800 to 2500 MHz and has an impedance of 50 ohm is used for that purpose.

Depending on the specific installation, the following splitter models can be used:

• two-way A6812,
• three-way A6813,
• four-way A6814.

The number and type of splitters depends on output signal strength of GSM repeater. It is the resultant of several factors, among others: signal strength outside the building, gain of outdoor antenna, attenuation of the cables and connectors, and the amplifier gain. The best rule of thumb is to use one two-way splitter in the case of strong signal outside a building, using GSM-305 A6765 repeater. For GSM-505 A6775 it is possible to use 2-3 antennas, whereas for the GSM-1205 A6785 repeater, the signal can be branched even to 4-5 antennas. The radius of the amplified signal beam from each antenna is about 8-9 m (excluding obstacles like walls).

The diagram of the installation below shows the use of three-way splitter A6813 to connect indoor antennas located on each floor of the building.

Why cannot UPC and APC fiber optic connectors be combined?

Installers new to fiber optics often overlook the fact that fiber optic connectors can come in two versions of ferrule bevel: UPC (Ultra Physical Contact) and APC (Angled Physical Contact). This difference affects the connector's ability to attenuate reflected signals and is used in systems operating in transmission window III and higher.

In the case of Ethernet systems up to 10 Gbps, CCTV systems, LANs, automation, etc., it does not matter whether UPC or APC type connectors are used, unless the manufacturer of active equipment top-down imposes the necessity of using a specific type of connector. Nevertheless, it is important that, when deciding on a particular type of connector, one should try to maintain a single standard throughout the transmission path. It will not be wrong to use APC-type disconnect connections in the middle of the system while UPC connectors will be used at the beginning, but it is absolutely forbidden to mix plugs within a single connection.

Typical attenuation of a fiber optic connector is 0.2 – 0.5 dB. The "mixed" connection shown above generally generates 4-6 dB of additional attenuation. This has a huge negative impact on transmission regardless of the system. Another issue is the large reflection of the signal on such a connection. Even if the power budget turns out to be sufficient, a large number of reflections interfering with the transmitter can negatively affect the operation of the system.

Filtering unwanted signals in RF systems.

In most countries of the European Union, the work on sorting out the radio spectrum for terrestrial digital television DVB-T2 has been completed. The process has resulted in the release of more bands for mobile operators (5G services). Currently, the 700 MHz TV band is being freed up. The highest TV channels, numbered 49 and 50, are therefore most at risk of interference from LTE transmitters. The image on the TV screen may freeze, colored stripes and squares (picture frameup) may appear. To exclude the interference of LTE transmitters on DVB-T/T2 reception, special external filters were developed.

Network communication with CyberPower UPS.

SNMP card is a remote management card that uses Simple Network Management Protocol (SNMP), a standard protocol for collecting and organizing information about managed devices in IP networks. It can be installed in devices equipped with an appropriate slot. It is most often found in models designed for installation in a 19" rack: N9702, N9706, N9716. When connected as a plug-and-play device, it , allows users to monitor and control one or multiple UPS systems from any location, as well as to perform management tasks including scheduled shutdown, startup or restart.

Intuitive web-based user interface supports automatic event notifications via email, SNMP trap, Syslog, and text messages to notify of power problems and allow the user to take immediate action.

The user can conveniently find relevant information on the status of the device, configure advanced settings, and perform a battery test through the web interface.

Automatic start of live monitoring when connecting to Hikvision DVR via Internet browser.

When connected to Hikvision DVR via web browser, automatic live preview playback is disabled by default. The preview can be activated for all cameras each time from the main window and the type of stream played can be specified. In the local configuration, after logging in to the DVR, it is possible to enable automatic live playback. It is also possible to specify the type of stream from which the cameras are to be displayed during automatic playback (main or auxiliary stream). This configuration applies to the specific browser running on the computer. The settings can be changed after logging in to the DVR in the Configuration -> Local tab.

SMATV/SAT system in a multi-family building. Multiswitch systems intended to supply DVB-T2 digital terrestrial TV and DVB-S/S2 satellite TV signals to apartments are an excellent complement, as well as an alternative, to cable network systems in multi-family residential buildings. The use of fiber optics in them can be associated with many advantages, both technically and financially. If typical fiber-optic cables are chosen, the cost of building a multiswitch bus can be several or more times lower than that of a copper bus. This is due both to the fact that the unit price of fiber-optic cable can be lower than that of good-grade coaxial cable, and to the fact that fewer cables need to be laid...>>>more