There is a popular saying about Urban Governance: sewer is the conscience of a city. In the city, there are all kinds of densely distributed pipe networks underground, which are used for sewage discharge, drainage, various pipeline laying, etc. In these pipe networks, a node is the well cover we can see, walking in the road, sidewalk, park, community, factory and other environments. However, due to the lack of effective real-time monitoring and management means, a large number of manhole covers provide opportunities for lawbreakers. Illegal activities such as moving and stealing the manhole covers occur from time to time. At the same time, when the manhole covers are loosened, sagged or the surrounding concrete structure is cracked due to the inherent construction problems and the continuous rolling of passing vehicles every day, it becomes a human being The "trap" of fear. Due to the large number of urban well covers, in order to better ensure the safety of public facilities and protect the main underground resources, it is urgent to adopt new technology and new mode to strengthen the safety management of well covers. With the rapid development of Internet of things technology, the concept of smart city was born based on the combination of satellite positioning, mobile communication and cloud computing. Along this development direction, the traditional municipal infrastructure was transformed to make it intelligent and Internet of things, improve the level of urban governance, and promote the construction of smart city. For a small well cover, the well cover monitoring system based on Lora / ZigBee transmission has been widely used without changing its physical properties and use. The intelligent hardware is installed on the common well cover to realize the intelligent upgrade, which makes the well cover visible, controllable and manageable, and becomes the front guard of urban pipe network monitoring. It can realize the monitoring and management of the intelligent well cover. There are various ways of data communication between the up and down lines, which can be transmitted by wireless way: ■ network port, connecting the server of well cover management center; ■ 4G, connect the Municipal Center Management cloud platform, and the operation and maintenance administrator mobile app; ■ RS485, which can be connected to other acquisition bottom instruments, sensors and IOT equipment; ■ Lora / ZigBee, to monitor the terminal status of intelligent well cover (optional module, one out of two); ■ after the installation of the client program, it can be used directly, fully meet the various functional interfaces, and avoid the trouble of hardware development and system transplantation. Intelligent well cover monitoring management process ❶ when the well cover inclines 10-15 ° or the well cover shifts, the detection signal will be sent out when the water level exceeds the limit; ❷ the detection signal is transmitted to the intelligent gateway through Lora ...

How many base stations are built? It depends on the wavelength of electromagnetic wave. The longer the wavelength, the less the base station and the less the investment. However, the longer the wavelength, the less information and data it carries, and the lower the transmission efficiency. Therefore, mobile communication is developing in the direction of shorter wavelength. So, what is the wavelength of5G? This is determined by the formula: the speed of light = wavelength * frequency. The speed of light is constant. It is300,000 kmper second. The frequency of5Gis 24 gHz-32 gHz. According to the calculation of 28gHz, the wavelength is about108 mm. Therefore, 5G communication belongs to millimeter wave communication. Its advantages are large transmission bandwidth, high transmission efficiency, but its disadvantages are short transmission distance and easy to be blocked. The cost is high. Compared with4G, the transmission efficiency is improved by hundreds of times, but the expansion of base station alone is increased by more than 20 times. At present, the construction density of 4G base stations in cities has basically achieved 500 meters, while in some urban central areas, it has reached 200-300 meters, and even in some areas, the density of base stations can even reach 100 meters. The two main reasons are as follows: first, there are too many high-rise buildings in the city, and the obstruction is serious, so we have to build more base stations; second, the population density in the city is much larger than that in the rural suburbs, considering the user perception, we also have to build more base stations. In fact, the biggest problem of 5G coverage is still on the upstream, as well as indoor coverage. Because of the high frequency of5G, the indoor coverage effect will be worse than the current4Gcoverage, which is why the user experience speed ofKoreaand theUnited Statesis not so fast after5Gcoverage. In fact, the reason why5Gwants to build more base stations in cities is not to say that the city's macro base stations. Now the density of4Gmacro base stations in cities is large enough. Maybe more is to build some indoor 5G base stations. In rural areas, there are fewer high-rise buildings and fewer barriers, so there is no need to build a base station with the same density as a city.                                                                                                                                              Write By  WHWIRELESS

Understanding the characteristics of PCB antenna and FPC antenna Internet of Things and intelligent hardware products need antenna to transmit data on the Internet. The smaller the space and the more frequency bands, the more complex the antenna design is. External antennas are generally standard products, suitable frequency band, without debugging, plug and play. For example, express cabinets and vending machines, magnetic antennas are commonly used, which can be sucked onto the iron shell. These antennas can't be placed inside the tin cabinet. Metal can shield the antenna signal, so they can only be placed outside. The advantage is easy to use and cheap, but the disadvantage is that it can not be used in small-sized products. The antenna length is about 1/4 of the wavelength of electromagnetic wave, so the lower the signal frequency, the longer the antenna length.Therefore, a long pole antenna is needed for a FM radio of about 100 MHz, a walkie-talkie of about 400 MHz, and an external long pole antenna is also needed. The 433MHz wireless serial port commonly used in the Internet of Things is usually also equipped with an external antenna. SL-Base Station Antenna Plate Antennas that are made shorter, such as 1/8 or 1/16 wavelengths, can also be used, but the efficiency will decrease. Some devices will adopt "short antenna + LNA" mode, and can also achieve the reception effect of long antenna. However, short antennas need to increase the transmitting power to achieve the effect of long antennas. Therefore, the radio needs to transmit signals, which are long external antennas, while FM radio only receives no transmission, and has built-in receiving antennas. For example,2G(900MHz),4G(700-2600MHz), WIFI and Bluetooth (2.4GHz), GPS (1.5GHz), these commonly used Internet of Things communication methods can be used as built-in antennas. For small size products such as handsets, wearable design and smart home, external antennas are seldom used, and built-in antennas are commonly used.The product has high integration, beautiful appearance and slightly weaker performance than the external antenna. The built-in antennas include ceramic antenna, PCB antenna, FPC/steel antenna and LDS antenna. Ceramic antenna Ceramic antenna, the most used in Internet of Things products, is the GPS antenna and Bluetooth antenna. The advantages are: small space occupation and good performance. The disadvantage is that it is difficult to achieve multi-band, so it is difficult to be applied in4Gproducts. The requirement of circuit board clearance is relatively high, and it is not suitable for the products with special compactness. GPS, Bluetooth and GSM Ceramic Antenna Slider Board of Deep Connection Circuit Communication Base Station PCB antenna As mentioned above, an antenna is a wire of a certain length. This line can also be drawn on the PCB board, which is the PCB antenna. PCB antenna is widely used in Bluetooth ...

Multiple-Input Multiple-Output (MIMO) refers to the use of multiple transmit and receive antennas at the transmit and receive ends to transmit and receive signals through multiple antennas at the transmit and receive ends. Communication quality. It can make full use of space resources, realize multiple transmission and multiple reception through multiple antennas, and can increase the system channel capacity by multiple times without increasing spectrum resources and antenna transmission power, showing obvious advantages and being regarded as next generation mobile. The core technology of communication. The MIMO (Multiple-Input Multiple-Output) system is a core technology applied to 802.11n. 802.11n is a new wireless LAN technology after IEEE 802.11b\a\g, with a speed of up to 600Mbps. At the same time, proprietary MIMO technology can improve the performance of existing802.11a/b/g networks. The technique was first proposed by Marconi in 1908, which uses multiple antennas to suppress channel fading. Depending on the number of antennas at both ends of the transceiver, MIMO can also include a SIMO (Single-Input Multi-ple-Output) system and a MISO (Multiple-Input Single-Output) system compared to a conventional SISO (Single-Input Single-Output) system.                                                                                                                                              Write By  WHWIRELESS