Understand the application scenarios of Nb IOT, Lora, EMTC, sigfox and ZigBee Expected to finish reading in 5 minutes Internet is connected to computers and mobile phones, so that people can send messages anytime, anywhere. The Internet of things may be connected to your lights, kettles, door locks, pipes, electricity meters and water meters, as well as the lamp posts on the side of the road when you walk your dog, the sprinklers on the way to work, small devices and large components, which are all inclusive, involving scenes that are also heaven and earth. People's consciousness is more complex than things, and the world of things is more complicated than people. The spectrum needed to connect people and things is completely different. People want to be online 24 hours a day and send messages and videos online at any time. Now try to take away a person's mobile phone and have a look, for fear that you will be called. But your lamp doesn't need to be connected with another lamp 24 hours at any time. If the Internet of things uses the early wireless network, it's not suitable for energy consumption, traffic and operation. No matter NB IOT, Lora, EMTC, etc., in the long run, there should be no monopoly of the king. Think of Pepsi, Sprite and fanda. In these Internet of things network connection technologies, users can choose appropriate network connection technologies according to their own needs. After all, there is no perfect technology, only suitable technology. What are the application scenarios of Nb IOT, Lora, EMTC, sigfox and ZigBee? NB-IoT&eMTC Let's start with Nb IOT and EMTC, which are the Heaven Sword and dragon sword in the hands of operators. Each has its own advantages. In terms of cost, Nb IOT is more cost-effective than EMTC; in terms of coverage, Nb IOT is 30% larger than EMTC, and EMTC coverage is about 9dB worse than NB IOT; in terms of capacity, EMTC can not meet the demand of large capacity, but in terms of speed and mobility, EMTC has more advantages than NB IOT, in addition, EMTC supports voice. That is to say, dynamic scenes involving frequent interaction with people have requirements for voice, bandwidth rate and mobility, such as Internet of vehicles, intelligent wear, logistics tracking, etc., EMTC is selected, while NB IOT is selected considering module cost, mass connection and other needs, such as intelligent electricity meter, air monitoring, intelligent water meter and other scenes. In the future, the hybrid networking of Nb IOT and EMTC, with complementary advantages of differentiation, is one of the main trends of Internet of things network connection. LoRa Next, let's talk about Lora. I mentioned the difference between Lora and Nb IOT before. Compared with Nb IOT, Lora has wider coverage and lower cost, and supports flexible networking. To some extent, Lora extends the boundary of Internet of things network connection. In some specific segmentation scenarios, such as remote or marginal areas, such as scenic sp...

How to calculation of antenna gain Expected to finish reading in 10 minutes Gain refers to the ratio of the power density of the signal generated by the actual antenna and the ideal radiating unit at the same point in space under the condition of equal input power. It quantitatively describes the degree to which an antenna concentrates input power to radiate. The gain is obviously closely related to the antenna pattern. The narrower the main lobe of the pattern, the smaller the side lobe, and the higher the gain. The physical meaning of gain can be understood in this way ------ To generate a signal of a certain size at a certain point over a certain distance, if an ideal non-directional point source is used as the transmitting antenna, 100W input power is required, and When a directional antenna with a gain of G = 13 dB = 20 is used as the transmitting antenna, the input power only needs 100/20 = 5W. In other words, the gain of an antenna, in terms of its radiation effect in the direction of maximum radiation, is a multiple of the input power compared with an ideal non-directional point source. The gain of the half-wave symmetric oscillator is G = 2.15dBi. The four half-wave symmetrical oscillators are arranged up and down along the vertical line to form a vertical quaternary array with a gain of approximately G = 8.15dBi (the unit of dBi indicates that the comparison object is an ideal point source with uniform radiation in all directions). If a half-wave symmetrical oscillator is used as the comparison object, the unit of the gain is dBd. The gain of the half-wave symmetric oscillator is G = 0dBd (because it is compared with itself, the ratio is 1 and the logarithm is zero.) The vertical quaternary array has a gain of about G = 8.15-2.15 = 6dBd. Several calculation formulas of antenna gain 1) The narrower the antenna main lobe width, the higher the gain. For a general antenna, the gain can be estimated using the following formula: G (dBi) = 10Lg {32000 / (2θ3dB, E × 2θ3dB, H)} In the formula, 2θ3dB, E and 2θ3dB, H are the lobe widths of the antenna on the two main planes; 32000 is statistical experience data. 2) For a parabolic antenna, the gain can be approximated by the following formula: G (dBi) = 10Lg {4.5 × (D / λ0) 2} Where D is the diameter of the paraboloid; λ0 is the central working wavelength; 4.5 is statistical experience data. 3) For upright omnidirectional antennas, there are approximate calculation formulas G (dBi) = 10Lg {2L/ λ0} Where L is the length of the antenna; λ0 is the central working wavelength; About db, dBi, dBd and other units of the antenna Some friends tend to confuse these units more easily. The dB values are based on logarithmic values. (1) dB, which is simply a relative value, that is, the logarithm of the value of A over B. It is often used to say how much dB A is higher or lower than B, but it is unreasonable to say how much A's gain is dB, because we don't know what B is. It is just that many of our fellows so...

Uncovering large scale MIMO technology: key factor of 5g super high speed rate Expected to finish reading in 5 minutes In 5 gera, even if the signal is only one or two boxes, we can download files, video chat or watch online movies without any scruple. In most cases, these are as smooth as listening to music online. 5g large-scale MIMO (multiple input and multiple output) technology is one of the keys to open these5guser experiences. What is large scale MIMO? MIMO system has been widely used in wireless communication - mobile devices and networks generally use multiple antennas to enhance connectivity, improve network speed and user experience. Now, with the design of the new5gNR network, MIMO technology has a new look. By deploying a large number of antennas on the base station, large-scale MIMO can bring far more performance than traditional systems. Uncover large scale MIMO technology There are three key concepts in the construction of MIMO system: spatial diversity, spatial multiplexing and beamforming Spatial diversity and spatial reuse Spatial diversity is one of the main advantages of MIMO technology. In short, diversity aims at improving the reliability of the system by simultaneous interpreting the same data on different propagation paths or paths. Spatial multiplexing Spatial diversity has gradually evolved into a more complex concept, namely "spatial reuse". Its significance is not only to improve the performance through the diversity of air channels, but also to transmit multiple messages at the same time, and in the process of transmission, each way does not interfere with each other. We can imagine that there is a data transmission pipeline between the base station and the mobile phone in the mobile network, and there is an antenna on the base station and the mobile phone, and the data that the pipeline can transmit is very limited. If more antennas can be deployed on the base station and mobile phone, and appropriate space separation can be carried out, multiple virtual channels can be established between the mobile phone and the base station, so as to achieve a large number of data transmission. Beamforming Another key wireless technology is beamforming. Through advanced antenna technology on mobile devices and network base stations, it can gather wireless signals in a specific direction, rather than spread to a wide area. Just like the difference between a flashlight and a laser pen, the former can illuminate the whole room, while the latter can continuously point or track individual users. 3D beamforming With the increase of the number of antennas in MIMO system, beamforming becomes "3D beamforming". 3D beamforming technology can generate user oriented horizontal and vertical beams, so as to improve the data transmission rate and capacity of all users, including users on the top floor of high-rise buildings. With the feedback of mobile terminal, the beam can find any point in the space. Therefore, whether users are moving in the...

How to enhance the signal of walkie talkie? ① Increase the launching height: outdoor players who often play with the handsets have such experience. When the signal is not good, stand higher. In fact, with the increase of the transmitting height, the coverage of the radio transmitting signal increases, which can greatly improve the communication effect. ② Improve the communication sensitivity: when the general hand-held walkie talkie leaves the factory, the sensitivity has been adjusted to the best state according to the relevant technical requirements, so it is not allowed to adjust the receiving sensitivity of the walkie talkie without the guidance of professional instruments and technicians. If you want to further improve the communication sensitivity, you can use a high gain antenna, but pay attention to ensure that the antenna is in the same frequency band. ③ Choose a wide communication environment and direction: when the radio wave of the walkie talkie is in the open area without obstacles, the loss of radio wave propagation is the minimum. The reinforced concrete buildings in the city absorb the electric wave seriously, and the outdoor use should avoid the block of the surrounding tall buildings or trees. ④ Increase the antenna length: Generally speaking, the special extended hand table antenna is better than the original hand table antenna; the vehicle antenna is better than the small whip antenna; the rod antenna is better than the vehicle antenna; the multi unit unidirectional antenna is better than the rod antenna. ⑤ Enhance the transmitting power: the transmitting power of the hand station is related to the voltage and capacity of the battery. When the hand station is fully charged, the transmitting power is high, otherwise it is small. The interphone with large capacity battery can effectively improve the transmission power. For example, Beifeng 511uv walkie talkie has three transmit power options: high (5W), medium (3w) and low (1W). When it is convenient to use, it can be adjusted according to distance, environment and other factors.