What is edge computing (MEC)? To avoid the dullness of technology, let me give you an example. There is a very intelligent animal in nature-octopus. It has the highest IQ among invertebrates. Whether it is for escape or predation, it has many long tentacles that can be used freely. Scientists have found that the tentacles of the octopus are full of neurons, which can handle many actions independently. The octopus's brain only accounts for 40% of the processing. The other processing power is distributed on its 8 tentacles, which greatly enhances its strain processing. ability. If the human body is the central processing method of the brain, and 99% of its capabilities require the brain to respond, the octopus is a distributed processing system, and 60% relies on its "small brain" processing distributed in the antennae. Yes, this is the principle of edge computing. The calculation and processing capabilities are submerged to the edge closest to the business to complete. Most of them do not need to interact with the core network, and a few are interoperable with the core network. This is edge computing. The concept of Multi-Access Edge Computing (MEC) technology was first proposed in 2009 on the cloudlet computing platform developed by Carnegie Mellon University. In 2014, the European Telecommunications Standards Institute (ETSI) formally defined the basic concepts of MEC and established the MEC specification working group to start related standardization work. In 2016, ETSI extended this concept to multi-access edge computing, and extended the application of edge computing in mobile cellular networks to other wireless access networks (such as Wi-Fi). Under the promotion of ETSI, other international and Chinese standardization organizations including 3GPP and China Communications Standards Association (CCSA) have also initiated related work. Currently, MEC has evolved into one of the important technologies of 5G mobile communication systems. Why does 5G have to use edge computing? In the 5G era, mobile communication has shifted from the initial communication between people to the communication between people and things to the communication between things. AR/VR, Internet of Things, industrial automation, unmanned driving and other services have been introduced in large numbers, bringing network requirements for high bandwidth, low latency, and large connections. New services have increasingly demanding requirements for bandwidth, delay, and security, and the centralized deployment of traditional cloud computing has been unable to meet service requirements. Let's take a look at the following "5G flower" that can reflect the vision of 5G capabilities. We can see that the key capability requirements of the 5G vision are almost the pursuit of the ultimate, so that many people in the industry have always questioned: Can such a demanding 5G key capability really be realized? For example, how to realize the key capability of end-to-end delay of 1 milliseco...

Does NB iot module need a sim card? The simple answer is needed. (More wireless communication knowledge; IoT knowledge, antenna cable https://www.whwireless.com ) NB iot is deployed under the signal coverage of the existing cellular network and uses the licensed frequency band, so it can only be used through the network provided by the operator. Someone may ask why lora, which is also a low-power wide area network, can not use a sim card, while nbiot has to use a sim card? This is still related to the network frequency bands used by the two networks. NB iot devices do not need a gateway, and they rely on 4G coverage and use the spectrum in LTE, so NB-IoT is not easy to work in remote areas without 4G signals. Lora uses an unlicensed frequency band, which means that there is no frequency band operated by an operator. Therefore, Lora needs to pass through a gateway during use. NB-IoT network The NB-IoT network is shown in the figure. It can be seen that it consists of 5 parts: NB-IoT terminal. As long as the corresponding SIM card is installed, IoT devices in all industries can access the NB-IoT network; NB-IoT base station. It mainly refers to base stations that have been deployed by operators, and it supports all three deployment modes mentioned earlier; NB-IoT core network. Through the NB-IoT core network, the NB-IoT base station can be connected to the NB-IoT cloud; NB-IoT cloud platform. The NB-IoT cloud platform can process various services and forward the results to the vertical business center or NB-IoT terminal; Vertical business center. It can obtain NB-IoT service data and control NB-IoT terminals in its own center. Compared with the transport layer in the traditional IoT, NB-IoT changes the complex network deployment, in which the relay gateway collects information and feeds it back to the base station. Therefore, many problems such as multi-network networking, high cost and high-capacity batteries are solved. A network throughout the city can bring convenience to maintenance and management, and can easily solve and install advantages by separating it from property services. However, there are new security threats: Access to high-capacity NB-IoT terminals One sector of NB-IoT can support connections with approximately 100,000 terminals. The main challenge is to perform effective authentication and access control on these large-scale real-time high-volume connections to avoid malicious nodes from injecting false information. Open network environment The communication between the perception and transport layer of NB-IoT is completely through the wireless channel. The inherent vulnerabilities of the wireless network bring potential risks to the system. That is, an attacker can transmit interference signals to cause communication interruption. In addition, because there are a large number of nodes in a single sector, an attacker can use nodes controlled by him to sponsor a denial of service (DoS) attack, so he can affect network performance...

The difference between RTK and PPK UAVs are widely used, with low cost, multi-tasking, good maneuverability, high efficiency, and low radiation. They are widely used in all aspects of military and civilian production. Because GPS has the characteristics of all-weather, high-precision and automatic measurement, the UAVs currently used for surveying and mapping basically use GPS for positioning and navigation. The GPS single-point positioning accuracy of UAV flight control is too poor. Previously, a large number of image control points were used to correct image distortion. However, in some special terrains (such as mountains, valleys, rivers, etc.), it is difficult for field personnel to deploy image control points. In order to reduce the workload, most image control points are not even needed, and it is necessary to improve the positioning accuracy of the aircraft, RTK technology and PPK technology can achieve centimeter-level accuracy. Below we start from the two technical principles of RTK and PPK, and conduct a comparative analysis to find a more suitable method for GPS air positioning. 1. The working principle of RTK   RTK (real-time motion) measurement system usually includes three parts: GPS receiving equipment, data transmission system and software system for dynamic measurement. The RTK measurement technology is based on the carrier phase observation and has a fast and high-precision positioning function. The carrier phase differential measurement technology can obtain real-time three-dimensional positioning results of the measuring station in the specified coordinate system, and has centimeter-level positioning accuracy. The working principle of RTK measurement is: put one receiver on the base station and put the other receiver on the carrier (called the mobile station). The base station and the mobile station simultaneously receive signals sent by the same GPS satellite. The obtained observation value is compared with the known position information to obtain the GPS differential correction value. Then, the correction value is sent to the mobile station of the public satellite via the radio data link station in time to refine its GPS observation value so as to obtain a more accurate real-time position of the mobile station after the differential correction. At present, the positioning plane accuracy of the mainstream manufacturer RTK can reach 8mm + 1ppm, and the elevation accuracy can reach 15mm + 1ppm. There are two main communication methods between base station and mobile station: radio station and network. The radio station signal is stable, and the network signal transmission distance is long, and each has its own advantages. Second, the working principle of PPK   The working principle of PPK (post-processing kinematics, GPS dynamic post-processing differential) technology is to use base station receivers for simultaneous observation, and at least one mobile receiver for simultaneous observation of GPS sate...

In which conventional civil frequency bands are the control signals used by drones mostly? The device consists of a handheld host and a battery pack. The handheld host is a three-band transmitter antenna integrated design, which can simultaneously generate 2.4GHz/5.8GHz frequency UAV flight control jamming signals and satellite positioning jamming signals, through the UAV's uplink flight control channel and satellite positioning channel Blocking interference causes it to lose flight control commands and satellite positioning information, making it unable to fly normally. Depending on the design of the UAV, it will have the control effect of returning, landing and falling.  In the offensive and defensive situation, there is usually a certain distance between the drone operator and the sensitive area that needs to be fortified. The drone took off from the vicinity of the manipulator, and then gradually approached the fortified area. When the drone arrives near the fortified area and can carry out effective reconnaissance or sabotage activities, the distance from the drone to the fortified area is usually much closer than the distance between it and the operator.  In the above situation, all uplink signals sent by the operator (sent from the ground to the drone) will be relatively weak due to the long distance. With the same power, because the defender is closer to the drone, the signal will be stronger than the manipulator. The downlink signal received by the defender will also be stronger than the manipulator. But the goal of defense against the downlink signal is to prevent the operator from receiving it, and the distance from the drone to the operator at this time is about the same as the distance from the defender to the operator. Therefore, the blocking of the downward signal does not have a topographical advantage.  It can be seen from the above analysis that interference with uplink signals is more beneficial. It just so happens that the uplink signal is usually a remote control signal, which is directly related to the control of the drone. If the uplink signal is interfered, the drone will lose immediate control and can only operate according to the steps preset by the program (usually landing or hovering). The downlink signals are mainly telemetry and images. Although there may be sensitive information, it is not as important as the control signal. In addition, the defender is not dominant in the situation and usually takes a laissez-faire attitude to the downlink signal.  GPS relies on medium orbit satellites. Generally speaking, the signal reaches the surface of the earth after tens of thousands of kilometers, which is already very weak. Therefore, it is easier to interfere with GPS signals when the UAV is very close to the defender. If you want to deceive it, you need to use more complicated methods to simulate GPS satellites, which is much more difficult.  At present, the control of UAVs mostly uses radio commu...