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With the rapid development of domestic wireless communication, IoT sensing and other related technologies, a large number of intelligent upgrading of housing, hotels, commercial buildings, and office buildings have begun, and people are slowly beginning to adapt to more intelligent daily work and life. Not only for civilian use, the Internet of Things technology is also slowly integrating into the industrial field.
Among the short-distance wireless communication technologies for realizing the Internet of Things, Bluetooth, Wi-Fi, and zigbee are the three widely used short-distance wireless communication technologies; while 4G, 5G, NB-IoT, Sigfox, and LoRa are long-distance wireless transmission technologies representative.
Short-distance transmission technology
1. Bluetooth:
Bluetooth is a technology for wireless communication between devices, which can realize short-distance data exchange between fixed devices, mobile devices and building personal area networks. Bluetooth can connect multiple devices and overcome the problem of data synchronization. Bluetooth uses short-baud high-frequency (UHF) radio waves to communicate via the ISM frequency band from 2.4 to 2.485 GHz. The communication distance ranges from a few meters to hundreds of meters.
advantage:
Under the "Bluetooth Low Energy" mode, low power consumption is realized, and the coverage area is enhanced, and the maximum range can exceed 100 meters. Support complex network: Optimize for one-to-one connection, and support one-to-many connection of star topology, etc. Smart connection: Increase the support for setting the connection frequency between devices, and Ipv6 network support. High security: use AES-128 CCM encryption algorithm for data packet encryption and authentication. The Bluetooth module is small and easy to integrate. Temporary ad-hoc connection can be established: According to the role of the Bluetooth device in the network, it can be divided into a master device (Master) and a slave device (Slave). Disadvantages:
The various versions of Bluetooth are not compatible and have poor networking capabilities; there are few network nodes and are not suitable for multi-point deployment. 2. Wi-Fi:
Wi-Fi is a wireless local area network communication technology, the full name is Wireless-Fidelity, wireless fidelity, the IEEE 802.11 standard organized by the IEEE established the technical standard for Ethernet. Wi-Fi terminals refer to the use of high-frequency radio signals to send and receive data, and use the Ethernet communication protocol. The communication distance is usually tens of meters. The current standard has been updated to 802.11ax.
advantage:
The advantage of Wi-Fi is that there is no need to use wires for LAN deployment, which reduces the cost of deployment and expansion. In addition, according to the Wi-Fi Alliance, "Wi-Fi certification" is backward compatible, and it specifies a set of global unified standards: unlike mobile phones*, any Wi-Fi standard equipment will operate correctly anywhere in the world. Disadvantages:
The disadvantages of Wi-Fi are limited communication distance, poor stability, high power consumption, poor networking capability, poor security, and poor anti-interference ability, which cannot be effectively applied in the industrial field. Long-distance transmission technology
With the development of smart cities, one of the representatives of long-distance wireless transmission technology is that traditional manual meter reading will also be replaced by remote meter reading. Wireless remote meter reading can not only solve the shortcomings caused by manual meter reading, but also reduce the power supply company to improve the management level, improve work efficiency, and reduce operating costs.
Cat.1, an outstanding representative of 1.4G and 5G applications in the Internet of Things
Shared bicycles, mobile POS machines, etc. can all be typical application scenarios for cat1. Compared with NB-IoT and 2G modules, Cat.1 has advantages in network coverage, speed and delay. In addition, Cat.1 has certain cost advantages. For example, in network construction, LTE Cat.1 can now be seamlessly connected to the In LTE networks, there is no need to upgrade the base station software and hardware, and the network coverage cost is very low. In terms of chip cost, after system optimization, the integration level is higher, the hardware structure of the module is simpler, and the peripheral hardware cost is lower. In terms of delay, it has the same millisecond-level transmission delay as LTE Cat.4, and supports mobile speeds above 100KM/H.
However, it also has problems similar to the development of NB-IoT. After all, the price of modules is the key to rapid volume. The current price is still a bit high, I believe that after a period of time, cat.1 will flourish.
2. LoRa
LoRa modulation and demodulation: LoRa (Long Range, long distance) is a modulation technology that provides a longer communication distance compared with similar technologies. Modulation is based on spread spectrum technology, a variant of linear modulation spread spectrum (CSS), with forward error correction (FEC). LoRa significantly improves the receiving sensitivity. Like other spread spectrum technologies, the entire channel bandwidth is used to broadcast a signal, thereby making the channel noise and the insensitivity to frequency offset caused by the use of low-cost crystals more robust. LoRa can modulate the signal 19.5dB lower than the noise floor, and most frequency shift keying (FSK) needs a signal power of 8-10dB on the noise floor to be able to modulate correctly. LoRa modulation is the physical layer (PHY), which can be used for different protocols and different network architectures-Mesh, Star, point-to-point, etc.
An ad hoc network state can be formed between lora terminals, and data can be uploaded to the cloud platform through a concentrator, which is suitable for scenarios where terminals are dispersed and data processing is centralized. LoRa has strong penetrating power, and the wireless line of sight can reach 3 kilometers. Each terminal with a module can be used as a relay point for a remote terminal. No wiring required, easy installation, stable data transmission, and measurement data can be monitored online. The LoRa-based remote system not only has the advantages of easy embedding, large network capacity, low power consumption, and free of charge, but also the LoRa wireless module has high receiving sensitivity and communication through the wall Strong ability, the measured communication distance can reach more than 3 kilometers, which perfectly solves the problem of ultra-long-distance communication in complex environments with small data volumes.
The above-mentioned various IoT wireless communication technologies are designed to meet their respective communication needs in different scenarios:
1. High-power, high-speed wide area network transmission technology, such as 4G, 5G cellular communication technology, this type of transmission technology is suitable for GPS navigation and positioning, video surveillance and other high-volume transmission applications with high real-time requirements.
2. Low-power, low-speed wide area network transmission technology, such as Lora, Cat1, NB-IoT, etc., this type of transmission technology is suitable for data transmission of remote equipment operating status, data transmission of industrial intelligent equipment and terminals, etc.
3. High-power, high-speed short-distance transmission technologies, such as WIFI and Bluetooth, which are suitable for connection and data transmission between smart homes, wearable devices, and M2M.
4. Low-power, low-speed short-distance transmission technology, such as ZigBee. This type of transmission technology is suitable for flexible networking applications of LAN equipment, such as hotspot sharing.
Currently, the development trend of wireless transmission technology for the Internet of Things is based on low-power wide-area networks. It can be predicted that in the next few years, low-power wide-area network transmission technologies represented by Lora, Cat1, and NB-IoT will gradually become the mainstream of IoT transmission layer connection technologies.
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