“With the rapid development of related technologies such as wireless communication and IoT sensing in China, a large number of housing, hotels, commercial buildings, and office buildings have been upgraded to intelligence, and people are slowly beginning to adapt to more intelligent daily work and life. Not only in civilian use, but IoT technology has also begun to slowly integrate into the industrial field.
With the rapid development of related technologies such as wireless communication and IoT sensing in China, a large number of housing, hotels, commercial buildings, and office buildings have been upgraded to intelligence, and people are slowly beginning to adapt to more intelligent daily work and life. Not only in civilian use, but IoT technology has also begun to slowly integrate into the industrial field.
Among the short-range wireless communication technologies for realizing the Internet of Things, Bluetooth, Wi-Fi, and zigbee are the three most widely used short-range wireless communication technologies; while 4G, 5G, NB-IoT, Sigfox, and LoRa are long-distance wireless transmission technologies. representative of technology.
short distance transmission technology
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 of 2.4 to 2.485 GHz, with communication distances ranging from a few meters to hundreds of meters.
“Bluetooth Low Energy” mode achieves low power consumption and enhanced coverage, with a maximum range of more than 100 meters
Support for complex networks: optimized for one-to-one connections, and supports one-to-many connections for star topology, etc.
Smart Connection: Added support for setting the connection frequency between devices, 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.
A temporary peer-to-peer connection (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).
The various versions of Bluetooth are incompatible, and the networking capability is poor; there are few network nodes, which is not suitable for multi-point control.
Wi-Fi is a wireless local area network communication technology, the full name of Wireless-Fidelity, wireless fidelity, the IEEE 802.11 standard organized by the IEEE has formulated the technical standard of Ethernet. Wi-Fi terminal refers to the use of high-frequency radio signals to send and receive data, using the Ethernet communication protocol, the communication distance is usually tens of meters, and the current standard has been updated to 802.11ax.
The advantage of Wi-Fi is that LAN deployment does not require wires, reducing the cost of deployment and expansion. In addition, “Wi-Fi Certified” is backward compatible, as specified by the Wi-Fi Alliance, which specifies a set of globally uniform standards: Unlike mobile phones, any Wi-Fi standard device will function correctly anywhere in the world.
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 drawbacks caused by manual meter reading, but also reduce the power supply company to improve the management level, improve work efficiency and reduce operating costs.
1. Cat. 1
Shared bicycles, mobile POS machines, etc. can be typical application scenarios of cat1. Cat. 1 Compared with NB-IoT and 2G modules, it has advantages in network coverage, speed and delay. In addition, Cat. 1 has certain cost advantages, such as network construction, now LTE Cat. 1 It can seamlessly access the existing LTE network, without the need to upgrade the software and hardware for the base station, and the network coverage cost is very low. In terms of chip cost, after system optimization, the integration level is higher, the hardware architecture of the module is simpler, and the cost of peripheral hardware is lower. In terms of delay, with LTE Cat. 4 The same millisecond-level transmission delay, and support for moving speeds above 100KM/H.
However, it also has problems similar to the development of NB-IoT. After all, the price of the module is the key to whether it can start quickly. The current price is still a bit high, I believe that after a period of time, cat. 1 will flourish.
LoRa modulation and demodulation: LoRa (Long Range, long range) is a modulation technology that provides longer communication distances compared to similar technologies. The modulation is based on spread spectrum techniques, a variant of linear modulation spread spectrum (CSS), with forward error correction (FEC). LoRa significantly improves receiver sensitivity and, like other spread spectrum techniques, uses the entire channel bandwidth to broadcast a signal, making it more robust to channel noise and insensitivity to frequency offsets due to the use of low-cost crystals. LoRa can modulate the signal 19.5dB lower than the noise floor, and most frequency shift keying (FSK) requires a signal power of 8-10dB on the noise floor to be properly modulated. LoRa modulation is the physical layer (PHY) and can be used for different protocols and different network architectures – Mesh, Star, peer-to-peer, etc.
An ad hoc network state can be formed between lora terminals, and data is uploaded to the cloud platform through a concentrator, which is suitable for scenarios where terminals are scattered 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, easy installation, stable data transmission, online monitoring of metering data, LoRa-based remote system not only has the advantages of easy embedding, large networking capacity, low power consumption, free of charge, etc., but also the LoRa wireless module has high receiving sensitivity through wall communication Strong ability, the measured communication distance can reach more than 3 kilometers, which perfectly solves the problem of ultra-long-distance communication with small data volume in complex environments.
The above various IoT wireless communication technologies are designed to meet the respective communication needs in different scenarios:
1. High-power, high-speed WAN transmission technologies, such as 4G and 5G cellular communication technologies, are suitable for large-traffic transmission applications with high real-time requirements such as GPS navigation and positioning, and video surveillance.
2. Low-power, low-rate WAN transmission technology, such as Lora, Cat1, NB-IoT, etc. This type of transmission technology is suitable for data transmission of remote equipment operating status, industrial intelligent equipment and terminal data transmission, etc.
3. High-power, high-speed short-range transmission technologies, such as WIFI and Bluetooth, are suitable for connection and data transmission between smart homes, wearable devices, and M2M.
4. Low-power, low-rate short-range transmission technology, such as ZigBee. This type of transmission technology is suitable for flexible networking applications of LAN devices, such as hotspot sharing.
At present, the development trend of the wireless transmission technology of the Internet of Things is based on low-power wide-area networks. It can be expected that in the next few years, the low-power wide-area network transmission technology represented by Lora, Cat1, and NB-IoT will gradually become the mainstream of the Internet of Things transport layer connection technology.