Let's talk about the concept first
Narrowband IoT has become an important branch of IoT. nb-iot is built on a5g and nb iot cellular network that consumes only about 180 kHz of bandwidth and can be deployed directly on gsm networks, umts networks or lte networks to reduce deployment costs and smooth upgrades. The bearer capacity of Lwpa-based ITS is achieved at the expense of some speed, latency and mobility. nb-iot, as a new narrowband cellular communication solution, will bring great changes and innovations to the IoT industry.
Four features of NB-IOT
Super coverage:Compared with existing GSM and broadband LTE networks, the coverage is enhanced by 20dB and the signal transmission coverage is larger, which can cover places that cannot be covered by GSM network deep underground.
Ultra-low frictional power consumption:The maximum current consumption is 5uA in PSM mode and about 6mA in IDLE mode.According to the simulation analysis data of TR45.820, a 5Wh battery can carry out sending 200bytes of data per day and is expected to last 12.8 years. Therefore, it can be used for research and development of equipment for students placed in remote rural areas of an alpine country wilderness.
Ultra-large connectivity: will provide improved indoor coverage, with nb-iot gaining 20 dB over existing networks in the same band, equivalent to 100 times the capacity of the coverage area. For underground garages and manhole covers where data collection devices are needed, nb-iot is better suited for 3g/4g wireless modules or 433mhz wireless devices.
Super low time cost: the cheapest module learning is currently less than $30, which will lead to lower in the future when a large number of rollouts are needed.
Use of NB-IOT
B-IoT has three operating modes:DRX (discontinuous reception) discontinuous reception mode, eDRX (extended DRX) extended discontinuous reception mode and PSM (power saving mode) power saving mode. The following figure shows the process of NB-IOT networking:
Specific operation AT command record (UDP)
1)Start/restart, the module has been started normally;
2) AT+NBAND? Check the current band information to determine if it corresponds to the module model.
3) AT+NBAND=5 telecom management module, set different frequency band to 850 MHZ.
4) AT+NRB reboot the module.
Check the module band information again to confirm the successful setting.
6) AT+NCONFIG? Query the configuration information, mainly including the configuration information of auto-connect enable, which is enabled by default.
7) AT+CFUN? whether the module design can be in full working management mode, open an RF system circuit, search for relevant signals, if we return 0, please determine whether the AUTOCONNECT value is TRUE, and whether the enterprise carries out the installation of NBIOT special SIM card.
8) 8) AT+CIMI query IMSI information, if it returns a specific value, it means that the SIM card has been recognized normally.
9) AT+CSQ query signal strength, the first value returned indicates the signal strength, 0-31 indicates that the signal exists, the larger the value, the stronger the signal, 99 indicates that there is no NBIOT network signal, the second parameter has not been achieved, 99.
10) Query module status ;
11) AT+CGATT? query whether they carry out the module can be attached successfully, return 1 on behalf of China success.
12. AT+CEREG? query network registration status, the second value returns 1 means the network registration success, returns 2 means the network is being registered, the registration time is related to the signal strength.
13) At Connecticut State University? Check the connection status of the module. The second return value indicates the operating status of the module. 1 indicates a connected state and 0 indicates an idle sleep state. If there is still no data interaction, the module will go into psm deep sleep after 10 seconds in the idle state. At this point, the module will not receive any downlink data. If downlink data needs to be transmitted, it must be in the connected and idle state.
14) AT+NSOCR=DGRAM, 17, 5683, 1 to create a UDP SOCKET transmission channel, DGRAM and 17 are fixed, 5683 represents the local port number, 1 means enable to receive downlink data; up to 7 SOCKET transmission channels can be created, the return value represents the signal ID number, which needs to be specified when sending and receiving data.
15) AT+NSOST=0,...,####,3,303132 Send UDP data, 0 represents the UDP SOCKET channel ID, ... represents the IP address of the remote control server (public IP address), #### represents the Chinese remote management server via port number, 3 represents the number of characters that can be The number of character characteristics that can be sent (3 characters were sent), 303132 represents "012" 3 hex characters; the return value represents the enterprise successfully sent 3 bytes of data from the 0 channel.
(16) AT+NSONMI: 0, 67 indicates that the module received new data need to read the information, if not read in time, then receive the next data. The information will not be actively reported, but can be read continuously; 0 indicates a UDP SOKect channel and 67 indicates that there are 67 bytes of data to be read.
17) At nsorf = 0, 30 indicates an udp socket channel. 3 indicates the length of the data bytes to be read. The valid data representing the character "012" needs to be extracted from the return value 303132;
18) AT+NSOCL = 0 to close the UDP socket transmission channel.
Summary
The author has recently been doing NB-IOT-related research and design technology applied to some sensors in the field for remote data collection of signals. In the current wireless network communication management mode, 2G-GSM currently has the largest holdings in the field, but there are some social problems for enterprises, such as relatively large power consumption, poor signal in some base stations at relatively long distances, and the development of the existence and future crisis of 2G being replaced. 4G also has the following problems, such as larger power consumption and higher cost analysis.
In this case, NB-IOT has unique advantages, especially in the application scenario where the data volume is relatively small. If friends with such needs can use the new wireless transmission mode of NB-IOT, I think this will bring you a lot of surprises.
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