LoRa module has become a rising star of IoT communication technology with its advantages of "long distance and low power consumption". LoRaWAN with its obvious advantages: large capacity, global unified standard, free frequency band, low cost and flexibility, like WiFi, has become the first choice for "private Internet of Things" (NB-IoT, like GPRS, is a "public property" Internet" scheme). Now, many domestic enterprises and universities have set off a climax of building the LoRa Internet of Things. How to choose the most suitable LoRa product to become the top-level design of the Internet of Things. To this end, let's discuss together.
1. Construction elements
Demand is the source of the project! Similarly, to build an Internet of Things, you first need to plan the following requirements:
1.1 Distance
1
Because of the long-distance characteristics, the mainstream of LoRa IoT is "star network", which means that the distance refers to the communication distance between the farthest node and the gateway, as shown in the figure above.
Under the same conditions of "transmission power + communication rate + antenna", the communication distance of LoRa depends heavily on the terrain and environment, such as: high-altitude weather balloon communication reaches 40km; communication between two hills or towers reaches 15km, and communication in open areas reaches 5km ...Because the wireless communication environment is different, only the "open line of sight" can be used as the benchmark; other environments are subject to actual measurement.
What if the communication distance is not enough? There are generally 3 methods:
Reducing the communication rate can improve the receiving sensitivity;
Replace the high-gain antenna and adjust the direction of the antenna;
Add gateways to effectively cover signal dead zones.
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LinkLabs has announced a method for calculating LoRa network distance. As shown in the figure above, it is very interesting. Drag some variables on the left, and the effective communication distance will be automatically calculated on the right.
The link to the method is: https://www.link-labs.com/symphony
1.2 Scale
Scale is a colloquial term for "number of nodes," an easy-to-count variable.
1.3 Bandwidth
The bandwidth here, more commonly known as the demand for "network throughput", is measured in "bits per second".
For example: 100 nodes, each node reports 37 bytes every 60 seconds, because the LoRaWAN protocol generally needs to add 13 bytes of "metadata" (frame header and verification), then the required "bandwidth" is:
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