How to realize LoRa networking without a gateway?

As a low-power wide area network communication technology, LoRa achieves the requirements of long distance and low power consumption in the Internet of Things, making LoRa technology applied to more and more fields. However, facing the networking requirements of many nodes in the network, how can we quickly and easily achieve networking?

Let’s first understand what LoRa is?

LoRa is an ultra-long-distance wireless transmission solution based on spread spectrum technology. It is one of the Internet of Things communication technologies. Its name comes from the abbreviation of "Long Range". As the name suggests, its greatest feature is long-distance transmission.

According to investigation, spread spectrum communication technology was invented in 1944 by 26-year-old Hollywood actress Hedy Lamarr (known as the most beautiful woman in the world). It was inspired by the principle of musician George Antheil playing the piano synchronously. This frequency hopping technology can effectively resist interference and achieve encryption.

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Hedy Lamarr, the mother of CDMA

The schematic diagram of spread spectrum modulation is shown as follows. The original signal of the user data is XORed with the spread coded bit stream to generate a transmit signal stream. The impact of this modulation is that the bandwidth of the transmission signal is significantly increased (the spectrum is expanded).

Schematic diagram of spread spectrum modulation

Of course, spread spectrum technology is not perfect. It has at least two disadvantages:

• Spread coded modulation generates more slices of data stream, resulting in a decrease in the communication data rate;
• More complex modulation and demodulation mechanisms.

In August 2013, the American company Semtech released a new chip based on ultra-long-distance and low-power data transmission technology below 1GHz to the industry, which is what we call the LoRa chip.

As shown in the module block diagram of Figure 2, the SX127X series LoRa chip, in addition to spread spectrum modulation, also supports multiple other standard modulation methods such as FSK/GFSK, and can switch between them. Together, they achieve long-distance modulation capabilities while using standard FSK or OOK modulation technology.

Once launched, LoRa has won wide attention with its amazing sensitivity (-148dBm), strong anti-interference ability and excellent system capacity performance.

SX127X Block Diagram

However, faced with the complex modulation and demodulation mechanism of LoRa, many engineers really have no idea where to start. In order to solve the trouble of users in debugging the underlying LoRa protocol stack, ZLG Zhiyuan Electronics has developed and designed an industrial-grade LoRa networking transparent transmission module - LM400T, to help users quickly develop products and seize market opportunities.

The module uses a transparent transmission protocol, which is like building an invisible transmission line between modules. Users can quickly build a network without having to understand complex wireless transmission protocols, which greatly reduces the cost of project installation and the complexity of construction.

In addition to complete functions such as network access, network exit, channel division, node management and whitelist, the LoRa networking transparent transmission module simplifies the networking process into a one-click operation, making it more convenient for users to configure the network.

The module's self-organizing network function is a star network topology with one master and multiple slaves. The user first sets the module as the corresponding host and slave module and turns on the self-organizing network function. Then the user only needs to control the module's JOIN pin and DETECT pin to achieve rapid networking of the modules in the network.

In the self-organizing network mode, the host module will automatically select the physical channels and modulation parameters that are not used around to form an independent network, and can automatically assign a unique local network address to the slave module. When the slave module is used, no configuration operation is required after the self-organizing network function is enabled. The slave module can communicate with the host after joining the network. A host module can connect up to 200 slave modules.

Flowchart of network connection between host module and slave module

The slave information stored in the host network can then be traced back through command queries, making management and communication easier, and truly getting rid of the LoRa gateway coordinator.

The figure below is the overall solution for LoRa applications. Currently, LoRa is playing a big role in the development of the industrial Internet with its advantages of long distance, low power consumption, and anti-interference.

The LoRa networking transparent transmission module not only embeds the self-organizing network transparent transmission protocol and meter reading protocol (water meter, gas meter, heat meter), but also integrates the CLAA protocol and LoRaWAN protocol for the LoRa Alliance. Users do not need to spend a lot of time on the protocol and can directly develop applications, greatly shortening the R&D cycle.