Introduction to low-rate long-distance transmission scheme

1.    Introductionto the program technology
1.1 Introduction to LoRa

LoRa is a low-power wide area network (LPWAN) communication technology. It isan ultra-long-range wireless transmission scheme based on spread spectrumtechnology adopted and promoted by Semtech. This solution has changed theprevious trade-offs between transmission distance and power consumption,providing users with a simple system that can realize long-distance, longbattery life, and large capacity, and thus sensor networks. Currently operatingmainly in the global free frequency band, including 433, 868, 915MHz and so on.

LoRa direct-sequence spread spectrum technology will bring longer communicationdistance and has the advantage of strong anti-interference ability. The modulehas a software FEC forward error correction algorithm, which has high codingefficiency and strong error correction capability. Under the condition ofsudden interference, it can actively correct the interfered data packets,greatly improving reliability and transmission distance. In the absence of FEC,such packets can only be discarded.

1.2  Introductionto Technical Modules

E32-TTL-100 is a wireless serial port module independently developed by ChengduEbyte Electronic Technology Co., Ltd., transparent transmission mode, working inthe 410~441MHz frequency band (default 433MHz), LoRa spread spectrumtechnology, TTL level output, compatible 3.3V and 5V IO port voltage.

The module has data encryption and compression capabilities. The datatransmitted by the module in the air is random, and the data interception ismeaningless through strict encryption and decryption algorithms. The datacompression function has the probability of reducing the transmission time,reducing the probability of interference, improving reliability andtransmission efficiency. Loss formula for wireless signals transmitted in air

The physical picture of the module is shown below:


1.    Schemetechnical argumentation
2.1 Theoretical argumentation

The process of radio propagation will be attenuated due to the continuousconsumption of energy, especially when obstacles are encountered, and there arethree main parameters affecting the transmission of wireless WiFi:

A. transmit power

b. Antenna gain

c. Receive sensitivity

Loss formula for on-demand transmission in free space:


Los: transmissionloss in dB;

d: distance, the unit is Km;

f: working frequency, the unit is MHz.

It can be seen from equation (1) that the transmission loss is proportional tothe frequency under the same antenna gain and the same receiving sensitivityunder the same environment. The higher the frequency, the greater thetransmission loss. Or in the case of the same transmission loss, thetransmission distance is inversely proportional to the frequency. That is, thehigher the frequency, the shorter the reception distance.
2.2 Actual verification

The E32-TTL-100 has a transmit power of 20dBm, an airspeed of 0.3k~19.2kpbs, atransmit frequency of 410~441, and a receiver sensitivity of -130dBm@0.3kpbs.The forward error correction algorithm is used to improve the reliability ofthe transmission. Transmission distance. The actual communication distance is3Km (antenna gain 5dBi, height 2m, airspeed 2.4kpbs).
3. Summary of the program

Through testing, E32-TTL-100 433Mhz LoRa spread spectrum technology caneffectively solve low-rate long-distance transmission. In addition, in additionto long-distance, it also highlights the low-power advantage of LoRacommunication technology, which can be applied in a large number ofapplications and Promotion.

(Remarks: Chengdu Ebyte Electronic Technology Co., Ltd. also hasE32-TTL-500, E32-DTU-1W/5W, etc., to support longer transmission distance, andcan provide an effective solution for low-rate long-distance wirelesstransmission. For more details, please go to the official website: Learn more.)