Speaking of the wireless communication technology of the Internet of Things, everyone must be familiar with LoRa, because it adopts the principle of spread spectrum modulation and a unique error correction mechanism to achieve ultra-long-distance wireless transmission. Wireless communication distance is longer.
Of course, the focus of this article is not to discuss the characteristics of LoRa, but to talk about several key core parameters in LoRa modulation.
1. Spreading Factor (SF)
LoRa spread spectrum employs multiple information chips to represent each bit of payload information. The speed at which spread information is sent is called the symbol rate (Rs), and the ratio between the chip rate and the nominal symbol rate is the spreading factor, which represents the number of symbols sent per information bit. The popular understanding is to represent a single data bit with multiple information chips.
To simplify the explanation in the digital domain, if we agree that 101110 means that the actual data bit is 1, a valid data packet such as 0xFF needs to be transmitted in the application, and the corresponding binary representation is: 1111 1111, then the information chip to be actually transmitted is:
Through the above method, the bit error rate of transmission can be reduced, thereby increasing the effective communication distance. However, when the number of transmitted information symbols is the same, the actual amount of effective data transmitted is reduced. Therefore, when other parameters are the same, The larger the SF parameter is set, the smaller the actual transmitted data rate.
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