Libelium Waspmote LoRa, Сетевое руководство

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-17- v7.0
Transmission modes
Note: When transmitting in ISM frequency bands, the user must ensure that the communication is not exceeding the permitted time
using the chosen frequency channel (for example, 1% of time). It is the responsibility of the user to know the allowed time of use in the
occupied frequency band and respect it. Ignoring this, could lead to considerable penalties.
Example of use:
{
sx1272.setMode(3); // Sets the LoRa mode in transmission mode 3
}
SX1272 configuration example:
www.libelium.com/development/waspmote/examples/sx-01-configure-lora-parameters
If the user is going to select a mode with this function, it is not necessary to set also the bandwidth, coding rate and spreading
factor later.
5.1.1. Bandwidth
The value of the bandwidth shows how wide is going to be the transmission signal. It only can be chosen among 3 options:
125 kHz, 250 kHz or 500 kHz. If a fast transmission is required, a 500 kHz value is better. But if a great reach is needed, a 125 kHz
value must be configured. The smaller the bandwidth is, the higher the time-on-air is in a transmission but also the better the
sensitivity is, so the communication has better link budget. The user should also note that the increasing in time-on-air involves
an increasing in battery consumption.
Example of use:
{
sx1272.setBW(BW_250); // Sets the 250 kHz bandwidth in LoRa mode
}
5.1.2. Coding Rate
The coding rate value must be chosen among 4 options: 4/5, 4/6, 4/7 and 4/8. It denotes that every 4 useful bits are going to be
encoded by 5, 6, 7 or 8 transmission bits depending on its value. The smaller the coding rate is (the smallest is 4/8), the higher
the time-on-air is in a transmission, so it takes more time to transmit a packet. This will ease the task of receiving, because each
symbol is wider in time, so the receiver can demodulate packets with lower reception power. This means the receiver has better
sensitivity, so the user has better link budget. But slow data transmissions have an impact in the battery consumption: spending
more time in transmission mode involves more battery consumption.
Example of use:
{
sx1272.setCR(CR_7); // Sets the 4/7 coding rate in LoRa mode
}
5.1.3. Spreading Factor
The spreading factor is the number of chips per symbol used in the data treatment before the transmission signal. Its value is
an integer number between 6 and 12. This parameter is relevant in the spread spectrum technique. In the spread spectrum
techniques, the greater value of this parameter, the more capability the receiver has to move away the noise from the signal.
So the greater value taken, the more time it takes to send a packet, but also the better range is reached because the receiver
sensitivity is better.
Example of use:
{
sx1272.setSF(SF_9); // Sets the 9 spreading factor in LoRa mode
}