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What is a symbol in LoRa?
The set of SF consecutive bits constitutes a symbol. The number of possible symbols is hence equal to M = 2SF . In the LoRa context, SF indicates also the Spread- ing Factor (SF). Therefore, the relation between the bit rate Db and the symbol rate Ds can be written as: Ds = Db/SF.
What is coding rate in LoRa?
The coding rate refers to the proportion of transmitted bits that actually carry information. Coding rate can be 6/8, 4/8, etc… So if CR is 4/8 we are transmitting twice as many bits as the ones containing information.
What is bandwidth in LoRa?
A proprietary spread-spectrum modulation technique derived from existing Chirp Spread Spectrum (CSS) technology, LoRa offers a trade-off between sensitivity and data rate, while operating in a fixed-bandwidth channel of either 125 KHz or 500 KHz (for uplink channels), and 500 KHz (for downlink channels).
What is LoRa modulation?
LoRa (Long Range) is a proprietary low-power wide-area network modulation technique. It is based on spread-spectrum modulation techniques derived from chirp spread spectrum (CSS) technology.
How do you calculate coding rate?
In other words, it means “The code rate is defined as the ratio between the transport block size and the total number of physical layer bits per subframe that are available for transmission of that transport block”.
What’s the difference between a Lora and a chirp?
LoRa is a chirp-based spread-spectrum modulation. A symbol is a chirp. To generate symbols/chirps, the modem modulates the phase of an oscillator. The number of times per second that the modem adjusts the phase is called the chip rate and defines the modulation bandwidth.
Which is the coding rate for LoRa modulation?
In the implementation of the LoRa modulation, every 4 bits of data will be encoded as 5, 6, 7, or 8 total bits as a form of forward error correction, and these are selected by setting the coding rate CR = 1, 2, 3, 4. So the actual rate of user data bits must be reduced by the factor: B R u s e r = B R 4 4 + C R.
Which is higher the chip rate or the bit rate?
Chip rate is the number of chips transmitted or received per time unit, and it is much larger than the symbol rate, meaning that multiple chips can represent one symbol. Symbol rate is lower than or equal to the bit rate, chip rate is higher than symbol rate and also higher than the bit rate.
As far as I can understand, the chip rate CR is always going to be numerically equal to the selected bandwidth. So if the selected bandwidth = 125 kHz, the chip rate is 125,000 chips/second. The symbol BW is then used interchangeably with chip rate. The spreading factor relates chips and symbols.