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// Package loraradio provides functionality to determine values for a LoRa radio link,
// including maximum data rate and link budget while accounting for receiver sensitivity.
package lora
import (
"fmt"
"math"
)
// TODO: needs cleanup. lots of gpt generated code
// MaxDataRate calculates the maximum data rate for a LoRa radio link based on the provided parameters.
func MaxDataRate(bandwidth, spreadingFactor, codeRate float64) float64 {
// Assuming the LoRa modulation's data rate equation:
// Data Rate = BW / (2^SF) * CR
// where SF is the spreading factor, BW is the bandwidth in Hz, and CR is the code rate.
return (bandwidth / math.Pow(2, spreadingFactor)) * codeRate * spreadingFactor
}
// Simplified link budget calculation per the Semtech calculator
func LinkBudget(rxSensitivity, transmitPower float64) float64 {
return transmitPower - rxSensitivity
}
// SensitivityParams holds the parameters used for sensitivity calculations.
type SensitivityParams struct {
Bandwidth float64 // in Hz
ImplementationL float64 // Implementation loss in dB, typically 1-3 dB
SpreadingFactor int // LoRa Spreading Factor
}
// SpreadingFactorData holds the data for each spreading factor.
type SpreadingFactorData struct {
SF int
ChipsPerSymbol int
DemodulatorSNR float64
}
var SpreadingFactors = []SpreadingFactorData{
{SF: 5, ChipsPerSymbol: 32, DemodulatorSNR: -2.5},
{SF: 6, ChipsPerSymbol: 64, DemodulatorSNR: -5},
{SF: 7, ChipsPerSymbol: 128, DemodulatorSNR: -7.5},
{SF: 8, ChipsPerSymbol: 256, DemodulatorSNR: -10},
{SF: 9, ChipsPerSymbol: 512, DemodulatorSNR: -12.5},
{SF: 10, ChipsPerSymbol: 1024, DemodulatorSNR: -15},
{SF: 11, ChipsPerSymbol: 2048, DemodulatorSNR: -17.5},
{SF: 12, ChipsPerSymbol: 4096, DemodulatorSNR: -20},
}
// CalculateSensitivity calculates the LoRa receiver sensitivity based on the provided parameters.
func CalculateSensitivity(params SensitivityParams, spreadingFactors []SpreadingFactorData) (float64, error) {
if params.Bandwidth <= 0 {
return 0, fmt.Errorf("bandwidth must be greater than 0")
}
// Find the SNR for the given spreading factor from the provided data.
var snr float64
found := false
for _, sfData := range spreadingFactors {
if sfData.SF == params.SpreadingFactor {
snr = sfData.DemodulatorSNR
found = true
break
}
}
if !found {
return 0, fmt.Errorf("spreading factor data not found for SF=%d", params.SpreadingFactor)
}
// Thermal noise in dBm for the given bandwidth at room temperature (290K).
thermalNoise := -174.0 // dBm/Hz
// Noise figure in dBm for the given bandwidth.
noiseFigure := thermalNoise + 10*math.Log10(params.Bandwidth)
// Receiver sensitivity calculation in dBm.
sensitivity := noiseFigure + snr + params.ImplementationL
return sensitivity, nil
}
func SNR(spreadingFactor int) float64 {
result := (float64(spreadingFactor) - 4) * -2.5
return result * 100 / 100
}
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