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39 lines
1.7 KiB
C++
39 lines
1.7 KiB
C++
// SPDX-License-Identifier: Apache-2.0
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#include <mesh/mesh_airtime.h>
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#include <algorithm>
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#include <cmath>
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uint32_t mesh_airtime_estimate_ms(const MeshRadioProfile& profile, size_t length) {
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if (profile.modulation == RADIO_MODULATION_LORA && profile.bandwidth > 0) {
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// Semtech AN1200.13, explicit header with CRC
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const double symbolMs = std::pow(2.0, profile.spreading_factor) * 1000.0 / profile.bandwidth;
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const int lowDataRateOptimize = (symbolMs > 16.0) ? 1 : 0;
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const int codingRate = std::clamp<int>(profile.coding_rate - 4, 1, 4);
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const double numerator = 8.0 * (double)length - 4.0 * profile.spreading_factor + 28.0 + 16.0;
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const double denominator = 4.0 * (profile.spreading_factor - 2 * lowDataRateOptimize);
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const double payloadSymbols = 8.0 + std::max(std::ceil(numerator / denominator) * (codingRate + 4), 0.0);
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const double preambleMs = (profile.preamble_length + 4.25) * symbolMs;
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return (uint32_t)std::ceil(preambleMs + payloadSymbols * symbolMs);
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}
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// FSK-family: preamble, sync word, length byte, payload and CRC. The data rate is not part of the
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// profile, so a conservative 4.8 kbit/s is assumed.
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constexpr double FALLBACK_BIT_RATE = 4800.0;
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const double bits = profile.preamble_length + (4 + 1 + length + 2) * 8.0;
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return (uint32_t)std::ceil(bits * 1000.0 / FALLBACK_BIT_RATE);
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}
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uint32_t mesh_airtime_duty_cycle_percent(RadioRegion region, int32_t frequency) {
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switch (region) {
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case RADIO_REGION_EU_868:
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return (frequency >= 869400000 && frequency <= 869650000) ? 10 : 1;
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case RADIO_REGION_EU_433:
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return 10;
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case RADIO_REGION_RU_868:
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return 1;
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default:
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return 100;
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}
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}
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