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RX window calculation algorithm version 2 

In this version we try to mitigate a situation when we start listening
right in the middle of a preamble sequence (e.g., in high SF case).
pull/8822/head
Hasnain Virk 2018-11-28 15:19:54 +02:00
parent ca083671ff
commit 5170daa00a
2 changed files with 25 additions and 14 deletions
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29
features/lorawan/lorastack/phy/LoRaPHY.cpp
View File

@ -406,32 +406,39 @@ void LoRaPHY::get_rx_window_params(float t_symb, uint8_t min_rx_symb,
uint32_t *window_length, int32_t *window_offset,
uint8_t phy_dr)
{
float min_rx_symbol_overlap_required = float (min_rx_symb);
float target_rx_window_offset;
float window_len_in_ms;
if (phy_params.fsk_supported && phy_dr == phy_params.max_rx_datarate) {
min_rx_symbol_overlap_required = MAX_PREAMBLE_LENGTH;
min_rx_symb = MAX_PREAMBLE_LENGTH;
}
// We wish to be as close as possible to the actual start of data, i.e.,
// we are interested in the preamble symbols which are at the tail of the
// preamble sequence.
target_rx_window_offset = (MAX_PREAMBLE_LENGTH - min_rx_symbol_overlap_required) * t_symb; //in ms
target_rx_window_offset = (MAX_PREAMBLE_LENGTH - min_rx_symb) * t_symb; //in ms
// Actual window offset in ms in response to timing error fudge factor and
// radio wakeup/turned around time.
*window_offset = floor(target_rx_window_offset - error_fudge - wakeup_time);
*window_offset = floor(target_rx_window_offset - error_fudge - MBED_CONF_LORA_WAKEUP_TIME);
// possible wait for next symbol start if we start inside the preamble
float possible_wait_for_symb_start = MIN(t_symb,
((2 * error_fudge) + MBED_CONF_LORA_WAKEUP_TIME + TICK_GRANULARITY_JITTER));
// how early we might start reception relative to transmit start (so negative if before transmit starts)
float earliest_possible_start_time = *window_offset - error_fudge - TICK_GRANULARITY_JITTER;
// time in (ms) we may have to wait for the other side to start transmission
float possible_wait_for_transmit = -earliest_possible_start_time;
// Minimum reception time plus extra time (in ms) we may have turned on before the
// other side started transmission
window_len_in_ms = (min_rx_symbol_overlap_required * t_symb) - MIN(0, (*window_offset - error_fudge - TICK_GRANULARITY_JITTER));
window_len_in_ms = (min_rx_symb * t_symb) + MAX(possible_wait_for_transmit, possible_wait_for_symb_start);
// Setting the window_length in terms of 'symbols' for LoRa modulation or
// in terms of 'bytes' for FSK
*window_length = (uint32_t) ceil(window_len_in_ms / t_symb);
}
int8_t LoRaPHY::compute_tx_power(int8_t tx_power_idx, float max_eirp,
@ -874,13 +881,13 @@ bool LoRaPHY::rx_config(rx_config_params_t *rx_conf)
// Radio configuration
if (dr == DR_7 && phy_params.fsk_supported) {
modem = MODEM_FSK;
_radio->set_rx_config(modem, 50000, phy_dr * 1000, 0, 83333, 5,
_radio->set_rx_config(modem, 50000, phy_dr * 1000, 0, 83333, MAX_PREAMBLE_LENGTH,
rx_conf->window_timeout, false, 0, true, 0, 0,
false, rx_conf->is_rx_continuous);
} else {
modem = MODEM_LORA;
_radio->set_rx_config(modem, rx_conf->bandwidth, phy_dr, 1, 0,
MBED_CONF_LORA_DOWNLINK_PREAMBLE_LENGTH,
MAX_PREAMBLE_LENGTH,
rx_conf->window_timeout, false, 0, false, 0, 0,
true, rx_conf->is_rx_continuous);
}
@ -926,8 +933,8 @@ bool LoRaPHY::tx_config(tx_config_params_t *tx_conf, int8_t *tx_power,
// High Speed FSK channel
modem = MODEM_FSK;
_radio->set_tx_config(modem, phy_tx_power, 25000, bandwidth,
phy_dr * 1000, 0, 5, false, true, 0, 0, false,
3000);
phy_dr * 1000, 0, MBED_CONF_LORA_UPLINK_PREAMBLE_LENGTH,
false, true, 0, 0, false, 3000);
} else {
modem = MODEM_LORA;
_radio->set_tx_config(modem, phy_tx_power, 0, bandwidth, phy_dr, 1,

10
features/lorawan/mbed_lib.json
View File

@ -70,12 +70,16 @@
"value": true
},
"max-sys-rx-error": {
"help": "Maximum timing error of the receiver in ms. The receiver will turn on in [-RxError : + RxError]",
"value": 1
"help": "Max. timing error fudge. The receiver will turn on in [-RxError : + RxError]",
"value": 5
},
"wakeup-time": {
"help": "Time in (ms) the platform takes to wakeup from sleep/deep sleep state. This number is platform dependent",
"value": 5
},
"downlink-preamble-length": {
"help": "Number of whole preamble symbols needed to have a firm lock on the signal. Default: 5 + 1",
"value": 6
"value": 5
},
"uplink-preamble-length": {
"help": "Number of preamble symbols to transmit. Default: 8",