mirror of https://github.com/ARMmbed/mbed-os.git
Final cleanup and ASCII art for algorithm v2
Final code cleanup and adding ascii art for the version 2 of the algorithm.pull/8822/head
Hasnain Virk
parent
5170daa00a
commit
e1e48b492b
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@ -32,8 +32,8 @@ SPDX-License-Identifier: BSD-3-Clause
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#define BACKOFF_DC_1_HOUR 100
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#define BACKOFF_DC_10_HOURS 1000
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#define BACKOFF_DC_24_HOURS 10000
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#define MAX_PREAMBLE_LENGTH 8.0
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#define TICK_GRANULARITY_JITTER 1.0
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#define MAX_PREAMBLE_LENGTH 8.0f
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#define TICK_GRANULARITY_JITTER 1.0f
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#define CHANNELS_IN_MASK 16
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LoRaPHY::LoRaPHY()
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@ -397,7 +397,7 @@ float LoRaPHY::compute_symb_timeout_lora(uint8_t phy_dr, uint32_t bandwidth)
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float LoRaPHY::compute_symb_timeout_fsk(uint8_t phy_dr)
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{
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return (8.0 / (float) phy_dr); // 1 symbol equals 1 byte
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return (8.0f / (float) phy_dr); // 1 symbol equals 1 byte
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}
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@ -420,11 +420,11 @@ void LoRaPHY::get_rx_window_params(float t_symb, uint8_t min_rx_symb,
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// Actual window offset in ms in response to timing error fudge factor and
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// radio wakeup/turned around time.
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*window_offset = floor(target_rx_window_offset - error_fudge - MBED_CONF_LORA_WAKEUP_TIME);
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*window_offset = floor(target_rx_window_offset - error_fudge - wakeup_time);
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// possible wait for next symbol start if we start inside the preamble
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float possible_wait_for_symb_start = MIN(t_symb,
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((2 * error_fudge) + MBED_CONF_LORA_WAKEUP_TIME + TICK_GRANULARITY_JITTER));
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((2 * error_fudge) + wakeup_time + TICK_GRANULARITY_JITTER));
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// how early we might start reception relative to transmit start (so negative if before transmit starts)
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float earliest_possible_start_time = *window_offset - error_fudge - TICK_GRANULARITY_JITTER;
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@ -845,7 +845,7 @@ void LoRaPHY::compute_rx_win_params(int8_t datarate, uint8_t min_rx_symbols,
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rx_conf_params->frequency = phy_params.channels.channel_list[rx_conf_params->channel].frequency;
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}
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get_rx_window_params(t_symbol, min_rx_symbols, (float) rx_error, RADIO_WAKEUP_TIME,
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get_rx_window_params(t_symbol, min_rx_symbols, (float) rx_error, MBED_CONF_LORA_WAKEUP_TIME,
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&rx_conf_params->window_timeout, &rx_conf_params->window_offset,
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rx_conf_params->datarate);
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}
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@ -202,40 +202,63 @@ public:
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/** Computing Receive Windows
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*
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* For more details please consult the following document, chapter 3.1.2.
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* http://www.semtech.com/images/datasheet/SX1272_settings_for_LoRaWAN_v2.0.pdf
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* or
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* http://www.semtech.com/images/datasheet/SX1276_settings_for_LoRaWAN_v2.0.pdf
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* The algorithm tries to calculate the length of receive windows (i.e.,
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* the minimum time it should remain to acquire a lock on the Preamble
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* for synchronization) and the error offset which compensates for the system
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* timing errors. Basic idea behind the algorithm is to optimize for the
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* reception of last 'min_rx_symbols' symbols out of transmitted Premable
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* symbols. The algorithm compensates for the clock drifts, tick granularity
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* and system wake up time (from sleep state) by opening the window early for
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* the lower SFs. For higher SFs, the symbol time is large enough that we can
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* afford to open late (hence the positive offset).
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* The table below shows the calculated values for SF7 to SF12 with 125 kHz
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* bandwidth.
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*
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* Downlink start: T = Tx + 1s (+/- 20 us)
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* |
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* TRxEarly | TRxLate
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* | | |
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* | | +---+---+---+---+---+---+---+---+
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* | | | Latest Rx window |
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* | | +---+---+---+---+---+---+---+---+
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* | | |
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* +----+-----+----------+---------+-------------------------+----------------------+-------------------------+
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* | SF | BW (kHz) | rx_error (ms) | wake_up (ms) | min_rx_symbols | window_timeout(symb) | window_offset(ms) |
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* +----+-----+----------+---------+-------------------------+----------------------+-------------------------+
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* | 7 | 125 | 5 | 5 | 5 | 18 | -7 |
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* | 8 | 125 | 5 | 5 | 5 | 10 | -4 |
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* | 9 | 125 | 5 | 5 | 5 | 6 | 2 |
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* | 10 | 125 | 5 | 5 | 5 | 6 | 14 |
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* | 11 | 125 | 5 | 5 | 5 | 6 | 39 |
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* | 12 | 125 | 5 | 5 | 5 | 6 | 88 |
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* +----+-----+----------+---------+-------------------------+----------------------+-------------------------+
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*
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* For example for SF7, the receive window will open at downlink start time
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* plus the offset calculated and will remain open for the length window_timeout.
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*
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* Symbol time = 1.024 ms
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* Downlink start: T = Tx + 1s (+/- 20 us)
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* |
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* |
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* |
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* |
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* |
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* +---+---+---+---+---+---+---+---+
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* | 8 Preamble Symbols |
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* +---+---+---+---+---+---+---+---+
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* | RX Window start time = T +/- Offset
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* +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
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* | | | | | | | | | | | | | | | | | | |
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* +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
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*
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* Similarly for SF12:
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*
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* Symbol time = 32.768 ms
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* Downlink start: T = Tx + 1s (+/- 20 us)
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* |
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* |
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* |
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* |
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* |
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* +---+---+---+---+---+---+---+---+
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* | Earliest Rx window |
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* | 8 Preamble Symbols |
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* +---+---+---+---+---+---+---+---+
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* |
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* +---+---+---+---+---+---+---+---+
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*Downlink preamble 8 symbols | | | | | | | | |
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* +---+---+---+---+---+---+---+---+
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*
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* Worst case Rx window timings
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*
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* TRxLate = DEFAULT_MIN_RX_SYMBOLS * tSymbol - RADIO_WAKEUP_TIME
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* TRxEarly = 8 - DEFAULT_MIN_RX_SYMBOLS * tSymbol - RxWindowTimeout - RADIO_WAKEUP_TIME
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*
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* TRxLate - TRxEarly = 2 * DEFAULT_SYSTEM_MAX_RX_ERROR
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*
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* RxOffset = ( TRxLate + TRxEarly ) / 2
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*
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* RxWindowTimeout = ( 2 * DEFAULT_MIN_RX_SYMBOLS - 8 ) * tSymbol + 2 * DEFAULT_SYSTEM_MAX_RX_ERROR
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* RxOffset = 4 * tSymbol - RxWindowTimeout / 2 - RADIO_WAKE_UP_TIME
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*
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* The minimum value of RxWindowTimeout must be 5 symbols which implies that the system always tolerates at least an error of 1.5 * tSymbol.
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* | RX Window start time = T +/- Offset
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* +---+---+---+---+---+---+
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* | | | | | | |
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* +---+---+---+---+---+---+
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*/
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/*!
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* Computes the RX window timeout and offset.
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@ -78,7 +78,7 @@
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"value": 5
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},
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"downlink-preamble-length": {
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"help": "Number of whole preamble symbols needed to have a firm lock on the signal. Default: 5 + 1",
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"help": "Number of whole preamble symbols needed to have a firm lock on the signal.",
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"value": 5
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},
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"uplink-preamble-length": {
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@ -44,9 +44,6 @@
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typedef uint32_t lorawan_time_t;
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#endif
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// Radio wake-up time from sleep - unit ms.
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#define RADIO_WAKEUP_TIME 1.0
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/*!
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* Sets the length of the LoRaMAC footer field.
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* Mainly indicates the MIC field length.
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@ -1259,8 +1256,8 @@ typedef struct {
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/*!
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* LoRaMac reception windows delay
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* \remark normal frame: RxWindowXDelay = ReceiveDelayX - RADIO_WAKEUP_TIME
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* join frame : RxWindowXDelay = JoinAcceptDelayX - RADIO_WAKEUP_TIME
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* \remark normal frame: RxWindowXDelay = ReceiveDelayX - Offset
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* join frame : RxWindowXDelay = JoinAcceptDelayX - Offset
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*/
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uint32_t rx_window1_delay;
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uint32_t rx_window2_delay;
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