RAIL_LbtConfig_t Struct Reference

A configuration structure for the LBT transmit algorithm.

#include <rail_types.h>

Data Fields

uint8_t lbtMinBoRand
 The minimum backoff random multiplier.
 
uint8_t lbtMaxBoRand
 The maximum backoff random multiplier.
 
uint8_t lbtTries
 The number of LBT iterations that can fail before reporting RAIL_EVENT_TX_CHANNEL_BUSY.
 
int8_t lbtThreshold
 The LBT RSSI threshold, in dBm, above which the channel is considered 'busy'.
 
uint16_t lbtBackoff
 The backoff unit period, in RAIL's microsecond time base.
 
uint16_t lbtDuration
 The minimum desired LBT check duration in microseconds.
 
RAIL_Time_t lbtTimeout
 An overall timeout, in RAIL's microsecond time base, for the operation.

A configuration structure for the LBT transmit algorithm.

One of RAIL's schemes for polite spectrum access is an implementation of a Listen-Before-Talk (LBT) algorithm, loosely based on ETSI 300 220-1.
Currently, however, it is constrained by the EFR32's CSMA-oriented hardware so is turned into an equivalent RAIL_CsmaConfig_t configuration and passed to the CSMA engine:

// Fixed backoff
csmaMinBoExp = csmaMaxBoExp = 0;
if (lbtMinBoRand == 0) {
ccaBackoff = lbtBackoff;
} else {
ccaBackoff = lbtMinBoRand * lbtBackoff;
}
ccaDuration = lbtDuration;
} else {
// Random backoff: map to random range 0 .. (lbtMaxBoRand - lbtMinBoRand)
csmaMinBoExp = csmaMaxBoExp = ceiling(log2(lbtMaxBoRand - lbtMinBoRand));
ccaBackoff = round((lbtBackoff * (lbtMaxBoRand - lbtMinBoRand))
/ (1 << csmaMinBoExp));
ccaDuration = lbtDuration + (lbtMinBoRand * lbtBackoff);
}
csmaTries = lbtTries;
ccaThreshold = lbtThreshold;
csmaTimeout = lbtTimeout;

Definition at line 2169 of file rail_types.h.

Field Documentation

◆ lbtBackoff

uint16_t RAIL_LbtConfig_t::lbtBackoff

The backoff unit period, in RAIL's microsecond time base.

It is multiplied by the random backoff multiplier controlled by lbtMinBoRand and lbtMaxBoRand to determine the overall backoff period. For random backoffs, any value above 511 microseconds will be truncated. For fixed backoffs, it can go up to 65535 microseconds.

Definition at line 2201 of file rail_types.h.

◆ lbtDuration

uint16_t RAIL_LbtConfig_t::lbtDuration

The minimum desired LBT check duration in microseconds.

Note
Depending on the radio configuration, due to hardware constraints, the actual duration may be longer. Also, if the requested duration is too large for the radio to accommodate, RAIL_StartCcaLbtTx() will fail returning RAIL_STATUS_INVALID_PARAMETER.

Definition at line 2210 of file rail_types.h.

◆ lbtMaxBoRand

uint8_t RAIL_LbtConfig_t::lbtMaxBoRand

The maximum backoff random multiplier.

It must be greater than or equal to lbtMinBoRand.
If both backoff multipliers are identical, a non-random fixed backoff of lbtBackoff times the multiplier (minimum 1) duration results.

Definition at line 2180 of file rail_types.h.

◆ lbtTimeout

RAIL_Time_t RAIL_LbtConfig_t::lbtTimeout

An overall timeout, in RAIL's microsecond time base, for the operation.

If the transmission doesn't start before this timeout expires, the transmission will fail with RAIL_EVENT_TX_CHANNEL_BUSY. This is important for limiting LBT due to LBT's unbounded requirement that if the channel is busy, the next try must wait for the channel to clear. A value 0 means no timeout is imposed.

Definition at line 2219 of file rail_types.h.

◆ lbtTries

uint8_t RAIL_LbtConfig_t::lbtTries

The number of LBT iterations that can fail before reporting RAIL_EVENT_TX_CHANNEL_BUSY.

Typically ranges from 1 to RAIL_MAX_LBT_TRIES; higher values are disallowed. A value 0 always transmits immediately without performing LBT, similar to calling RAIL_StartTx().

Definition at line 2188 of file rail_types.h.


The documentation for this struct was generated from the following file:
  • common/rail_types.h