RAIL_LbtConfig_t Struct Reference
RAIL API > Transmit

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:

if ( lbtMaxBoRand == lbtMinBoRand ) {
// 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 1932 of file rail_types.h .

Field Documentation

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 1962 of file rail_types.h .

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.

Definition at line 1969 of file rail_types.h .

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 (minimim 1) duration results.

Definition at line 1943 of file rail_types.h .

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 1978 of file rail_types.h .

uint8_t RAIL_LbtConfig_t::lbtTries

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

It can range from 1 to RAIL_MAX_LBT_TRIES ; other values are disallowed.

Definition at line 1949 of file rail_types.h .

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