Listen Before Talk with 128 us scan time does not allow tx of 400ms duration

[reissjason]

ARIB STD-T108 Version 1. 3 Lists 400ms tx duration from start of transmission is allowed. The packet forwarder is counting time between channel was free and start of transmission in delta time. Once delta time passes 400ms the tx is not allowed.

With LBT debug enabled I see the following output when a 21 byte payload is to be transmitted. The packet duration is only 370ms but the delta_time is greater than 400ms.

tx_mode = TIMESTAMPED
lbt_is_channel_free:273: LBT: select channel 1 (923400000 Hz)
lbt_is_channel_free:333: sx1301_time = 3682304
lbt_is_channel_free:334: tx_freq = 923400000
lbt_is_channel_free:336: packet_duration = 370000
lbt_is_channel_free:337: tx_start_time = 2285568
lbt_is_channel_free:338: lbt_time1 = 2232320
lbt_is_channel_free:339: lbt_time2 = 0
lbt_is_channel_free:340: lbt_time = 2232320
lbt_is_channel_free:341: delta_time = 421888
ERROR: TX request rejected (LBT)