User Manual

RF control interface
9-14 Confidential - For internal use 99-137719-D
The standard values of Burst init (t
init
) and Burst start (t
start
) are illustrated in the table
below, but values are configured using the parameters .rfctrl.tx.burst.init and
.rfctrl.tx.burst.start (see section 6.5.5.1 on page 6-25).
9.2.4 Tx acknowledge signal (B2B_Tx_Ack)
The Tx acknowledge signal is used for fail-safe supervision of the external part of the
transmitter chain (i.e. HPA supervision). When the external part transmits a burst an
acknowledge indication must be signalled back to the BGAN XL Radio Module via this
dedicated Tx acknowledge signal.
The RM expects the Tx acknowledge signal to follow the following format:
• In no-transmissions periods, the B2B_Tx_Ack must be de-asserted.
• In transmission periods, the B2B-Tx_Ack must be asserted.
Figure 9-14 illustrates the timing requirements of the Tx acknowledgement signal
when the transmission supervisory functionality is activated. The figure includes the
two periods: no-transmission and transmission. The transition between these periods
are guarded by a guard period that allows a delay between the two. The length of the
guard is set by the parameter .rfctrl.tx.ack.guard (see section 6.5.5.3 on page 6-26).
Furthermore the B2B_Tx_Ack signal is filtered to avoid erroneous trigs by glitches and
consecutive burst spacing time.
• During transmission: If B2B_Tx_Ack is de-asserted, an informational syslog event
will be generated to inform the integrator about the abnormality.
• During no-transmission: If B2B_Tx_Ack is asserted, the BGAN XL Radio Module will
generate an abnormal behaviour message, MSG_ABNORMALITY (see section 8.5.6.1
Signal description Signal timing in respect to t
0
. Tolerance
Burst init (rising) - 180 s±250 ns
Burst start (falling) - 44.63 s±250 ns
Table 9-3: Standard timing of Tx synchronization signal
Note
Notice that the actual supervision and control of the HPA must be done by a
fail-safe supervisor located outside the BGAN XL Radio Module (e.g. in the
board processor).
Note
For BGAN classes using BGAN LDR transmission with 80 ms preambles, the
guard parameter should be set to give a larger than normal delay, since the
preamble uses very slow ramp-up and ramp-down timing (1.5 ms).