SDR# TETRA demodulator plug-in netinfo shows congestion related param values (BS downlink) when there is congestion in infrastructure.
https://forums.radioreference.com/voice-control-channel-decoding-software/370639-sdr-tetra-demodulator-trunk-tracking-demonstration-6.html

Disconnect_cause:Congestion_in_infrastructure D_Release

"ETSI TR 102 300-2 V1.2.1 (2013-09)
NOTE 1: Scenario 1 represents a public network; a suitable strategy for the call management in case of lack of
resources is to block the call. No pre-emption mechanisms have been considered in these simulations. The
adopted strategy consists of immediately releasing (see annex C, D, E for the call release procedure) the
call request when no resources are available.
NOTE 2: Simulated MSs are not able to support parallel transactions. When a new call is generated by the user and
the MS is busy, in case of data services (circuit and packet calls) the MS puts this parallel transaction in a
local queue; in case of voice calls it is released. When the present transaction is finished the local queue is
checked in order to give service to the queued transactions.
NOTE 3: During the call set-up procedure, the TCH assignment policy in the SwMI is an implementation option; in
the standard document two possibilities are given: early assignment and late assignment. In scenario 1
simulations late assignment has been adopted.
All network and access control parameters in the reference situation for the simulations are summarized in table 8. The
results have been evaluated for a suitable set of network scenarios that have been derived by this reference, changing
one parameter each time.
The definition of the evaluated performance given in clause 5.4 applies. In the following clauses they are presented for
each network configuration. The number of allocated traffic channels has been evaluated in order to have a low
blocking probability (< 5 %) for all the services. Before showing the overall performance, a table reports the number of
allocated channels with the associated blocking probability of different kind of services:
- full duplex calls in the same cell site, requiring 2 TCHs per call;
- half duplex calls or full duplex calls in different cell sites, requiring 1 TCH per call.
Table 8: Summary of network parameters of the reference scenario 1
Parameter Reference value
Random access: value of the timer
regulating the first access attempt (IMM)
15
Random access: maximum number of
access attempts (Nu)
5
Random access: Back off time (WT) 5 TDMA frames
Random access: Access frame length 10 access opportunities

"

Some interesting observations:
Disconnect_cause:Called_party_requires_encryption D_Release Notification_Indicator:Call_rejected_due_to_SS_AS
Disconnect_cause:Called_party_does_not_support_encryption D_Release
Disconnect_cause:SwMI_requested_disconnection D_Release Notification_Indicator:Reserved28
Disconnect_cause:Unknown_TETRA_identity D_Release Notification_Indicator:Reserved55
Disconnect_cause:Congestion_in_infrastructure D_Release Notification_Indicator:Identity_presentation_restricted
Disconnect_cause:Unknown_external_subscriber_identity D_Release
Disconnect_cause:Called_party_is_under_the_same_DM_GATE_of_the_calling_party D_Release

D-STATUS SSI:xxxxxxx IDX:000 IDT:1 ENCR:0
Type:UDT-4 Length:697 Protocol:DOTAM