Server Bridging

Asterisk PBX
SVXLink

Asterisk PBX

Disclaimer

TransitBridge is only available on the same host as TetraPack Core, so the target of this document is a server administrator. Other Asterisk systems can be connected to transit Asterisk system via IAX2, SIP, etc.
TransitBridge (as well as DetroitBridge) is plug-and-play, no extra configuration required.
TransitBridge channel driver uses only default dialplan context. Please use GotoIf or Lua.
Some TETRA Systems (at least CTS) don't support external numbers (PSTN on PABX) for messaging.
Some TETRA Systems (at least CTS) don't support PABX calls (PSTN or ISSI only).

Modules

codec_pack.so - TETRA codec definitions and translations, uses our own library CodecPack.so
chan_transit.so - TransitBridge channel driver

Environment variables

CODECPACK=/<path>/CodecPack.so

asterisk.conf

[options]
systemname = <numeric ID of local system>

Dialplan

Outbound calls

Dial(Transit/<Core ID>/<ISSI>[/<options>])

Where options are:

s - Use simplex call with PTT control (RADIO_KEY/RADIO_UNKEY, see app_rpt)
t - Use PSTN call (source ISSI 16777184, CALERID(num) is passed as an external number)
b - Use PBX call (source ISSI 16777186, CALERID(num) is passed as an external number)
n<ISSI> - Use specified source ISSI and pass CALLERID(num) as an external number
c<0-3> - Use service number 0-3 (at this moment only 0 / ACELP is supported)
p<0-15> - Set call priority

By-default duplex individual call with ACELP (0) and normal priority (0) will be created.

Example:

Dial(Transit/2505/${EXTEN}/t)

Inbound calls

Channel variables:

TRANSIT_TYPE=ISSI - Extension ID contains destination ISSI
TRANSIT_TYPE=Number - Extension ID contains destination external number
TRANSIT_FLOW=PTT - Simplex call
TRANSIT_ISSI=<ISSI> - Destination ISSI
(only when TRANSIT_TYPE=Number, should contain 16777184 for PTSN call or 16777186 for PBX call)
TRANSIT_PRIORITY=<0-15> - Call priority

Outbound messages

MessageSend(Transit:<Link ID>[/<Destination ISSI>][,<Source ISSI>[ <External Number>]])

Please keep your eyes on formatting. There no spaces in <to> section, no space after comma in <from> section and only single space between source ISSI and external number.

Channel variables:

MESSAGE(to)=<ISSI>
MESSAGE(from)=<ISSI>
MESSAGE(body)=<Text>
MESSAGE_SEND_STATUS - Will be set to SUCCESS, when the message accepted by the basestation (TNSDS-REPORT result=0), timeout is 500 milliseconds.
Asterisk API said, it corresponds to message enqueuing, not delivery, but we have a bit more. :)

Inbound messages

Channel variables:

MESSAGE(to)=<ISSI/External Number>
MESSAGE(from)=<ISSI>
MESSAGE(body)=<Text>
MESSAGE_DATA(TRANSIT_TYPE)=ISSI - Extension ID and MESSAGE(to) contain destination ISSI
MESSAGE_DATA(TRANSIT_TYPE)=Number - Extension ID and MESSAGE(to) contain destination external number
MESSAGE_DATA(TRANSIT_ISSI)=<ISSI> - Destination ISSI
(only when MESSAGE_DATA(TRANSIT_TYPE)=Number, should contain 16777184 for PTSN call or 16777186 for PBX)

TransitBridge sends delivery report when terminal requested that. Delivery status depends on the status of dialplan proceeding.

Technical Information

Channel ID format

Transit/<Link ID>:<Session UUID>

Link ID - decimal TetraPack Core instance identifier
Session UUID - global call session UUID, used in TetraPack Core and BrandMeister Core (in lower case)

Specific Hangup-Cause codes

Transit <TETRA disconnect-cause code>

Get TETRA disconnect-cause codes at Table 14.55 in ETSI EN 300 392-2 V3.8.1. Read more about Hangup Cause here.

Dialplan example

exten => 9XXXXXXX,1,Dial(Transit/2505/${EXTEN:1}/t)
same  => n,NoOp(Disconnect Cause: ${HANGUPCAUSE(${HANGUPCAUSE_KEYS()},tech)})
same  => n,HangUp()
exten => 16777184,1,NoOp(Incoming message)
same  => n,NoOp(From: ${MESSAGE(from)})
same  => n,NoOp(To: ${MESSAGE(to)})
same  => n,NoOp(Body: ${MESSAGE(body)})
same  => n,NoOp(TRANSIT_TYPE: ${MESSAGE_DATA(TRANSIT_TYPE)})
same  => n,MessageSend(Transit:2505/${MESSAGE(from)},16777184 911)
same  => n,NoOp(Message send status: ${MESSAGE_SEND_STATUS})

SVXLink

SVXLink sources

https://github.com/dl1hrc/svxlink/tree/tetra-contrib/ - Custom version that passes ISSIs through SVXReflector, it also has our patches applied to SVXReflector and ReflectorLogic.
https://github.com/sm0svx/svxlink/ - Original version

Note for owners of SVXLink nodes running TetraLogic

Please use latest version of SVXLink software.
Please use the same CALLSIGN in [ReflectorLogic] and [TetraLogic] to make our bridges pass talker ISSI correctly.

Note for owners of SVXReflector servers for TETRA

Please use latest version of SVXReflector (at least 16082023) software.
Reflector to Reflector links does not pass originating ISSI.

Administrating SVXLink bridges

Disclaimer about information bellow

DockStation is only available on the same host as TetraPack Core, so the target of following information in this article is a server administrator.
DockLogic is an external Logic module is supplied outside SVXLInk.

Modules

DockLogic.so - SVXLink Logic module that implements our own Dock IPC protocol, uses our own library CodecPack.so
DockLogic.tcl - Supplementary script, required by SVXLink

Environment variables

CODECPACK=/<path>/CodecPack.so

svxlink.conf

[GLOBAL]
MODULE_PATH=/opt/SVXLink/lib/svxlink
CFG_DIR=/opt/SVXLink/etc/svxlink/svxlink.d
LOGICS=DockLogic,ReflectorLogic
LINKS=Link
TIMESTAMP_FORMAT="%c"

# Should be always 8 KHz!
CARD_SAMPLE_RATE=8000

[DockLogic]
TYPE=Dock
RX=Rx1
TX=Tx1
CALLSIGN=<Node call, should be completely the same as ReflectorLogic has>
EVENT_HANDLER=/opt/SVXLink/share/svxlink/events.tcl

# TetraPack Core IPC socket path
SOCKET=/tmp/Dock-<TetraPack Core ID>

# GSSI at TetraPack Core
GSSI=<GSSI of talk group at TetraPack>

# Default ISSI (used when ISSI is unknown)
ISSI=9999

# MNI for Qso:info messages (4 digits for MCC and 5 digits for MNC)
MNI=090116383

[Rx1]
TYPE=Dock

[Tx1]
TYPE=Dock

# Delay (in 60 ms frames) in bridged call start (SVXLink -> TetraPack), required for ISSI detection heuristics 
DELAY=5

# Preprocessing: Gain -> AGC -> Suppressor -> Normalizer

# Gain BEFORE preprocessing (0.1 .. 1.0, default is 1.0)
GAIN=0.75

# AGC, value is AGC target
# Comment or remove to disable
# AGC=8000

# Suppressor:
# 0 - Berouti spectral subtraction
# 1 - Wiener scalar filtering
# 2 - Two-step scalar filtering
# 3 - Two-step scaler filtering with gain
# 4 - Two-step phishing filtering
# 5 - Two-step phishing filtering with gain
# Comment or remove to disable
SUPPRESSOR=0

# Normalize audio, including dynamic compression and DC correction
NORMALIZER=1

[ReflectorLogic]
TYPE=Reflector
HOSTS=<SVXReflector's DNS/IP address>
CALLSIGN="<Node call>"
AUTH_KEY="<Key>"
UDP_HEARTBEAT_INTERVAL=5
DEFAULT_TG=<Bridged SVXReflector's TG>
MONITOR_TGS=<Bridged SVXReflector's TG>
EVENT_HANDLER=/opt/SVXLink/share/svxlink/events.tcl
MUTE_FIRST_TX_LOC=0
MUTE_FIRST_TX_REM=0

[Link]
CONNECT_LOGICS=DockLogic,ReflectorLogic
DEFAULT_ACTIVE=1
TIMEOUT=0