With SCADA systems, ACE3600 RTUs can be connected to a Tetra radio. Tetra infrastructure and radio should support packet data.
The connection to Tetra can be made via LAN or via radio. An IP Gateway or an RTU with an Ethernet plug-in or on-board port can be connected to a LAN. In Tetra terms, an RTU that is connected through LAN is called a LAN RTU. An RTU that is connected to a radio is called a PEI (Peripheral Interface) RTU. A PEI RTU is connected to a radio through RS232 using standard PPP (Point to Point Protocol).
In the figure below, the SCADA central and IP Gateway are connected via LAN to Tetra infrastructure. Each RTU has an MTM700 radio connected to its MDLC over IP Port using PPP. A unique IP address is assigned to each RTU according to its radio’s identifier (SSI). All communication between RTUs and the IP Gateway involve sending datagrams in packets over the Internet (IP). A PC running ACE3600 STS can be connected directly to an RTU or operate remotely over IP.
RS-232 LINE 1 LINE 1
RS-232
SCADA Central
STS
IP Routing
Net
RTU-A Tetra MTP700
radio Ethernet
IP Gateway
RTU-B Tetra MTP700
radio Tetra
Infrastructure SW MI
STS
The STS can communicate with remote RTUs over IP using the Tetra infrastructure. The PC running the STS is connected to the Tetra radio (e.g. MTH500 radio) or to the RTU. For this
MDLC over IP Communication
purpose, the PC should have a Tetra PD installation (as specified in the CPS user manual).
After setting up the connection, the user should run the STS Communication Setup utility, select Ethernet port and specify in a focal point RTU/IP Gateway IP Address under ‘Local Site IP Address’.
It is important to note that RTU to RTU communication is routed through the infrastructure LAN system and not directly.
Note that a paging mechanism to each site (peer) in IP conversion table makes MDLC over IP more reliable. For details, see MDLC over IP Site Paging.
Tetra does not support group calls (RTU-to-RTU broadcasts). To send a frame to a group of sites, the application should send to each site individually, leaving a short wait time between each transmission (about 300 milliseconds).
MDLC over Tetra Setup
The general steps of the MDLC over Tetra Setup are similar to the MDLC over IP Setup. For MTM700, MTM800, a modem configuration file is not required. If a different radio used, a modem configuration file is required. Refer to Downloading Modem Configuration Files above.
RTU Site Configuration
In the Site Configuration, set up either PI1/PI2 or SI1/SI2 as RS232, Async, PPP. Select Tetra:
RS232, Async, PPP, Tetra
Use the FTN6359A connector (RS232-E+). This will enable the RTU to control DTR of the radio. Refer to Appendix A of this manual for details on the FTN6359A (RS232-E+)
connector.
The Advanced parameters are the same as described above for general MDLC over IP with the following exceptions:
Link Parameters for PI1/PI2 or SI1/SI2
Links: Range: LINE 1-LINE 29.
Default: LINE 1
User can assign more than one link name in the same physical port. ACE3600 supports several Link names on the same MDLC over IP port. This feature enable RTU
#1 that has one MDLC over IP port, for example ETH1, to communicate directly with RTU #2 that has two MDLC over IP ports, LINE1 and LINE2. In this case, assign LINE1 and LINE2 to RTU #1 MDLC over IP ETH1 port.
Data Speed Range: 1200 – 115200 Default: 9600
MDLC over IP Communication
DNS Servers The user may enter three DNS servers. Note that TETRA MTM700 and MTM800 radios do not learn the server information from the modem, so if host names are used in the Customer Enterprise Network (CEN)/LAN, the user should enter this information. On the other hand, most applications do not have host names in the CEN of TETRA.
NTP Server The user may specify up to three NTP Servers. If defined, they will be polled for the time of day every 2 seconds-17 minutes. Expect a clock offset of around 100
milliseconds. The NTP Server can be the FEP on CEN or any PC acting as an NTP server that the user set up in the CEN.
If an FEP is used, and it is not connected to GPS, it is up to the user to set its clock. Note that NTP servers are never learned from the modem.
Advanced Physical Layer
The values of these parameters are identical to other variations of MDLC over IP as described above.
Format The valid values are:
7 bits Even Parity 2 stop bit 7 bits Odd Parity 2 stop bit 7 bits Even Parity 1 stop bit 7 bits Odd Parity 1 stop bit 8 bits No Parity 2 stop bit 8 bits Even Parity 1 stop bit 8 bits Odd Parity 1 stop bit Default: 8 bits No Parity 1 stop bit Port Mode Default: DTR/CTS Support
Hardware flow control of the port includes DTR and CTS signals.
Optional AT command string
This additional AT string can be used to enhance the modem just before the modem is returned to online mode after configuration. For more details, see Special AT Commands for the Tetra Radio below.
RTS Always On The RTS of the RTU is connected to the modem’s DTR.
It is controlled by software, and is On. By default, it is On.
MDLC over IP Communication
If the RTU fails to configure or register a modem, and the modem supports this feature, it can restart the modem using AT commands. This parameter determines how many failed attempts to connect to the modem are required before restarting it.
If a modem configuration file was downloaded, the n_failstoreset variable in file overrides this setting.
Wait time after Reset radio [sec]
Default: 7 seconds.
Range: 0 to 255 seconds.
Specify how long to wait after restarting the radio as above before attempting to configure and register it.
If a modem configuration file was downloaded, the SetRtsTimeout variable overrides this setting.
If a PPP connection type is used, the following optional parameters exist as well, but for iDEN they should be left unchanged. They are intended to support more modems/radios.
PPP echo send max retries
Default: 0 Range: 0 to 255.
If not 0 it determines the number of retries to poll the modem if it does not reply. If retried with no response for max retries, the data cable to the modem is regarded as disconnected.
For iDEN leave it 0.
This parameter is intended to be used when no DCD input signal is provided by the modem.
If a modem configuration file was downloaded, the pppechosendmaxretry variable overrides this setting.
PPP echo send interval [sec]
Default: 0 Range: 0 to 255.
If not set to 0, it determines the time interval to poll the modem over PPP. If no reply is received within PPP echo send max retries, it will declare the cable as disconnected, and start to reconnect with the modem.
For iDEN leave it as 0.
This parameter is intended to be used when no DCD input signal is provided by the modem.
If a modem configuration file was downloaded, the pppechosendinterval variable overrides this setting.
MDLC over IP Communication
PPP protocol compression
Default: Enable Range: Disable/Enable
If enabled, this configures PPP to use protocol field compression as defined in RFC1661.
For iDEN leave it enabled.
If a modem configuration file was downloaded, the pppprocomp variable overrides this setting.
PPP address compression
Default: Enable Range: Disable/Enable
If enabled, this configures PPP to use address field compression as defined in RFC1661.
For iDEN leave it enabled.
If a modem configuration file was downloaded, the pppaddrcomp variable overrides this setting.
User name Set appropriate user name for connecting to the modem when performing PPP authentication.
If a modem configuration file was downloaded, the username variable in the file overrides this setting.
Password Set appropriate password for connecting to modem when performing PPP authentication.
If a modem configuration file was downloaded, the password variable in the file overrides this setting.
Advanced Link Layer
ACE3600 supports several link names on the same port. This feature enables RTU #1 that has one MDLC over IP port, for example ETH1, to communicate directly with RTU #2 that has two MDLC over IP ports, LINE1 and LINE2. In this case, assign LINE1 and LINE2 to RTU
#1 MDLC over IP ETH1 port.
The following parameters are specific for each link name:
TX to failed RTU every
<O: DISABLE 0-30>
Min
Range: 0-30
Default: 0 (also disables)
It specifies a period of time in seconds, after which a failed link will be considered as being back in order, provided the value of the Periodic check of failed RTU parameter is set to Disable.
If the Periodic check of failed RTU parameter is enabled, it specifies the period of time in seconds after which the Network layer issues a control frame to check the failed link.
MDLC over IP Communication
Periodic check of failed RTU
Default: Disable
The network sends a control frame to check whether the link is still in "failed" status. The frame is issued if the link has been in "failed" status for the period of time specified in the TX to failed RTU every <O:DISABLE 0-30> Min parameter.
Default group IP address
Range: 000.000.000.000-255.255.255.255
Identifies Site ID 0 which is used for Group Call on specific link ID.
Get host by name using DNS
Default: Enable.
This parameter enables host name within IP Conversion Table for the specified link name. If set to Disable, host names cannot be used within that link name in IP Conversion Table.
The following parameters are common to all Link names configured for this port.
MDLC over IP port number
Range: 1-65535 Default: 2002
This number is common to all RTUs and IP Gateways connected to this link. This number identifies the MDLC.
This is a UDP port number and the provider should be consulted.
It is important that this number not be in use as specified by the TCP/IP standard RFC0960.
Enable Sync Range: Disable/Enable Default: Disable
If this parameter is Enabled, this port can send an MDLC Sync to other RTUs, and receive an MDLC sync.
If this parameter is Disabled, this port does not send an MDLC Sync, and ignores received sync frames. It can however forward sync words that were initiated from other Link Ids, or from Toolbox.
It is recommended to use the NTP protocol instead for time settings.
Notify IP Address when connected
Range: Disable/Enable Default: Enable
When enabled, if an RTU’s IP address is changed or obtained from a modem, the RTU will send a message to update its IP Address in all sites.
Note: these messages are sent one after the other, and it is not guaranteed they will be delivered and accepted.
MDLC over IP Communication
Enable routing on MDLC over IP port
Range: Disable/Enable Default: Disable
When enabled, an RTU or FEP can route back MDLC over IP packets received that destined to a different site ID. When disable, an RTU or FEP ignore packets received which are destined to other sites.
This parameter allows two RTUs to communicate via this RTU, is useful if they have dynamic IP address. Note also they need to transmit periodically for their IP address to be updated in its IP Conversion Table.
Modem configuration timeout (Sec)
Range: 40-255 sec Default: 40
The period of time the network will wait for successful configuration of the modem upon power up of modem or RTU. If within this period, the modem configuration does not complete, RTU marks the port as Failed, though configuration continues. If configuration fails, the modem may not be properly configured. Configuration status can be checked using the Error Logger and Software Diagnostics (LIN1L Level 0, 101.
For more details, see Modem Configuration below.
Disconnect on icmp:netunreach
Range: Disable/Enable Default: Disable
If set to Enable, connection to the modem/radio will be terminated by force when getting an icmp:netunreach.
This message specifies that the peer site was unreachable because of network problems. Sometimes these problems can be resolved by reconnecting to the modem.
For Tetra, it is recommended to leave it set to Disable.
Disconnect on idle timeout sec
Range: 1- 65535 Default: 0
When specifying a timeout in seconds, the RTU monitors the delay from the last time anything was received from the modem (during PPP mode). If this time expires, this means there is a problem with the modem connection.
The RTU will disconnect and reconnect to the modem.
If 0, this parameter ignored.
MDLC over IP Communication
Does modem support abort sequence
Range: YES/NO Default: NO
With Tetra radios such as MTM700, no abort sequence is supported. Abort sequence is a +++ string sent with a 1 second delay before and after, causing the modem to move into command mode.
Specifying this parameter as NO will expedite connection to Tetra radio.
Ignore CD Range: Never, Always, When connect Default: Never.
When connecting to the modem, its CD is constantly being polled, and if inactive, the RTU will reconnect to it.
This parameter enables the user to bypass the polling by ignoring CD. Setting this parameter to Always will cause RTU not to check CD at all. Setting it into When connect will ignore CD during the PPP connection phase. When PPP is connected, CD will be polled.
Setting this parameter to Never will always check CD.
Registration life time Range: 0 to 65535 seconds Default: 7200
If not 0, this sets an interval in which a connected radio/modem is deregistered and reregistered for packet data.
The RTU adds an offset to this number, which is derived from its site ID, so not all radios are restarted and context activated at the same time.
If a file was downloaded, this parameter can be overridden using the regLifeTimeout variable.
With Tetra, a paging mechanism to each site (peer) in the IP conversion table has been added to make MDLC over IP more reliable. If the parameters below are not visible, they will have the default values as specified. The parameters are the same as in other variations of MDLC over IP, but their default values were changed to suit Tetra infrastructure. For more
information, refer to MDLC over IP Site Paging.
Check Alive timeout in
MDLC over IP Communication
Special AT Commands for the Tetra Radio
The following AT commands are sent by the RTU when configuring the Tetra radio. They can be overridden/added by specifying the Optional AT command string in the Advanced Physical Layer parameters in the Site Configuration utility.
It is recommended to override these defaults by downloading a modem configuration file adopted for the radio, such as MTM700.stm for MTM700. For details, see Modem Configuration File below.
AT+IFC=2,2 – Instruct the radio to use hardware flow control.
AT+WS45=4 – Instruct the radio to initiate PPP with the RTU when getting the ATD command.