User manual

5 NETWORK OPTIMIZATION
Detailed system engineering is beyond the scope of this manual. However, there are some simple tips that can be used to
optimize performance of a radio based SCADA or telemetry system.
5.1 CHOOSE THE BEST PROTOCOL
Some SCADA devices allow a choice of more than one operating protocol. In some cases, performance can be improved by
selecting a different protocol. Contact Technical Service for assistance.
5.2 CHECK TIMER SETTINGS
Polling protocols issue a poll and wait a certain time for a response. Integra-TR adds a short amount of delay to each poll
and response (typically in the order of 60 to 70 ms). Timer settings that are too short may cause erroneous indication of
missed polls, in which case the application may retry or continue to cycle, ignoring the missed station. In this case, the
response may collide with the next poll, further increasing errors. Setting an adequate timer margin will avoid problems and
maximize performance.
5.3 AVOID FLOW CONTROL
Set the COM port baud rate to a value less than or equal to the radio network speed (2400, 4800, 9600 or 19200 b/s). In a
polling system, this will prevent buffer overflow with possible missed transmissions. If the port baud rate must be set higher
than the radio network speed, you may have to limit message length to prevent possible buffer overflow. Integra-TR will
exert a flow control signal (CTS dropped) if buffers are almost full, but not all DTE honor such signals.
5.4 USE THE HIGHEST SUITABLE PORT BAUD RATE
Do not exceed the radio network speed. Operating an RTU at 1200 b/s on a 9600 b/s network will increase data
transmission delays and reduce system performance.
5.5 EVALUATE THE NEED FOR ONLINE DIAGNOSTICS
Enabling online diagnostics increases delays by 2.5 to 20 ms (depending on speed). In critical applications, this extra delay
can be eliminated by disabling online diagnostics. Offline Diagnostics (diagnostics on request) remain available.
5.6 INTERPRETING RSSI READINGS
Typical values of RSSI will be in the range of -110 to -60 dBm (depending on network speed), with higher values (i.e. less
negative values) indicating a stronger signal.
Reliability of data reception depends largely on signal strength. Good design practice calls for a minimum 30 dB “fade
margin”, based on a threshold reception level of -107 dBm (1 uV) at speed of 9600 b/s. Experience indicates that this will
give about 99.5% reliability.
Page | 60