User's Manual

905U-D Radio Modem Module User Manual
Page 44 © May 2000
6.2.3 Bit Error Rate Test (BER)
BER may be tested in one direction by typing AT&TA (BER master) at the sending unit and
typing AT&TB (BER slave) at the receiving unit. The sending unit will repeatedly send
pseudo-random frames, and the receiving unit will check these frames for errors. If a
terminal is connected to the sending unit, the pseudo-random data is displayed as it is
transmitted. If a terminal is connected to the receiving unit, then the test results are
displayed.
An example of the receiving unit’s display is here.
Test Errors Extra Level TotErr TotTest
109 0 0 -77dBm 3 109 kbit
Test - the sequence number of the last received frame
Errors - the number of bit errors in the last received frame
Extra - any extra characters at the end of the frame (negative numbers indicate
frame dropped out early)
Level - the RSSI level when the frame was received.
TotErr - The total errors received during this test.
TotTest - The total number of bits sent (in 1000’s)
Occasionally during testing, the following may be displayed:
Test Errors Extra Level TotErr TotTest
Bad Header
This indicated that the header information has been corrupted. Corrupted headers do not
contribute to the bit errors, which are calculated only on the 1,000 bit frame.
BER testing may also be performed in both directions simultaneously. In this case, a remote
module is set up to Transparent mode repeater operation, (ATS0=8) and the BER test is
performed on the local module using the command AT&TC (loopback Bit Error Test). In this
case, the display is identical to the display on the BER slave unit above, but the displayed bit
errors are a total for the round trip, so will be the sum of the bit errors in both directions.