User's Manual

Radio Operation

Crescendo VHF Half-Duplex User Manual Page 30 of 74

5.6 Diagnostics

5.6.1 Data Quality

The Crescendo continually measures the „quality‟ of the received signal by comparing the received

waveform against an internally generated „ideal‟ baseband signal. The result is a value from 0-255 that is

indicative of the quality of the data. In general, a data quality of greater than 100 is good, and less then 50 is

poor. The following data quality values are kept:

Data Quality: The most recent data quality measurement.

Lowest Data Quality: The lowest data quality measurement since the radio was powered up, or

since the baseband statistics were reset (see section 5.6.5).

5.6.2 RSSI

The Crescendo provides received signal strength indication (RSSI) with a range from -40dBm to -120dBm.

The following RSSI values are kept:

Average Noise: The average RSSI level while no valid carrier is present on the receive channel.

Average RSSI: The average RSSI level while data is being received.

Bad Trigger: The RSSI level for the last bad trigger while receiving.

5.6.3 Monitor RSSI

The monitor RSSI function reports a weighted RSSI value. It is different from the average RSSI and average

noise values provided above in that it reports a value regardless of whether a valid carrier is present. When

used with the terminal interface, the monitor RSSI function has a rapid refresh rate, making short

transmissions easily detectable.

5.6.4 PRBS Generator

When the PRBS generator is enabled, the Crescendo continually transmits a PN-9 sequence over the RF

interface. This diagnostic feature can be used in conjunction with the Monitor RSSI feature to diagnose

possible RF propagation issues in a radio network.

5.6.5 Statistics

The Crescendo provides three sets of radio performance statistics:

Baseband statistics relate to the performance of the lowest level of the radio data path, and are

described in Table 11.

Data driven MAC statistics relate to the performance of the radio when using the data driven serial

protocol, and are described in Table 12.

Packet driven MAC statistics relate to the performance of the radio when using a serial protocol

other than the data driven protocol, and are described in Table 13.

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