When the software does not detect a Downlink short preamble in the burst, this message is displayed on the screen. All demodulation measurement results are cleared (“--” is seen in the result area). The short preamble is required for all demodulation measurements.
The short preamble is also required for the Power versus Time trace to be synchronized, but if the preamble is not present, then an unsynchronized time domain trace is displayed, and all data results are cleared except the Channel Power result. The instrument continues to check for the presence of the short preamble.
Demodulation Error
This message is typically displayed if the input signal is a proprietary implementation of Mobile WiMAX.
The Demodulation Error is displayed when the following conditions are not met:
• FFT size is 1024 or 512
• preamble index is within the range of 0 to 113
• modulation type is QPSK, 16QAM, or 64 QAM
• reserved bit is not zero in DL‑MAP
• first zone is not PUSC
DL‑MAP not CC encoded
When Demod Type is set to Auto, and the decoded information from the DL‑MAP indicates that the encoding type is not Convolutional Coding (CC), then this message is displayed because the instrument supports only Convolutional Coding at this time.
Too many symbols in DL‑MAP
When the number of symbols exceeds the maximum number that is supported by the instrument, then this message is displayed.