MIMO Ch Frequency Response (802.16 OFDMA)

MIMO Ch Frequency Response shows the equalizer channel frequency response as decoded by the Matrix Decoder. The MIMO Ch Frequency Response is the reciprocal of the FFT Fast Fourier Transform: A mathematical operation performed on a time-domain signal to yield the individual spectral components that constitute the signal. See Spectrum. of the MIMO Eq Impulse Response. The Normalize Chan Freq Resp parameter can be used to select either Normalized or non-Normalized trace data.

This trace is available only for Downlink STC Space Time Coding (STC) allows the transmitter to transmit signals (information) both in time and space, meaning the information is transmitted by two antennas at two different times consecutively./MIMO Multiple Input, Multiple Output: A physical layer (PHY) configuration in which both transmitter and receiver use multiple antennas. measurements..

MIMO Ch Frequency Response has one point per subcarrier. Ch Frequency Response is the measured equalizer frequency response for the analyzed signal. It contains one complex value for each subcarrier, plus an interpolated value at the middle unused subcarrier. The total number of subcarriers is dependent on the FFT Length and Zone Definition type (e.g. DL-PUSC analysis for a signal with FFT1024 will have a total of 841 values).

When the channel estimation contains unused subcarriers, the Ch Frequency Response is linearly interpolated (magnitude and phase interpolation) between the used subcarriers in the channel estimation.

When the measurement parameter Include Inactive Antenna Paths on MIMO Traces is selected, the Ch Frequency Response trace displays overlays of all antenna paths, regardless of how low in power they are. When the measurement parameter Include Inactive Antenna Paths on MIMO Traces is not selected, the Ch Frequency Response trace displays only the results of active antenna paths.

Inconsistent Trace Results

There may unexplained frequency response differences between the MIMO Eq Ch Frequency Response trace and the Ch Frequency Response trace. There may be exaggerated spurs at edges of the MIMO Eq Ch Frequency Response trace, but no spurs exist in the Ch Frequency Response trace. This is may occur for MIMO bursts that contain only 2 symbols and the multi-channel filter is selected. The inaccurate data result is caused by interaction of the multi-channel filter and extrapolation of the pilot-based channel estimation. To solve the problem, disable the multi-channel filter (clear the Enable Multicarrier Filter on the Advanced tab).