In downlink mode, LTE signal contains only one layer, shows the values of the subcarriers from the OFDM symbol FFT.
shows the IQ values for channels/signals in the selected layer. When theWhen analyzing channels transmitted on C-RS antenna ports with transmit diversity or spatial multiplexing, this trace shows the channel data values after precoding has been removed. When precoding is removed, the subcarrier notation does not apply to channel data values since the values do not have a one-to-one correspondence with on-air subcarriers. See the MIMO Decoding topic for more information.
For downlink signals, PDSCH IQ data used in calculating this trace comes from the layer chosen when selecting this trace. Other LTE channels/signals are included in Layer traces for convenience. For more details, see the Layer Traces and Resource Element Distribution topic.
For uplink signals, the IQ data comes directly from the OFDM symbol FFT, except for PUSCH. PUSCH subcarriers are despread before being used in calculations.
To view the on-air subcarrier values for signals with multiple C-RS antenna ports, set the MIMO Decoding parameter to . When this is done, only the reference measurement channel will be analyzed, and each layers' traces will be identical to the other layers' traces.
In uplink mode, when PUSCH is included in analysis, IFFT), overlaid on the the other channels/signals' reference IQ values, which come directly from the output of the symbol FFT. See the SC-FDMA Symbol Points section below for more information.
shows PUSCH IQ values after despreading (To view frequency-domain data points for PUSCH, use the IQ Freq Meas or IQ Freq Ref trace.
Only the points of channels/signals selected in Composite Include are shown on this trace. The color of a point indicates which channel/signal the point belongs to. The colors of the channel/signals are shown in the Frame Summary trace.
In the constellation (Power Boost Normalize is selected.
) format, reference constellation circles/crosses are drawn where the symbol points are expected to fall only whenWith the Equalizer Training and EVM Minimization to see how well, and in what way, they are correcting the signal.
constellation view, you can get a feel for how close the constellation points are to the reference. And, you can turn off various corrections such asWith the exception of PUSCH described above, the data in Time trace) is a 2x2 matrix with frequency along one dimension and time along the other. In addition, each one of the points in the matrix is a complex value; therefore there are 4 total dimensions. The choice of trace format determines which two dimensions will be on the x-y plane, and which dimensions will be overlapped, averaged, or ignored. The relevant trace formats and their corresponding view of the data are described below.
(which comes from the data shown in theSC-FDMA modulation is performed by the following process:
The data is
shows the IQ symbol data for PUSCH in the time domain (step 1) before being spread in frequency by steps 2-4.
See the uplink modulation section of the LTE Physical Layer Overview for more information about SC-FDMA modulation.
See Also
Copyright © 2000-2023 Keysight Technologies, Inc. |