About UE-specific RS Weights Summary Table (LTE)

UE-specific RS Weights shows the subcarrier locations and weights for all UE User Equipment (e.g. cell phone)-specific Reference Signal resource elements on a UE-RS UE-specific Reference Signal antenna port (see Layer Traces and Resource Element Distribution for mapping information). The data in this trace is calculated from the part of the frame specified by Measurement Interval and Measurement Offset.

The lower section of the UE-specific RS Weights summary indicates whether the UE-RS analysis is On or Off. The upper part of the table is divided into sections, one for each PDSCH Physical Downlink Shared Channel user allocation.

Each section contains the following information:

UserXX - indicates which PDSCH user allocation the section belongs to. 'XX' is the user allocation index from the Composite Include list.
UERS-RBs - total number of UE-RS Resource Blocks per subframe

When a PDSCH allocation is transmitted on UE-RS antenna ports, the following information is present in the corresponding section in the UE-specific RS Weights summary table.

Frequency index for UE-RS weight
- RB # - resource block index (Weights Display Mode set to Per RB)
hn.w (part) or wn (part) - weights applied to the UE-RS subcarriers, averaged for each resource block or for the user, depending on the setting of the Weights Display Mode parameter.

Compensate Chan Freq Resp cleared: the channel effects have not been removed from the UE-RS weight, which is indicated by hn.w where hn is the row of the H channel response matrix for receive antenna Rxn. The period (.) indicates a multiplication of the hn row vector and the w column vector.

Compensate Chan Freq Resp selected: the channel effects are removed from the UE-RS weights and the channel-compensated weights are shown on the UE-RS Weights as wn.
- n - a number that indicates the receive channel Rxn. For example, w0 is the UE-RS weight applied to transmit antenna which is connected to receive channel Rx0 (measurement channel 1).
- part - indicates how the complex weight value is expressed. UE-RS weights are shown in Real/Imaginary pairs when Display Weights in Real/Imag Format is selected or in Magnitude/Phase pairs when Display Weights in Real/Imag Format is cleared.
For single-layer beamforming, when cross-channel C-RS Cell-specific RS is detected in the signal being analyzed, the LTE Long Term Evolution demodulator cannot undo the channel effects since the same PDSCH data is transmitted on all antennas (on logical antenna port 5, 7, or 8). In this case, non-channel-compensated UE-RS weights are shown on the UE-RS Weights trace as hn.w (part) regardless of the Compensate Chan Freq Resp setting.

For multi-layer beamforming, the VSA cannot analyze PDSCH allocations that are transmitted on the same resource elements but are separated in space by different beam patterns (since the VSA is at a single location).

Weights are averaged over all subframes in the Measurement Interval.

By default, the channel frequency response is not removed before the calculation of UE-specific RS weights. When there is significant frequency selectivity in the channel, the UE-specific weights shown in the table will include the channel’s frequency response as well. To compensate UE-RS weights for the channel, select the Compensate Chan Freq Resp parameter.

Querying summary table data results programmatically

To programmatically query the Trace Summary Table data results using the Summary() and SummaryUnit() methods in the MeasurementData object.

See the How To Query Summary Table Data Results topic for more information.

Syntax: app.Display.Traces.SelectedItem.DataName = "Demod UE-specific RS Weights1"

To simplify the extraction of information from this trace, a macro (UERSWeightsToArrayConverter) is provided that will read and parse the values of this trace and arrange them in multidimensional arrays.

To load this macro, click Utilities > Macros > Import and then import this folder:

%PROGRAMFILES%\Keysight\89600 Software <ReleaseVersion>\89600 VSA Software\Examples\Macros\UERSWeightsToArrayConverter

This macro does nothing more than create the arrays and is meant to be used as part of your own VSA control application.

The number of UE-specific RS Weights data values change depending on how many PDSCH allocations in the frame contain UE-RS. Instead of using hardcoded indexes to retrieve the data values, you can use a data result name to query the data value.

Below is a table with the list of possible data result names.

UE-specific RS Weights data results
Data Result	Description
UersWeightsDisplayMode = UersWeightsDisplayModeType.PerSubcarrier
NumUERSSubcarsUsernn	Number of UE-RS subcarriers per subframe for user nn
UERSUsernnSCIdxm	Frequency location for UE-RS subcarrier m in user nn's allocation.

Weights Display Mode is set to Per RB:
NumUERSRBsUsernn	Number of UE-RS resource blocks per subframe for user nn
UERSUsernnRBIdxm	Frequency location for UE-RS resource block m in user nn's allocation.

Weights Display Mode is set to Per User:
NumUERSWeightsUsernn	Number of UE-RS resource blocks per subframe for user nn.

UERSUsernnRxpWeight{part}Idxm	UE-RS subcarrier weight over all data in the Measurement Interval for User nn, frequency index m, and Rx antenna p Possible values for {part}: Phase - phase of UE-RS weight Mag - magnitude of UE-RS weight Real - real part of UE-RS weight Imag - imaginary part of UE-RS weight UE-RS weights are expressed as Real/Imag or Mag/Phase pairs depending on the Display Weights in Real/Imag Format parameter.

UERSAnalysis	Indicates whether UE-specific RS analysis is On or Off.