About the Channel Symbol Table (TD-SCDMA)

When TD-SCDMA Demodulation is enabled, selecting Chan Error Summary trace data shows the symbol table and error summary trace data for the specified Sub-frame, TimeSlot, Code Channel and Spread Code Length. The bottom section of the display shows the symbol table data and the upper section shows the error summary data. This topic discusses the code channel Symbol Table trace data, the Error Summary trace data is discussed under Channel Error Summary.

Symbol Data

The bottom half of the symbol table shows the raw data symbol bits for each measured symbol in the specified Sub-frame, TimeSlot, Code Channel and Spread Code Length.

Detection of the DwPTS Phase Coding and hence accuracy of the Demodulated Symbols depends on low phase noise input data. Because of this, it may be necessary to lock frequency references, between the input hardware and the device under test in order to achieve good results for these measurements.

Selecting Data

The Analysis Sub-frame and Analysis TimeSlot parameters are specified in MeasSetup > TD-SCDMA Demod Properties > Time tab. The Code Channel and Code Layer are specified in MeasSetup > TD-SCDMA Demod Properties > Channel/Layer tab.

Interpreting the Symbol Table

When the symbol table marker is enabled, the trace marker highlights the data symbol bits for the selected symbol and the marker readout provides the symbol number and its value in decimal.

When the DwPTS phase encoding is unknown, the downlink Traffic TimeSlots symbols may be rotated due to a phase uncertainty in the signal. Because the uplink traffic timeslots are not phase related to DwPTS timeslot, this applies at all times for the Uplink timeslot symbols.

To make the table easier to read, the data bits are shown in groupings of eight characters followed by a space. The characters represent a binary digit and the number to the left of each row indicate either the bit offset position as described below:

For example, if 192 is displayed to the left of third row, the first bit in the third row is the 192nd bit in the digital data stream.

Measurement Tips:

Here's an easy way to see the bits that correspond to a point in the channel IQ constellation diagram: display the IQ constellation diagram in one grid, the symbol table in another, and turn on the Marker and Marker Coupling. When the marker is placed on a point in the constellation diagram, the VSA highlights the corresponding bits in the symbol table.
Use the arrow keys on the keyboard or the mouse wheel to move the marker from one symbol to the next. Or use the marker X Position to move to any specified symbol location.

Error Summary Data

For more information on error summary data, see Channel Error Summary Data.