About the Symbol Table (802.16 OFDMA Demodulation)

When 802.16 OFDMA Demodulation is enabled, selecting Syms/Errs trace data opens the symbol table. The symbol table shows both the error summary data and the symbol data (binary bits) for each symbol-time and subcarrier in the measurement analysis zone.

Symbol Data

The lower half of the Syms/Errs trace data provides the raw data bits for each non-preamble symbol and subcarrier in the measurement analysis zone. These bits are not decoded and include bits for all subcarrier symbols including the pilot subcarriers. These bits are demapped from complex symbols shown in the Meas IQ trace, which is not derotated by the modulation PRBS Pseudo-Random Binary Sequence. The first bit in the table corresponds to the first bit of the lowest numbered subcarrier of the first measured non-preamble OFDMA symbol. The symbol bits for subcarrier number 0 (DC subcarrier In an orthogonal frequency division multiplexing (OFDM) or orthogonal frequency division multiple access (OFDMA) signal, the subcarrier whose frequency would be equal to the RF center frequency of the station.) is blanked (not shown). When "Include inactive subchannels" is selected, the inactive subcarriers used for the UnmodulatedRCE computation are shown with a dash ("-"). This indicates the subcarrier has no data value, but is actually composed exclusively of noise or other interference. When "Include inactive subchannels" is clear, the unused subcarriers are blanked (not shown).

Each subcarrier symbol in the table is comprised of the same number of bits per symbol which is either 6 binary bits or two hexadecimal characters. When a subcarrier symbol requires fewer than 6 bits, leading pad bits are added to complete the 6 bit requirement and are displayed as zero. These additional pad bits do not affect the measurement data results.

To make the table easier to read, the symbol data is shown in groupings of eight characters separated by a space. You can choose to view the symbol bits in either binary or hexadecimal format using the Trace > Digital Demod > Symbol Table Format parameter. The first column and leading number in each row indicate either the bit or symbol offset position depending on the selected symbol table format, either Binary or Hexadecimal respectively:

Binary Format: The symbol data bit format is binary and each character represents a binary digit. The number to the left of each row indicates the bit offset of the first bit in the row.

Hexadecimal Format: The symbol data bit format is hexadecimal and each character represents a hexadecimal digit. The number to the left of each row indicates the subcarrier symbol offset of the first subcarrier symbol in the row.

There must be at least 4 bits/symbol to use the hexadecimal format; symbols that have less than 4 bits/symbol are shown only in binary format regardless of the Symbol Table Format setting.

Marker

When the symbol table marker is enabled, the marker highlights and captures the required number of data bits for the selected subcarrier symbol. The marker readout provides the subcarrier number, the data burst name, the symbol number, and the decimal value.

Symbol Table Colors

The symbol table uses color to distinguish and identify related symbol data bits as described below:

Data Burst Analysis mode:
Each defined data burst in the analysis zone is assigned a unique color by the VSA, symbol bits reflect the same color as the burst that they are defined in. The assigned color for each defined data burst can be viewed in the "Zone Definition Grid" in the Zone Definition tab of the 802.16 OFDMA Demod Properties dialog box.
Symbol data bits not belonging to active bursts are shown as dashes and use the default trace symbol colors specified by the display preferences "Symbol" parameter (Utilities > Display Preferences > Color > Symbol).
Pilots symbol bits use the default trace display preferences "Pilot" parameter (Utilities > Display Preferences > Color > Pilot).
Uniform Zone Analysis mode:
The color assigned to the selected symbol bits indicate the modulation format type. The default colors are magenta for BPSK Binary phase shift keying - A type of phase modulation using 2 distinct carrier phases to signal ones and zeros., red for QPSK Quadrature phase shift keying, blue for 16QAM, and green for 64QAM. The default colors can be changed using display preferences ModType 1-4 parameters (Utilities > Display Preferences > Color > Mod Type 1 - Mod Type 4 ).

You can chose to show the symbol data bits in either binary or hexadecimal format, see Symbol Table Format
The Result Length mode and parameters determines the number of symbols shown in the table.
Here's an easy way to identify bits that correspond to a point in the constellation diagram: display the constellation diagram in one grid and the symbol table in another. Then add a marker for one trace and enable marker coupling. When you place the marker on a point in the constellation diagram, the VSA highlights the corresponding symbol bits in the symbol table.
Use the keyboard arrow keys or the mouse wheel to move the marker from one symbol to the next. You can use the Marker Position - X and Z Position parameters to move to a specific symbol location.

Error Summary Data

The upper section of this trace data shows the Error Summary data for OFDMA Demodulation. See About Error Summary Data information about OFDMA Error Summary Data.