About the Symbol Table (802.11n/ac/ax/be)

Syms/Errs trace data shows the symbol table. The symbol table shows error summary data and the symbol data (binary bits) for each symbol-time and subcarrier following the preamble.

Symbol Data

The lower section of the Syms/Errs trace data display shows the raw data bits for each symbol and subcarrier following the preamble. These bits are not decoded and include bits for all subcarrier symbols including the pilot subcarriers. The first bit in the table corresponds to the first bit of the lowest subcarrier in frequency for the first OFDM Orthogonal Frequency Division Multiplexing: OFDM employs multiple overlapping radio frequency carriers, each operating at a carefully chosen frequency that is Orthogonal to the others, to produce a transmission scheme that supports higher bit rates due to parallel channel operation. OFDM is an alternative tranmission scheme to DSSS and FHSS. data symbol.

By default, the bit order displayed is LSB Least Significant Bit: In a binary coding scheme, the bit having the least numerical value. Analogous to the units position in a decimal number.-first, meaning the first digit is interpreted as the least significant bit in a hexadecimal digit. You can switch to showing the hex digits as MSB-first by changing the Trace > Digital Demod > Symbol Table Bit Order property (Hex format only).

When there are varying bits per symbol (e.g., the HE_BW80_RU484-26-106-26-106-106-26-106-SIGB demo signal), the bits per symbol in the Syms/Errs trace is set to the maximum bits per symbol present.

The default symbol table display shows the Data Subcarrier symbol bits in color, the Pilot subcarrier symbol bits in white, and all the unused subcarrier symbol bits blanked (not shown). The color of the symbol table bits indicates the modulation format of that symbol. The default colors are white for Pilots, magenta for BPSK Binary phase shift keying - A type of phase modulation using 2 distinct carrier phases to signal ones and zeros. (Mod Type 1), red for QPSK Quadrature phase shift keying (Mod Type 2), blue for 16QAM (Mod Type 3), green for 64QAM (Mod Type 4), and yellow for 256 QAM Quadrature Amplitude Modulation (Mod Type 5). To change the symbol bit's color, click Utilities > Display Preferences > Color tab and select a new color for the active Mod Type Element.

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

Pilot subcarriers always use BPSK modulation and only require 1 bit per subcarrier. If the data subcarriers use a different modulation format, they will require more than one bit per subcarrier. In this case, the pilots are shown with the same number of bits as the data subcarriers, with extra pad bits shown as zero. These extra bits are only pad bits and do not affect the measurement data results.

To make the table easier to read, the symbol data is shown in groupings of eight characters followed by a space. The characters can represent a binary digit or a hexadecimal digit as specified by the Symbol Table Format parameter. The number to the left of each row indicates either the bit or symbol offset position depending the symbol table format as described below:

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--that is, symbols that have less than 4 bits/symbol are displayed only in binary format regardless of the Symbol Table Format setting.

The symbol data bits can be shown 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 is 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 turn on the markers for both displays and enable marker coupling. When the marker is placed 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. Use the Marker Position - X and Z Position parameters to move to a specific symbol location.

OFDM Error Summary Data

This trace data shows the Error Summary data for OFDM Demodulation. See About Error Summary Data for information about OFDM Error Summary Data.