About the Symbol Table (802.16 OFDM)
When Demodulation is enabled, selecting Syms/Errs trace data shows the symbol table. The symbol table shows the error summary data and the symbol data (binary bits) for each symbol-time and subcarrier following the preamble. For IEEE Institute of Electrical and Electronics Engineers. A US-based membership organisation that includes engineers, scientists, and students in electronics and related fields. The IEEE developed the 802 series wired and wireless LAN standards. Visit the IEEE at http://www.ieee.org 802.16a/d this includes symbol data for both the FCH and DATA symbol-times.
Symbol Data
The lower section of the 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 subcarrier number -100 of 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. symbol following the preamble symbols in the data stream.
The default symbol table display shows the Data subcarrier symbol bits in color, the Pilot subcarrier symbol bits in white, and all the subcarrier number 0 symbol bits are 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., red for QPSK Quadrature phase shift keying, blue for 16QAM, and green for 64QAM; however, the colors can be changed using .
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 its value in decimal.
For IEEE 802.16a/d signals, the subcarrier data modulation format can change from one symbol to the next. The symbol table always shows the same number of bits per symbol, so the symbols are displayed with the maximum number of bits needed. Normally, this means that each subcarrier is represented by 6 bits (two hexadecimal characters) because that many bits are needed for 64QAM. When a subcarrier requires fewer bits than this, the extra bits are displayed 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 indicate either the bit or symbol offset position depending the symbol table format as described below:
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.
The symbol data bit format is hexadecimal and each character represents a hexadecimal digit. The number to the left of each row indicate 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.
Here are some helpful tips:
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'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 turn on the markers for both displays and enable marker coupling. Place the marker on a point in the constellation diagram and the VSA will highlight 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. The Marker Position - X and Z Position parameters can be used to move to a specific symbol location.
Error Summary Data
The upper section of this trace data shows the Error Summary data for OFDM Demodulation. See About Error Summary Data for information about OFDM Error Summary Data.
See Also
Syms/Errs trace data (802.16 OFDM)
