About the Despread Channel Symbol Table (W-CDMA(3GPP)/HSPA)
When W-CDMA Code Division Multiple Access: One of several digital wireless transmission methods in which signals are encoded using a specific pseudo-random sequence, or code, to define a communication channel. A receiver, knowing the code, can use it to decode the received signal in the presence of other signals in the channel. This is one of several "spread spectrum" techniques, which allows multiple users to share the same radio frequency spectrum by assigning each active user an unique code. CDMA offers improved spectral efficiency over analog transmission in that it allows for greater frequency reuse. Other characteristics of CDMA systems reduce dropped calls, increase battery life and offer more secure transmission. See also IS-95. (3GPP)/HSPA Demodulation is enabled, selecting trace data shows the symbol data and error summary data for the specified Code Channel and Spread Code Length. The bottom section of the display shows the symbol data and the upper section shows the error summary data. This topic discusses the Symbol Table trace data, the Error Summary trace data is discussed in the About Channel Error Summary trace data topic.
The Chan Symbol table shows the binary bits for each measured symbol in the specified Code Channel and Spread Code Length. These parameters are specified in the Despread Channel and Despread Channel text boxes, located in the tab of the W-CDMA (3GPP) Demod Properties dialog box ().
The first bit in the table corresponds to the first bit of the first symbol. To make the table easier to read, the analyzer shows a fixed number of bits (eight), followed by a space.
For downlink signals, the symbol table has two bits per symbol containing both the "I" and "Q" data.
However, for Uplink signals, "I" and "Q" data channels are logically separate signals. All trace data contains both the "I" and the "Q" branches of the signal, except the symbol table data. For uplink signals, the symbol table has one bit per symbol. The bit is either from the "I" branch or the "Q" branch of the channel, as specified by the "IQ" Branch parameter ().
In addition, the analyzer shows numbers to the left of each row. These numbers indicate the bit position of the first bit in the row. For example, if 192 is displayed by the third row, the first bit in the row is the 192nd bit in the digital data stream.
Here's an easy way to see the bits that correspond to a point in the channel constellation diagram: display the constellation diagram in one grid, the symbol table in another, and turn on the marker and marker coupling. When you place the marker on a point in the constellation diagram, the analyzer 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 you can use the marker X Position to move to any symbol.
Selecting Reverse link IQ Symbol Bit data
For Reverse link signals, the "I" and "Q" data channels are logically separate signals. All trace data results contain both the "I" and the "Q" branches of the signal, except the symbol binary bit data. The symbol data shows either the "I" or the "Q" symbol bits as specified by the I/Q channel parameter ().
Error Summary Data Information
The Error Summary Data is described in the About Channel Error Summary Data topic.
See Also
