# Symbols

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symbol is constituted from a group of bits that are mapped onto a defined set of values known as a symbol map on the transmitter. The rate at which the symbols are transmitted per second is called the symbol rate. For the analyzer to demodulate the signal correctly, the transmitted symbol rate must be specified.

When demodulating the signal, impairments are corrected, and the recovered symbols are then compared against all points on the symbol map to find the closest ideal symbol. In RFmx, the bit representation in the symbol map is read as b(log2M)-1...b0 , with the least significant bit on the right.

For example, the default symbol map for QPSK (Modulation Type = PSK, M = 4) is as shown in the following image.

The demodulated bits are as follows.

The demodulated bits are reported as an array of bits in the following order.

{b0 ... b(log2M)-1 }0 {b0 ... b(log2M)-1}1 ... {b0 ... b(log2M)-1}n-1

where M is the M-ary and n is the number of symbols analyzed.

To provide a custom symbol map, set the Symbol Map Type to Custom and provide an array of symbols. The index of the array determines the grouped bits that are to be mapped onto the symbol.

Note

Refer to the appropriate topic in the Modulation Types section in this help file to know the default symbol map used by the demodulator.
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