MT Generate QAM System Parameters (map)
- Updated2023-02-17
- 4 minute(s) read
MT Generate QAM System Parameters (map)
Calculates parameters for use with either MT Modulate QAM or MT Demodulate QAM. The node accepts an input array of symbol values that explicitly specifies the positions of the symbol map.
.png?_LANG=enus)
Inputs/Outputs

samples per symbol
An even number of samples dedicated to each symbol. Multiply this value by the symbol rate to determine the sample rate.
Default value: 16

symbol values
An array of symbol values with an order that corresponds to the symbol map. The number of QAM states in the array must be 2N, where N is the number of bits per symbol. The length or magnitude of the vector for the symbols farthest from the origin must be 1.
This node expects a two-dimensional, square array of integers for the symbol values parameter. 4-QAM expects a 2×2 array (2 rows, 2 columns), 16-QAM expects a 4×4 array, and so on. The integers 0 through (M-1) must all be included only once in the symbol values array, where M is the M-ary number of the modulation. M must be less than 256. The binary representation (LSB first convention) of the integers represents the bit pattern that is mapped to the corresponding symbol location in the symbol values array.
For example, for 4-QAM, if you specify symbol values as
[3 1]
[0 2]
the generated QAM symbol map is [(-0.707 - 0.707i), (0.707 + 0.707i), (0.707 - 0.707i), (-0.707 + 0.707i)].
In order to create a custom QAM symbol map that does not fit into a square 2 dimensional array, for example 32-QAM, set the additional spaces in the array to negative numbers. The negative number will not be considered as a part of the symbol map.

error in
Error conditions that occur before this node runs.
The node responds to this input according to standard error behavior.
Default value: No error

QAM system parameters
Parameter values defining the QAM system. Wire this cluster to the corresponding system parameters cluster of MT Modulate QAM or MT Demodulate QAM.

samples per symbol
Number of samples per symbol in the modulated output complex waveform. For error-free operation, the samples per symbol must be an even number.

symbol map
An ordered array that maps each symbol value to its desired coordinates in the complex plane. The number of QAM states in the array must be 2N, where N is the number of bits per symbol. The length of the vector for the symbols farthest from the origin must be 1.

bits per symbol
Number of bits represented by each symbol. This value is equal to Log2(M), where M is the order of the modulation (for example, for 16-QAM, M = 16).

error out
Error information.
The node produces this output according to standard error behavior.