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MT Generate System Parameters (MT Generate QAM System Parameters (map)) (G Dataflow)

Version:
    Last Modified: February 7, 2018

    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.

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    samples per symbol

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

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    Note  

    The demodulation and detector nodes use timing recovery, which is optimized for four or more samples per symbol.

    Default: 16

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    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 2 N , 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.

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    error in

    Error conditions that occur before this node runs.

    The node responds to this input according to standard error behavior.

    Standard Error Behavior

    Many nodes provide an error in input and an error out output so that the node can respond to and communicate errors that occur while code is running. The value of error in specifies whether an error occurred before the node runs. Most nodes respond to values of error in in a standard, predictable way.

    error in does not contain an error error in contains an error
    If no error occurred before the node runs, the node begins execution normally.

    If no error occurs while the node runs, it returns no error. If an error does occur while the node runs, it returns that error information as error out.

    If an error occurred before the node runs, the node does not execute. Instead, it returns the error in value as error out.

    Default: No error

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    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.

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    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.

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    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 2 N , where N is the number of bits per symbol. The length of the vector for the symbols farthest from the origin must be 1.

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    bits per symbol

    Number of bits represented by each symbol. This value is equal to Log 2 (M), where M is the order of the modulation (for example, for 16-QAM, M = 16).

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    error out

    Error information.

    The node produces this output according to standard error behavior.

    Standard Error Behavior

    Many nodes provide an error in input and an error out output so that the node can respond to and communicate errors that occur while code is running. The value of error in specifies whether an error occurred before the node runs. Most nodes respond to values of error in in a standard, predictable way.

    error in does not contain an error error in contains an error
    If no error occurred before the node runs, the node begins execution normally.

    If no error occurs while the node runs, it returns no error. If an error does occur while the node runs, it returns that error information as error out.

    If an error occurred before the node runs, the node does not execute. Instead, it returns the error in value as error out.

    Where This Node Can Run:

    Desktop OS: Windows

    FPGA: Not supported

    Web Server: Not supported in VIs that run in a web application


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