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MT Generate Synchronization Parameters (MT Generate QAM Synchronization Parameters (number array)) (G Dataflow)

Version:
    Last Modified: February 7, 2018

    Generates synchronization parameters for QAM demodulation using a synchronization sequence defined by a sync numbers array in which each number represents a group of bits. The generated synchronization parameters cluster avoids phase ambiguity at the demodulator, thus allowing recovery of the actual message bits.

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    QAM system parameters

    Parameter values defining the QAM system. Wire the QAM system parameters cluster of MT Generate QAM System Parameters (M) or MT Generate QAM System Parameters (map) to this cluster. Do not alter the values.

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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 value must be an even number.

    Default: 16

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    symbol map

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

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    sync numbers

    An array of synchronization numbers in which the binary representation of each number is used to generate the sync bit array. By default, the internal conversion of each sync number into the corresponding synchronization bit sequence is performed with the most significant bit first (left-aligned) approach.

    For example, if you specify a preamble word of 1111 1111 1111 1110 for symbol synchronization, you can specify sync numbers as an array with a single element xFFFE. Specify the bits per sync number value to be 16. You can also specify sync numbers as an array of two elements (xFF and xFE), and specify the bits per sync number value as 8. For reliable symbol synchronization, specify an array of length (10 × bits per symbol).

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    Note  

    To prevent false synchronization, select a bit pattern with low correlation to nonsynchronized portions of the data stream.

    Default: 0

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    bits per sync number

    Number of bits corresponding to each sync number in the sync numbers array.

    Default: 32

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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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    expected sync location

    The expected location of the synchronization parameters in symbols. Set this value to -1 to search the entire waveform for the synchronization symbols.

    Default: -1

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    sync location uncertainty

    Number of symbols before or after the expected sync location where the first symbol of the sync sequence may be located. The node ignores this parameter if the expected sync location parameter is set to -1.

    Default: 10

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    sync indent

    Distance that the sync sequence is indented into the information block.

    The distance is the number of demodulated symbols preceding the sync sequence. For example, a value of 10 indicates that the output bit stream consists of 10 data symbols, followed by the sync sequence, followed by the remaining data symbols.

    Default: 0

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    QAM synchronization parameters

    Synchronization parameters to pass to the demodulation node.

    If the synchronization parameter passed to the demodulation node is left empty, the constellation of the demodulated waveform has a 90° carrier phase ambiguity for two-dimensional modulation schemes (QAM, QPSK, and higher order PSK) and a 180° carrier phase ambiguity for one-dimensional modulation schemes (PAM/ASK/BPSK).

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    expected sync location

    The expected location of the first symbol of the sync sequence.

    This value is an index to the input complex waveform. A value of -1 searches the entire input complex waveform and ignores the sync location uncertainty parameter.

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    sync sequence

    The mapped symbol array from the specified synchronization bits or synchronization numbers.

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    sync location uncertainty

    Number of symbols before or after the expected sync location where the first symbol of the sync sequence may be located. The node ignores this parameter if the expected sync location parameter is set to -1.

    Default: 10

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    sync indent

    Distance that the sync sequence is indented into the information block.

    The distance is the number of demodulated symbols preceding the sync sequence. For example, a value of 10 indicates that the output bit stream consists of 10 data symbols, followed by the sync sequence, followed by the remaining data symbols.

    Default: 0

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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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