Table Of Contents

MT Generate MSK Synchronization Parameters (bit array) (G Dataflow)

Last Modified: January 9, 2017

Generates synchronization parameters for MSK demodulation using a synchronization sequence directly represented by the sync bits input array. The generated synchronization parameters cluster avoids phase ambiguity at the demodulator, thus allowing recovery of the actual message bits.

connector_pane_image
datatype_icon

MSK system parameters

Parameter values defining the MSK system. Wire the MSK system parameters cluster returned by MT Generate MSK System Parameters to this cluster. Do not alter the values.

datatype_icon

differential encoding enable

A value that indicates whether the bit sequence is differentially encoded.

Name Description
disable

Disables bit sequence encoding.

enable

Enables bit sequence encoding.

Default: enable

datatype_icon

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. Applying Carson's rule for MSK modulation [peak frequency deviation = 0.25 × symbol rate (Hz)], the 98% MSK bandwidth is given by 0.5 × (1 + r) × symbol rate + peak frequency deviation, where 0 < r ≤ 1 is the filter parameter. To satisfy Nyquist criterion, a good guideline is given by samples per symbol = 2 × ceil(1.5 × bandwidth/symbol rate) to obtain 3× oversampling.

Default: 16

datatype_icon

sync bits

An array of synchronization bits used to generate the MSK synchronization parameters cluster. For example, if you specify a preamble word of 1111 1111 1111 1110 for symbol synchronization, you can wire a 16-bit array with the above entries to the sync bits parameter. For reliable symbol synchronization, specify an array of length (10 × bits per symbol).

spd-note-note
Note  

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

Default: 0

datatype_icon

error in

Error conditions that occur before this node runs. The node responds to this input according to standard error behavior.

Default: no error

datatype_icon

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

datatype_icon

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

datatype_icon

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

datatype_icon

symbol rate

The desired symbol rate, in hertz (Hz).

Default: 1.0

datatype_icon

MSK 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).

datatype_icon

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.

datatype_icon

sync sequence

The mapped symbol pattern used to synchronize the bit stream. To prevent false synchronization, select this pattern such that there is a low probability of accidental correlation to nonsynchronized parts of the data stream. For MSK, the real portion of the mapped symbols is the frequency deviation of the symbol value, and the imaginary portion is 0. If this parameter is left empty, the signal is still demodulated.

datatype_icon

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

datatype_icon

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

datatype_icon

error out

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

Where This Node Can Run:

Desktop OS: Windows

FPGA: Not supported


Recently Viewed Topics