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MT Map Bits to PSK Symbols (G Dataflow)

Last Modified: January 9, 2017

Maps an incoming bit stream to complex-valued PSK symbols.

Programming Patterns
Use this node in conjunction with MT Matched Filter, MT Align to Ideal Symbols, MT Decimate Oversampled Waveform, and MT Calculate BER to perform waveform analysis on the modulated waveform.
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Note  

The mapping of symbols to bits depends on the number of bits per symbol, which equals log 2 ( M ) with M representing the size of the modulation scheme. For example, in a 256-QAM system, 500 QAM symbols are mapped to ( 500 ) × log 2 ( 256 ) = 4000 m e s s a g e b i t s .

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input bit stream

The incoming bit stream to be mapped to symbols.

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symbol map

An ordered array that maps each Boolean symbol to its desired coordinates in the complex plane. The number of PSK states in the array must be 2 N , where N is the number of bits per symbol.

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PSK type

Type of PSK modulation.

Name Description
normal

Sets the modulation type to regular PSK.

shifted

Rotates the constellation by π /M each symbol.

offset

Sets the modulation type to offset quadrature phase-shift keying (OQPSK). This modulation scheme is a form of phase-shift keying in which four different phase angles are used. This scheme is sometimes referred to as staggered quadrature phase-shift keying (SQPSK). For offset PSK, the ideal symbol timing for Q is offset by 1/2 of a symbol period from the ideal symbol timing for I. offset is currently only supported for M= 4.

Default: normal

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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.

Default: no error

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differential PSK

A value that indicates how the PSK modulation represents symbols.

Differential operation is used to implement PSK formats such as differential quadrature PSK (DQPSK) and π /4-DQPSK.

Name Description
disable

Symbols are represented as constellation points.

enable

Symbols are represented as the transitions between constellation points.

Default: disable

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reset?

A Boolean that determines whether stored state information is cleared on each call to this node.

When the input bit stream is not comprised of an integer number of symbols, the carryover bits are buffered.

TRUE Clears the buffered data, checks the input parameters on a first call, and reflects any change in the input parameter values during subsequent iterations.
FALSE Adds the buffered data to the beginning of data from next iteration, in continuous operations.

Default: TRUE

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symbols

An array of complex-valued PSK symbols with a one-to-one mapping to the input bit stream based on the specified PSK symbol map.

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Note  

When you configure PSK type to shifted, the mapped symbols are additionally multiplied by the complex phasor, as shown by the following equation:

e j m π M , m = 0... M 1 , j = 1

where M specifies the M-ary PSK format. This multiplication ensures that the generated PSK oversampled waveform never transitions through the origin after pulse shaping.

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Note  

Wire this parameter to MT Pulse Shaping Filter to generate the oversampled baseband complex waveform.

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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


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