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MT RS Symbol Decoder (shortened) (G Dataflow)

Last Modified: January 9, 2017

Decodes a Reed-Solomon (RS) encoded integer symbol stream in shortened format.

RS codes are specialized Bose-Chaudhari-Hocquenghem (BCH) codes in which the code elements are drawn from the Galois field, GF(2m). RS codes are extremely powerful at burst error correction. The operations involved in Reed-Solomon encoding and decoding are performed in the GF(2m). The RS encoder operates on code words that are symbols or groups of bits. The parameters code word length (n), symbols and data word length (k), symbols are specified in terms of symbols. Each symbol represents a group of Log2(n+1) bits.

Using shortened RS codes, the k and n values represent symbols. Each symbol has a length of m bits, which is set using the bits per rs symbol parameter. Create a shortened RS code by setting the shortened values of n and k, as well as the bits per symbol that correspond to the underlying Galois field arithmetic. For example, you can set n = 32, k = 28, and bits per rs symbol = 8, to generate a shortened RS (32,28,2) code with an error-correcting capacity of 2 RS symbols. For this code, the underlying Galois field arithmetic is performed in GF(2 8 )=256.

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input symbols

The array of integer symbols to be decoded using the Reed-Solomon (RS) decoding scheme. Use the RS symbol encoder nodes to generate the integer symbols required for this parameter.

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Note  

The RS decoder is a block decoder, which means that it operates on a block of n integers. To ensure that the output symbols stream corresponds to the entire input symbols array, set the length L of input symbols to be an integer multiple of n symbols. If the length L is not a multiple of n symbols, the last L modulo n symbols are buffered inside the decoder. These symbols are added to the incoming input symbols stream at the beginning of the next iteration if reset? is set to FALSE.

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code word length (n), symbols

The length of the Reed-Solomon (RS) code word. Each RS symbol represents log 2 (n+1) bits.

Default: 7

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data word length (k), symbols

The length of the Reed-Solomon (RS) data word. Each RS symbol represents log 2 (n+1) bits.

Default: 3

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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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bits per rs symbol

The number of bits per Reed-Solomon (RS) symbol. This parameter sets the Galois field over which the encoding operation is performed as GF(2 bits per rs symbol ). Valid values are 3 to 16, inclusive. For example, to set a shortened RS (32,28) code in the Galois field GF(256), set code word length (n), symbol as 32 symbols, data word length (k), symbol as 28 symbols, and bits per rs symbol as 8.

Default: 3

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reset?

A Boolean that determines whether the internal state of the decoder is cleared.

TRUE Clears any buffered bits from previous iterations. Also initializes the Galois field structure corresponding to the Reed-Solomon n, k values.
FALSE Continues decoding from the previous iteration. Any buffered bits from the previous iteration are added to the beginning of the input bit stream prior to decoding.

Default: TRUE

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modulation session

The modulation session for configuring selected properties of the Modulation nodes. Use this parameter to configure the advanced properties in the MT RS Symbol Encoder nodes. If MT RS Symbol Encoder is called with an uninitialized modulation session, the node returns an error.

Default: 0

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output symbols

The decoded integer symbol stream. Wire this parameter to MT UnPack Bits to recover the message bits that comprise the transmitted message data.

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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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