RS Encoder

Encode message to RS codeword

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  • Library:

  • Wireless HDL Toolbox / Error Detection and Correction

  • RS Encoder block

Description

The RS Encoder block encodes message data to a Reed-Solomon (RS) codeword. The block accepts message data and a samplecontrol bus and outputs codeword data symbols and a samplecontrol bus.

Because the latency of the block varies, the block provides output port nextFrame that indicates when the block is ready to accept new input message data. The block provides an architecture suitable for HDL code generation and hardware deployment and supports shortened message lengths.

You can use this block to model many communication system forward error correcting (FEC) codes. The block supports digital subscriber line (DSL), WiMAX (802.16 m and e), digital video broadcast handheld (DVB-H) terminals, digital video broadcast satellite (DVB-S) services, and digital video broadcast satellite services to handheld (DVB-SH) devices below 3 MHz.

Ports

Input

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Input message data, specified as a scalar representing one symbol.

The input word length must be an unsigned integer equal to ceil(log2(Codeword length (N))). For an input data word length of 3, the codeword length parameter, Codeword length (N), must be 7.

double and single data types are allowed for simulation, but not for HDL code generation.

Data Types: double | single | uint8 | uint16 | fixed point

Control signals accompanying the sample stream, specified as a samplecontrol bus. The bus includes the start, end, and valid control signals, which indicate the boundaries of the frame and the validity of the samples.

  • start — Indicates the start of the input frame

  • end — Indicates the end of the input frame

  • valid — Indicates that the data on the input data port is valid

For more detail, see Sample Control Bus.

Data Types: bus

Output

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Encoded codeword data, returned as a scalar. This output data width is same as the input data width.

Data Types: double | single | uint8 | uint16 | fixed point

Control signals accompanying the sample stream, returned as a samplecontrol bus. The bus includes the start, end, and valid control signals, which indicate the boundaries of the frame and the validity of the samples.

  • start — Indicates the start of the output frame

  • end — Indicates the end of the output frame

  • valid — Indicates that the data on the output data port is valid

For more detail, see Sample Control Bus.

Data Types: bus

Block ready indicator, returned as a scalar.

The block sets this signal to 1 (true) when the block is ready to accept the start of the next frame. If the block receives an input ctrl.start signal while nextFrame is 0 (false), the block discards the frame in progress and begins processing the new data.

Data Types: Boolean

Parameters

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Specify the codeword length.

The codeword length must be an integer equal to 2M – 1, where M is an integer in the range from 3 to 16. For more information on representing data for RS codes, see Integer Format (Reed-Solomon Only).

Specify the message length.

For more information on representing data for RS codes, see Integer Format (Reed-Solomon Only).

Specify the source of the primitive polynomial.

  • Select Auto to specify the primitive polynomial based on the Codeword length (N) parameter value. The degree of the primitive polynomial is calculated as M = ceil(log2(Codeword length (N))).

  • Select Property to specify the primitive polynomial using the Primitive polynomial parameter.

Specify a binary row vector representing the primitive polynomial in descending order of powers.

For more information on how to specify a primitive polynomial, see Primitive Polynomials and Element Representations.

Dependencies

To enable this parameter, set the Source of primitive polynomial parameter to Property.

Specify the source of the starting power for roots of the primitive polynomial.

  • Select Auto to use the default B value parameter value, 1.

  • Select Property to enable the B value parameter.

Specify the starting power for roots of the primitive polynomial.

Dependencies

To enable this parameter, set the Source of B, the starting power for roots of the primitive polynomial parameter to Property.

Select this parameter to enable the Puncture pattern vector parameter.

Specify a binary column vector of length Codeword length (N) – Message length (N). A value of 1 indicates that the block data symbol is not punctured, and remained unchanged from the data stream. A value of 0 indicates that the data symbol is punctured, or removed, from the data stream.

Dependencies

To enable this parameter, select the Enable puncturing parameter.

Model Examples

Encode message to RS codeword

Encode message to RS codeword

Use the RS Encoder block to encode a message to a Reed-Solomon (RS) codeword. In this example, a set of random inputs frames are generated and provided to the comm.RSEncoder function. Using the whdlFramesToSamples function, these frames are converted into samples and provided as input to the RS Encoder block. The output of the RS Encoder block is then compared with the output of the comm.RSEncoder function to check whether the encoded output codeword for the given input message is same. By default, the puncturing option is disabled in this example. To enable puncturing, set the puncturing value to true. This example model supports HDL code generation for the RS Encoder subsystem.

Algorithms

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The RS Encoder block encodes a message data of length K into an RS codeword of length N. The block requires a minimum gap of N – K clock cycles to add N – K parity length to the message data of length K. During these N – K parity length clock cycles, the block does not accept new data. So, the minimum duration between messages must be N – K clock cycles.

  • Every start signal that is high indicates the start of a new message. When multiple start high signals exist, the block accepts only the latest start signal.

  • start and end high signals are valid only when the valid signal of the block is high.

  • The block accepts end signals with the corresponding start signal. In case of multiple end high signals, the block accepts only the first end high signal and ignores the remaining end high signals.

References

[1] Wicker, Stephen B. Error Control Systems for Digital Communication and Storage. Englewood Cliffs, NJ: Prentice Hall, 1995.

[2] Clark, George C., and J. Bibb Cain. Error-Correction Coding for Digital Communications. Applications of Communications Theory. New York: Plenum Press, 1981.

Extended Capabilities

See Also

Blocks

Introduced in R2020b

Wireless HDL Toolbox Documentation

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