RS Encoder

Encode message to RS codeword

Since R2020b

• 

Libraries:
Wireless HDL Toolbox / Error Detection and Correction

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.

Examples

Encode Message to RS Codeword

Encode message to Reed-Solomon (RS) codeword.

• Open Script

Ports

Input

data — Input message data

scalar

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

ctrl — Control signals accompanying sample stream

samplecontrol bus

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 details, see Sample Control Bus.

Data Types: bus

Output

data — Encoded codeword data

scalar

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

ctrl — Control signals accompanying sample stream

samplecontrol bus

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 details, see Sample Control Bus.

Data Types: bus

nextFrame — Block ready indicator

scalar

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

Codeword length (N) — Length of codeword

7 (default) | integer in the range from 7 to 65,535

Specify the codeword length.

The codeword length must be an integer equal to 2^M – 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).

Message length (K) — Length of message

3 (default) | integer in the range from 3 to (Codeword length (N) – 2)

Specify the message length.

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

Source of primitive polynomial — Primitive polynomial source

Auto (default) | Property

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.

Primitive polynomial — Primitive polynomial

[1 0 1 1] (default) | binary row vector

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.

Source of B, the starting power for roots of the primitive polynomial — Source of starting power for roots of primitive polynomial

Auto (default) | 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.

B value — Starting power for roots of primitive polynomial

1 (default) | positive integer

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.

Enable puncturing — Puncture pattern source

off (default) | on

Select this parameter to enable the Puncture pattern vector parameter.

Puncture pattern vector — Puncture vector

[1; 1; 0; 0] (default) | binary column vector

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.

Algorithms

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.

Latency

This figure shows a sample output of the RS Encoder block with latency according to the DVB-S standard configuration, Codeword length (N) and Message length (K) parameter values specified as 255 and 239, respectively, and with puncturing disabled. In this case, the latency of the block is 1 clock cycle.

Performance

The performance of the synthesized HDL code varies with your target and synthesis options. The input data type used for generating HDL code is fixdt(0,8,0).

This table shows the resource and performance data synthesis results when using the block with Codeword length (N) and Message length (K) parameter values specified as 255 and 239, respectively. The generated HDL is targeted to the AMD^® Zynq^®- 7000 ZC706 evaluation board. The design achieves a clock frequency of 440 MHz.

Resource	Number Used
LUTs	237
Registers	154
DSPs	0
Block RAMs	7.5

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

C/C++ Code Generation

Generate C and C++ code using Simulink® Coder™.

This block supports C/C++ code generation for Simulink^® accelerator and rapid accelerator modes and for DPI component generation.

HDL Code Generation

Generate VHDL, Verilog and SystemVerilog code for FPGA and ASIC designs using HDL Coder™.

HDL Coder™ provides additional configuration options that affect HDL implementation and synthesized logic.

HDL Architecture

This block has one default HDL architecture.

HDL Block Properties

ConstrainedOutputPipeline	Number of registers to place at the outputs by moving existing delays within your design. Distributed pipelining does not redistribute these registers. The default is 0. For more details, see ConstrainedOutputPipeline (HDL Coder).
InputPipeline	Number of input pipeline stages to insert in the generated code. Distributed pipelining and constrained output pipelining can move these registers. The default is 0. For more details, see InputPipeline (HDL Coder).
OutputPipeline	Number of output pipeline stages to insert in the generated code. Distributed pipelining and constrained output pipelining can move these registers. The default is 0. For more details, see OutputPipeline (HDL Coder).

Version History

Introduced in R2020b