NR Polar Encoder

Perform polar encoding according to 5G NR standard

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Libraries:
Wireless HDL Toolbox / Error Detection and Correction

Description

The NR Polar Encoder block implements a streaming polar encoder with hardware-friendly control signals. The 5G NR standard requires polar encoding for channel coding of the DCI, UCI, and BCH transmit channels.

The encoder implementation matches the nrPolarEncode (5G Toolbox) function.

You must specify the link direction because the coding scheme defined by the 5G NR standard is different for downlink and uplink messages. Downlink messages are encoded with interleaving and uplink messages do not use interleaving.

Because the latency of this operation can vary, the block provides an output signal, nextFrame, that indicates when the block is ready to accept new inputs. For more details, see the Latency section on this page.

Examples

Polar Encode and Decode of Streaming Samples

Simulate NR Polar Encode and Decode blocks and compare the hardware-optimized results with results from 5G Toolbox™ functions.

• Open Script

Ports

Input

data — Input data bit

scalar

Input data bit, specified as a scalar.

The software supports double and single data types for simulation, but not for HDL code generation.

Data Types: fixdt(0,1,0) | Boolean | double | single

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

K — Length of information block in bits

positive integer

Length of information block in bits, specified as a positive integer. For downlink messages, K must be in the range 36 to 164. For uplink messages, K must be in the range 18 to 25 or 31 to 1023.

Dependencies

To enable this port, set the Configuration source parameter to Input port.

Data Types: fixdt(0,10,0)

E — Rate-matched output length in bits

positive integer

Rate-matched output length in bits, specified as a positive integer. Specify a value for E that is greater than K and less than or equal to 8192.

Dependencies

To enable this port, set the Configuration source parameter to Input port.

Data Types: fixdt(0,14,0)

Output

data — Encoded data bit

scalar

Encoded data bit, returned as a scalar. The block returns a message of N sequential bits. N is a power of two determined from the values of K and E. The maximum output message size is 512 bits when the Link direction is Downlink and 1024 bits when the Link direction is Uplink.

Data Types: fixdt(0,1,0) | Boolean | double | single

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 — Ready for new inputs

scalar

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

For more information, see Using the nextFrame Output Signal.

Data Types: Boolean

Parameters

Link direction — Direction of 5G NR link

Downlink (default) | Uplink

When you select Downlink, the block performs interleaving, as specified in the 5G NR standard. When you select Uplink, the block omits the interleaving logic.

Configuration source — Source for K and E

Property (default) | Input port

Select Input port to enable the K and E ports. Select Property to use the Message length (K) and Rate-matched length (E) parameters.

Message length (K) — Length of information block in bits

56 (default) | positive integer

For downlink messages, K must be in the range 36 to 164. For uplink messages, K must be in the range 18 to 25 or 31 to 1023.

Dependencies

To enable this parameter, set the Configuration source parameter to Property.

Rate-matched length (E) — Rate-matched output length in bits

864 (default) | positive integer

Specify a value for E that is greater than K and less than or equal to 8192.

Dependencies

To enable this parameter, set the Configuration source parameter to Property.

Tips

• You cannot use this block inside an Enabled Subsystem or Resettable Subsystem.

Algorithms

This block implements the encoder by using log2(N) parallel encoding stages. The block stores the whole message in the buffer, then interleaves and maps the information bits based on the pattern specified in the standard for the values of K and E. The interleaving step is included only when you set the Link direction parameter to Downlink.

This diagram shows the architecture of the polar encoder.

The block uses the Configuration stage when the input K and E values change. The block computes the new message length, N, and the locations of the information bits, then passes them to the buffer and the mapping stage. Because the mapping patterns are computed as needed, rather than stored in hardware, the block supports all K and E values within the supported range. The Configuration stage also computes the interleave pattern when you set the Link direction parameter to Downlink.

When you set the Configuration source parameter to Property, the K and E values are constants, so the decoder does not implement the Configuration stage. In this case, the block includes static lookup tables that contain the precomputed configuration.

Latency

The exact latency varies based on the values of K and E. The latency is longer for frames where the K and E values change and the block must compute the new configuration. Because the latency varies, use the output nextFrame control signal to determine when the block is ready for a new input frame.

This waveform shows how the latency varies with values of K and E. For the first frame with a given K and E value, the block must determine the message length and information bit mapping for those values. This configuration step means that the block takes longer to start returning the encoded samples. In this case, the block also takes longer before it is ready to accept the next input frame. When the input K and E values are 132 and 256, respectively, the block has a latency of 535 cycles from the input start signal to the output nextFrame. For subsequent frames with the same values for K and E, the block is ready sooner because it does not need to recompute the configuration. The waveform shows this new latency is 389 cycles. When the K and E values change to 54 and 124, respectively, the block must compute the new configuration and the latency changes to 443 cycles.

Performance

This table shows the resource and performance data synthesis results of the block when it is configured with K and E as input ports and the Link direction parameter set to Uplink. The generated HDL is targeted to an AMD^® Zynq^®-7000 ZC706 evaluation board. The design achieves a clock frequency of 450 MHz.

Resource	Number Used
Slice LUTs	637
Slice Registers	934
Block RAM	2.5

This table shows the resource and performance data synthesis results of the block when it is configured with K and E as input ports and the Link direction parameter set to Downlink. The generated HDL is targeted to a AMD Zynq-7000 ZC706 evaluation board. The design achieves a clock frequency of 450 MHz.

Resource	Number Used
Slice LUTs	600
Slice Registers	948
Block RAM	3.5

The block uses fewer resources when K and E are specified by parameters.

References

[1] 3GPP TS 38.212. "NR; Physical channels and modulation." 3rd Generation Partnership Project; Technical Specification Group Radio Access Network. URL: https://www.3gpp.org.

[2] Arikan, Erdal. "Channel Polarization: A Method for Constructing Capacity-Achieving Codes for Symmetric Binary-Input Memoryless Channels." IEEE Transactions on Information Theory 55, no. 7 (July 2009): 3051–73. https://doi.org/10.1109/TIT.2009.2021379.

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).

Restrictions

You cannot generate HDL for this block inside a Resettable Synchronous Subsystem (HDL Coder).

Version History

Introduced in R2020a