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LTE Convolutional Encoder

Encode binary samples using tail-biting convolutional algorithm

  • Library:
  • Wireless HDL Toolbox / Error Detection and Correction

  • LTE Convolutional Encoder block

Description

The LTE Convolutional Encoder block implements the encoding polynomials specified by LTE standard TS 36.212 [1]. The convolutional code has constraint length 7 and is tail biting with coding rate 1/3 and octal polynomials G0=133, G1=171 and G2=165. The block provides a hardware-optimized architecture and interface.

This block uses a streaming sample interface with a bus for related control signals. This interface enables the block to operate independently of frame size, and to connect easily with other Wireless HDL Toolbox™ blocks. The block accepts and returns a value representing a single sample, and a bus containing three control signals. These signals indicate the validity of each sample and the boundaries of the frame. To convert a matrix into a sample stream and these control signals, use the Frame To Samples block or the whdlFramesToSamples function. For a full description of the interface, see Streaming Sample Interface.

The message size can change dynamically. The encoded output bits for each input bit are returned as a 3-by-1 vector, [G0 G1 G2].

The block takes M + 5 cycles to encode a frame of M samples. Therefore, you must leave M + 5 idle cycles between input frames. Alternatively, you can use the output signal ctrl.end to determine when the block is ready for new input.

This waveform shows an input message of 40 samples, with 45 idle cycles between frames. The output data is a vector of three encoded bits. The input and output ctrl buses are expanded to show the control signals. start and end show the frame boundaries, and valid qualifies the data samples.

Ports

Input

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Input sample, specified as a binary scalar. double and single are supported for simulation but not for HDL code generation.

Data Types: single | double | Boolean | ufix1

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 sample, returned as a 3-by-1 column vector. Each encoded sample is represented by three bits, one from each encoder polynomial.

The output data type matches the input data type.

Data Types: single | double | Boolean | ufix1

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

Parameters

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Maximum input frame size, specified as a positive integer from 6 to 216. This parameter defines the required amount of frame memory. If you do not specify a power of two, the block uses the next largest power of two.

If an input frame is larger than the specified maximum message length, the block returns a warning.

Algorithms

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The block implements a tail-biting convolutional encoder as specified by LTE standard TS 36.212 [1].

References

[1] 3GPP TS 36.212. "Multiplexing and channel coding." 3rd Generation Partnership Project; Technical Specification Group Radio Access Network; Evolved Universal Terrestrial Radio Access (E-UTRA). URL: https://www.3gpp.org.

Extended Capabilities

See Also

Blocks

Functions

Introduced in R2017b