CRC Decoder

CRC Decoder assumes the parity bits attached at the end of the payload to detect the errors in the information bits. If the CRC Check is False, there is error in the received data otherwise the received data is error free. CRC Decoder uses Sionna CRC Encoder internally. The has been design to pass input exactly same as Sionna CRC Encoder for compatibility.

Important

  • If CRC check fails, the receiver request for retransmission using hybrid automatic repeat request (HARQ).

The CRC decoder can be used as follows:

CRC Encoding for 1D NumPy Arrays

bits       = np.random.randint(0, 2, size = (1,32)) # Bits to be Encoded
crcType    = "CRC24C"

## CRC Encoding
crcEncoder = CRCEncoder(crcType) # Create object of CRC Encoder
crcBits    = crcEncoder(bits)    # Encode the bits (attach the CRC at the end)
## Shape of crcBits will be (1, 56)

## CRC Decoding
crcDecoder    = CRCDecoder(crcType)
rBits, checks = crcDecoder(crcBits)
## Shape of rBits will be (1, 32), checks will be true or false

CRC Encoding for 2D NumPy Arrays

bits       = np.random.randint(0, 2, size = (21,64)) # Bits to be Encoded
crcType    = "CRC16"

## CRC Encoding
crcBits    = CRCEncoder(crcType)(bits)    # Encode the bits (attach the CRC at the end)
## Shape of Output will be (21, 80)

## CRC Decoding
crcDecoder    = CRCDecoder(crcType)
rBits, checks = crcDecoder(crcBits)
## Shape of rBits will be (21, 64) | checks is an array of dimension (21,) containing true or false

CRC Encoding for Higher dimension NumPy Arrays

bits       = np.random.randint(0, 2, size = (8,6,119)) # Bits to be Encoded
crcType    = "CRC6"

## CRC Encoding
crcBits    = CRCEncoder(crcType)(bits)    # Encode the bits (attach the CRC at the end)
## Shape of Output will be (8, 6, 125)

## CRC Decoding
crcDecoder    = CRCDecoder(crcType)
rBits, checks = crcDecoder(crcBits)
## Shape of rBits will be (8,6,119), checks is an array of dimension (8, 6) containing true or false

The details about the input-output interface of the Mapper modules is provided below.

class toolkit5G.CRC.CRCDecoder(crcType, dtype=None, *arg)[source]

The module inserts the cyclic redundency bits to the bits passed to the call method. The parity bits are generated using the cyclic generator polynomials passed to the constructor (init) method. This class uses CRCEncoder from sionna.fec.crc.CRCEncoder .

Parameters:

  • crcType (str) – It defines the CRC type \(\in \{\text{"CRC24A"}, \text{"CRC24B"},\) \(\text{"CRC24C"}, \text{"CRC16"}, \text{"CRC11"}, \text{"CRC6"}\}\).

  • *args (arguments) – As per sionna.fec.crc.CRCDecoder .

Input:

[…, length], np.int8 – Input sequence

Output:

  • […, length-crcLength], np.int8 – CRC decoded sequence.

  • […, 1], np.bool – CRC checks for each dimension.

Warning

length of Input sequence should be > crcLength

Note

crcLength is 24, 24, 24,16, 11, 6 for crcType \(= \{\text{"CRC24A"}, \text{"CRC24B"}, \text{"CRC24C"},\) \(\text{"CRC16"}, \text{"CRC11"}, \text{"CRC6"}\}\) respectively.

Raises:

ValueError – [Error-CRCDecoder]: ‘inBits’ must be an NumPy array of number!