Scrambler

This modules provide interface for implementing the scrambler for PBCH, PDCCH and PDSCH. The implementation details of the Scramblers for PDSCH, PDCCH and PBCH are provided in Section 7.3.1.1, 7.3.2.3 and 7.3.3.1 of [3GPPTS38211_Scr].

Important

Scrambling just randomize the bit pattern. It doesn’t change the length of the input sequence

The scrambled can be used as follows: Scrambling for PBCH:

## Bits to be scrambled
bits    = np.random.randint(2, size = 32)

cellID  = 471 # Physical cell ID
Lmax    = 8   # Maximum number of candidate SS/PBCH blocks in a half frame

# Scrambler Object for PBCH
pbchScr = Scrambler("PBCH", cellID, Lmax)
# Scrambling the input Bits using the object
scrBits = pbchScr(bits)

Scrambling for PDCCH:

numBatch= 8    # Number of batches of input bits
# bits for scrambling
bits    = np.random.randint(2, size = (numBatch, 32))
rnti    = 1051  # RNTI value
nID     = 18548 # Scrambling ID
# Scrambler Object for PDCCH
pbchScr = Scrambler("PDCCH", rnti, nID)
## Scrambling the bits using object
scrBits = pbchScr(bits)

Scrambling for PDSCH:

numBatch= 8     # Number of batches
numBSs  = 3     # Number of BSs
# bits for scrambling
bits    = np.random.randint(2, size = (numBatch, numBSs, 512))
rnti    = 1151  # RNTI value
cbIndex = 0     # Codeblock Index
nID     = 39742 # Scrambling ID
# Scrambler Object for PDCCH
pbchScr = Scrambler("PDSCH", rnti, cbIndex, nID)
scrBits = pbchScr(bits) # Scrambling the bits using object

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

class toolkit5G.Scrambler.Scrambler(purpose, *args)[source]

Scrambles the input bits passed to the call method. The bits are scrambled using another set of bits randomly generated using a seed. This seed is calculated using the parameters passed as input the constructor. The first variable purpose defines the physical channel for whom scrambling is performed and *args accepts variable inputs with different understanding based on the purpose.

Parameters:

purpose (str) – Defines the physical channel for which the scrambling is being performed. It can take 6 values currently {“PBCH-1”, “PDCCH”, “PDSCH”, “PBCH-2”, “PSBCH”, “PSCCH”}.
*args – Its a Variable length argument list which accepts values based on the parameter purpose.
If purpose == “PBCH-1”:
- arg[0] is N_cell_ID (int) - physical cell ID \(N_{ID}^{cell} \in \{0,1,...,1007\}\)
- arg[1] is Lmax (int) - maximum number of candidate SS/PBCH blocks in a half frame (\(L_{max}\)), \(\in \{4, 8, 64\}\).
If purpose == “PBCH-2”:
- arg[0] is N_cell_ID (int) - physical cell ID \(N_{ID}^{cell} \in \{0,1,...,1007\}\)
- arg[1] is Lmax (int) - maximum number of candidate SS/PBCH blocks in a half frame (\(L_{max}\)), :math:`in {4, 8, 64}.
- arg[2] is ssbIndex (int or Numpy array, np.int) - It is the index pointing towards the SS/PBCH Block and must be lesser than (\(L_{max}\))
If purpose == “PDCCH”:
- arg[0] is rnti (int or NumPy array, np.int) - It defines the radio network temporary identifier (RNTI) \(\in \{1,2,..,65519\}\).
- arg[1] is id (int) - It is defined by pdcch-DMRS-ScramblingID \(\in \{0,1,2,..,65535\}\).
If purpose == “PSCCH”:
- No arguments required
If purpose == “PDSCH”:
- arg[0] is rnti (int or NumPy array, np.int) - It defines the radio network temporary identifier (RNTI) \(\in \{1,2,..,65519\}\).
- arg[1] is q (int or NumPy array, np.int) - It defines codeword index \(\in \{0,1\}\).
- arg[2] is nID (int or NumPy array, np.int) - It defines dataScramblingIdentityPDSCH(2), \(\text{n}_{\text{ID}} \in \{0,1,2,..,65535\}\).
If purpose == “PSBCH”:
-arg[0] is N_cell_ID (int) - Physical-layer sidelink synchronization identity. \(N_{ID}^{cell} \in \{0,1,...,671\}\).

Important

The array parameters passed to constructor must have equal lengths.

Input:: […, length], np.int8 – Input sequence
Output:: […, length], np.int8 – scrambled sequence.

Note

For PBCH, the length must be 32.

Raises:

ValueError – [Error-Scrambler]: Invalid choice for purpose!n Valid inputs are “”PBCH-1””, “”PDCCH””, “”PBCH-2””, “”PSBCH””, “”PSCCH”” and, “”PDSCH””
ValueError – [Error-Scrambler]: inBits must be an NumPy integer array!
ValueError – [Error-Scrambler]: Number of MIB bits must be 32 only!
ValueError – [Error-Scrambler]: rnti in PD(S|C)CH scramber must be an integer/array!
ValueError – [Error-Scrambler]: rnti in PD(S|C)CH scramber must be +ve integer/array!
ValueError – [Error-Scrambler]: q ‘(codeword-Index)’ in PD(S|C)CH scramber must be an integer/array!
ValueError – [Error-Scrambler]: q ‘(codeword-Index)’ in PD(S|C)CH scramber must be +ve integer/array!
ValueError – [Error-Scrambler]: q ‘(codeword-Index)’ in PD(S|C)CH scramber must be have size same as ‘rnti’!
ValueError – [Error-Scrambler]: nID in PD(S|C)CH scramber must be an integer/array!
ValueError – [Error-Scrambler]: nID in PD(S|C)CH scramber must be +ve integer/array!
ValueError – [Error-Scrambler]: nID in PD(S|C)CH scramber must be have size same as ‘rnti’!
ValueError – [Error-Scrambler]: rnti in pdcch scramber must be +ve integer!
ValueError – [Error-Scrambler]: id in pdcch scramber must be +ve integer!
ValueError – [Error-Scrambler]: Lmax in pdcch scramber must be +ve integer!
ValueError – [Error-Scrambler]: ssbIndex in scrambler must be lesser than (\(L_{max}\))!
ValueError – [Error-Scrambler]: A ‘size of payload’ in pdcch scramber must be +ve integer!

property Lmax: Defines the maximum number of candidate SS/PBCH blocks in a half frame (\(L_{max}\)), \(\in \{4, 8, 64\}\).

property c_init: Defines the seed used for generating the random variables for scrambling.

property id: Defines the pdcch-DMRS-ScramblingID \(\in \{0,1,2,..,65535\}\).

property mu: \({\nu}\) is internally calculated for scrambling PBCH-2.

property nID: Defines dataScramblingIdentityPDSCH(2), \(\text{n}_{\text{ID}} \in \{0,1,2,..,65535\}\).

property purpose: Defines the physical channel for which the scrambling is being performed. It can take 4 values currently {“PBCH”, “PDCCH”, “PDSCH”}.

property q: Defines codeword index \(\in \{0,1\}\).

property rnti: Defines the radio network temporary identifier (RNTI) \(\in \{1,2,..,65519\}\).

property ssbIndex: Defines the maximum number of candidate SS/PBCH blocks in a half frame (\(L_{max}\)), \(\in \{4, 8, 64\}\).

References:: [3GPPTS38211_Scr]
3GPP TS 38.211 “Physical channels and modulation (Release 17)”, V17.1.0 (2022-03).