LDPC 5G
This module contains the API for using the GPU-accelerated LDPC coding chain from the cuPHY library. This includes encoding and decoding as well as rate matching. Code block segmentation and concatenation are implemented in Python. Additionally, this module contains a number of utility functions for example for determining the LDPC base graph, transport block size, etc.
- class aerial.phy5g.ldpc.decoder.LdpcDecoder
LDPC decoder.
This class supports decoding of LDPC code blocks encoded following TS 38.212. It uses cuPHY accelerated LDPC decoding routines under the hood.
- __init__(num_iterations=10, throughput_mode=False, cuda_stream=None)
Initialize LdpcDecoder.
- Parameters
num_iterations (int) – Number of LDPC decoder iterations. Default: 10.
throughput_mode (bool) – Enable throughput mode. Default: False.
cuda_stream (int) – The CUDA stream. If not given, one will be created.
- Return type
None
- decode(input_llrs, tb_sizes, code_rates, redundancy_versions, rate_match_lengths, num_iterations=None)
Decode function for LDPC decoder.
The decoder outputs decoded code blocks which can be further concatenated into the received transport block using
code_block_desegment()
.- Parameters
input_llrs (List[np.ndarray]) – Input LLRs per UE, each array is a N x C array of 32-bit floats, N being the number of LLRs per code block and C being the number of code blocks.
tb_sizes (List[int]) – Transport block size in bits, without CRC, per UE.
code_rates (List[float]) – Target code rates per UE.
redundancy_versions (List[int]) – Redundancy version, i.e. 0, 1, 2, or 3, per UE.
rate_match_lengths (int) – Number of rate matching output bits of each UE. This is equal to N.
num_iterations (Optional[int]) –
- Returns
The decoded bits in a numpy array.
- Return type
List[np.ndarray]
- set_num_iterations(num_iterations)
Set a particular value for the number of iterations to be run.
- Parameters
num_iterations (int) – Value of the number of iterations.
- Return type
None
- set_throughput_mode(throughput_mode)
Enable throughput mode.
- Parameters
throughput_mode (bool) – Enable (True) throughput mode.
- Return type
None
- get_soft_bits()
Get the soft bit output from the decoder.
- Returns
The soft bits in a numpy array.
- Return type
List[np.ndarray]
- class aerial.phy5g.ldpc.encoder.LdpcEncoder
LDPC encoder.
This class provides encoding of transmitted transport block bits using LDPC coding following TS 38.212. The encoding process is GPU accelerated using cuPHY routines. As the input, the transport blocks are assumed to be attached with the CRC and segmented to code blocks (as per TS 38.212).
- __init__(num_profiling_iterations=0, puncturing=True, max_num_code_blocks=152, cuda_stream=None)
Initialize LdpcEncoder.
Initialization does all the necessary memory allocations for cuPHY.
- Parameters
num_profiling_iterations (int) – Number of profiling iterations. Set to 0 to disable profiling. Default: 0.
puncturing (bool) – Whether to puncture the systematic bits (2Zc). Default: True.
max_num_code_blocks (int) – Maximum number of code blocks. Memory is allocated based on this. Default: 152.
cuda_stream (int) – The CUDA stream. If not given, one will be created.
- Return type
None
- encode(input_data, tb_size, code_rate, redundancy_version)
Encode function for LDPC encoder.
The input to this function is code blocks, meaning that the code block segmentation is expected to be done before calling this function. Code block segmentation can be done using
code_block_segment()
.- Parameters
input_data (np.ndarray) – The input code blocks as a K x C array where K is the number of input bits per code block (including CRCs) and C is the number of code blocks. The dtype of the input array must be np.float32.
tb_size (int) – Transport block size in bits, without CRC.
code_rate (float) – Target code rate.
redundancy_version (int) – Redundancy version, 0, 1, 2, or 3.
- Returns
Encoded bits as a N x C array where N is the number of encoded bits per code block.
- Return type
np.ndarray
- set_profiling_iterations(num_profiling_iterations)
Set a particular value for the number of profiling iterations to be run.
- Parameters
num_profiling_iterations (int) – Value of the number of profiling iterations.
- Return type
None
- set_puncturing(puncturing)
Set puncturing flag.
- Parameters
puncturing (bool) – Whether to puncture the systematic bits (2*Zc). Default: True.
- Return type
None
- class aerial.phy5g.ldpc.rate_match.LdpcRateMatch
LDPC rate matching.
- __init__(enable_scrambling=True, num_profiling_iterations=0, max_num_code_blocks=152, cuda_stream=None)
Initialize LdpcRateMatch.
Initialization does all the necessary memory allocations for cuPHY.
- Parameters
enable_scrambling (bool) – Whether to enable scrambling after code block concatenation.
num_profiling_iterations (int) – Number of profiling iterations. Set to 0 to disable profiling. Default: 0 (no profiling).
max_num_code_blocks (int) – Maximum number of code blocks. Memory will be allocated based on this number.
cuda_stream (int) – The CUDA stream. If not given, one will be created.
- Return type
None
- rate_match(input_data, tb_size, code_rate, rate_match_len, mod_order, num_layers, redundancy_version, cinit)
LDPC rate matching function.
This function does rate matching of LDPC code blocks following TS 38.212. If scrambling is enabled, it also scrambles the rate matched bits. In this case the c_init value needs to be set to an appropriate scrambling sequence initialization value.
- Parameters
input_data (np.ndarray) – Input bits as a N x C numpy array with dtype np.float32, where N is the number of bits per code block and C is the number of code blocks.
tb_size (int) – Transport block size in bits without CRC.
code_rate (float) – Code rate.
rate_match_len (int) – Number of rate matching output bits.
mod_order (int) – Modulation order.
num_layers (int) – Number of layers.
redundancy_version (int) – Redundancy version, i.e. 0, 1, 2, or 3.
cinit (int) – The c_init value used for initializing scrambling.
- Returns
Rate matched bits.
- Return type
np.ndarray
- set_profiling_iterations(num_profiling_iterations)
Set a particular value for the number of profiling iterations to be run.
- Parameters
num_profiling_iterations (int) – Value of the number of profiling iterations.
- Return type
None
- class aerial.phy5g.ldpc.derate_match.LdpcDeRateMatch
LDPC derate matching.
- __init__(enable_scrambling=True, cuda_stream=None)
Initialize LdpcDeRateMatch.
Initialization does all the necessary memory allocations for cuPHY.
- Parameters
enable_scrambling (bool) – Whether to descramble the bits before derate matching. Default: True.
cuda_stream (int) – The CUDA stream. If not given, one will be created.
- Return type
None
- derate_match(input_llrs, tb_sizes, code_rates, rate_match_lengths, mod_orders, num_layers, redundancy_versions, ndis, cinits, ue_grp_idx=None)
LDPC derate matching function.
- Parameters
input_llrs (List[np.ndarray]) – Input LLRs as a N x 1 numpy array with dtype np.float32, where N is the number of LLRs coming from the equalizer. Ordering of this input data is bitsPerQam x numLayers x numSubcarriers x numDataSymbols. One entry per UE group.
tb_sizes (List[int]) – Transport block sizes in bits without CRC, per UE.
code_rates (List[float]) – Code rates per UE.
rate_match_lengths (List[int]) – Number of rate matching output bits, the same as N, per UE.
mod_orders (List[int]) – Modulation order per UE.
num_layers (List[int]) – Number of layers per UE.
redundancy_versions (List[int]) – Redundancy version, i.e. 0, 1, 2, or 3, per UE.
ndis (List[int]) – New data indicator per UE.
cinits (List[int]) – The c_init value used for initializing scrambling for each UE.
ue_grp_idx (List[int]) – The UE group index for each UE. Default is one-to-one mapping.
- Returns
Derate matched LLRs for each UE.
- Return type
List[np.ndarray]
- aerial.phy5g.ldpc.util.get_mcs(mcs, table_idx=2)
Get modulation order and code rate based on MCS index.
- Parameters
mcs (int) – MCS index pointing to the table indicated by table_idx.
table_idx (int) – Index of the MCS table in TS 38.214 section 5.1.3.1. Values: - 1: TS38.214, table 5.1.3.1-1. - 2: TS38.214, table 5.1.3.1-2. - 3: TS38.214, table 5.1.3.1-3.
- Returns
A tuple containing:
int: Modulation order.
float: Code rate * 1024.
- Return type
int, float
- aerial.phy5g.ldpc.util.get_tb_size(mod_order, code_rate, dmrs_syms, num_prbs, start_sym, num_symbols, num_layers)
Get transport block size based on given parameters.
Determine transport block size as per TS 38.214 section 5.1.3.2.
- Parameters
mod_order (int) – Modulation order.
code_rate (float) – Code rate * 1024 as in section 5.1.3.1 of TS 38.214.
dmrs_syms (List[int]) – List of binary numbers indicating which symbols contain DMRS.
num_prbs (int) – Number of PRBs.
start_sym (int) – Starting symbol.
num_symbols (int) – Number of symbols.
num_layers (int) – Number of layers.
- Returns
Transport block size in bits.
- Return type
int
- aerial.phy5g.ldpc.util.get_base_graph(tb_size, code_rate)
Get LDPC base graph.
- Parameters
tb_size (int) – Transport block size in bits, without CRC.
code_rate (float) – Code rate.
- Returns
Base graph, 1 or 2.
- Return type
int
- aerial.phy5g.ldpc.util.max_code_block_size(base_graph)
Get maximum LDPC code block size based on base graph.
- Parameters
base_graph (int) – Base graph, 1 or 2.
- Returns
Maximum code block size.
- Return type
int
- aerial.phy5g.ldpc.util.find_lifting_size(base_graph, tb_size)
Find lifting size for base graph.
- Parameters
base_graph (int) – Base graph, 1 or 2.
tb_size (int) – Transport block size in bits without CRC.
- Returns
Lifting size.
- Return type
int
- aerial.phy5g.ldpc.util.get_num_info_nodes(base_graph, tb_size)
Get number of information nodes.
Note: This is the value K_b in TS 38.212.
- Parameters
base_graph (int) – Base graph, 1 or 2.
tb_size (int) – Transport block size without any CRCs.
- Returns
The number of information nodes (K_b).
- Return type
int
- aerial.phy5g.ldpc.util.get_code_block_num_info_bits(base_graph, tb_size)
Get number of information bits in a code block.
This is the number K’ in TS 38.212, i.e. the number of information bits without the filler bits.
- Parameters
base_graph (int) – Base graph, 1 or 2.
tb_size (int) – Transport block size in bits, without CRC.
- Returns
Number of information bits in a code block.
- Return type
int
- aerial.phy5g.ldpc.util.get_code_block_size(tb_size, code_rate)
Get code block size.
This is the number K in TS 38.212, i.e. the number of information bits including filler bits.
- Parameters
tb_size (int) – Transport block size in bits, without CRC.
code_rate (float) – Code rate.
- Returns
Code block size.
- Return type
int
- aerial.phy5g.ldpc.util.get_num_code_blocks(tb_size, code_rate)
Return the number of code blocks for a transport block.
- Parameters
tb_size (int) – Transport block size in bits, without CRC.
code_rate (float) – Code rate.
- Returns
The number of code blocks (C).
- Return type
int
- aerial.phy5g.ldpc.util.code_block_segment(tb_size, transport_block, code_rate)
Do code block segmentation.
This function does code block segmentation as per TS 38.212 section 5.2.2. Randomly generated 24-bit string is attached to each code block to emulate code block CRC if there is more than one code block.
- Parameters
tb_size (int) – Transport block size in bits, without CRC.
transport_block (np.ndarray) – Transport block in bits, CRC included.
code_rate (float) – Code rate.
- Returns
The code blocks.
- Return type
np.ndarray
- aerial.phy5g.ldpc.util.code_block_desegment(code_blocks, tb_size, code_rate, return_bits=True)
Concatenate code blocks coming from LDPC decoding into a transport block.
This function desegments code blocks into a transport block as per TS 38.212, and removes the CRCs, i.e. does the opposite of
code_block_segment()
.- Parameters
code_blocks (np.ndarray) – The code blocks coming out of the LDPC decoder as a N x C array.
tb_size (int) – Transport block size, without CRC.
code_rate (float) – Code rate.
return_bits (bool) – If True (default), give the return value in bits. Otherwise convert to bytes.
- Returns
The transport block with CRC, in bits or bytes depending on the value of return_bits.
- Return type
np.ndarray
- aerial.phy5g.ldpc.util.add_crc_len(tb_size)
Append CRC length to transport block size.
- Parameters
tb_size (int) – Transport block size in bits without CRC.
- Returns
Transport block size in bits with CRC.
- Return type
int
- aerial.phy5g.ldpc.util.random_tb(mod_order, code_rate, dmrs_syms, num_prbs, start_sym, num_symbols, num_layers, return_bits=False)
Generate a random transport block.
Generates random transport block according to given parameters. The transport block size is first determined as per TS 38.214 section 5.1.3.2.
- Parameters
mod_order (int) – Modulation order.
code_rate (float) – Code rate * 1024 as in section 5.1.3.1 of TS 38.214.
dmrs_syms (List[int]) – List of binary numbers indicating which symbols contain DMRS.
num_prbs (int) – Number of PRBs.
start_sym (int) – Starting symbol.
num_symbols (int) – Number of symbols.
num_layers (int) – Number of layers.
return_bits (bool) – Whether to return the transport block in bits (True) or bytes (False).
- Returns
Random transport block payload.
- Return type
np.ndarray
- aerial.phy5g.ldpc.util.get_crc_len(tb_size)
Return CRC length based on transport block size.
- Parameters
tb_size (int) – Transport block size in bits without CRC.
- Returns
CRC length (either 16 or 24 bits).
- Return type
int