Adaptive OFDM Bit Interleaving for Variable Coded Bit Lengths
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional block interleaving in wireless communication systems is challenging when the number of coded bits is variable, as it requires a fixed number of bits to fill the interleaving matrix, which is not compatible with systems transmitting OFDM symbols with a variable number of bits.
Innovation Solution
The implementation of an adaptive interleaver that calculates the size of the interleaver matrix based on the variable number of coded bits per OFDM symbol and adds padding bits to ensure proper interleaving, allowing for efficient permutation and deinterleaving even when the number of coded bits is not fixed, using a transmitter and receiver with circuitry to perform adaptive bit loading and subcarrier modulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional block interleaving is used with a fixed interleaving matrix size, then the interleaving structure is simple and fixed, but it cannot accommodate variable numbers of coded bits in OFDM systems
Solution Approach 1:
The interleaver matrix dimensions are made dynamic rather than fixed. The number of rows and columns are determined adaptively based on the actual number of coded bits to be interleaved and the desired interleaving depth, allowing the system to handle variable bit lengths efficiently
Solution Approach 2:
The interleaver parameters (matrix dimensions, bit distribution pattern) are changed dynamically according to the input bit length. When the number of coded bits varies, the interleaver recalculates its parameters to maintain proper interleaving functionality without requiring a completely different structure
2Quantity of substance
If the interleaving matrix size is increased to accommodate more bits, then more bits can be interleaved, but the system becomes less efficient when fewer bits are transmitted
Solution Approach 1:
The interleaver matrix size dynamically adjusts to match the actual data volume. Instead of using a fixed large matrix that wastes resources when handling smaller data, the system calculates the appropriate matrix dimensions based on the current number of coded bits, maintaining high efficiency across different transmission conditions
Solution Approach 2:
The interleaver changes its operational parameters (matrix rows, columns, filling pattern) based on the input bit quantity. This allows the same interleaver structure to efficiently handle both small and large numbers of bits by adapting its parameters rather than being constrained to a fixed size
3Adaptability or versatility
If padding bits are added to fill the interleaving matrix, then variable bit lengths can be accommodated, but additional processing is required to add and remove padding bits
Solution Approach 1:
Padding bits are added in advance to fill the interleaving matrix before the interleaving operation occurs. This preliminary action ensures that the matrix is properly filled and the interleaving can proceed smoothly, with the understanding that padding removal will occur at the appropriate time
Solution Approach 2:
Padding bits serve as an intermediary element that facilitates the interleaving process for variable-length data. These temporary bits allow the fixed-structure interleaving operation to work correctly on variable inputs, and are subsequently removed to restore the original data length
Data Source
AI summary
An adaptive interleaver for wideband orthogonal frequency division multiplexed (OFDM) communications permutes a variable number of coded bits per OFDM symbol (Ncbps). The variable number of coded bits is calculated based on individual subcarrier modulation assignments for orthogonal subcarriers of a wideband channel. The interleaver matrix size may be based on the variable number of coded bits per OFDM symbol and the number of subchannels that comprise the wideband channel. The interleaver may add padding bits to the interleaver matrix to fill any remaining positions, and after performing an interleaving operation, the interleaver may prune the padding bits to provide a sequence of interleaved bits for subsequent modulation on the orthogonal subcarriers. A receiver may include an adaptive deinterleaver to reverse the process.