Wireless Bit Grouping for Uniform Reliability in QAM Transmission
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Solution Overview
Problem
The existing bit grouping method in IEEE 802.16m systems does not distribute bit reliability uniformly, particularly for high-order modulation schemes like 16 QAM or 64 QAM, leading to uneven bit reliability distribution for systematic and parity bits during decoding trellis transitions.
Innovation Solution
The proposed method involves mapping systematic bits to the first and second subblocks and parity bits to the third to sixth subblocks, followed by subblock interleaving and circularly shifting the first subblock by a predetermined bit, generating output sequences that are then transmitted.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If bit grouping is performed using conventional methods in IEEE 802.16m systems, then the encoding and transmission process can be completed, but bit reliability is not distributed uniformly across systematic and parity bits during decoding trellis transitions
Solution Approach 1:
The encoded bit sequence is divided into six subblocks (A, B, Y1, Y2, W1, W2) with systematic bits mapped to subblocks A and B, and parity bits mapped to subblocks Y1, Y2, W1, and W2. This segmentation allows independent interleaving and circular shifting operations on each subblock, enabling uniform bit reliability distribution while maintaining manageable processing complexity for each individual subblock.
Solution Approach 2:
Circular shifting is performed on the interleaved subblocks before the final bit grouping and transmission. This preliminary reordering action ensures that bits with different reliability levels are properly distributed across the codeword sequence before modulation, achieving uniform reliability distribution without requiring complex real-time adjustments during decoding.
2Productivity
If high-order modulation schemes (16 QAM or 64 QAM) are used to increase data rate, then transmission capacity is improved, but bit reliability distribution becomes uneven during decoding trellis transitions
Solution Approach 1:
Different subblocks are assigned different functions: subblocks A and B contain systematic bits while subblocks Y1, Y2, W1, and W2 contain parity bits. Circular shifting is applied specifically to the interleaved subblocks to ensure that both systematic and parity bits achieve uniform reliability distribution. This localized differentiation allows high-order modulation to maintain both high data rates and uniform bit reliability.
3Reliability
If subblock interleaving is performed on all six subblocks, then bit scrambling and reliability distribution are improved, but processing complexity increases
Solution Approach 1:
The same subblock interleaver structure and interleaving procedure are applied uniformly to all six subblocks (A, B, Y1, Y2, W1, W2). This merging of the interleaving approach across all subblocks simplifies the overall processing complexity by reusing the same algorithm and data structures, while still achieving improved bit reliability distribution through the combined effect on all subblocks.
Data Source
AI summary
An apparatus and method for transmitting a signal using a bit grouping method in a wireless communication system is disclosed. Interleaved subblocks are maintained, and output bit sequences are modulated in due order after bit grouping and bit selection. The bit grouping method is advantageous in that bit reliability is uniformly distributed.