802.11n MIMO Interleaver With Multi-Rotation Bit Separation
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Solution Overview
Problem
Conventional OFDM MIMO systems do not fully utilize diversity gain due to limited column rotation in interleaving processes, leading to reduced reliability in correlated channels.
Innovation Solution
Implementing multiple column rotations and additional row rotations in the interleaving process, along with frequency rotation, to separate adjacent bits across spatial streams and subcarriers, enhancing diversity and flexibility in channel coding and modulation schemes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If single column rotation is used in conventional interleaving, then implementation is simple, but diversity gain is not fully utilized and reliability is reduced in correlated channels
Solution Approach 1:
The interleaving process is divided into multiple independent column rotation operations (first column rotation and second column rotation) with different rotation amounts. This segmentation allows each rotation to contribute differently to diversity gain, resolving the contradiction by making the system more reliable through multiple rotations while keeping each individual rotation operation simple and manageable.
Solution Approach 2:
The invention adds an additional dimension to the interleaving process by introducing a second column rotation operation with a different rotation amount than the first rotation. This multi-dimensional approach to column rotation enhances diversity gain and reliability without significantly increasing implementation complexity, as each rotation operates independently along the same dimensional space.
2Reliability
If multiple column rotations are implemented, then diversity gain is enhanced, but implementation complexity increases
Solution Approach 1:
The multiple column rotations are segmented into distinct operations with different rotation amounts (first column rotation with amount R1, second column rotation with amount R2). This segmentation allows the system to achieve enhanced diversity gain through multiple rotations while maintaining manageable implementation complexity by treating each rotation as a separate, well-defined operation.
Solution Approach 2:
The invention applies partial rotations (rotations by specific amounts R1 and R2 that are less than complete 360-degree rotations) rather than full cycles. This partial action approach achieves the necessary diversity gain for improved reliability while avoiding the excessive complexity that would result from multiple complete rotation cycles.
3Reliability
If adjacent bits are mapped close together, then mapping is simple, but bits are likely to experience the same fading channel reducing decoding capability
Solution Approach 1:
The bit mapping process is segmented into multiple stages: first column rotation separates adjacent bits by R1 positions, followed by second column rotation that further separates them by additional R2 positions. This segmented approach ensures bits are distributed across different fading channels, improving decoding capability while keeping each mapping stage relatively simple and systematic.
Solution Approach 2:
The invention uses multi-dimensional separation by applying column rotations in sequence with different rotation amounts. This creates a multi-layered separation effect where bits are dispersed not just by a single rotation amount but by cumulative effects of multiple rotations, enhancing protection against fading channels while maintaining systematic mapping complexity.
Data Source
AI summary
A MIMO wireless system includes a transmitter having a parser that parses a bit stream into multiple spatial data streams and multiple interleavers corresponding to the multiple spatial data streams, where each interleaver interleaves the bits in the corresponding spatial data stream by performing frequency rotation after an interleaving operation, to increase diversity of the wireless system. The MIMO wireless system also includes a receiver that has deinterleavers that deinterleaves spatial bit streams transmitted by the transmitter.