Tone-Interleaved MIMO OFDM Decoding With Lower Demapping Complexity
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Solution Overview
Problem
Existing MIMO OFDM systems face high computational complexity, particularly when the number of transmit antennas is large and the size of the QAM mapper is large, which degrades performance in typical MIMO channel conditions.
Innovation Solution
The MIMO OFDM system employs a tone-interleaved coded modulation (TICM) scheme, using a block of NT symbols as its basic unit for interleaving, merging soft-bit demapping into Viterbi decoding, and simplifying the list sphere decoding (LSD) algorithm to reduce computational complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an optimal multi-dimensional soft-bit demapper is applied to improve performance, then the computational complexity becomes very high
Solution Approach 1:
The patent segments the complex multi-dimensional demapping problem into multiple one-dimensional soft-bit demapping operations. By applying tone-interleaved coded modulation, the system divides the received signal processing into separate tone-based operations, where each tone can be independently demapped using simple 1-D soft-bit demappers instead of requiring a complex multi-dimensional demapper.
Solution Approach 2:
The patent introduces tone-interleaved coded modulation as an intermediary technique between the received signal and the demapping process. This intermediary structure reorganizes the signal processing flow, allowing the use of simpler 1-D soft-bit demappers while maintaining performance through the intermediate tone-interleaving and deinterleaving operations.
2Quantity of substance
If the number of transmit antennas and QAM mapper size are increased to improve channel capacity, then the computational complexity of decoding increases
Solution Approach 1:
The patent segments the decoding process into multiple independent one-dimensional operations based on tone-interleaving. Instead of performing complex joint decoding across all antennas and QAM dimensions simultaneously, the system divides the work into separate tone-based demapping operations, each handling a subset of the total complexity.
Solution Approach 2:
The patent transforms the high-dimensional decoding problem into a series of one-dimensional problems by introducing the tone dimension. The tone-interleaved structure adds a new dimension to the signal processing, allowing the system to handle multiple antennas and large QAM constellations by processing them across the tone dimension rather than requiring simultaneous high-dimensional operations.
Data Source
AI summary
A MIMO OFDM system for TICM includes a tone-level interleaver at the transmitter using a block of NT symbols as its basic unit. This results in different decoding architectures at the receiver. The main advantage of TICM is to merge soft-bit demapping into the Viterbi algorithm. Taking advantage of the trellis structure inherent in the Viterbi algorithm, TICM can have lower computational complexity and potentially better performance than BICM with the LSD detector and the vector demapper. Although the tone-level interleaving may not have spatial diversity gain, the performance is not affected in 802.11n environments.