Successive Single-Stream Demapper for MIMO Interference Cancellation
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Solution Overview
Problem
High-rate multiple-input multiple-output (MIMO) systems face complexity challenges in achieving near-capacity performance due to exponential complexity in demapper computations, particularly in joint stream demappers, which limits practical implementation for spectral-efficiency beyond 16 coded bps/Hz, and parallel single-stream demappers struggle with interference cancellation and diversity gain in non-ideal channel conditions.
Innovation Solution
A successive single-stream demapper approach that demaps streams sequentially, utilizing updated soft-information from previously demapped streams for interference cancellation and spatial filtering, enabling interference cancellation from the first iteration and exploiting the latest soft-information for improved diversity gain.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If joint stream demapper (JSD) approach is used, then near-capacity performance is achieved, but demapper complexity becomes exponential
Solution Approach 1:
The patent segments the joint stream demapping process into multiple sequential single-stream demapping passes. Instead of performing joint detection over all transmitted streams simultaneously (which causes exponential complexity), the system demaps one stream at a time in succession, using the received signal and soft information from previously demapped streams to cancel interference and improve the detection of subsequent streams. This segmentation reduces complexity from exponential to manageable levels while maintaining near-capacity performance through iterative refinement.
2Device complexity
If parallel single-stream demapper (P-SSD) approach is used, then complexity is reduced, but interference cancellation performance deteriorates in non-ideal channel conditions
Solution Approach 1:
The patent applies preliminary action by performing interference cancellation using soft information from previously demapped streams before attempting to demap the current stream. In each successive pass, the system uses the latest soft information (a posteriori probabilities) from already-demapped streams to reconstruct and subtract interfering signals from the received signal. This preliminary interference cancellation improves the signal quality for the current stream being demapped, thereby enhancing detection performance in non-ideal channel conditions while maintaining low complexity.
3Ease of manufacture
If successive single-stream demapper uses decoder soft-information only, then implementation is simple, but diversity gain is limited
Solution Approach 1:
The patent implements feedback by using the latest soft information from previously demapped streams in the successive demapping process. Instead of relying solely on soft information from the outer decoder, the system feeds back the a posteriori probabilities computed during each single-stream demapping pass and uses them to improve interference cancellation for subsequent streams. This feedback mechanism allows the system to exploit the most recent detection results, thereby harvesting maximum diversity gain during each iteration while maintaining implementation simplicity through the single-stream demapping architecture.
Data Source
AI summary
A multiple-input multiple-output (MIMO) system for demapping uses a single stream system of iterative passes in a preferred order using the latest soft-information for better interference cancellation and the minimum mean square error (MMSE) criterion.