Interference Cancellation Using Hard Decisions and Soft Scaling
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Solution Overview
Problem
In wireless communication systems, interference between signals due to transmission synchronization errors and channel effects complicates signal recovery, especially in MIMO systems, where current interference cancellation methods require full-complexity processing, making them inefficient for low-complexity receivers.
Innovation Solution
Implementing hard decision logic for simplified estimation of interfering signals combined with soft scaling based on received signal quality to improve interference cancellation performance, particularly in low signal quality conditions, without the need for complex heuristic mechanisms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If full-complexity demodulation and decoding is applied to interfering signals, then interference cancellation accuracy is improved, but receiver processing complexity increases significantly
Solution Approach 1:
The patent segments the interference cancellation process into two distinct stages: (1) hard decision processing for initial interference signal estimation, and (2) soft scaling for performance enhancement. This segmentation allows the system to avoid full-complexity processing while maintaining acceptable accuracy through the combination of simplified hard decisions and adaptive soft scaling factors.
Solution Approach 2:
Instead of applying full soft-value processing to interfering signals, the patent applies partial processing by using hard decisions followed by soft scaling. This partial action approach achieves sufficient interference cancellation performance for low-complexity receivers without the excessive computational burden of complete demodulation and decoding of interfering signals.
2Device complexity
If hard detection processing is used for interferer signal estimation, then receiver complexity is reduced, but interference cancellation performance deteriorates
Solution Approach 1:
The patent introduces soft scaling factors as an intermediary element between hard detection and interference cancellation. These scaling factors, derived from signal quality metrics, act as a mediator that compensates for the accuracy loss inherent in hard detection, thereby improving interference cancellation performance without requiring full soft-value processing.
Solution Approach 2:
The patent changes the parameter of interference signal estimation from fixed hard decisions to adaptive hard decisions with soft scaling. By dynamically adjusting the scaling factor based on signal quality conditions, the system transforms a static low-accuracy estimation process into a dynamic process that adapts to varying channel conditions, improving performance across different signal quality ranges.
Data Source
AI summary
The teachings herein disclose interference cancellation processing that uses hard decision logic for simplified estimation of interfering signals, in combination with soft scaling of the hard decisions for better interference cancellation performance, particularly in low signal quality conditions. In one aspect, the soft scaling may be understood as attenuating the amount of interference cancellation applied by a receiver, in dependence on the dynamically changing received signal quality at the receiver. More attenuation is applied at lower signal quality because the hard decisions are less reliable at lower signal qualities, while less (or no) attenuation is applied at higher signal qualities, reflecting the higher reliability of the hard decisions at higher signal qualities. Signal quality may be quantized into ranges, with a different value of soft scaling factor used for each range, or a soft scaling factor may be calculated for the continuum of measured signal quality.