Adaptive CIR Phase Classification for Reduced-Complexity Equalization
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Solution Overview
Problem
Dual antenna receivers in wireless communication systems face high computational complexity due to processing two streams of samples, which is exacerbated by the need for efficient interference cancellation and prefiltering in complex-valued modulation schemes like 8PSK, where existing methods like prediction error filters are complex and not suitable for all scenarios.
Innovation Solution
A method that identifies the Channel Impulse Response (CIR) as minimum, maximum, or mixed phase, and applies adaptive all-pass prefiltering only when necessary, using root identification and time-reversed processing to transform mixed and maximum phase signals to their minimum phase equivalents, thereby reducing complexity and improving performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If full state MLSE is employed for 8PSK modulation, then equalization performance is improved, but computational complexity becomes excessively high
Solution Approach 1:
The patent segments the equalization process into two parts: MLSE for leading taps and decision feedback for remaining taps. This segmentation reduces the state space from full MLSE to reduced state MLSE, making 8PSK equalization computationally feasible while maintaining performance through the decision feedback component.
Solution Approach 2:
The patent employs adaptive prefiltering that dynamically adjusts filter coefficients based on channel conditions. The prefilter transforms the channel impulse response to minimum phase form adaptively, optimizing the equalization performance for varying channel characteristics without requiring full state MLSE.
2Device complexity
If reduced state equalizers are used for 8PSK, then computational complexity is reduced, but performance loss is inevitable
Solution Approach 1:
The patent applies prefiltering as a preliminary action before the reduced state equalizer. By transforming the channel to minimum phase form beforehand, the equalization task becomes easier and more accurate, reducing the performance loss typically associated with reduced state equalizers.
Solution Approach 2:
The patent incorporates decision feedback in the reduced state equalizer structure. The feedback mechanism uses previously detected symbols to compensate for equalization errors, thereby improving overall performance and reducing the performance gap compared to full state MLSE.
3Reliability
If minimum phase prefiltering is applied, then performance loss in reduced state equalizers is reduced, but computational complexity increases
Solution Approach 1:
The patent changes the parameter representation of the channel by transforming it to minimum phase form. This parameter transformation concentrates energy in the leading taps, making the channel more suitable for reduced state equalization and improving performance without requiring full state MLSE.
4Reliability
If adaptive prefiltering is used in dual antenna receivers, then interference cancellation is improved, but computational complexity increases significantly
Solution Approach 1:
The patent segments the interference cancellation process across multiple antennas, applying prefiltering independently to each antenna's channel estimate. This segmentation allows parallel processing that improves interference cancellation while managing computational complexity through efficient resource utilization.
Data Source
AI summary
A method and transceiver for processing a signal in a communication system are provided. The method includes identifying a Channel Impulse Response (CIR) of the signal as of minimum phase, maximum phase, or mixed phase, processing the signal without performing prefiltering when the CIR is identified as minimum phase and performing all pass prefiltering of the signal when the CIR is identified as maximum phase or mixed phase. The transceiver includes a computation block and an all pass filter. The computation block identifies CIR of a signal as minimum phase, maximum phase, or mixed phase, performs root identification when the CIR of the signal is identified to be mixed phase and enables all pass filtering of the signal when the CIR of the signal is identified as mixed phase or maximum phase. The all pass filter transforms the signal to its minimum phase equivalent.