Successive Interference Cancellation in Generalized RAKE Receiver
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Solution Overview
Problem
Current wireless communication systems, particularly 3G WCDMA, face limitations in capacity due to multiple access interference (MAI) and intersymbol interference (ISI), which conventional RAKE receivers fail to address effectively, especially as the number of users increases, leading to poor signal detection for weak users.
Innovation Solution
A receiver circuit employing a Generalized RAKE (GRAKE) architecture with successive signal detection stages that cancel detected signals from prior stages, using impairment correlations to generate combining weights for improved signal detection and interference suppression.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional RAKE receivers are used to detect signals, then the signal detection process is simple, but multiple access interference (MAI) and intersymbol interference (ISI) cannot be effectively suppressed, limiting system capacity
Solution Approach 1:
The received signal is processed through multiple sequential detection stages, where each stage detects and cancels one user's signal. This segmentation of the detection process allows systematic removal of interference from multiple users, enabling effective suppression of MAI while maintaining manageable complexity at each stage.
Solution Approach 2:
Stronger user signals are detected and canceled first before detecting weaker signals. This preliminary action of removing dominant interference sources beforehand enables subsequent detection of weaker signals with improved accuracy, effectively addressing the interference limitation without requiring complex simultaneous processing.
2Productivity
If the number of users increases to enhance system capacity, then bandwidth utilization improves, but interference levels increase making weak user signals undetectable
Solution Approach 1:
The system performs preliminary detection and cancellation of stronger user signals before attempting to detect weaker signals. This sequential approach removes dominant interference sources in advance, enabling accurate detection of weak users even when many users are present, thus maintaining measurement precision while scaling system capacity.
Solution Approach 2:
The interference from other users, which normally degrades detection accuracy, is converted into a structured process where each user's signal is deliberately detected and canceled. By treating interference as detectable and removable components rather than random noise, the system maintains weak signal detection accuracy despite high user density.
3Measurement precision
If successive interference cancellation is implemented to suppress MAI and ISI, then signal detection accuracy improves, but receiver complexity increases
Solution Approach 1:
The complex task of multi-user detection is segmented into multiple simpler sequential stages, where each stage handles one user's signal detection and cancellation. This segmentation reduces the complexity of each individual processing block while achieving the overall goal of interference suppression, making the receiver practically implementable.
Solution Approach 2:
The receiver dynamically adapts its processing based on the detected signal strengths and interference conditions. By using decision feedback to adjust subsequent detection processes and employing selective cancellation based on detected bit values, the system optimizes its operation to balance accuracy improvement with complexity management.
Data Source
AI summary
A receiver includes a receiver circuit that decodes multiple signals of interest contained in a composite received signal. The receiver comprises a plurality of successive signal detection stages to detect respective signals contained in the composite received signal. Each detection circuit comprises at least one Generalized RAKE combining circuit and generates a detected signal at an output. Each but the last stage further comprises a signal regeneration circuit that cancels the signal of interest detected by that stage from a stage input signal provided to the next stage such that successive detection of the signals of interest benefits from cumulative cancellation of the previously detected signals.