Rake Receiver Finger Assignment by Signal Path Concentration
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Solution Overview
Problem
In high-speed fading scenarios, conventional rake receivers struggle to identify all signal paths within the limited time available when user equipment wakes up from sleep mode, leading to suboptimal performance in CDMA systems.
Innovation Solution
A rake receiver finger assignor assigns fingers to time offsets based on the concentration of identified signal paths, with at least one finger assigned between identified paths during fat path conditions, and remaining fingers assigned at half-chip intervals from the signal path with the least loss, maximizing the use of signal paths for demodulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the searcher identifies all signal paths in conventional rake receivers, then the receiver performance is improved, but the time required for path identification increases, reducing battery life
Solution Approach 1:
The patent applies partial action by assigning fingers based on the subset of identified signal paths rather than requiring complete identification of all paths. During fat path conditions, the system uses concentration metrics to determine finger assignment from the identified paths, accepting that not all paths are identified but achieving sufficient performance with the identified subset. This resolves the contradiction by achieving acceptable receiver performance without requiring complete path identification within the limited wake-up time.
Solution Approach 2:
The patent changes the parameter of finger assignment strategy based on the concentration metric of identified signal paths. When the concentration indicates fat path conditions, the system adjusts its finger assignment approach to utilize the identified paths more effectively. This dynamic parameter change allows the system to adapt to different channel conditions and achieve good performance without requiring complete path identification, thus resolving the time-performance tradeoff.
2Reliability
If the searcher identifies all signal paths, then the receiver performance is improved, but the complexity of the identification process increases
Solution Approach 1:
The system performs partial path identification by using the subset of paths identified within the available time rather than attempting to identify all paths. The finger assignor works with the identified paths and their concentration metrics, avoiding the need for complete path identification. This reduces searcher complexity while maintaining acceptable receiver performance.
Solution Approach 2:
The finger assignor automatically determines the assignment strategy based on the concentration metric of identified paths without requiring external control or complex optimization algorithms. The system self-adjusts its finger assignment based on the observed path concentration, simplifying the overall system complexity while maintaining performance.
3Reliability
If fingers are assigned to all identified signal paths, then the receiver performance is improved, but the number of fingers required increases
Solution Approach 1:
The patent merges the function of multiple fingers by assigning multiple fingers to process signals from the same or nearby time offsets when path concentration is high. Instead of assigning one finger per identified path, the system consolidates finger usage by exploiting the concentration information, thereby reducing the total number of fingers needed while maintaining or improving receiver performance through effective combining of signal paths.
Data Source
AI summary
A rake receiver finger assignor is configured to assign a rake receiver finger to a time offset between identified signal path time offsets in accordance with a concentration of identified signal paths from a transmitter to a rake receiver. In accordance with the exemplary embodiment, a number of identified signal paths having time offsets within a time window are observed to determine the concentration of signal paths identified by a path searcher. If the number of identified signal paths indicates a concentrated distribution of signal paths such as during a fat path condition, at least one rake finger is assigned between at a time offset between two identified signal paths.