OFDM Sub-Carrier Selection Diversity Receiver Architecture
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Solution Overview
Problem
Current OFDM receiver architectures with multiple antennas face challenges in reducing hardware complexity while maintaining performance, especially in mobile devices where power conservation is crucial, due to the need for multiple A/D and DFT processors and potential sub-carrier amplitude imbalances across antennas.
Innovation Solution
A sub-carrier selection diversity receiver architecture that senses a predetermined OFDM frequency band with multiple antennas, applies filtering to pass separate portions of the band, selects the strongest signal from each antenna in the time domain, and combines them using a single A/D and DFT, reducing hardware complexity and improving performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If frequency domain combining technique is used, then BER performance is improved, but hardware complexity increases due to multiple A/D and DFT processors
Solution Approach 1:
The patent extracts only the essential diversity combining function from the complex frequency domain processing chain. By selecting a single antenna's signal for each sub-carrier based on signal strength metrics, it achieves diversity benefits without requiring multiple A/D converters and DFT processors for each antenna, thus reducing hardware complexity while maintaining BER performance
Solution Approach 2:
The patent employs simple selection logic that compares signal metrics (such as pilot tone amplitude or estimated signal strength) from multiple antennas and selects the best one for each sub-carrier. This lightweight approach uses minimal processing resources compared to full frequency domain combining, achieving acceptable BER performance with significantly reduced hardware requirements
2Reliability
If multiple A/D and DFT processors are used for each antenna, then combining performance is improved, but power consumption increases
Solution Approach 1:
The patent extracts only the necessary signal metric information (such as pilot tone amplitude or signal strength estimate) from each antenna without performing full A/D conversion and DFT processing on all antenna signals. This selective extraction approach maintains combining performance by identifying the best antenna for each sub-carrier while dramatically reducing power consumption by avoiding redundant processing
Solution Approach 2:
The patent performs partial processing by calculating only the necessary signal metrics for diversity selection rather than complete frequency domain transformation for each antenna. This partial action approach achieves sufficient combining performance for mobile devices with constrained power budgets, avoiding the excessive power consumption of full multiple-A/D multiple-DFT processing
3Device complexity
If antenna selection diversity is used, then hardware complexity is reduced, but performance degrades due to sub-carrier amplitude imbalances
Solution Approach 1:
The patent applies different selection strategies to different sub-carriers based on their individual signal characteristics. For each sub-carrier, the system evaluates signal metrics and selects the antenna that provides the best quality signal for that specific sub-carrier, rather than using a single antenna for all sub-carriers. This local optimization approach maintains performance while using simpler hardware compared to full frequency domain combining
Solution Approach 2:
The patent changes the selection parameter from simple antenna switching to metric-based selection, where the decision of which antenna to use for each sub-carrier is based on measured signal characteristics such as pilot tone amplitude, signal strength, or estimated channel quality. This parameter-based selection compensates for sub-carrier amplitude imbalances and maintains performance with reduced hardware complexity
Data Source
AI summary
Sub-carrier selection methods and receiver architectures for receiving an Orthogonal Frequency Division Multiplexing band sensed by a plurality of antennas (101-10N). Filtering is applied to separately pass portions of the predetermined Orthogonal Division Multiplexing frequency band. Each separate portion encompasses one or more sub-bands of the predetermined Orthogonal Division Multiplexing frequency band. For each of the separate portions of the predetermined Orthogonal Division Multiplexing frequency band, the signal received from one of the plurality of antennas is selected. The selected signals for each separate portion are then combined in the time (analog) domain.