MIMO OFDMA Transmitter Diversity via CINR-Based Antenna Selection
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Solution Overview
Problem
MIMO OFDMA systems face challenges in transmitter diversity, including performance degradation in AWGN channels, complexity in weight vector calibration, and limited service range, as well as complex processes requiring special standards and interactions between base stations and mobile stations.
Innovation Solution
A signal processing technique that uses a channel estimator to estimate channel responses, an equalizer and combiner to generate equalized and combined signals, and a CINR estimator to select the best antenna path for transmitter diversity, achieving improved performance without requiring special standards or complex processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If space time coding (STC) scheme is used for transmitter diversity, then coding gain and space-temporal diversity are achieved, but performance degrades in AWGN channel and maximum service range is limited
Solution Approach 1:
The system dynamically switches between different operational modes (STC mode and selection diversity mode) based on channel conditions. The base station determines whether to use space-time coding or antenna selection based on feedback from mobile stations about channel quality, allowing the system to adapt to varying channel environments including AWGN conditions where STC performs poorly.
Solution Approach 2:
The system changes operational parameters by switching between different transmitter diversity schemes. When channel conditions indicate poor multi-path characteristics, the system transitions from STC scheme to antenna selection scheme, effectively changing the diversity mechanism to match channel characteristics and maintain performance.
2Reliability
If equal power joint maximum ratio combining method is used, then beam-forming based system is achieved, but complexity increases requiring complex weight vectors and calibration procedures
Solution Approach 1:
The invention extracts and uses only the channel response information that is already being estimated for equalization purposes. Instead of implementing complex joint maximum ratio combining with full weight vector calculation, the system selects antenna paths based on the magnitude of channel responses that are already available from the channel estimator, simplifying the diversity implementation.
Solution Approach 2:
The channel estimator, which is already performing channel response estimation for equalization, additionally provides channel magnitude information for antenna selection. This self-service approach allows the diversity function to utilize existing estimation results without requiring separate complex calibration procedures or weight vector calculations.
3Productivity
If time domain processing or interactive processing is used, then signal processing capability is improved, but complexity increases requiring hand-shaking or collaboration between base station and mobile station
Solution Approach 1:
The mobile station performs channel response estimation and reports channel quality information to the base station in advance, before the actual data transmission. The base station uses this pre-reported information to determine the appropriate operational mode and select antenna paths, eliminating the need for complex real-time interactive processing or hand-shaking procedures during data transmission.
Data Source
AI summary
The present disclosure includes techniques to process signals in a communication system, in which multiple signal processing units process signals received from multiple antennae. The signal processor units are controlled by operational-mode control signals, which are generated using an estimated Carrier-to-Interference-Noise-Ratio (CINR). The estimated CINR is generated using an equalized and combined signal, which is generated from the received signals and the estimated channel responses using the processed signals according to an operational mode. In another embodiment, a controller generates sub-carrier allocation signals using an allocation base. A channel status information (CSI) and multiple-input-multiple-output (MIMO) controller generates sub-carrier CSI signals and operational-mode control signals using the sub-carrier allocation signals, estimated channel responses, and estimated CINR. The operational-mode control signals select one of multiple antenna paths. A transmitter-diversity processor generates transmitter-diversity signals as a function of at least a mapped signal, sub-carrier CSI signals, and operational mode control signals.