Adaptive QAM Estimation Circuits for SIC Receiver Complexity
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Solution Overview
Problem
Existing Soft Interference Cancellation (SIC) receivers face challenges with complex and slow circuitry for generating soft symbol means and variances, particularly in wireless systems with multiple user connections, where efficient and flexible processing of multiple data streams with different constellation orders is required.
Innovation Solution
The development of adaptive mean and variance estimation circuits, including mean estimation unit (MEU) and second moment estimation unit (SEU) circuits, which are configured to handle various QAM orders and formats, enabling sequential, parallel, or hybrid processing through a control unit that allocates and configures multiple estimation units for efficient data stream processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional circuitry is used for generating soft symbol means and variances, then the estimation can be performed, but the circuit becomes large, complex and slow in performance
Solution Approach 1:
The patent divides the symbol estimation circuit into separate functional blocks: mean estimation unit, variance estimation unit, and LLR computation unit. Each unit handles a specific aspect of the estimation process independently, reducing overall circuit complexity while maintaining estimation accuracy through modular design
Solution Approach 2:
The patent designs universal estimation circuits that can handle multiple QAM constellation types (16-QAM, 64-QAM, 256-QAM, etc.) using the same hardware structure. The circuits compute soft symbol means and variances for any QAM order through parameterized calculations, eliminating the need for separate dedicated circuits for each modulation type
2Reliability
If traditional circuitry is used for generating soft symbol means and variances, then the estimation can be performed, but the processing speed becomes slow
Solution Approach 1:
The patent pre-computes and stores constellation parameters (such as symbol values and their relationships) in lookup tables before runtime. During actual symbol estimation, the circuit rapidly retrieves these pre-computed values and combines them with received signal data, significantly reducing computation time while maintaining estimation accuracy
Solution Approach 2:
The patent replaces complex iterative mathematical computations with direct hardware circuit implementations using combinational logic and arithmetic units. The mean and variance estimation operations are performed through dedicated arithmetic circuits rather than software-based iterative algorithms, enabling parallel processing and faster execution
3Measurement precision
If separate circuits are designed for each QAM order, then accurate estimation for specific constellations is achieved, but the device complexity and processing time for multiple data streams increases
Solution Approach 1:
The patent designs universal estimation circuits that can handle multiple QAM constellation types (16-QAM, 64-QAM, 256-QAM, etc.) using the same hardware structure. The circuits compute soft symbol means and variances for any QAM order through parameterized calculations, eliminating the need for separate dedicated circuits for each modulation type
Solution Approach 2:
The patent maintains estimation precision across different QAM orders by dynamically adjusting circuit parameters such as normalization factors and constellation scaling values. The same hardware circuit adapts to different modulation schemes by changing these parameters rather than requiring structural modifications, ensuring accurate estimation for each specific QAM type
4Productivity
If multiple estimation circuits are used for multiple data streams, then processing capacity increases, but circuit complexity and resource requirements increase
Solution Approach 1:
The patent merges multiple estimation functions into unified circuit blocks that can process multiple data streams simultaneously. The mean estimation unit and variance estimation unit are designed to accept multiple input streams and produce corresponding output estimates in parallel, reducing the total number of separate circuits needed while increasing processing capacity
Solution Approach 2:
The patent extends the estimation circuits to process multiple data streams by adding stream identification dimensions and parallel processing paths. The circuits handle multiple users and modulation types by incorporating stream indexing and configurable parameter sets, enabling one circuit to perform the work of multiple dedicated circuits through multi-dimensional processing
Data Source
Figure 1A~1B
Figure 1C~1D
Figure 2~3
AI summary
Receivers including estimation unit (EU) circuits and related processing techniques for wireless systems are provided. Efficient expressions for quadrature amplitude modulation (QAM) sybmol mean and variance calculations are utilized with efficient expressions and implementations that are adaptive to different orders of QAM formats. An EU circuit includes a mean estimation unit (MEU) circuit and/or second moment estimation unit (SEU) circuit. Each estimation unit circuit is configured to receive a variable QAM normalization factor so that the circuit can be adpated to different QAM orders. Each MEU or SEU circuit can be configured for sequential and/or parallel processing. A pool including multiple MEU circuits and/or a pool including multiple SEU circuits is provided in one embodiment, with a control unit for configuring and reconfiguring the pools of circuits for mean and variance estimation for data streams of QAM symbols.