Channel Estimation by Shifting CDMA Code Samples
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Solution Overview
Problem
Correlating data sequences with CDMA codes to estimate channel responses in wireless communication systems is computationally intensive, consuming significant processing resources and power, especially when using scalar hardware that may not provide sufficient performance for rapid channel estimation.
Innovation Solution
Shifting code samples instead of data samples to simplify channel estimation, allowing for the use of simplified vector hardware and reducing complex computations, which is particularly effective when data samples are sixteen-bit vectors and code samples are two-bit vectors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If scalar hardware is used to perform channel estimation operations, then device complexity is reduced, but processing speed and performance become insufficient for rapid channel estimation
Solution Approach 1:
The patent segments the channel estimation process into distinct vector operations (loading data samples, loading code samples, performing correlation, shifting code samples) that can be executed efficiently by vector hardware. This segmentation allows the system to leverage specialized vector processing units for each operation, achieving high performance without requiring a complete scalar architecture.
Solution Approach 2:
Instead of shifting data samples through a scalar processor as in conventional approaches, the patent inverts the approach by shifting code samples using vector hardware operations. This inversion exploits the fact that code samples have a fixed, known structure that can be efficiently manipulated with vector shift operations, thereby achieving rapid channel estimation with reduced complexity.
2Productivity
If vector hardware is used to perform channel estimation, then processing performance is improved, but device complexity increases
Solution Approach 1:
The patent employs vector hardware that can perform multiple functions: loading data samples, loading code samples, performing correlation operations, and shifting code samples. This multi-functional vector hardware replaces what would otherwise require multiple separate scalar processing units, achieving high productivity while actually reducing overall device complexity through consolidation.
3Measurement precision
If data samples are shifted during correlation operations, then channel estimation accuracy is maintained, but power consumption increases due to large shifting operations
Solution Approach 1:
The patent inverts the conventional approach by shifting code samples instead of data samples during correlation operations. Since code samples are typically shorter and have a fixed structure (e.g., spreading codes), the shifting operations require fewer computational resources and consume less power while maintaining the same correlation accuracy needed for channel estimation.
Solution Approach 2:
The patent changes the parameter being shifted from data samples (which are typically 16-bit or higher precision) to code samples (which are often lower precision and have fixed length). This parameter change reduces the computational burden of shifting operations, thereby reducing power consumption while preserving channel estimation accuracy through the mathematical properties of the correlation operation.
Data Source
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AI summary
An apparatus includes selection logic configured to select a first subset of a first set of samples stored at a first set of registers. The first subset includes a first sample stored at a first register of the first set of registers and further includes a second sample stored at a second register of the first set of registers. The apparatus further includes shift logic configured to shift a second set of samples stored at a second set of registers. The apparatus further includes a channel estimator configured to generate a first value associated with a channel estimate based on the first subset and further based on a second subset of the shifted second set of samples.