Non-Contiguous Channel Estimation Using FIR and IIR Filters
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Solution Overview
Problem
Mobile communication systems face challenges in maintaining link quality and throughput due to limitations in time domain filtering, especially in low SNR scenarios with non-contiguous pilot signal transmission, leading to poor user experience and failure to meet performance requirements.
Innovation Solution
A communication device that uses a combination of FIR and IIR filters, with iterative minimum mean square error filter computation and steady-state filter coefficients, to generate channel estimates across non-adjacent subframes, reducing the number of filter coefficients stored and maintaining high performance even with non-contiguous pilot signal transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional time domain filtering is used for channel estimation, then the filtering process is simple, but channel estimation accuracy deteriorates in low SNR scenarios with non-contiguous pilot signal transmission
Solution Approach 1:
The patent segments the channel estimation process into two distinct filtering stages: FIR filtering for initial channel estimate generation from reference signals, and IIR filtering for refined channel estimate computation. This segmentation allows each filter type to be optimized for its specific function, improving overall estimation accuracy without requiring a single overly complex filtering system.
Solution Approach 2:
The FIR filter performs preliminary channel estimation before the IIR filter processes the data. By pre-computing an initial channel estimate using FIR filtering, the system prepares refined input for the subsequent IIR filtering stage, enabling the more complex IIR processing to work from a higher-quality baseline rather than raw reference signals.
2Measurement precision
If the number of filter coefficients is increased to improve channel estimation accuracy, then measurement precision improves, but memory requirements and processing overhead increase
Solution Approach 1:
The patent merges FIR and IIR filtering approaches into a unified two-stage channel estimation system. The FIR filter provides a preliminary estimate with moderate coefficient requirements, while the IIR filter refines this estimate with its own coefficient set. This combination achieves superior accuracy compared to either filter type alone while distributing the computational and memory burden across two specialized components rather than requiring one excessively complex filter.
Data Source
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AI summary
A communication device is described comprising a receiver configured to receive a plurality of first reference signal values in a first subframe of a radio frame structure and to receive a plurality of second reference signal values in a second subframe of the radio frame structure, wherein the first subframe and the second subframe are separated by one or more subframes of the radio frame structure, a first filter configured to filter the plurality of first reference signal values received in the first subframe to generate a first channel estimate, a second filter configured to filter the plurality of second reference signal values received in the second subframe based on the first channel estimate to generate a second channel estimate and a processor configured to process received signals based on the second channel estimate.