Basis Waveform Coefficient Feedback for OFDM Systems
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Solution Overview
Problem
Current wireless communication systems face inefficiencies in feedback and scheduling schemes, particularly in multi-carrier OFDM systems, where high feedback rates are required due to the need for frequent channel updates, leading to operational challenges in systems with a large number of data carriers.
Innovation Solution
The implementation of a transmitter and receiver system that generates and transmits coefficients of basis waveforms representing channel quality metrics, allowing for efficient uplink feedback and downlink scheduling by decorrelating channel expansion coefficients and reducing feedback data through tone grouping and modulation coding scheme sub-grouping.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If per-tone rate control is used to maximize multiplexing gain, then system throughput is improved, but feedback requirement becomes directly proportional to the number of OFDM tones making it operationally prohibitive
Solution Approach 1:
The patent segments the channel frequency response into a set of basis waveforms (e.g., Fourier basis functions) and transmits only the coefficients of these basis waveforms rather than all individual tone values. This segmentation reduces the feedback dimensionality from O(N tones) to O(K coefficients) where K is much smaller than N, making the feedback requirement manageable while preserving the ability to perform per-tone rate control for maximizing throughput.
Solution Approach 2:
The patent introduces basis waveforms as an intermediary representation between the actual channel frequency response and the feedback transmission. Instead of directly transmitting the full channel response across all tones, the system uses basis waveform coefficients as an intermediate compressed representation that captures the essential channel characteristics with significantly reduced data requirements.
2Measurement precision
If channel frequency response is communicated across all data tones from each user to the base station, then accurate per-tone scheduling is achieved, but feedback data volume becomes directly proportional to the number of data carriers
Solution Approach 1:
The patent extracts only the essential information needed for scheduling by representing the channel frequency response through a limited set of basis waveform coefficients. Instead of transmitting all N tone values, the system extracts and transmits only K coefficients that capture the channel characteristics, reducing feedback data volume while maintaining sufficient precision for accurate per-tone scheduling decisions.
Solution Approach 2:
The patent changes the representation parameters from N individual tone values to K basis waveform coefficients. This parameter transformation reduces the feedback data volume from O(N) to O(K) while preserving the ability to accurately represent the channel frequency response for scheduling purposes.
3Device complexity
If channel taps are fed back to estimate channel frequency response, then feedback rate is proportional to the number of filter taps, but effective feedback rate is proportional to the rate of change of channel coefficients which is usually high for fading channels
Solution Approach 1:
The patent addresses the dynamic nature of fading channels by using basis waveform coefficients that adapt to changing channel conditions. The coefficients are computed from the current channel frequency response, allowing the feedback to naturally adapt to the rate of change of channel coefficients without requiring separate dynamic adjustment mechanisms, thus maintaining accurate channel estimation across varying channel conditions.
Data Source
AI summary
The present invention provides a transmitter. In one embodiment, the transmitter includes a coefficient circuit configured to generate coefficients of a set of basis waveforms that represent channel quality metrics and a transmit circuit that transmits the coefficients. The present invention also provides a receiver. In one embodiment, the receiver includes a receive circuit configured to receive coefficients of a set of basis waveforms that represent channel quality metrics and a reconstruction circuit configured to reconstruct the channel quality metrics from the coefficients.