Delay-Doppler Channel State Information for FDD Systems
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Solution Overview
Problem
Current frequency division duplex systems face challenges in efficiently acquiring and managing channel state information due to high feedback overhead, particularly in modeling reciprocal multipath fading effects between uplink and downlink transmissions.
Innovation Solution
Converting channel state information from the traditional frequency-time domain to the Delay-Doppler domain, allowing for reduced feedback overhead by accounting for reciprocal multipath characteristics through sign adjustments of the Doppler value and array responses based on frequency differences between uplink and downlink frequencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of information
If traditional frequency-time domain channel state information is used, then complete channel information can be obtained, but feedback overhead becomes excessively high
Solution Approach 1:
The patent transforms channel state information from the traditional frequency-time domain to the Delay-Doppler domain by changing the representation parameters. This domain transformation allows the channel characteristics to be described more efficiently, reducing the number of feedback bits required while maintaining essential channel information for MIMO precoding in FDD systems.
Solution Approach 2:
The patent introduces a new dimensional representation of channel state information by using Delay-Doppler domain instead of the conventional frequency-time domain. This dimensional change enables more compact representation of channel characteristics, particularly for reciprocal multipath fading effects, thereby reducing feedback overhead without significant loss of channel information.
2Quantity of substance
If MIMO precoding is implemented without PMI and RI feedback, then feedback overhead is reduced, but precoding accuracy deteriorates
Solution Approach 1:
The patent enables the system to perform MIMO precoding without requiring explicit PMI (Precoding Matrix Indicator) and RI (Rank Indicator) feedback from the user equipment. The base station utilizes the Delay-Doppler domain channel state information to autonomously determine appropriate precoding parameters, effectively making the system self-sufficient in generating precoding configurations without additional feedback overhead.
Solution Approach 2:
By changing the domain representation to Delay-Doppler, the patent provides sufficient channel information that allows the base station to directly compute precoding matrices without relying on compressed PMI/RI indicators. This parameter transformation preserves the essential spatial and temporal channel characteristics needed for accurate precoding while eliminating the need for additional feedback messages.
3Productivity
If large antenna port configurations are used, then system capacity increases, but CSI feedback requirements increase
Solution Approach 1:
The patent applies Delay-Doppler domain transformation that efficiently captures the channel characteristics even for large antenna port configurations. This parameter change in the representation domain allows the system to handle increased antenna ports and higher system capacity while maintaining compact CSI feedback, as the Delay-Doppler representation inherently compresses the channel information more effectively than frequency-time domain for MIMO systems.
Data Source
AI summary
Various embodiments disclosed herein provide for a reciprocity based channel state information acquisition scheme for frequency division duplex wireless communications systems. By converting channel state information from a traditional frequency-time domain to a Delay-Doppler domain, the channel state information feedback overhead can be reduced since the multi-path of radio propagation is reciprocal in terms of each ray and each cluster of antenna elements. Since the surrounding objects create the same multipath fading for both uplink and downlink transmissions, modeling the channel state information in the Delay-Doppler domain, and adjusting the sign of the Doppler value (negative/positive) can account for the multipath characteristics in both uplink and downlink.