Multi-cell Joint Codebook Feedback for CoMP Systems
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Solution Overview
Problem
In wireless communications systems, especially in CoMP transmission, the existing channel state feedback methods result in high overhead, particularly for joint PMI/RI feedback, which is necessary for coherent multi-point transmissions, leading to increased processing requirements and feedback complexity.
Innovation Solution
A method for multi-cell joint codebook feedback that estimates channels between a communications device and multiple controllers, computes feedback information based on phase adjustments or joint optimization of channels, and transmits this information to enable simultaneous precoded transmissions, reducing feedback overhead and processing requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If joint PMI/RI feedback is used for coherent multi-point CoMP transmission, then CoMP performance is improved, but feedback overhead increases
Solution Approach 1:
The feedback information is segmented into two parts: (1) individual PMI/RI for each cell in the CoMP cooperation set, and (2) differential PMI for the joint codebook. This segmentation allows the system to maintain joint transmission performance while reducing feedback overhead compared to full joint PMI/RI feedback.
Solution Approach 2:
The patent changes the feedback parameter representation by using differential encoding. Instead of feedback the absolute joint PMI, the system feeds back the difference between the joint PMI and the individual PMIs. This parameter transformation significantly reduces the number of bits required for feedback while preserving the inter-cell spatial information needed for coherent CoMP.
2Reliability
If explicit channel state information feedback is used, then CoMP performance is improved, but processing requirements increase
Solution Approach 1:
The patent extracts only the essential inter-cell spatial information from the full channel state matrix. By identifying and feeding back only the differential PMI that captures the relative phase and amplitude relationships between cells, the system reduces processing requirements at both the UE and eNB sides while maintaining CoMP performance.
Solution Approach 2:
Instead of having the UE process and feedback the complete channel state information matrix which requires extensive computation, the patent inverts the approach by having the UE select individual codebooks for each cell and then only feedback the differential information. This inversion of the processing approach significantly reduces computational complexity.
3Loss of information
If joint PMI/RI feedback is used, then inter-cell spatial information is obtained, but feedback complexity increases
Solution Approach 1:
The patent merges the individual cell PMI feedback with the joint PMI feedback into a unified differential feedback mechanism. By combining these feedback streams and encoding their relationship differentially, the system obtains inter-cell spatial information while simplifying the feedback structure and reducing overall feedback complexity.
Data Source
AI summary
A system and method for multi-cell joint codebook feedback in wireless communications systems are provided. A method for operations at a communications device receiving joint transmissions from a plurality of communications controllers includes estimating a channel between the communications device and each communications controller in the plurality of communications controllers, thereby producing a plurality of channel estimates, computing feedback information based on the plurality of channel estimates, transmitting the feedback information, and receiving simultaneous transmissions from the plurality of communications controllers. The computing is based on a phase adjustment for the plurality of channels or a joint optimization of the plurality of channels, and the simultaneous transmissions are precoded based on the feedback information.