OFDMA Channel Feedback Computation with Phase Rotations
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Solution Overview
Problem
In wireless communication systems, especially in LTE and OFDMA, there is a need to reduce interference from neighboring base stations while minimizing channel state communication overhead, particularly for cell-edge users, where traditional methods require detailed channel state information and have high overhead.
Innovation Solution
The method involves determining predetermined linear mappings and pseudo-random phase rotations used by serving and interfering base stations, allowing user equipment (UE) to compute channel feedback and decode data streams with reduced interference by aligning interference from adjacent base stations, thereby improving the signal-to-interference-plus-noise ratio (SINR) without requiring explicit channel state information at transmitters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional channel feedback methods are used for cell-edge users, then channel state information can be obtained, but communication overhead increases significantly
Solution Approach 1:
The patent extracts only the essential channel quality information (CQI) needed for data transmission optimization, rather than transmitting complete channel state information. The UE determines channel feedback based on received pilot signals and phase rotations, extracting only the necessary quality metrics while discarding redundant detailed channel state data, thereby reducing feedback overhead while maintaining sufficient accuracy for effective communication.
Solution Approach 2:
The patent uses predetermined pseudo-random phase rotations that are known to both transmitting base stations and the UE. Instead of transmitting actual channel state information, the system uses these predetermined phase rotation patterns as a reference framework, allowing the UE to compute channel feedback relative to these known patterns, thereby reducing the information that needs to be communicated while preserving channel quality assessment capability.
2Productivity
If detailed channel state information is transmitted, then transmission optimization can be achieved, but system complexity increases
Solution Approach 1:
The patent changes the parameter representation from detailed channel state information to simplified channel quality indicators (CQI) based on phase rotations. By transforming the channel state representation into phase rotation differences relative to predetermined patterns, the system maintains the ability to optimize data transmission while significantly reducing the complexity of channel state communication and processing.
Solution Approach 2:
Instead of having the UE measure and report detailed channel state information to the base station, the patent inverts the approach by having the UE compute channel feedback based on predetermined phase rotations that are already known to both parties. This inversion eliminates the need for complex bidirectional channel state information exchange while maintaining transmission optimization capability.
3Reliability
If interference alignment is implemented, then SINR improves for cell-edge users, but coordination between base stations becomes more complex
Solution Approach 1:
The patent applies preliminary action by using predetermined pseudo-random phase rotations that are established before data transmission begins. These phase rotations are configured in advance and are known to all involved base stations and the UE. This preliminary configuration enables interference alignment to occur naturally during data transmission without requiring real-time coordination or complex dynamic adjustments between base stations, thereby improving SINR while maintaining system simplicity.
Data Source
AI summary
A method, an apparatus, and a computer program product for wireless communication are provided. The apparatus may be a UE. The UE receives pilot signals from a serving base station and at least one interfering base station. The UE determines phase rotations used by the serving base station and the at least one interfering base station for transmitting resource blocks. The UE determines channel feedback based on the received pilots signals and the determined phase rotations for each of the serving base station and the at least one interfering base station. The UE sends the channel feedback to the serving base station. The UE receives data based on the determined phase rotations.