Open-Loop Uplink Precoding Matrix with SFBC for High-Speed Mobility
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Solution Overview
Problem
Current uplink precoding frameworks in wireless communications systems face challenges with limited precoder information feedback, leading to performance drops due to deep fades and inefficiencies in scenarios with varying coherence assumptions, especially in high-speed environments.
Innovation Solution
Implementing an open-loop UL precoding scheme based on Space-Frequency Block Coding (SFBC) with SRS and DMRS for PUSCH transmissions, along with closed-loop precoding using common TPMI signaling and differential TPMI reporting to balance signaling overhead and performance across different antenna configurations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If codebook-based precoding is used, then precoder information can be fed back to the network, but signaling overhead increases and performance drops in high-speed scenarios with varying coherence assumptions
Solution Approach 1:
The precoding approach is segmented into open-loop precoding (SFBC) that does not require feedback and closed-loop precoding that uses feedback. This segmentation allows the system to choose the appropriate mode based on channel conditions, avoiding the feedback overhead issue while maintaining reliability when needed
Solution Approach 2:
Sounding Reference Signals (SRS) are introduced as an intermediary to enable the network to estimate channel quality and determine appropriate precoding parameters without requiring direct precoder feedback from the UE. The SRS acts as a mediator that provides channel information in the uplink direction
2Loss of information
If sub-band cyclic precoding is used, then signaling overhead is reduced, but performance deteriorates in scenarios with deep fades and high-speed mobility
Solution Approach 1:
The system dynamically adapts between open-loop and closed-loop precoding modes based on channel conditions, mobility scenarios, and coherence assumptions. This dynamic adaptation allows the system to maintain reliability in high-speed scenarios while managing signaling overhead efficiently
Solution Approach 2:
The precoding parameters (such as cyclic shift values, comb structures, and resource allocation) are changed based on channel conditions and mobility detection. When deep fades or high-speed mobility are detected, the system adjusts parameters to maintain performance without increasing overhead
3Reliability
If open-loop SFBC precoding is implemented, then coverage is improved and high-speed performance is maintained, but signaling overhead must be carefully managed
Solution Approach 1:
The feedback mechanism is extracted from the open-loop SFBC precoding implementation. The system uses SRS for channel estimation and derives precoding parameters without requiring explicit precoder feedback, thereby maintaining the benefits of open-loop precoding while minimizing signaling overhead
Solution Approach 2:
The UE performs self-service by autonomously selecting precoding parameters based on configured options and channel conditions without requiring network feedback. The UE uses SRS transmissions and network measurements to determine appropriate precoding modes, reducing the need for extensive signaling
Data Source
AI summary
Various aspects of the present disclosure relate to a User Equipment (UE) configured to or operable to receive a configuration signal indicating a precoding scheme for transmitting a sequence of data symbols over a set of antenna ports and a set of frequency resources for uplink (UL) transmissions, and transmit each symbol in the sequence of symbols from at least two antenna ports of the set of antenna ports, and at least two frequency resources of the set of frequency resources. Transmitting each symbol in the sequence of symbols includes transmitting a first symbol using a first port of the at least two antenna ports and a first frequency resource of the at least two frequency resources, and transmitting a transformed function of the first symbol using a second port of the at least two antenna ports and a second frequency resource of the at least two frequency resources.