Spatial Time-Division Multiplexing SRS Ports for Beam Alignment
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Solution Overview
Problem
Current wireless communication systems, particularly in 5G NR, face challenges in efficiently multiplexing sounding reference signals (SRS) to achieve optimal beamforming and spatial multiplexing gains due to limitations in existing multiplexing techniques, which affect channel state estimation and resource allocation.
Innovation Solution
The method involves spatial time-division multiplexing of multiple SRS ports with orthogonal weights for phase shifting, allowing for simultaneous transmission of SRSs to form a quasi-co-location receive beam subspace, enabling alignment with the base station's beamforming direction and achieving spatial multiplexing gain.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple SRS ports are multiplexed using existing techniques, then channel state estimation and beamforming performance are improved, but resource allocation efficiency and system complexity deteriorate
Solution Approach 1:
The patent segments the SRS transmission by dividing multiple SRS ports into different time slots for multiplexing. Each SRS port is transmitted in a dedicated time slot, allowing the base station to estimate channel state for each port separately while maintaining efficient resource allocation through structured time-division multiplexing patterns.
Solution Approach 2:
The patent implements dynamic SRS resource allocation where the number of SRS repetitions and time slot assignments are adaptively configured based on channel conditions and traffic requirements. This dynamic approach allows the system to optimize between measurement precision and resource efficiency according to real-time needs.
2Productivity
If multiple SRS ports are multiplexed simultaneously, then spatial multiplexing gain is improved, but signal interference and measurement accuracy deteriorate
Solution Approach 1:
The patent employs periodic time-division multiplexing where each SRS port is transmitted in alternating time slots with orthogonal weights applied. This periodic structure ensures that signals from different ports do not interfere with each other while still achieving spatial multiplexing gain through the orthogonal transformations applied at the receiver.
Solution Approach 2:
The patent introduces orthogonal weights as an intermediary mechanism that transforms SRS signals from different ports into orthogonal domains. This transformation acts as a mediator that separates overlapping signals in the time-frequency domain, eliminating interference while preserving the spatial multiplexing information needed for channel estimation.
3Measurement precision
If SRS transmission uses more time slots for multiplexing, then channel estimation accuracy is improved, but transmission latency and resource overhead increase
Solution Approach 1:
The patent applies partial action by configuring the number of SRS repetitions and time slots based on actual channel conditions and service requirements. Rather than always using maximum time slots for multiplexing, the system dynamically adjusts the multiplexing level to achieve sufficient estimation accuracy with minimal latency overhead.
Solution Approach 2:
The patent changes key parameters such as the number of SRS repetitions, time slot assignments, and orthogonal weight configurations adaptively based on channel quality indicators and traffic patterns. This parameter optimization allows the system to achieve high estimation accuracy when needed while reducing time overhead during favorable conditions.
Data Source
AI summary
A user equipment (UE) may spatial time-division multiplex a plurality of sounding reference signal (SRS) ports, each of the plurality of SRS ports being associated with at least one of a set of orthogonal weights, the set of orthogonal weights corresponding to phase shifting, and transmit a plurality of SRSs via the plurality of spatially time-division multiplexed SRS ports simultaneously, each of the plurality of SRSs including at least two SRS repetition. The plurality of SRSs may be configured to form or present a quasi-co-location (QCL) receive (Rx) beam subspace. The UE may configure the plurality of SRSs to form the subspace as the QCL Rx beam subspace, and a base station may signal the UE to a specific Rx beam subspace such that it is aligned to the base station's beamforming direction, and achieve spatial multiplexing gain in the QCL Rx beam subspace.