SRS Beam Configuration for Multi-TRP Uplink Interference
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Solution Overview
Problem
In wireless communication systems, uplink signals from user equipment (UE) can interfere with each other, leading to delays, inefficient communications, and high signaling overhead due to the lack of effective beam coordination between UEs transmitting to different transmission and reception points (TRPs).
Innovation Solution
A method and system where a UE receives sounding reference signal (SRS) configuration messages from a base station, indicating reference signals from both target and non-target TRPs. The UE determines an SRS transmission beam based on these reference signals and a specified procedure, which maximizes uplink channel gain to the target TRP while minimizing interference to non-target TRPs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a base station schedules a UE to transmit an uplink signal to a target TRP, then the uplink communication is established, but the uplink signal may interfere with uplink signals from other UEs transmitting to different TRPs
Solution Approach 1:
The patent applies local quality by configuring UE-specific SRS transmission beams with directional characteristics tailored to each UE's location and target TRP. Each UE transmits SRS signals in specific spatial directions toward its designated TRP, creating localized uplink coverage zones. This directional transmission approach ensures that each UE's signal is concentrated where needed while minimizing spill-over interference to other TRPs, thereby maintaining reliable uplink communication without causing harmful interference to neighboring cells.
Solution Approach 2:
The patent introduces spatial dimensionality to uplink transmission by implementing three-dimensional beamforming for SRS signals. Instead of omnidirectional or simple sector-based transmission, the system utilizes 3D beam directions (azimuth and elevation angles) to precisely control signal propagation paths. This dimensional approach allows the network to schedule multiple UEs on the same time-frequency resources to different TRPs by steering their SRS beams in distinct spatial directions, effectively separating interfering signals in the spatial domain and eliminating interference while maintaining communication reliability.
2Productivity
If multiple UEs transmit uplink signals to different TRPs using the same time-frequency resources, then spectrum efficiency is improved, but interference between UEs increases
Solution Approach 1:
The patent resolves the interference issue while maintaining spectrum efficiency by transitioning from two-dimensional (time-frequency) resource allocation to three-dimensional (time-frequency-space) resource allocation. The base station schedules multiple UEs to transmit SRS signals simultaneously on the same time-frequency resources to different TRPs by assigning distinct 3D beam directions to each UE. The spatial dimension acts as an additional resource dimension, allowing the system to multiplex more UEs without increasing interference, as each UE's signal is confined to its specific spatial direction toward its target TRP.
Solution Approach 2:
The patent employs copying by creating virtual spatial copies of the uplink transmission resources. Each UE receives a configured SRS resource configuration that includes reference to downlink reference signals from its target TRP. The UE uses these reference signals to determine and replicate the appropriate uplink beamforming weights and spatial filters, effectively copying the downlink channel characteristics to the uplink. This copying mechanism ensures that each UE transmits with the correct spatial orientation toward its target TRP, enabling interference-free simultaneous transmissions from multiple UEs on the same time-frequency resources.
3Object-generated harmful factors
If the UE determines SRS transmission beams based on reference signals from target and non-target TRPs, then interference to non-target TRPs is reduced, but the complexity of beam determination increases
Solution Approach 1:
The patent applies preliminary action by having the base station pre-configure SRS resource parameters for each UE before the actual SRS transmission occurs. The base station provides each UE with an SRS resource configuration that includes references to specific downlink reference signals from the target TRP and non-target TRPs. The UE uses these pre-configured references to determine its uplink beam direction in advance, before needing to transmit the SRS signal. This preliminary configuration approach simplifies the real-time beam determination process, as the UE only needs to apply the pre-determined beamforming weights rather than performing complex real-time optimization, thereby reducing device complexity while still achieving interference reduction to non-target TRPs.
Data Source
AI summary
Methods, systems, and devices for wireless communications are described. The methods, systems, and devices may enable a user equipment (UE) to receive a sounding reference signal (SRS) configuration message that indicates one or more first reference signals from a first node or one or more SRS transmission beams associated with the first node and one or more second reference signals from a second node. The UE may determine an SRS transmission beam for transmitting an SRS signal based on a procedure for determining SRS transmission beams and the one or more reference signals from the first and second nodes. The UE may transmit the SRS signal using the SRS transmission beam.