SRS Transmission Power Control for CoMP CSI Accuracy
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Solution Overview
Problem
Current wireless communication systems face challenges in accurately controlling the transmission power of Sounding Reference Signals (SRS) to support Coordinated MultiPoint (CoMP) operations, which are essential for improving coverage and cell-edge throughput, and require decoupling the power control processes for PUSCH and SRS to effectively manage interference and ensure reliable CSI feedback.
Innovation Solution
The solution involves introducing a separate SRS transmission power control process that uses distinct maximum power values and offset configurations, along with decoupled TPC commands for SRS and PUSCH transmissions, to support both UL CoMP and DL CoMP, allowing for flexible power adjustments based on path loss and interference considerations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single power control process is used for both PUSCH and SRS, then the system complexity is reduced, but the accuracy of SRS transmission power control deteriorates, leading to insufficient SINR for accurate CSI feedback
Solution Approach 1:
The patent segments the power control process into two independent components: PUSCH power control and SRS power control. Each has its own TPC commands and maximum power configurations. This segmentation allows SRS to have dedicated power control parameters (p0_NOMINAL_SRS, p0_UE_SRS, alpha_SRS) separate from PUSCH parameters, enabling accurate SINR control for CSI feedback while maintaining manageable system complexity through modular design.
Solution Approach 2:
The patent applies local quality by configuring different power control parameters specifically for SRS transmissions based on local requirements. The SRS power control uses cell-specific parameters (p0_NOMINAL_SRS) and UE-specific parameters (p0_UE_SRS, alpha_SRS) that are independently optimized for SRS purposes, allowing tailored power control for CSI acquisition without affecting PUSCH performance.
2Measurement precision
If SRS transmission power is increased to improve CSI accuracy, then the SINR for CSI feedback is improved, but the interference to other users and cells increases
Solution Approach 1:
The patent implements feedback mechanisms where TPC commands are sent from the network to the UE to dynamically adjust SRS transmission power. The network receives CSI feedback from UEs and uses this information to generate appropriate TPC commands that adjust SRS power levels, creating a closed-loop system that balances CSI accuracy requirements with interference management to other users and cells.
Solution Approach 2:
The patent makes SRS transmission power dynamic through separate TPC commands (delta_SRS) that can independently adjust SRS power without being tied to PUSCH power changes. This dynamic adjustment allows the system to optimize SRS power in real-time based on current channel conditions and interference levels, improving CSI accuracy when needed while reducing interference during normal operations.
3Reliability
If separate TPC commands are introduced for SRS and PUSCH, then the power control accuracy for SRS is improved, but the signaling overhead and system complexity increase
Solution Approach 1:
The patent achieves universality by using the same DCI format structure and TPC command encoding mechanisms for both PUSCH and SRS power control. The separate SRS TPC commands (delta_SRS) are transmitted using existing downlink control channel infrastructure and follow the same accumulation and application rules as PUSCH TPC commands, reducing signaling overhead while maintaining independent power control reliability.
4Object-generated harmful factors
If the maximum power offset for SRS is limited to match PUSCH constraints, then the interference control is simplified, but the SRS transmission power flexibility is reduced, affecting CSI quality
Solution Approach 1:
The patent changes the power control parameters specifically for SRS by introducing separate maximum power offset configurations (p0_NOMINAL_SRS, p0_UE_SRS) that are independent from PUSCH parameters. The alpha_SRS parameter allows different fractional power control adjustments for SRS compared to PUSCH, providing the flexibility needed for high-quality CSI feedback while the network maintains overall interference control through coordinated parameter selection.
Data Source
AI summary
A method and apparatus for transmitting a reference signal from a User Equipment (UE) are provided. The method includes transmitting a first reference signal using a sequence determined from an identity of the at least one transmission point and transmitting a second reference signal with a transmission power having an offset with a first maximum value configured by higher layer signaling from the at least one transmission point; and transmitting a first reference signal using a sequence configured to the UE by higher layer signaling from the at least one transmission point and transmitting a second reference signal with a transmission power having an offset with a second maximum value configured by higher layer signaling from the at least one transmission point, wherein the second maximum value is larger than the first maximum value, and the first reference signal and the second reference signal are either identical or non-identical.