SRS Power Control for Carrier Aggregation, MIMO, and TDM
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Solution Overview
Problem
Existing LTE technologies do not adequately address SRS power control for wireless transmitter/receiver units (WTRUs) in scenarios involving carrier aggregation, multiple input multiple output (MIMO), and time division multiplexing, leading to inefficiencies in channel estimation and transmission requirements.
Innovation Solution
Implement methods and apparatus for carrier-specific and carrier-common SRS power control, incorporating techniques like time division multiplexing (TDM), frequency division multiplexing (FDM), and code division multiplexing (CDM) to manage SRS overhead and power settings, ensuring proper transmission in multiple antennas and carriers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If SRS transmission is implemented in LTE UL to enable channel estimation for frequency scheduling, then channel estimation accuracy is improved, but transmission overhead increases because the last SC-FDMA symbol of the subframe is occupied by SRS and cannot be used for PUSCH transmission
Solution Approach 1:
The patent segments the SRS transmission across multiple subframes or subframes with different cyclic shifts, allowing the channel estimation function to be distributed over time rather than requiring a single dedicated symbol that would block PUSCH transmission in that subframe
Solution Approach 2:
The patent implements periodic SRS transmission patterns where SRS is transmitted in specific subframes according to a configured periodicity, rather than in every subframe. This periodic action allows PUSCH transmission to occur in subframes where SRS is not transmitted, reducing the overall transmission overhead while maintaining channel estimation capability
2Productivity
If carrier aggregation and MIMO techniques are utilized to increase data rate and spectrum efficiency, then productivity is improved, but device complexity increases due to the need to manage SRS parameters and power settings across multiple carriers and antennas
Solution Approach 1:
The patent defines a universal SRS power control formula that can be applied across multiple component carriers and antenna ports in carrier aggregation and MIMO scenarios. The formula uses common parameters (such as path loss compensation factor alpha, nominal power PO_PUSCH, and closed-loop adjustments f(i)) that are either carrier-specific or common to all carriers, providing a multi-functional power control mechanism that simplifies management across multiple carriers and antennas
Solution Approach 2:
The patent introduces configurable SRS-specific parameters (such as delta_PUSCH_SRS, alpha_SRS, and PO_PUSCH_SRS) that can be adjusted to optimize SRS transmission power in carrier aggregation and MIMO scenarios. These parameter changes allow the system to adapt SRS power settings to different carrier conditions and antenna configurations without requiring completely separate power control mechanisms for each carrier or antenna
3Measurement precision
If SRS transmission power is increased to improve channel estimation reliability, then measurement precision is improved, but energy consumption increases
Solution Approach 1:
The patent implements closed-loop power control for SRS transmission where the transmission power is adjusted based on feedback from the eNodeB. The eNodeB provides TPC commands that instruct the WTRU to increase or decrease SRS transmission power based on the actual channel estimation quality and interference conditions, allowing the system to achieve reliable channel estimation while minimizing unnecessary energy consumption
Solution Approach 2:
The patent makes SRS transmission power dynamic by introducing time-varying adjustments through the closed-loop TPC mechanism. Instead of using a fixed high power level, the SRS power is dynamically adjusted up or down based on real-time channel conditions and estimation requirements, achieving reliable measurements only when necessary while reducing energy consumption when high power is not needed
Data Source
AI summary
Methods and apparatus for sounding reference signal (SRS) power control for a wireless transmitter/receiver unit (WTRU) are disclosed. These methods and apparatus include methods and apparatus for carrier-specific and carrier-common SRS power control in WTRUs that utilize carrier aggregation techniques. These methods and apparatus also include methods and apparatus for SRS power control in WTRUs utilizing both carrier aggregation and time division multiplexing (TDM) techniques. Additionally, these methods and apparatus include methods and apparatus for SRS power control for WTRUs utilizing multiple input multiple output MIMO operation. Methods and apparatus for SRS overhead reduction and power management in a WTRU are also disclosed.