Sounding Reference Signal Configuration for MU-MIMO Capacity
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Solution Overview
Problem
In high-dimensional multiple user multiple input multiple output (MU-MIMO) systems, the existing SRS capacity and power are insufficient to support a large number of users, leading to limited system capacity and increased feedback overhead due to the need for rapid channel feedback from mobile users with large-scale antennas, which affects transmission robustness and frequency selectivity.
Innovation Solution
The proposed solution enhances downlink channel estimation by configuring additional resources for SRS transmission, including increased subcarrier frequency intervals, reduced SRS sampling density, and coordinated SRS resources across cells, allowing for more efficient use of time and frequency domains, and utilizing channel reciprocity to reduce reference signal overhead.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If traditional SRS resources are used in high-dimensional MU-MIMO systems, then channel estimation can be performed, but the system capacity is limited and feedback overhead increases due to insufficient SRS capacity
Solution Approach 1:
The patent extends SRS transmission from traditional two-dimensional (time-frequency) resources to a three-dimensional resource space by adding the code domain dimension. This allows multiple users to be multiplexed using orthogonal codes in addition to time and frequency resources, significantly increasing the SRS capacity and enabling support for more users in high-dimensional MU-MIMO systems.
Solution Approach 2:
The patent makes the SRS resource configuration universal by allowing flexible allocation across time domain symbols, frequency domain comb patterns, and code domain orthogonal codes. This multi-functional resource structure can serve multiple users simultaneously with different antenna configurations, maximizing system capacity utilization.
2Productivity
If more users are supported through three-dimensional multi-antenna technology, then spatial multiplexing efficiency improves, but SRS transmission power requirements increase
Solution Approach 1:
The patent segments the SRS transmission power across multiple orthogonal code domains rather than requiring all users to transmit at high power simultaneously. By dividing the code domain resources, each user can transmit at lower individual power levels while the base station aggregates the information, reducing overall transmission power requirements.
Solution Approach 2:
The patent uses orthogonal code sequences as templates that can be reused and copied across different users. Instead of requiring each user to transmit unique high-power signals, users can modulate their SRS on replicated code patterns, reducing the power needed for each individual transmission while maintaining distinguishability through code orthogonality.
3Measurement precision
If rapid channel feedback is required from mobile users with large-scale antennas, then channel estimation accuracy improves, but feedback overhead increases
Solution Approach 1:
The patent enables the base station to perform downlink channel estimation by utilizing uplink SRS transmissions through channel reciprocity. The base station transmits SRS on uplink resources, receives the signals, and directly estimates the downlink channel characteristics without requiring mobile users to feed back channel information, making the system self-sufficient for channel estimation.
Solution Approach 2:
The patent inverts the traditional channel estimation approach by having the base station estimate the downlink channel through uplink SRS measurements rather than relying on downlink reference signals or user feedback. This inversion eliminates feedback overhead while maintaining estimation accuracy through the channel reciprocity property.
4Strength
If three-dimensional multi-antenna technology is deployed, then antenna gains improve and beam widths reduce, but mutual interference between users increases
Solution Approach 1:
The patent applies different orthogonal code sequences to different user groups or spatial regions. By assigning distinct code patterns to users with similar antenna configurations, the system maintains high antenna gains for each user while using code orthogonality to eliminate mutual interference between users, allowing simultaneous transmission without interference.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach significantly improves system capacity by supporting more users with reduced transmission power requirements and feedback overhead, while maintaining channel estimation quality and reducing mutual interference.
Implementation Method 1
the base station performs uplink channel estimation according to the SRS; and the base station acquires downlink channel information according to uplink channel information obtained through the uplink channel estimation
Data Source
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AI summary
A base station comprising: a transmitter configured to transmit to User Equipment (UE) a first signal including SRS configuration information; and a receiver configured to receive a Sounding Reference Signal (SRS) transmitted by UE, wherein the SRS configuration information includes a Comb number information that is 2 or 4, the SRS is configured in part of the resource blocks in a frequency domain, and a subcarrier frequency interval of the SRS in the frequency domain is determined according the Comb number information.