Precoding for joint transmission in distributed MIMO with explicit and implicit signaling
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Solution Overview
Problem
In low carrier frequency systems, the limited number of co-located CSI-RS antenna ports due to antenna form factor constraints hinders the achievement of MU-MIMO spatial multiplexing gains, limiting spectral efficiency.
Innovation Solution
A precoding design for joint transmission in distributed MIMO systems using explicit and implicit signaling to mitigate interference and preserve signal power, involving a base station that receives explicit and implicit CSI signaling to configure precoders for UEs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the number of CSI-RS antenna ports is increased to achieve MU-MIMO spatial multiplexing gains, then spectral efficiency is improved, but antenna form factor size increases making it impractical at low carrier frequencies
Solution Approach 1:
The patent divides the large number of antenna ports (e.g., 32 ports) into multiple distributed panels or remote radio heads (RRHs), each containing a smaller number of antenna elements. This segmentation allows the system to achieve the equivalent of 32 antenna ports through spatial distribution rather than co-location, resolving the contradiction between achieving high spectral efficiency and maintaining practical antenna form factor sizes at low carrier frequencies.
2Area of moving object
If antenna elements are distributed to different panels/RRHs to maintain form factor constraints, then antenna size is reduced, but system complexity increases due to distributed architecture
Solution Approach 1:
The patent merges the control and processing functions of multiple distributed panels/RRHs into a centralized base unit. This allows the distributed antenna system to be managed as a single logical entity, reducing the perceived system complexity while maintaining the physical distribution benefits for form factor constraints.
Solution Approach 2:
The base unit acts as an intermediary between the distributed panels/RRHs and the network, coordinating precoding, resource allocation, and signal processing across all distributed antenna elements. This intermediary structure simplifies the overall system architecture by providing a central point of control.
3Object-affected harmful factors
If precoding is configured based on explicit CSI signaling only, then interference mitigation is achieved, but signal power preservation for implicit CSI UEs is compromised
Solution Approach 1:
The patent implements a feedback mechanism where the base station determines whether to update precoders for implicit CSI UEs based on channel conditions, explicit CSI feedback from explicit CSI UEs, and interference measurements. This feedback loop allows the system to adaptively adjust precoding configurations to simultaneously mitigate interference for explicit CSI UEs while preserving signal power for implicit CSI UEs.
Solution Approach 2:
The patent dynamically changes precoding parameters based on the type of CSI signaling (explicit or implicit) received from different UEs. By adjusting precoder selection and update frequency according to the CSI feedback type, the system optimizes the trade-off between interference mitigation and signal power preservation for each UE.
Data Source
AI summary
A method of operating a BS includes receiving, from a first UE in a distributed MIMO system, an explicit CSI signaling, receiving, from a second UE in the distributed MIMO system, an implicit CSI signaling, and configuring, based on at least one correlation between the explicit CSI signaling and the implicit CSI signaling, at least one precoder for a transmission to the first UE. The at least one precoder for transmission to the first UE is configured to mitigate interference between the first UE and the second UE, and preserve a target signal power receivable by at least one of the first UE and the second UE. The method also includes determining, based on the explicit CSI signaling, the implicit CSI signaling, and at least one specified condition whether to update at least one previously determined precoder for transmission to the second UE.