Uplink MU-MIMO Two-Phase Processing for C-RAN Fronthaul
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Solution Overview
Problem
Current wireless communication systems face challenges in efficiently managing spectrum resources, particularly in unlicensed bands, which limits the capacity and performance of multi-user multiple-input-multiple-output (MU-MIMO) configurations.
Innovation Solution
The proposed solution involves a two-phase processing technique for centralized radio access networks (C-RAN) systems, where the first phase performs efficient receive beamforming at the remote radio unit (RRU) to reduce the number of spatial dimensions, and the second phase handles interference suppression and multi-user MIMO detection at the baseband unit (BBU).
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If uplink MU-MIMO processing is performed entirely at the BBU, then interference suppression and multi-user MIMO detection can be optimized, but the fronthaul link capacity requirements become excessively stringent
Solution Approach 1:
The patent segments the MU-MIMO processing into two phases: Phase 1 (receive beamforming and spatial dimension reduction) is performed at the RRU, while Phase 2 (interference suppression and MIMO detection) is performed at the BBU. This segmentation reduces the data rate requirement on fronthaul links by processing signals locally at RRUs before transmission to the BBU, thereby resolving the contradiction between optimization performance and fronthaul capacity requirements.
2Quantity of substance
If the number of spatial dimensions is reduced at the RRU, then fronthaul capacity requirements are alleviated, but the complexity of beamforming processing increases
Solution Approach 1:
The patent applies preliminary receive beamforming at the RRU to reduce the number of spatial dimensions before transmitting signals to the BBU. This preliminary action reduces the data rate on fronthaul links and prepares the signals for subsequent interference suppression processing, thereby resolving the contradiction between reducing fronthaul capacity requirements and managing processing complexity.
3Productivity
If more users are supported in uplink MU-MIMO, then spectral efficiency increases, but the processing complexity and resource requirements increase
Solution Approach 1:
The patent segments processing across multiple RRUs and the BBU to support more users in uplink MU-MIMO. Each RRU performs local receive beamforming and spatial dimension reduction, while the BBU performs centralized interference suppression and MIMO detection. This distributed segmentation enables support for a larger number of users while managing processing complexity through hierarchical processing.
Solution Approach 2:
The patent transforms the high-dimensional received signals at RRUs into lower-dimensional beamformed signals through receive beamforming. This dimensionality reduction in the spatial domain enables the system to support more users by reducing the processing burden on fronthaul links and the BBU, thereby resolving the contradiction between supporting more users and managing processing complexity.
Data Source
AI summary
An apparatus for a base station configured for operation in a C-RAN includes processing circuitry coupled to a memory. To configure the base station for multi-user multiple input multiple output (MU-MIMO) signal processing, the processing circuitry is to decode a plurality of sounding reference signals received from a corresponding plurality of UEs via a corresponding plurality of channels. The plurality of channels are estimated based on the plurality of sounding reference signals. A beamforming matrix is determined based on a channel matrix corresponding to the plurality of channels. Beamforming is performed on a plurality of uplink (UL) data streams received from the plurality of UEs, to generate a plurality of beamformed streams. The beamforming is based on the beamforming matrix. Interference suppression is performed on the plurality of beamformed streams to generate a plurality of output data streams. The interference suppression is based on non-orthogonal DMRSs received from the UEs.