Uplink Beamforming for High Mobility Users in C-RAN Networks

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Solution Overview

Problem

The capacity bottleneck of the fronthaul link in massive MIMO aided cloud radio access networks (C-RAN) is exacerbated by the increasing number of antennas and data traffic, which is not effectively addressed by conventional functional splits and beamforming techniques, especially under imperfect channel state information (CSI) conditions, particularly for high mobility users.

Innovation Solution

Implementing an extended maximum ratio combining (MRC) compression technique at the remote radio unit (RRU) using multiple sounding reference signal (SRS) channel measurements, which are aggregated in time, frequency, and spatial domains, to generate multiple receive beams. This processed signal is then sent to the baseband unit (BBU) for further processing using minimum mean-square error interference rejection combining (MMSE-IRC) to mitigate interference and improve spectral efficiency.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If the number of antennas and data traffic are increased to improve network capacity, then the capacity bottleneck of the fronthaul link is exacerbated

Engineering Contradiction:

Improvenetwork capacityVSAvoidfronthaul link load

Core Design Contradiction:

ProductivityVSQuantity of substance

Solution Approach 1:

The patent segments the processing functions between RRU and BBU, with RRU performing extended MRC compression on received signals before transmitting to BBU. This segmentation reduces the amount of data that needs to be transmitted over the fronthaul link while maintaining the benefits of massive MIMO processing.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent extracts and removes redundant information from the received signals at the RRU through extended MRC compression. By processing and compressing the signals locally, only the essential processed data is transmitted to the BBU, thereby reducing fronthaul link load.

Inventive Principle:

Principle #2Taking out (Extraction)

2Ease of operation

If conventional functional splits and beamforming techniques are used, then system simplicity is maintained, but performance under imperfect CSI conditions for high mobility users is insufficient

Engineering Contradiction:

Improvesystem simplicityVSAvoiduplink performance under imperfect CSI

Core Design Contradiction:

Ease of operationVSReliability

Solution Approach 1:

The patent performs preliminary channel measurements using multiple SRS signals before actual data transmission. By aggregating channel measurements from multiple SRS transmissions in time, frequency, and spatial domains, the system prepares more accurate channel state information in advance, improving robustness against CSI imperfections for high mobility users.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system uses multiple sounding reference signal measurements as feedback to continuously update channel state information. This feedback mechanism allows the extended MRC to adapt to changing channel conditions, particularly for high mobility users where channel conditions vary rapidly.

Inventive Principle:

Principle #23Feedback

3Reliability

If extended MRC compression with multiple SRS channel measurements is implemented at RRU, then robustness of uplink performance is enhanced, but device complexity increases

Engineering Contradiction:

Improveuplink performance robustnessVSAvoidRRU processing complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent merges multiple channel measurements from different SRS transmissions across time, frequency, and spatial domains into a single aggregated channel estimate. This combining approach improves the accuracy and robustness of channel state information while maintaining manageable processing complexity through systematic aggregation methods.

Inventive Principle:

Principle #5Merging (Combining)

4Productivity

If fronthaul loads are reduced through compression, then network efficiency is improved, but measurement precision of channel state information may be compromised

Engineering Contradiction:

Improvenetwork efficiencyVSAvoidchannel state information accuracy

Core Design Contradiction:

ProductivityVSMeasurement precision

Solution Approach 1:

The system performs preliminary aggregation of multiple channel measurements before compression. By combining multiple SRS measurements in advance, the system ensures that the compressed data retains sufficient channel state information accuracy while reducing the overall data load on the fronthaul link.

Inventive Principle:

Principle #10Preliminary action

Data Source

PatentUS12218733B2Uplink receive beamforming for high mobility user in networks with cloud radio access network (C-RAN) architecture

Publication Date: 2025.02.04 INTEL CORP

AI summary

Various embodiments herein provide techniques for minimum mean-square error interference rejection combining (MMSE-IRC) processing of a received signal, distributed between a baseband unit (BBU) and a remote radio unit (RRU). The RRU may perform uplink receive beamforming (e.g., using maximum ratio combining (MRC)) based on multiple channel measurements (e.g., a set of multiple sounding reference signal (SRS) channel measurements) obtained on respective measurement signals transmitted by a user equipment (UE). The RRU may send the processed signal to the BBU for further processing. The BBU may perform MMSE-IRC based on the processed signal received from the RRU, e.g., using demodulation reference signals (DM-RSs). Other embodiments may be described and claimed.