Cell-Free Massive MIMO Hybrid Beamforming for Interference Management
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Solution Overview
Problem
In high-frequency bands, cell coverage is reduced due to large propagation losses, and in ultra-dense networks, inter-cell interference limits system performance, necessitating improved interference management and cooperative transmission techniques beyond existing methods.
Innovation Solution
A centralized processor controls access nodes to switch between basic and cell-free massive MIMO transmission modes, using hybrid beamforming for cooperative transmission, determining optimal analog and digital precoders based on channel qualities to configure cell-free massive MIMO transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If high frequency bands are used to increase transmission capacity, then transmission speed is improved, but propagation losses increase and cell coverage is reduced
Solution Approach 1:
The patent combines multiple access nodes (ANs) into a cell-free massive MIMO system where multiple distributed ANs cooperate to serve multiple terminals simultaneously. This merging of multiple nodes provides spatial diversity and multiple transmission paths, compensating for the high propagation losses in frequency bands above 1 GHz while maintaining high transmission capacity and speed.
2Productivity
If cell density is increased to improve transmission rate, then transmission capacity is improved, but inter-cell interference increases
Solution Approach 1:
The patent segments the service area into multiple zones with different transmission modes. Terminals in certain zones can be served through cell-free massive MIMO cooperative transmission while others use basic transmission modes, allowing the system to manage interference by spatially separating different transmission strategies and optimizing overall transmission rate.
Solution Approach 2:
The centralized processor receives status reports from terminals and uses this feedback information to dynamically determine which terminals should use cell-free massive MIMO transmission and which should use basic transmission modes. This feedback mechanism allows the system to adapt to changing interference conditions and optimize transmission rates accordingly.
3Measurement precision
If hybrid beamforming is used to achieve high resolution, then beamforming accuracy is improved, but device complexity increases
Solution Approach 1:
The patent applies different beamforming techniques to different terminals based on their specific requirements and channel conditions. The centralized processor determines appropriate transmission modes for each terminal individually, applying cell-free massive MIMO with hybrid beamforming only where needed to achieve high resolution, while using simpler basic transmission modes for other terminals, thus managing system complexity locally rather than uniformly.
Data Source
AI summary
An operation method of a CP may comprise: requesting a status report from each of terminals and receiving the status report; determining switching from basic transmission mode to cell-free massive MIMO transmission mode for at least part of the terminals based on the status reports; instructing the at least part of the terminals and at least one AN to perform cell-free massive MIMO transmission for the at least part of the terminals to configure cell-free massive MIMO transmission mode; determining analog beam(s) and/or digital precoder(s) to be applied by the at least one AN to the at least part of the terminals based on channel qualities between the at least part of the terminals and the at least one AN; and allowing the at least one AN to perform cell-free massive MIMO transmission to the at least part of the terminals using the analog beam(s) and/or digital precoder(s).