Beamforming Vector Selection for mmWave SU-MIMO and MU-MIMO
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Solution Overview
Problem
Current beamforming technologies for mmWave systems face challenges in supporting both Single-User Multiple-Input Multiple-Output (SU-MIMO) and Multi-User Multiple-Input Multiple-Output (MU-MIMO) scenarios due to high sidelobes in untapered Discrete Fourier Transform (DFT) beams and power losses in Gaussian tapered beams, which limit Signal-to-Noise Ratio (SNR) and overall system performance.
Innovation Solution
The proposed solution involves a method to select between different sets of beamforming vectors for each direction and polarization, including untapered and tapered options, based on predicted radio conditions to maximize throughput, using an additional bit in the beam weight protocol to indicate SU- or MU-MIMO scheduling and retrieve appropriate beamforming vectors from a lookup table, allowing for optimal beamforming configuration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If untapered DFT beams are used, then maximum EIRP and DL coverage are achieved, but high sidelobes limit available SNR and cause beam leakage in MU-MIMO scenarios
Solution Approach 1:
The system dynamically selects between untapered and tapered beamforming vectors based on the scheduling scenario (SU-MIMO or MU-MIMO). For SU-MIMO, untapered vectors maximize EIRP, while for MU-MIMO, tapered vectors reduce sidelobe interference. This dynamic adaptation resolves the contradiction by adjusting beam characteristics according to operational context.
Solution Approach 2:
The invention changes the beamforming vector parameters by providing at least two different sets of vectors for each direction and polarization - one untapered set for maximum EIRP and one tapered set for reduced sidelobes. The selection between these parameter sets is controlled by the scheduling type, allowing optimization for either SU-MIMO or MU-MIMO scenarios.
2Object-affected harmful factors
If Gaussian tapered beams are used, then sidelobes are reduced, but power loss of approximately 3 dB occurs
Solution Approach 1:
The system dynamically switches between tapered and untapered beamforming vectors based on scheduling requirements. Tapered vectors are used only when MU-MIMO scheduling is detected, while untapered vectors are used for SU-MIMO, avoiding unnecessary power loss when sidelobe reduction is not required.
Solution Approach 2:
The invention provides multiple sets of beamforming vectors with different tapering parameters. The selection of which parameter set to use is determined by the scheduling scenario, allowing the system to maintain maximum power efficiency for SU-MIMO while achieving sidelobe reduction for MU-MIMO.
3Device complexity
If a single set of beamforming vectors is used for all scenarios, then device complexity is reduced, but system performance is limited in both SU-MIMO and MU-MIMO environments
Solution Approach 1:
The beamforming vector set is segmented into multiple subsets - at least two different sets for each direction and polarization, corresponding to different tapering configurations. This segmentation allows the system to select the appropriate subset for each scheduling scenario, improving performance without requiring a completely new beamforming architecture.
Solution Approach 2:
The multiple sets of beamforming vectors serve universal purposes - they can be used for both SU-MIMO and MU-MIMO scheduling by appropriate selection. The same antenna array and beamforming network hardware support both operating modes by switching between different vector sets, achieving multi-functionality without additional hardware complexity.
Data Source
AI summary
A method for providing signals for beam-formed transmission comprises retrieving, from a memory, of first vector-associated data defined by an obtained first beam index, assigned to a first signal, scheduled to be transmitted by beamforming in a first direction. The memory has vector-associated data characterizing at least two sets of beamforming vectors for each polarization and for each one of a plurality of beam directions. The beamforming vectors for each polarization and plurality of directions present different tapering and/or non-tapering. The first vector-associated data characterizes a first selected set of beamforming vectors that are designed to give a beam in the first direction. The first beam index comprises information for defining vector-associated data characterizing a particular one of the at least two sets for the first direction. A beamforming of the first signal is initiated by use of the first vector-associated data.