Multistage Beamforming Circuit for Full-Dimension MIMO Capacity
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Solution Overview
Problem
Current multiple-antenna communication systems face challenges in efficiently increasing system capacity and managing channel quality prediction due to the complexity of precoding and the mismatch between control and data channel precoding in full-dimension MIMO systems.
Innovation Solution
A multistage beamforming approach is implemented, comprising a frequency selective beamforming stage and a time-domain broadband beamforming stage, where the data unit converts received data streams into precoding output streams in the frequency domain and the remote radio head transforms these into transmit streams, forming both broadcast and user-specific narrow beams using a plurality of physical antennas.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If full-dimension MIMO systems deploy antennas vertically to increase system capacity, then spectral efficiency is improved, but precoding complexity increases and channel quality prediction becomes more difficult
Solution Approach 1:
The patent segments the precoding process into two distinct stages: frequency-selective precoding applied to data channels and broadbeam precoding applied to control channels. This segmentation allows each stage to be optimized independently, reducing overall complexity while maintaining high system capacity. The frequency-selective stage handles user-specific beamforming, while the broadbeam stage provides coverage, separating concerns that would otherwise be coupled in a single complex precoding operation.
Solution Approach 2:
The patent applies different precoding strategies to different parts of the transmission: frequency-selective precoding with narrow beams for data channels targeting specific users, and broadbeam precoding for control channels providing wide coverage. This local differentiation optimizes performance for each channel type without requiring complex joint optimization across all channels.
2Device complexity
If frequency-selective precoding is applied to data channels and broadbeam precoding to control channels, then precoding complexity is reduced, but mismatch between control and data channel precoding occurs
Solution Approach 1:
The patent applies frequency-selective precoding to the data channels in advance, before control channel transmission. This preliminary application of the user-specific precoding allows the system to establish the data channel beamforming pattern first, and then the control channel broadbeam precoding can be designed with knowledge of this pattern, improving channel quality prediction accuracy despite the two-stage approach.
3Productivity
If multiple transmit streams are generated from fewer precoding output streams, then system throughput is increased, but device complexity increases
Solution Approach 1:
The patent segments the beamforming functionality across two separate units: the data unit generates M precoding output streams through frequency-selective precoding, and the remote radio head generates N transmit streams through broadbeam precoding. This segmentation allows each unit to perform a simpler, specialized function rather than one unit handling all beamforming complexity, reducing individual device complexity while increasing overall throughput.
Data Source
AI summary
A multistage beamforming circuit includes a data unit that implements a frequency domain beamforming stage and a remote radio head that implements a time-domain broadband beamforming stage. The data unit implements the frequency domain beamforming stage by converting K received data streams into M precoding output streams in a frequency-domain. The data unit is configured to transform the M output streams to M OFDM time-domain signals. The remote radio head, or integrated radio unit is configured to implement a time-domain broadband beamforming stage by converting the M OFDM time-domain signals into N transmit streams of time-domain samples. The remote radio head, or integrated radio unit includes a transmit antenna array configured to transmit the N transmit streams that together form broadcast beams and user-specific beams. The antenna array includes a plurality of physical antennas. The number N of transmit streams is greater than the number M of precoding output streams.