Simultaneous Beamforming in OFDM Wireless Systems
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Solution Overview
Problem
Conventional closed-loop transmit beamforming in wireless systems is sensitive to feedback channel errors and requires significant overhead, while open-loop systems need constant phase calibration, which is costly and sensitive to radio channel variations.
Innovation Solution
A method for simultaneous beamforming in wireless networks that determines Channel Quality Indicators (CQI) for multiple mobile stations, ranks them, selects a conflict-free subset for beamforming, and uses a codebook-based approach to enable a base station to communicate with multiple mobile stations simultaneously, reducing the need for phase calibration and feedback overhead.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If closed-loop transmit beamforming is used, then beamforming gain and signal quality are improved, but feedback overhead and sensitivity to feedback channel errors increase
Solution Approach 1:
The patent segments the feedback information into two parts: quantized channel direction information (CDI) sent to the base station, and channel quality indicator (CQI) sent to the network. This segmentation reduces the amount of feedback data required while maintaining beamforming performance.
Solution Approach 2:
The patent extracts only the essential channel direction information from the full channel state, quantizing it to a reduced set of codebook indices. This extraction approach maintains the beamforming gain while significantly reducing feedback overhead compared to transmitting complete channel state information.
2Loss of information
If open-loop beamforming is used, then feedback overhead is reduced, but phase calibration overhead and sensitivity to radio channel variations increase
Solution Approach 1:
The patent performs preliminary quantization of channel direction information at the mobile station before transmission to the base station. By pre-processing the channel state into compact codebook indices, the system eliminates the need for continuous phase calibration while maintaining closed-loop beamforming performance.
3Measurement precision
If conventional closed-loop beamforming serves single user at a time, then beamforming precision is maintained, but system throughput is limited
Solution Approach 1:
The patent merges multiple users into simultaneous beamformed transmissions by quantizing and separating their channel direction information. The base station combines the quantized CDI from multiple users with appropriate weighting, enabling multi-user MIMO beamforming that maintains precision while increasing system throughput.
Solution Approach 2:
The patent transitions from single-user to multi-user beamforming by adding the spatial dimension of multiple users. Through codebook-based quantization of channel directions, the system simultaneously serves multiple users in different spatial directions, effectively utilizing the spatial dimension to increase throughput while maintaining beamforming precision.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enhances system throughput and reduces signaling overhead, providing significant gains in signal-to-noise ratio and signal-to-interference ratio, while being less sensitive to radio channel variations and eliminating the need for costly phase calibration.
Implementation Method 1
the base station controls the phase and relative amplitude of the signal at each transmitter and creates a pattern of constructive and destructive interference in the transmitting wavefront
Data Source
AI summary
Systems and methods are disclosed for use in a wireless network that promotes simultaneous beamforming. These systems and methods include determining the Channel Quality Indicator (CQI) and Best Beam Index (BBI) for communications between a plurality of mobile stations and a base station, ranking the plurality of mobile stations in a list according to the determined CQI and BBI, and selecting a subset of the plurality of mobile stations for simultaneous beamformed communications. These systems and methods may also include verifying that the selected subset of the plurality of mobile stations does not have a conflict and initiating beamformed communications. Certain embodiments of the BBI may be determined based on a predetermined codebook, which is a function of an antenna configuration, such as a uniform linear array (ULA) and a uniform circular array (UCA).