Reciprocity-Based Beamforming Weight Calculation Without UE Antenna Selection
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Solution Overview
Problem
Current wireless communication systems face challenges in calculating beamforming weights for reciprocity-based beamforming without UE transmit antenna selection, as most UEs do not support antenna selection, leading to incomplete channel information and performance degradation in massive MIMO systems.
Innovation Solution
A method is introduced where the base station determines the downlink channel response of a single UE antenna, calculates precoding weights, and generates orthogonal or quasi-orthogonal weights for additional downlink signal layers, allowing for efficient beamforming without antenna selection by toggling precoding weights between layers in predefined sub-bands.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If transmit antenna selection is implemented to reduce hardware cost, then device complexity is reduced, but channel information completeness deteriorates because not all UE antennas can transmit reference signals
Solution Approach 1:
The patent segments the channel sounding process into multiple phases by dividing the antenna set into different groups. Each group transmits reference signals in turn, allowing the base station to acquire channel information from all UE antennas through sequential measurement rather than requiring simultaneous transmission from all antennas.
Solution Approach 2:
The patent implements periodic antenna switching where different UE antennas are activated in a periodic sequence to transmit reference signals. This periodic action ensures that over time, channel information from all antennas is collected, maintaining information completeness while using simpler hardware that activates antennas sequentially rather than simultaneously.
2Loss of information
If reference signals are transmitted simultaneously over all antennas, then channel information completeness is improved, but device complexity increases due to multiple RF chains
Solution Approach 1:
The patent segments the simultaneous transmission requirement into sequential transmission phases. Instead of requiring all antennas to transmit reference signals at the same time (which would need multiple RF chains), the system divides transmission into multiple time slots where different antenna groups transmit in sequence, achieving the same information gathering goal with simpler hardware.
Solution Approach 2:
The patent uses periodic antenna activation patterns where antennas are switched on and off in a predetermined sequence. This periodic action allows the base station to collect channel information from all antennas over time without requiring all antennas to be active simultaneously, thereby reducing RF chain requirements while maintaining complete channel knowledge.
3Ease of manufacture
If antenna selection is used to reduce costs, then ease of manufacture is improved, but reliability deteriorates because current commercial UEs do not support antenna selection
Solution Approach 1:
The patent inverts the traditional antenna selection approach. Instead of requiring the UE to select which antenna to use (which demands UE capability), the base station controls the antenna switching and reference signal transmission timing. This inversion moves the control function from UE to base station, making the system compatible with existing commercial UEs while still achieving cost reduction through selective antenna activation.
Solution Approach 2:
The patent introduces the base station as an intermediary that coordinates antenna activation and reference signal transmission. The base station manages the antenna switching sequence and schedules reference signal transmissions, acting as a mediator between the UE's limited antenna capabilities and the network's need for complete channel information, thereby ensuring compatibility while achieving the goals of antenna selection.
Data Source
AI summary
Embodiments of a method in a base station configured to transmit and receive wireless signals to and from a user equipment, UE. A downlink channel response of a first UE antenna is determined, based on uplink signals received from the UE. First preceding weights are calculated based on the determined channel response of the first UE antenna. Orthogonal or quasi-orthogonal preceding weights are determined based on the first preceding weights. First and second downlink signal layers are transmitted using the first preceding weights and the orthogonal or quasi-orthogonal preceding weights.