Adaptive Beamforming Precoding Vector Selection
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Solution Overview
Problem
In wireless communication systems, especially in LTE and anticipated 5G networks, antenna beamforming becomes challenging during discontinuous transmission/reception periods due to short decorrelation times of beamforming precoding vectors, which limits power efficiency and beamforming gain when reference signals are unavailable.
Innovation Solution
A method in a transmitting device with multiple antennas that selects between two beamforming precoding vectors based on elapsed time since the last transmission, using a first vector with short decorrelation time if the elapsed time is below a threshold and a second vector with longer decorrelation time if it exceeds the threshold, allowing for improved beamforming gain and power efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a first beamforming precoding vector with short decorrelation time is used for transmissions during discontinuous periods, then beamforming gain is improved, but power efficiency deteriorates due to frequent precoding vector changes requiring reference signals
Solution Approach 1:
The patent applies dynamics by making the precoding vector selection adaptive based on elapsed time. The system dynamically switches between first precoding vectors (for short elapsed times) and second precoding vectors (for long elapsed times), allowing the beamforming strategy to adapt to changing channel conditions and reference signal availability, thereby resolving the contradiction between beamforming gain and power efficiency
Solution Approach 2:
The patent changes the parameter of precoding vector decorrelation time based on elapsed time conditions. By selecting precoding vectors with different decorrelation characteristics (short for recent transmissions, long for older transmissions), the system optimizes the trade-off between maintaining beamforming gain and reducing reference signal overhead during discontinuous transmission periods
2Use of energy by moving object
If discontinuous transmission/reception periods are used to reduce power consumption, then power efficiency is improved, but beamforming performance deteriorates due to unavailability of reference signals for precoding vector calculation
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing multiple precoding vectors (both first and second types) before entering discontinuous transmission/reception periods. This allows the UE to select appropriate precoding vectors from the pre-computed set when reference signals become unavailable, maintaining beamforming performance while preserving power savings during DTX/DRX periods
3Measurement precision
If the decorrelation time of beamforming precoding vectors is shortened to adapt to changing channel conditions, then beamforming accuracy is improved, but the frequency of reference signal transmission increases, reducing power efficiency
Solution Approach 1:
The system dynamically adjusts the effective decorrelation time by selecting between different precoding vector types based on elapsed time. For short elapsed times, first precoding vectors with short decorrelation times maintain high beamforming accuracy. For long elapsed times, second precoding vectors with longer decorrelation times are used, reducing the need for frequent reference signals and improving power efficiency
Data Source
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AI summary
A method, in a transmitting device having a plurality of transmitter antennas, for selecting antenna beam-forming precoding vectors for transmissions is provided. The method comprises transmitting to a receiving device at a first time, using a first beam-forming precoding vector that maps symbols to be transmitted to the plurality of transmitter antennas. The method further comprises determining, prior to transmitting to the receiving device at a second time, whether an elapsed time since the first time exceeds a first threshold. The method further comprises selecting one of at least two beam-forming precoding vectors for use in transmitting to the receiving device at the second time, based on said determining. Then, transmitting to the receiving device at the second time, using the selected one of the at least two beam-forming precoding vectors. There is also provided a transmitting device.