Adaptive Precoder Cycling for Wireless MIMO Systems
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Solution Overview
Problem
In MIMO wireless communications systems, precoder selection based on incomplete or stale channel state information can lead to ineffective interference cancellation and reduced signal-to-interference-plus-noise-ratio, due to the limitations of reference signals like DM-RS which may not accurately represent current channel conditions.
Innovation Solution
Implementing a method where a subset of precoders is periodically cycled through, with adaptive modification based on pre-defined criteria, to improve precoder selection and reduce interference, using a transmitter or receiver to iteratively select precoders from a codebook, thereby enhancing signal quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If precoder selection is based on channel state information estimated from precoded DM-RS reference signals, then the precoding process is simplified, but the channel state information may misrepresent the actual channel conditions leading to ineffective interference cancellation
Solution Approach 1:
The patent segments the codebook into multiple subsets and implements precoder cycling through different subsets. This segmentation allows the system to explore multiple precoding options beyond what a single CSI estimate would suggest, thereby resolving the contradiction between using simplified precoded DM-RS for CSI estimation and achieving accurate interference cancellation through diverse precoder selection.
Solution Approach 2:
The patent introduces dynamic precoder cycling where the precoder is periodically changed according to a cycling pattern, even when the selected precoder remains the same. This dynamic approach compensates for the static nature of CSI estimates from infrequent reference signals, maintaining measurement precision without complicating the precoding implementation.
2Loss of energy
If reference signals are transmitted infrequently to reduce overhead, then system resources are conserved, but channel state information becomes stale and does not reflect current channel conditions
Solution Approach 1:
The patent applies preliminary action by pre-defining multiple codebook subsets and establishing a precoder cycling pattern in advance. This preparation allows the system to quickly adapt to channel changes without requiring frequent reference signal transmissions, thus conserving resources while maintaining timely precoder adaptation through the pre-planned cycling mechanism.
Solution Approach 2:
The patent implements periodic precoder cycling where precoders are systematically rotated through different subsets at regular intervals. This periodic action ensures that the system periodically refreshes its precoding strategy without needing frequent CSI updates from reference signals, effectively addressing the staleness problem while minimizing reference signal overhead.
3Productivity
If a single precoder is selected based on available channel state information, then the precoding process is simple and fast, but the system cannot adapt to changing channel conditions between reference signal transmissions
Solution Approach 1:
The patent introduces dynamic precoder cycling that automatically transitions between different precoders according to a predefined pattern. This dynamic mechanism enables the system to adapt to channel changes without complex real-time CSI updates, maintaining fast precoder selection while significantly improving adaptability to varying channel conditions.
Solution Approach 2:
The patent changes the precoder parameter periodically by cycling through different codebook subsets. This parameter change strategy allows the system to explore multiple precoding configurations over time, improving adaptability to channel variations while keeping the selection process simple and fast through predetermined cycling patterns rather than complex optimization.
Data Source
AI summary
Methods and apparatus are disclosed for improving a precoder selection process in a wireless communications system. In a normal precoder selection process, a precoder is selected from a codebook based on channel state information estimated from received reference signals. In between two received reference signals, a subset of precoders is cycled through and each precoder in the subset is iteratively selected for use by a transmitter to precode transmit signals. The subset of precoders may be adaptively modified based on predefined criteria.