Precoding Matrix Design for Cyclic Delay Diversity Signaling Overhead
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Solution Overview
Problem
Current precoding systems, particularly those combining cyclic delay diversity (CDD) and channel-dependent precoding, face challenges such as increased signaling overhead and limited freedom in designing precoding for antenna ports, leading to communication errors due to severe signal cancellation and insufficient frequency diversity.
Innovation Solution
A transmission structure that applies an additional channel-dependent or independent precoder element after the CDD operation, allowing for dynamic selection of precoding matrices based on transmission rank, which reduces signaling overhead and enhances freedom in selecting precoders, thereby avoiding cancellation issues and improving frequency diversity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If cyclic delay diversity (CDD) and channel-dependent precoding are combined, then frequency diversity is improved, but signaling overhead increases
Solution Approach 1:
The patent segments the precoding operation into two distinct parts: CDD precoding (applying cyclic delays to create frequency diversity) and channel-dependent precoding (adapting to channel conditions). By separating these functions and applying them in sequence, the system achieves frequency diversity without requiring the channel-dependent precoder to operate at finer granularity, thus reducing signaling overhead while maintaining reliability.
2Reliability
If conventional CDD precoding is used, then frequency diversity is achieved, but freedom in designing precoders for antenna ports is limited
Solution Approach 1:
The patent introduces dynamic adaptability by allowing the channel-dependent precoder to be selected and configured based on transmission rank and channel conditions. This dynamic approach enables the system to adapt the precoding design freedom to match current channel conditions while maintaining the frequency diversity benefits of CDD, resolving the contradiction between fixed CDD structure and needed adaptability.
3Reliability
If finer precoding granularity is applied, then communication reliability improves, but signaling overhead increases
Solution Approach 1:
The patent applies CDD precoding as a preliminary action before channel-dependent precoding. By first establishing frequency diversity through cyclic delays, the subsequent channel-dependent precoding can operate at a coarser granularity while still achieving good communication reliability. This preliminary action reduces the signaling overhead that would otherwise be required if finer precoding granularity were applied from the start.
Data Source
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AI summary
In a transmitter or transceiver, symbol vectors (514), each comprising two or more symbols, are multiplied, in the following order, with a first column subset of unitary matrix (518) which spreads symbols in the symbol vectors across virtual transmit antennas, with a second diagonal cyclic delay diversity matrix (516) which changes a phase of the virtual transmit antennas, and with a third precoding matrix (515) which distributes the transmission across a plurality of transmit antennas (522).