Open-Loop Spatial Multiplexing Precoding Matrix Design
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Solution Overview
Problem
Existing MIMO systems face challenges in selecting a precoding matrix that simplifies achievement while obtaining a sufficient frequency diversity gain under various channel environments, particularly in open-loop spatial multiplexing modes, and efficiently transmitting and receiving signals.
Innovation Solution
A method involving precoding with a matrix structure of WDU, where W is an identity matrix for 2 transmit antennas and cyclically changed among 4 predetermined matrices for 4 antennas, is used for cyclic delay diversity (CDD) in open-loop spatial multiplexing, allowing for efficient signal transmission and reception.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a precoding matrix is selected to simplify achievement in open-loop spatial multiplexing mode, then device complexity is reduced, but frequency diversity gain may be insufficient
Solution Approach 1:
The precoding matrix is segmented into two parts: a first matrix W from a codebook and a second matrix D with large cyclic delays. This segmentation allows each part to fulfill specific functions - W provides basic precoding while D ensures frequency diversity gain through large delays, resolving the contradiction between simplicity and diversity performance
Solution Approach 2:
The invention changes the delay parameter in the second matrix D to be large (greater than or equal to 16 samples), which fundamentally alters the frequency diversity characteristics. This parameter change enables sufficient frequency diversity gain while maintaining open-loop operation without complex feedback mechanisms
2Reliability
If cyclic delay diversity is implemented with large delays in open-loop spatial multiplexing, then frequency diversity gain is improved, but system complexity increases
Solution Approach 1:
The invention merges spatial multiplexing and cyclic delay diversity into a unified precoding framework. The precoding matrix combines the spatial precoding function (matrix W) with the CDD diversity function (matrix D), allowing both techniques to work together without requiring separate implementation complexes
Solution Approach 2:
The proposed precoding matrix structure serves multiple functions simultaneously: it provides spatial multiplexing for high data rates, implements frequency diversity through large delays, and maintains compatibility with existing OFDM and MIMO frameworks. This multi-functionality reduces overall system complexity despite the enhanced capabilities
Data Source
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AI summary
A method for transmitting and receiving signals in an open-loop spatial multiplexing transmission mode is described. If the number of transmit antennas is 2 and a rank is 2, a base station performs precoding according to a cyclic delay diversity scheme by a matrix in which a first matrix corresponding to an identity matrix, a second matrix corresponding to a diagonal matrix, and a third matrix corresponding to a unitary matrix are sequentially multiplied and transmits the precoded signals. This may be substantially the same as the case where the base station performs precoding using a matrix in which the second matrix corresponding to the diagonal matrix and the third matrix corresponding to the unitary matrix are multiplied and transmits the precoded signals. A user equipment estimates a transmission mode according to the received rank indicator and the number of transmit antennas and receives signals.