MIMO Transmission Device Phase Rotation for LOS Reception
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Solution Overview
Problem
Conventional transmission methods for multiple-input multiple-output (MIMO) communications in line of sight (LOS) environments do not effectively improve single stream and multi-stream data reception quality, particularly when using a multi-carrier transmission scheme like OFDM.
Innovation Solution
A transmission device that performs precoding on baseband signals, applies phase changes to pilot signals, and uses a combination of weighting synthesizers and phase changers to generate and transmit precoded signals, ensuring improved data reception quality by optimizing signal processing and phase alignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional MIMO transmission methods are used in LOS environments, then multi-stream signal transmission is achieved, but single stream and multi-stream data reception quality deteriorates
Solution Approach 1:
The patent applies preliminary phase rotation to precoded signals before transmission. By pre-rotating the phase of multi-stream precoded signals based on the stream index, the system prepares signals in advance to combat LOS channel effects, improving reception quality before the actual transmission occurs
Solution Approach 2:
The patent changes the phase parameter of transmitted signals by applying different rotation angles to different streams. This parameter modification allows the receiver to distinguish between streams and improves data reception quality in LOS environments where conventional methods fail
2Reliability
If phase rotation is applied to precoded signals, then data reception quality improves, but signal processing complexity increases
Solution Approach 1:
The patent applies different phase rotation angles to different streams locally. Each stream receives a specific phase rotation based on its index, creating local quality differentiation that helps the receiver distinguish and decode individual streams in LOS conditions
Solution Approach 2:
The phase rotation is applied periodically to different streams in a systematic manner. This periodic phase changing pattern creates a predictable structure that simplifies receiver processing while maintaining improved reception quality
Data Source
AI summary
A transmission device includes: a weighting synthesizer that generates a first precoded signal and a second precoded signal from a first baseband signal and a second baseband signal, respectively; a phase changer that applies a phase change of i×Δλ to the second precoded signal; an inserter that inserts a pilot signal into the second precoded signal applied with the phase change; and a phase changer that applies a phase change to the second precoded signal applied with the phase change and inserted with the pilot signal. The weighting synthesizer performs, in the precoding process, a calculation that usesF=(ejθ11ej(θ11+π4)ejθ21ej(θ21+π+π4))on the first baseband signal and the second baseband signal modulated via a modulation scheme of QPSK.