MIMO Pilot Phase Control for Better LOS OFDM Reception
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Solution Overview
Problem
Existing transmission methods do not effectively improve single stream and multi-stream data reception quality in line of sight (LOS) propagation environments, particularly when using multi-carrier schemes like OFDM.
Innovation Solution
A transmission method involving a configuration that includes error correction encoding, mapping, signal processing with weighting synthesis and phase changing, and radio transmission using multiple antennas to enhance data reception quality, specifically applying phase changes and cyclic delay diversity to improve signal quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional MIMO transmission methods are used in LOS environments, then multi-stream transmission capability is maintained, but single stream and multi-stream data reception quality deteriorates
Solution Approach 1:
The patent segments the transmission approach by providing separate signal processing paths for single-stream and multi-stream transmissions. For single-stream transmission, it applies cyclic delay diversity (CDD) with different delay amounts to generate multiple versions of the same signal, which are then transmitted through multiple antennas. This segmentation allows the system to optimize for single-stream reception quality without compromising multi-stream capability, directly resolving the contradiction between reception quality and processing complexity.
Solution Approach 2:
The patent implements dynamic signal processing by adaptively adjusting phase changes and delay amounts based on transmission conditions. The phase changer dynamically modifies the phase of transmitted signals according to the cyclic delay diversity scheme, and the system can switch between different transmission modes (single-stream vs. multi-stream) based on channel conditions. This dynamic approach improves reception quality in LOS environments while maintaining system flexibility.
2Reliability
If phase changing and cyclic delay diversity are applied, then signal quality and diversity effect are improved, but transmission processing complexity increases
Solution Approach 1:
The patent applies preliminary phase changing and cyclic delay diversity processing in the transmission path before signal transmission. By pre-processing the signals with determined phase changes and delay amounts, the system prepares diversified signal versions that will be received with improved quality. This preliminary action ensures that the diversity effect is achieved without requiring complex real-time processing at the receiver, thus improving signal quality while controlling processing complexity.
3Reliability
If single stream signals are transmitted using conventional methods, then transmission simplicity is maintained, but reception quality in LOS environments deteriorates
Solution Approach 1:
The patent changes key transmission parameters including phase values and delay amounts to improve single-stream reception quality in LOS environments. By systematically varying these parameters through cyclic delay diversity, the system creates multiple signal paths that combat the direct-wave dominance characteristic of LOS environments. This parameter change approach significantly improves reception quality while maintaining relatively simple transmission operations through standardized processing blocks.
Data Source
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AI summary
A transmission device that improves data reception quality includes: a first pilot inserter (207A) that inserts a pilot signal into a first precoded signal; a phase changer (205B) that applies a phase change of i × Δλ to the second precoded signal, where i is a symbol number and an integer that is greater than or equal to 0; an inserter (207B) that inserts a pilot signal into the second precoded signal applied with the phase change; and a phase changer (209B) that applies a phase change to the second precoded signal applied with the phase change and inserted with the pilot signal. Δλ satisfies π/2 radians < Δλ < π radians or π radians < Δλ < 3π/2 radians. When the communications scheme is an OFDM scheme, the phase changer (205B) and the phase changer (209B) apply a phase change, and when the communications scheme is a single-carrier scheme, do not apply a phase change.