Differential Encoding Transmission Diversity Delay Dispersion
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional transmission diversity methods using phase modulation schemes are ineffective when delay dispersion relative to the symbol length is significant, leading to cancellation of incoming signals and deterioration of transmission characteristics, especially when delay dispersion occurs in the propagation path.
Innovation Solution
The method generates modulated signals with different symbol waveforms for each transmission antenna, where the phase difference between symbols is determined based on transmission data, allowing for differential encoding and quadrature modulation, enabling delay detection and low-pass filtering at the reception side to maintain transmission quality regardless of delay dispersion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If conventional phase modulation schemes are used in transmission diversity, then the transmission method is simple, but the incoming signals cancel each other out when delay dispersion is significant, causing deterioration of transmission characteristics
Solution Approach 1:
The patent changes the modulation parameter from constant phase to time-varying phase. Each transmission antenna modulates the signal with a different phase transition pattern over time, transforming the signal from a static phase state to a dynamic one that can distinguish between multiple propagation paths even when they arrive at the receiver with different delays.
Solution Approach 2:
The patent introduces dynamic phase transitions that change over time for each transmission antenna. Instead of using a fixed phase modulation scheme, the system employs time-varying phase patterns that evolve during the symbol period, allowing the receiver to differentiate between signals from different antennas based on their temporal phase characteristics.
2Loss of energy
If phase difference between incoming signals is 180 degrees, then the signals cancel each other out completely, but this phase relationship occurs naturally in multipath propagation, making error correction difficult
Solution Approach 1:
The patent converts the harmful effect of phase cancellation into a beneficial feature for identification. By intentionally creating different phase transition patterns for each transmission antenna, the system ensures that even when signals arrive with 180-degree phase differences, the temporal variation patterns remain distinct, allowing the receiver to identify which antenna's signal is which and maintain reliable detection.
Solution Approach 2:
The patent segments the symbol period into multiple time intervals and assigns different phase transition patterns to different transmission antennas within these segments. This temporal segmentation allows the receiver to distinguish between signals from different antennas by analyzing the phase changes over time, preventing complete cancellation and enabling error correction.
3Reliability
If intentional delay is introduced between transmission signals to prevent cancellation, then transmission characteristics improve, but the system requires precise timing adjustment and propagation path estimation
Solution Approach 1:
The patent enables the transmission system to self-distinguish between multiple antennas through inherent phase transition patterns without requiring external timing adjustment mechanisms. Each antenna's signal automatically carries identifiable temporal phase characteristics that the receiver can exploit for differentiation, eliminating the need for complex timing synchronization and propagation path estimation systems.
Data Source
AI summary
A transmission device includes a differential encoding section for differentially encoding transmission data, a first waveform generation section, a second waveform generation section, and two transmission antennas. A reception device includes a reception antenna, a delay detection section, and a data determination section for low-pass filtering a delay detection signal. The reception device receives modulated signals modulated by using two waveforms having low correlations with each other. Thus, regardless of the presence or absence of delay dispersion in a propagation path and even in a high-speed fading in which the propagation path varies at high speed, a transmission diversity effect can be achieved, thereby making it possible to improve transmission characteristics.