Orthogonal Reference Signals for OFDM Doppler and ICI Suppression
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional OFDM systems face challenges in maintaining orthogonality between subcarriers due to high-speed movement, leading to inter-carrier interference (ICI) and difficulty in obtaining channel state information for time and frequency doubly selective channels.
Innovation Solution
A communication method involving the generation and transmission of two-dimensional orthogonal reference signals, subjected to delay and Doppler transforms, to facilitate channel state information estimation through two-dimensional correlation operations, enabling accurate suppression of ICI.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional OFDM systems are used, then the system is simple to implement, but inter-carrier interference occurs due to high-speed movement
Solution Approach 1:
The patent changes the reference signal parameters by introducing two-dimensional sparsity with specific non-zero element distributions in time-frequency domain. The reference signal has non-zero elements at specific positions (i, j) where i satisfies certain conditions and j satisfies certain conditions, creating a sparse pattern that enables ICI suppression while maintaining implementation simplicity.
2Reliability
If channel state information is obtained through conventional methods, then ICI suppression is possible, but the spreading function cannot be obtained for time and frequency doubly selective channels
Solution Approach 1:
The patent employs feedback mechanisms where the received signal contains both the reference signal and channel state information. The receiver uses the known reference signal pattern to extract channel state information through correlation operations, creating a feedback loop that enables reliable ICI suppression while successfully acquiring the spreading function for doubly selective channels.
Solution Approach 2:
The two-dimensional sparse reference signal acts as an intermediary that bridges the transmitter and receiver. It carries embedded channel state information that can be extracted through correlation operations, serving as a mediator that enables both ICI suppression and spreading function acquisition without requiring direct complex measurements.
3Productivity
If two-dimensional orthogonal reference signals are used, then channel state information can be obtained simply and quickly, but the reference signal design becomes more complex
Solution Approach 1:
The patent segments the reference signal into two-dimensional sparse patterns with specific non-zero element distributions. The reference signal is divided into time and frequency dimensions with controlled sparsity, allowing efficient channel state information extraction through segmented correlation operations while maintaining manageable design complexity through systematic pattern generation.
Data Source
AI summary
Embodiments of this application provide a communication method. The method includes: generating a first reference signal, where the first reference signal is two-dimensional orthogonal to a second reference signal, the second reference signal is a reference signal obtained after delay τ transform and Doppler frequency shift ν transform are performed on the first reference signal in a communication process, 0≤τ≤τmax, 0≤|ν|≤νmax, τ≠0 or ν≠0,τmax is a first threshold, νmax is a second threshold, and |x| represents an absolute value of x; and transmitting the first reference signal.