OTFS Modulation for Time-Varying Channel Interference Mitigation
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Solution Overview
Problem
Current 4G wireless networks face challenges in supporting increasing data usage, quality of service, and mobility due to exponential data traffic growth, and are not equipped to handle new applications like immersive reality and IoT, requiring advanced interference mitigation and channel estimation techniques for efficient data delivery.
Innovation Solution
The implementation of Orthogonal Time Frequency Space (OTFS) modulation, which transforms the time-varying multipath channel into a time-invariant delay-Doppler channel, enabling efficient channel estimation and interference mitigation by spreading information symbols across both time and frequency domains, and using two-dimensional basis functions to maintain a stationary channel.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If 4G wireless networks are used to support increasing data usage, then network capacity and data delivery capability are improved, but interference mitigation and channel estimation complexity increase due to exponential data traffic growth and mobility
Solution Approach 1:
The patent transforms the traditional time-frequency domain channel representation into a delay-Doppler domain representation. This dimensional transformation allows the channel to be viewed and processed in a different coordinate system where time-varying multipath effects become stationary, thereby simplifying interference mitigation and channel estimation while maintaining high network capacity
Solution Approach 2:
The patent changes the fundamental parameters used to describe the channel by transforming from time-frequency coordinates to delay-Doppler coordinates. This parameter change converts a time-varying channel model into a stationary one, reducing the complexity of channel estimation and interference mitigation algorithms while supporting exponential data traffic growth
2Reliability
If Orthogonal Time Frequency Space (OTFS) modulation is implemented to transform the time-varying multipath channel, then channel coherence time is increased and channel estimation is simplified, but system complexity increases due to two-dimensional spreading across time and frequency domains
Solution Approach 1:
OTFS modulation spreads information symbols across both time and frequency dimensions, creating a two-dimensional constellation diagram. This dimensional expansion transforms the time-varying channel into a stationary delay-Doppler channel, increasing channel coherence time and simplifying channel estimation despite the increased modulation complexity
Solution Approach 2:
The patent introduces a two-dimensional basis function as an intermediary that maps information symbols onto the time-frequency grid. This basis function acts as a mediator that transforms the modulation process into the delay-Doppler domain, achieving stationary channel characteristics while managing the complexity through structured mathematical transformations
3Object-generated harmful factors
If information symbols are spread across both time and frequency domains using two-dimensional basis functions, then interference-free transmission is achieved and channel estimation is simplified, but processing complexity increases
Solution Approach 1:
The patent segments the channel estimation and interference mitigation processes into distinct steps: first transforming the received signal to the delay-Doppler domain, then performing channel estimation on the stationary channel, and finally transforming back to the time-frequency domain. This segmentation reduces processing complexity by breaking down the complex time-varying channel processing into manageable stationary sub-tasks
Solution Approach 2:
The two-dimensional basis function serves as an intermediary transformation that converts time-varying channel effects into stationary delay-Doppler representations. This intermediary transformation enables simple channel estimation and interference mitigation in the transformed domain, which can then be easily converted back to the original domain, reducing overall processing complexity
Data Source
AI summary
A method and system for multiple access in a system utilizing two-dimensional signal modulation. The method includes spreading data symbols arranged in a two-dimensional information domain onto sets of grid points respectively associated with different users in a time-frequency domain. The spreading is performed using two-dimensional basis functions uniquely associated with positions on a lattice in the information domain corresponding to the data symbols. A modulated signal is then generated using the sets of transformed symbols. The sets of grid points associated with the different users may be interleaved within the time-frequency domain or may form non-interleaved windows.