GFDM Pilot Signal Design for Interference Reduction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing Generalized Frequency Division Multiplexing (GFDM) pilot signal techniques face challenges such as higher overhead, out-of-band emissions, power penalties, and hardware requirements, particularly in multiple antenna systems, where channel estimation accuracy and interference cancellation are complex.
Innovation Solution
The use of pilot symbols on specific subcarriers, designed to avoid inter-subcarrier interference, with techniques like Zadoff-Chu sequences and phase shifting to ensure orthogonality, allowing for efficient channel estimation and data recovery without recalculating channel estimates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If scattered pilot symbols with interference pre-cancellation are used, then overhead efficiency is improved, but power penalty and hardware complexity increase
Solution Approach 1:
The patent extracts the interference cancellation requirement from the pilot signal processing chain by using Zadoff-Chu sequences with cyclic shifts that are inherently orthogonal to data subcarriers. This removes the need for complex interference pre-cancellation hardware while maintaining low overhead, as the orthogonality is built into the sequence properties rather than requiring active cancellation mechanisms.
Solution Approach 2:
The patent changes the fundamental parameter of pilot sequence design by adopting Zadoff-Chu sequences with specific cyclic shift properties. These sequences have constant amplitude and optimal autocorrelation properties that provide inherent orthogonality, eliminating the need for high dynamic range hardware and complex processing while maintaining efficient overhead utilization.
2Quantity of substance
If scattered pilot symbols with interference pre-cancellation are used, then overhead efficiency is improved, but power penalty increases
Solution Approach 1:
The patent removes the power-intensive interference pre-cancellation operation from the system by using Zadoff-Chu sequences that provide inherent orthogonality through their cyclic shift properties. The constant amplitude property of these sequences eliminates the need for high dynamic range operations, thereby reducing power consumption while maintaining low pilot overhead.
Solution Approach 2:
The Zadoff-Chu sequences provide self-orthogonality through their inherent mathematical properties, where cyclic shifts automatically ensure orthogonality between pilot and data subcarriers. This self-service property eliminates the need for external interference cancellation mechanisms, reducing both hardware complexity and power consumption.
3Measurement precision
If pilot symbols are placed on all subcarriers (preamble technique), then channel estimation coverage is improved, but overhead and out-of-band emissions increase
Solution Approach 1:
The patent applies local quality by placing pilot symbols only on specific subcarriers (every fourth subcarrier in the embodiment) rather than uniformly across all subcarriers. The Zadoff-Chu sequences with cyclic shifts provide localized orthogonality that enables accurate channel estimation at pilot locations while allowing interpolation to estimate channels at non-pilot locations, thereby reducing overhead while maintaining estimation accuracy.
Solution Approach 2:
The patent performs preliminary action by pre-designing Zadoff-Chu sequences with specific cyclic shift properties that guarantee orthogonality before transmission. This preliminary structuring of the pilot sequences ensures that channel estimation can be performed accurately at pilot locations without requiring pilots on all subcarriers, as the orthogonality properties enable reliable estimation through interpolation.
4Measurement precision
If pilot symbols are placed on all subcarriers (preamble technique), then channel estimation coverage is improved, but out-of-band emissions increase
Solution Approach 1:
The patent reduces out-of-band emissions by concentrating pilot energy locally on specific subcarriers rather than distributing it across all subcarriers. The Zadoff-Chu sequences with cyclic shifts maintain orthogonality and enable accurate channel estimation at pilot locations with interpolation to other locations, thereby achieving the required estimation accuracy with reduced spectral leakage and lower out-of-band emissions.
Data Source
Figure 1~2
Figure 3~4
Figure 5
AI summary
A method and apparatus is for generating a modulation signal that comprises a resource block. A resource element sequence, M p/n, of M pilot symbols is determined that corresponds to an nth of N subcarriers. A pilot frequency domain sample sequence, r p/n, corresponding to the resource element sequence M p/n comprises a quantity, R NZ/n, of non-zero magnitude pilot frequency domain samples. R NZ/n is determined based on M and an excess bandwidth, α, of an adjacent subcarrier filter. The resource element sequence M p/n, which has no inter-subcarrier interference, is multiplexed with N − 1 resource element sequences to form the resource block. The modulation signal is generated by modulating each subcarrier of the N subcarriers with a corresponding resource element sequence of the N resource element sequences and filtering each of the modulated subcarriers using a subcarrier filter. The resource element sequence M p/n is used during receiving for efficiently determining a channel estimate.