GFDM Transmitter With Adjustable Filtering For Spectrum Fragmentation
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Solution Overview
Problem
Existing frequency division multiplexing techniques, such as OFDM, face challenges in exploiting fragmented radio spectrum due to high peak-to-average power ratio and strong spectral leakage, which hinders efficient use of white spaces and causes interference with legacy signals.
Innovation Solution
The Generalized Frequency Division Multiplexing (GFDM) method employs a digital multi-carrier transmitter concept with adjustable Tx-filtering, cyclic prefix insertion, and efficient FFT-based equalization, allowing for lower peak-to-average power ratio and ultra-low out-of-band radiation, enabling flexible allocation of white spaces and efficient spectrum aggregation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If OFDM is used to exploit spectrum vacancies, then flexibility in switching sub-carriers on and off is improved, but strong spectral leakage occurs causing interference to legacy signals
Solution Approach 1:
The patent segments the transmitted signal into multiple independent carriers, each modulated separately and assigned to specific frequency bands. This segmentation allows selective activation of carriers in white spaces while maintaining spectral containment through individual carrier filtering, thereby reducing overall spectral leakage compared to traditional OFDM.
Solution Approach 2:
The patent applies different modulation and filtering characteristics to different carriers based on their specific frequency band requirements. Each carrier can be independently optimized for its allocated spectrum, with adjustable bandwidth and spectral shape to minimize interference to adjacent legacy signals while maximizing utilization of available white spaces.
2Object-generated harmful factors
If pulse shaping techniques or guard carriers are used in OFDM, then spectral leakage is reduced, but peak-to-average power ratio remains high
Solution Approach 1:
The patent dynamically adjusts the activation state of individual carriers based on real-time spectrum sensing results. Carriers are switched on or off independently according to the presence of white spaces, allowing the system to adapt to varying spectrum conditions without requiring all carriers to be active simultaneously, thereby reducing peak power requirements while maintaining spectral containment.
3Measurement precision
If receivers and transmitters are designed for high sensitivity to detect weak signals, then white space exploration capability is improved, but out-of-band radiation increases causing interference to legacy TV signals
Solution Approach 1:
The patent introduces spectrum sensing as an intermediary function that mediates between the need for high sensitivity detection and the requirement to protect legacy signals. The sensing mechanism identifies actual spectrum usage conditions, and this information guides selective carrier activation, ensuring that transmission only occurs in genuinely available white spaces and not in bands occupied by legacy signals, thus preventing out-of-band interference.
Data Source
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AI summary
A general frequency division multiplex (GFDM) transmission system is proposed. Vacant frequency ranges are detected and subsequently used for transmission, wherein a single carrier transmission system with cyclic prefixing is deployed. A corresponding transmitter and receiver are disclosed.