UFMC-OFDM Interference Reduction via Relative Delay and Filtering
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Solution Overview
Problem
The introduction of 5G waveform technology, specifically Universal Filtered Multi-Carrier (UFMC), in the same band as existing CP-OFDM systems leads to interference due to non-orthogonal subcarriers, which degrades system performance and requires additional measures like guard subcarriers or robust modulation schemes, resulting in reduced spectral efficiency.
Innovation Solution
Introducing a relative delay between the transmission of UFMC and OFDM signals, utilizing frequency sub-band specific sideband suppression filters, and potentially employing a shorter cyclic prefix for UFMC, to reduce interference without sacrificing spectral efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If UFMC signals are introduced in the same band as OFDM systems, then new 5G waveform capabilities are achieved, but interference between the two signal types occurs due to non-orthogonal subcarriers
Solution Approach 1:
The patent introduces frequency sub-band specific sideband suppression filters as intermediary elements between the UFMC and OFDM signals. These filters selectively suppress sidebands in specific frequency sub-bands, acting as a mediator to reduce interference while allowing both signal types to coexist in the same band. The filters are applied specifically to UFMC signals to suppress their sidebands that would otherwise interfere with adjacent OFDM subcarriers.
Solution Approach 2:
The patent applies different filtering characteristics to different frequency sub-bands. Instead of uniform filtering across the entire spectrum, sideband suppression filters are applied selectively to specific frequency sub-bands where interference occurs. This local quality approach allows the system to maintain spectral efficiency in non-interfering regions while suppressing interference in critical sub-bands.
2Reliability
If guard subcarriers or robust modulation schemes are used to reduce interference, then system performance is protected, but spectral efficiency is reduced
Solution Approach 1:
The patent changes the spectral parameters of UFMC signals by applying sideband suppression filters that modify the amplitude and frequency distribution of subcarriers. This parameter change allows the system to maintain reliable communication without requiring guard subcarriers, as the filtered signals have reduced spectral leakage and lower interference levels, thereby preserving spectral efficiency.
3Reliability
If strict time- and frequency alignments are maintained for OFDM, then orthogonality is preserved, but overhead increases and flexibility for asynchronous operations is lost
Solution Approach 1:
The patent enables dynamic operation modes where the system can switch between synchronous and asynchronous operation. By applying sideband suppression filters to UFMC signals, the system maintains orthogonality when needed while also supporting asynchronous operations with relaxed synchronization requirements. This dynamic capability allows flexible adaptation to different operational scenarios without sacrificing reliability.
Data Source
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AI summary
Embodiments relate to a methods and apparatuses for reducing interference between a legacy OFDM signal and a Universal Filtered Multi-Carrier (UFMC) signal. The UFMC signal comprises a first filtered frequency sub-band and at least a second filtered frequency sub-band. The first frequency sub-band comprises a first group of subcarriers, the first frequency sub-band being filtered with a first frequency sub-band specific sideband suppression filter (106-1) for sideband suppression outside of said first frequency sub-band. The second frequency sub-band comprises a second group of subcarriers, the second frequency sub-band being filtered with a second frequency sub-band specific sideband suppression filter (106-2) for sideband suppression outside of said second frequency sub-band. The apparatus (100) comprises a transmitter configured to transmit the OFDM signal and the UFMC signal with a relative delay to each other. The relative delay may be obtained by a delay module (110), for example.