Universal Filtered Multi-Carrier Receiver Sideband Suppression
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Solution Overview
Problem
Current multicarrier communication systems, particularly OFDM, face challenges with Peak-to-Average Power Ratio (PAPR) and require strict time- and frequency synchronicity, which is not suitable for asynchronous users and fragmented spectrum operations, leading to Inter-Carrier Interference (ICI) and increased overhead.
Innovation Solution
The Universal Filtered Multi-Carrier (UFMC) signal format filters blocks of multiple subcarriers, providing sideband suppression and temporally soft transitions, allowing for reduced overhead and improved robustness by grouping subcarriers into frequency blocks with specific filtering, enabling efficient sideband suppression and interference reduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If OFDM is used with strict time- and frequency synchronization, then system performance is improved, but overhead increases due to Cyclic Prefix (typically 5-25%)
Solution Approach 1:
The patent extracts and removes the Cyclic Prefix component from the OFDM signal structure, replacing it with a filtered multicarrier approach that achieves similar or better performance without the overhead. The filtering operation suppresses side lobes and inter-carrier interference without requiring the time-domain CP extension.
Solution Approach 2:
The patent changes the fundamental parameters of the multicarrier signal by applying frequency-domain filtering to suppress side lobes and control interference. This parameter change (filtering) replaces the need for CP, achieving the same protective function against interference with different signal characteristics and reduced overhead.
2Adaptability or versatility
If OFDM is used for asynchronous users, then adaptability is improved, but Inter-Carrier Interference increases due to loss of orthogonality
Solution Approach 1:
The patent applies preliminary filtering to the multicarrier signal in the frequency domain before transmission. This filtering proactively suppresses the side lobes that would otherwise cause inter-carrier interference in asynchronous conditions, preventing the harmful effect before it occurs rather than correcting it after reception.
Solution Approach 2:
The patent modifies the spectral characteristics of the multicarrier signal by applying windowing or filtering functions that control the side lobe levels. This parameter change in the frequency domain allows the signal to maintain orthogonality-like properties even when users are asynchronous, thereby reducing ICI while supporting flexible timing.
3Object-generated harmful factors
If FBMC with long filter lengths is used, then side-lobe suppression is improved, but efficiency for short bursts decreases due to filter ramp-up and ramp-down time
Solution Approach 1:
The patent segments the filtering operation into frequency-domain processing that can be applied independently to each subcarrier or subcarrier group. This segmentation allows the filter to reach steady state quickly and enables efficient processing of short bursts without requiring long ramp-up and ramp-down periods, while still achieving strong side-lobe suppression.
Solution Approach 2:
The patent replaces the time-domain filtering mechanism (which requires long filter lengths and gradual ramping) with frequency-domain filtering. This substitution changes the mechanical approach from temporal smoothing to spectral shaping, achieving side-lobe suppression with much shorter effective filter lengths and better suitability for short burst transmissions.
4Ease of manufacture
If oscillator requirements are relaxed for low-end devices, then device cost is reduced, but frequency shifts and phase jitters increase in baseband processing
Solution Approach 1:
The patent applies self-service principles by making the transmitted signal inherently more robust to frequency offsets and phase variations through frequency-domain filtering. The filtered signal structure automatically compensates for oscillator imperfections, allowing low-end devices with relaxed oscillator requirements to maintain reliable communication without needing high-precision frequency control.
Data Source
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AI summary
Embodiments relate to a receiver (310) for receiving a multicarrier signal. The multicarrier signal comprises a first frequency block with a first group of subcarriers, the first frequency block being filtered with a first frequency block specific sideband suppression filter (106-1) for sideband suppression outside of said first frequency block, and at least a second frequency block with at least a second group of subcarriers, the second frequency block being filtered with a second frequency block specific sideband suppression filter (106-2) for sideband suppression outside of said second frequency block. The receiver (310) comprises a filter module (320) operable to perform an inverse sideband suppression filter operation for the first and at least the second frequency block. The invention proposes a generalization of Filtered Bank Multi Carrier (FBMC) and filtered OFDM with shorter filter's length due to a broader band processing per filter.