Subband Spectrum Shaping for Tight Wireless Spectrum Confinement
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Solution Overview
Problem
Existing wireless communication systems face challenges in achieving tight spectrum confinement, leading to increased interference and emission leakage across symbol boundaries, which degrades reliability and reduces spectrum efficiency.
Innovation Solution
Implementing spectrum shaping and subband spectrum shaping techniques to filter data tones in edge subbands, reducing emission leakage and noise across symbols, allowing for smaller or no guard-bands and increasing spectrum efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If traditional waveform transmission is used without spectrum shaping, then the transmission structure is simple, but emission leakage occurs across symbol boundaries causing interference
Solution Approach 1:
The patent divides the frequency band into multiple subbands and applies different filtering strategies to each subband. Edge subbands are filtered with root-raised cosine filters to reduce emission leakage, while center subbands use different processing. This segmentation allows targeted spectrum shaping without requiring complete redesign of the entire transmission system.
Solution Approach 2:
The patent applies spectrum shaping filters selectively to specific portions of the signal (edge subbands) rather than uniformly across the entire frequency spectrum. This local quality approach reduces emission leakage where it matters most (at band edges) while maintaining simplicity in center regions, thereby reducing overall interference without excessive complexity.
2Object-affected harmful factors
If guard-bands are increased to reduce interference, then spectrum confinement improves, but spectrum efficiency decreases
Solution Approach 1:
The patent extracts and removes the harmful spectral components at the edge subbands using root-raised cosine filtering. By taking out these problematic emissions and confining them within symbol boundaries, the system achieves better spectrum confinement without requiring large guard-bands, thus maintaining spectrum efficiency.
Solution Approach 2:
The patent changes the spectral parameters of edge subbands by applying root-raised cosine filters with specific roll-off factors. This parameter modification shapes the spectrum to decay more rapidly at band edges, reducing interference without needing to increase guard-band size, thereby preserving spectrum efficiency.
3Object-affected harmful factors
If spectrum shaping filters are applied to edge subbands, then emission leakage is reduced, but processing complexity increases
Solution Approach 1:
The patent applies spectrum shaping filters only to edge subbands rather than to the entire frequency spectrum. This partial action approach reduces emission leakage where it occurs (at edges) while avoiding unnecessary processing in center subbands, thereby limiting the increase in processing complexity to only where it is beneficial.
4Reliability
If subband filtering is implemented to achieve tight spectrum confinement, then noise across symbols decreases, but transceiver structure becomes more complex
Solution Approach 1:
The patent segments the frequency band into edge subbands and center subbands, applying different processing to each segment. Edge subbands receive root-raised cosine filtering to reduce noise and interference across symbol boundaries, while center subbands use different processing. This segmentation achieves noise reduction without requiring complete system redesign.
Data Source
AI summary
Methods, systems, and devices for wireless communications are described. A transmitting device may filter data tones (e.g., in edge subbands of an allocated frequency band) to achieve time domain windowing or shaping. Data tones of edge subbands of a configured frequency band may be filtered to shape a waveform such that it does not extend beyond symbol boundaries (e.g., does not result in emission leakage). In some examples, the transmitter may provide an indication of subband frequency domain shaping filters used to the receiver, to support demodulation on the receiver side. In some examples, the transmitter may indicate a demodulation reference signal (DMRS) comb structure (e.g., of the edge subbands) to the receiver, and the receiver may determine or estimate the filters of the subband frequency domain shaping based on the comb structure or the indication of the filters.