OFDM Edge Band Filtering for Out-of-Band Radiation Reduction
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Solution Overview
Problem
Orthogonal frequency division multiplexing (OFDM) signals suffer from high out-of-band radiation due to square pulses on subcarriers, leading to inefficient spectrum use and interference between channels.
Innovation Solution
The method involves filtering a portion of the OFDM signal, specifically the edge band signals, rather than the entire signal, to reduce out-of-band radiation, using a filtering operation and time windowing on the center band signal, thereby reducing filtering complexity and improving spectral efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If filtering operation is applied to the entire OFDM signal to reduce out-of-band radiation, then spectral efficiency is improved, but device complexity increases
Solution Approach 1:
The patent divides the OFDM signal into multiple segments: center band signal and edge band signals. Different filtering operations are applied to different segments - time windowing for center band and filtering for edge bands. This segmentation reduces the overall filtering complexity while maintaining spectral efficiency benefits.
Solution Approach 2:
The patent applies different filtering operations to different parts of the signal based on their specific characteristics. The center band uses time windowing operation while edge bands use filtering operation. This local differentiation optimizes the balance between complexity reduction and OOB radiation mitigation for each signal portion.
2Object-affected harmful factors
If filtering operation is applied to reduce out-of-band radiation, then spectral efficiency is improved, but processing time increases
Solution Approach 1:
By segmenting the signal processing into parallel operations (time windowing on center band, filtering on edge bands), the processing can be optimized and executed more efficiently, reducing overall processing time while maintaining effectiveness in reducing out-of-band radiation.
Solution Approach 2:
The patent applies filtering only to edge band signals rather than the entire OFDM signal. This partial action approach reduces the processing burden and time required while still achieving the primary goal of reducing out-of-band radiation that causes spectral interference.
3Reliability
If guard bands are used to reduce interference between channels, then reliability is improved, but bandwidth utilization decreases
Solution Approach 1:
The patent converts the harmful out-of-band radiation into a controlled process by applying filtering operations. Instead of using guard bands to accommodate the radiation, the filtering operation actively reduces the radiation itself, allowing for tighter frequency packing and improved spectral efficiency while maintaining channel isolation.
Solution Approach 2:
The patent changes the signal parameters by applying filtering operations that modify the spectral characteristics of the OFDM signal. This reduces the out-of-band radiation levels and allows for more efficient bandwidth utilization without requiring protective guard bands, thereby improving spectral efficiency.
Data Source
AI summary
An OFDM signal may include a first edge band signal corresponding to a first edge band of the bandwidth of the OFDM signal, a second edge band signal corresponding to a second edge band of the bandwidth, and a center band signal corresponding to a center band of the bandwidth. The OFDM signal may be filtered by filtering the first edge band signal and/or the second edge band signal, so that out-of-band radiation of the OFDM may be reduced or eliminated.