Guard Band Utilization via Spectrally Contained Waveforms
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Solution Overview
Problem
Current wireless communication systems, such as OFDM, suffer from high out-of-band radiation due to square pulse usage, leading to inefficient guard band utilization and spectral inefficiency, especially in synchronous and asynchronous communications.
Innovation Solution
Allocating secondary communications to the guard band using spectrally contained waveforms, such as F-OFDM and OFDM/OQAM, which have smaller bandwidths than the guard bands, allowing for increased spectral efficiency by minimizing interference with primary communications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If OFDM uses square pulse on each subcarrier, then simple equalization and channel estimation are achieved, but high out of band radiation occurs causing interference between bands
Solution Approach 1:
The patent introduces filtering as an intermediary component between the OFDM modulator and the transmitter. This filter acts as a mediator that preserves the simplicity of OFDM equalization and channel estimation while eliminating the harmful out-of-band radiation caused by square pulses. The filter selectively attenuates frequencies outside the allocated band without affecting the in-band signal characteristics.
2Object-generated harmful factors
If guard band is used to avoid interference between bands, then interference is reduced, but spectral efficiency is lost due to unused bandwidth
Solution Approach 1:
The patent converts the previously wasted guard band spectrum into a useful resource for secondary communications. By applying filtering to contain the primary OFDM signal within its allocated band, the guard band frequencies that would otherwise be empty or used only for isolation are now available for carrying secondary data streams, thus transforming spectral waste into spectral efficiency.
Solution Approach 2:
The patent introduces a secondary communication dimension within the frequency spectrum by utilizing the guard band frequencies. Instead of treating the guard band as a one-dimensional isolation zone, the system creates a parallel communication channel in the frequency domain, allowing simultaneous primary and secondary transmissions without temporal interference.
3Object-generated harmful factors
If filtering is applied to reduce out of band radiation, then OOB radiation is reduced, but implementation complexity increases
Solution Approach 1:
The patent optimizes the filtering implementation by carefully selecting filter parameters such as cutoff frequency, transition band width, and filter order. These parameter changes allow the system to achieve effective out-of-band suppression while minimizing the computational complexity and implementation overhead. The filter design is tailored to the specific OFDM parameters and guard band requirements of the system.
Data Source
AI summary
Embodiments are provided for guard band utilization for synchronous and asynchronous communications in wireless networks. A user equipment (UE) or a network component transmits symbols on data bands assigned for primary communications. The data bands are separated by a guard band having smaller bandwidth than the data bands. The UE or network component further modulates symbols for secondary communications with a spectrally contained wave form, which has a smaller bandwidth than the guard band. The spectrally contained wave form is achieved with orthogonal frequency-division multiplexing (OFDM) modulation or with joint OFDM and Offset Quadrature Amplitude Modulation (OQAM) modulation. The modulated symbols for the secondary communications are transmitted within the guard band.