Sub-band Full Duplex Interference Mitigation via Frequency Segmentation
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Solution Overview
Problem
5G NR wireless communication systems face challenges in sub-6 GHz bands due to limited bandwidth, leading to high data rate limitations and increased costs, while millimeter-wave bands face issues with shadowing and high-frequency signal attenuation, necessitating a solution for efficient data transmission and interference reduction.
Innovation Solution
The implementation of a sub-band full duplex (SBFD) network architecture, which allows for simultaneous uplink and downlink transmissions in specific sub-bands, using frequency duplexing and antenna array separation to minimize UE-to-UE interference and reduce latency, while maintaining high data rates in the sub-6 GHz band.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If sub-band full duplex (SBFD) is implemented to enable simultaneous uplink and downlink transmissions, then data transmission efficiency and throughput are improved, but UE-to-UE interference increases
Solution Approach 1:
The patent divides the frequency band into multiple sub-bands, with specific sub-bands allocated for uplink transmissions and others for downlink transmissions. This segmentation allows simultaneous full-duplex operation while isolating interfering signals to specific frequency regions, thereby enabling high data transmission efficiency while controlling UE-to-UE interference through frequency-domain separation
Solution Approach 2:
The patent applies different filtering characteristics to different frequency sub-bands. Downlink receivers apply selective filtering that passes the downlink sub-band frequencies while attenuating uplink sub-band frequencies, and vice versa for uplink receivers. This local quality adjustment in the frequency domain enables interference mitigation while maintaining high data rates in each sub-band
2Productivity
If full bandwidth is used for downlink transmissions in TDD slots, then downlink throughput is improved, but uplink transmissions in subsequent SBFD slots experience increased interference
Solution Approach 1:
The patent segments the slot structure into different functional portions: initial downlink slots use full bandwidth for high throughput, while subsequent SBFD slots divide the bandwidth into uplink and downlink sub-bands. This temporal and spectral segmentation allows the system to achieve high downlink throughput when needed while minimizing interference to uplink transmissions in alternating slots
Solution Approach 2:
The patent implements a periodic pattern of slot types, alternating between full-bandwidth downlink slots and SBFD slots with frequency-divided uplink and downlink. This periodic action allows the system to cycle between high downlink throughput modes and interference-controlled uplink modes, achieving overall high productivity while managing interference through regular temporal separation
3Speed
If millimeter-wave bands are used to increase bandwidth, then data rates are improved, but signal attenuation and shadowing increase
Solution Approach 1:
The patent changes the operating frequency parameter from millimeter-wave to sub-6 GHz bands, thereby maintaining high data rates through wide bandwidth utilization in the sub-6 GHz range while avoiding the severe attenuation and shadowing problems inherent to millimeter-wave frequencies. Combined with SBFD and filtering techniques, this parameter change achieves high speed with improved reliability
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enables high data rates in the sub-6 GHz band, reducing the number of required base stations and lowering costs, while minimizing UE-to-UE interference and latency, thus addressing the limitations of both sub-6 GHz and millimeter-wave bands.
Implementation Method 1
down converting the RF signal in frequency to form a baseband signal that includes a down converted version of the DL signal and a down converted version of the UL signal
Implementation Method 2
filtering the baseband signal to pass the down converted version of the DL signal and to substantially attenuate the down converted version of the UL signal
Data Source
AI summary
During an uplink TDD slot, an UL UE transmits an UL signal that occupies a slot frequency range. Similarly, during a DL TDD slot, a DL UE receives a DL signal that occupies the slot frequency range. But during an SBFD slot, a UL UE transmits a UL signal that occupies only a first sub-band of the slot frequency range. Similarly, a DL UE receives a DL signal during an SBFD slot that occupies only a second sub-band of the slot frequency range. The second sub-band is distinct from the first sub-band. The DL UE may thus mitigate UE-to-UE interference during an SBFD slot by filtering the DL signal to substantially block the second sub-band from being received at the DL UE.