Dynamic Uplink Band Selection for Wearable SAR Compliance
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Solution Overview
Problem
Conventional FDD in cellular systems faces challenges such as SAR compliance issues, the need for a diplexer, and performance degradation in wearable devices due to the small frequency difference between uplink and downlink frequencies.
Innovation Solution
The proposed solution is to implement dynamic uplink band transmission techniques that decouple the uplink band from the downlink band, allowing the uplink to use a different operating band than the downlink, and in some cases, eliminating the need for a conventionally-paired uplink band.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional FDD operating bands are used with small frequency difference between UL and DL, then frequency pairing is simplified, but SAR compliance becomes difficult to satisfy and diplexer is required
Solution Approach 1:
The patent segments the uplink and downlink frequency selection into independent processes. The DL frequency is selected first based on available spectrum, then the UL frequency is independently selected from candidate bands that satisfy SAR constraints, rather than being constrained to conventional paired bands. This segmentation allows each direction to be optimized independently for its specific requirements.
Solution Approach 2:
The patent implements dynamic UL band selection where the UL frequency can change based on SAR compliance requirements. The system determines candidate UL bands dynamically based on the selected DL frequency and SAR constraints, allowing the UL band to adapt to different DL band selections and SAR requirements rather than being fixed to conventional pairings.
2Device complexity
If conventional FDD with small frequency difference is used, then hardware implementation is simpler, but diplexer is required which increases cost and loss
Solution Approach 1:
The patent extracts the diplexer component from the system by selecting UL and DL frequencies from different operating bands rather than from the same band with small frequency separation. By taking the UL and DL frequencies out of the same band context and placing them in differently suited bands, the need for a diplexer is eliminated, reducing cost and insertion loss.
3Volume of moving object
If single antenna per operating band is used in wearable devices, then device size is reduced, but UL performance degrades when optimized for DL frequency
Solution Approach 1:
The patent applies local quality by selecting a UL frequency in a different operating band than the DL frequency, allowing the single antenna to be optimized for DL performance in its designated band while the UL transmission occurs in a separate band where the antenna's characteristics are more favorable. This local optimization for each frequency direction resolves the conflict between single-antenna size constraints and UL performance.
4Reliability
If SUL is used to address FDD issues, then UL coverage is extended, but flexibility is reduced due to rigid band pairing requirements
Solution Approach 1:
The patent creates a universal UL band selection mechanism that can work with any DL band selection rather than requiring specific SUL-DL pairings. The system determines candidate UL bands based on SAR constraints and availability, allowing the same procedure to serve multiple DL bands and scenarios, providing multi-functionality and flexibility that rigid SUL pairing cannot achieve.
Data Source
AI summary
A method implemented by a RAN includes transmitting, by a first node of the RAN and to a user device, an indication of two or more candidate UL bands, the first node using a first operating band for DL communications to user devices, and each of the candidate UL bands being outside of the first operating band. The method also includes receiving from the user device an indication of a selection, from among the two or more candidate UL bands, of a UL band for UL communications from the user device to the RAN. The method further includes communicating bi-directionally with the user device using the UL band for the UL communications from the user device to the RAN, and using a DL band within the first operating band for DL communications from the RAN to the user device.