Soft-Duplex Spectrum Sharing for CATV Upstream-Downstream Split
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Solution Overview
Problem
Existing CATV systems bifurcate upstream and downstream transmissions, limiting bandwidth and preventing the delivery of multi-gigabit services and symmetric services, while full duplex systems face interference issues due to amplifiers and half-duplex operation at the cable modem level, leading to suboptimal performance.
Innovation Solution
Implementing a 'Soft-FDD' mode that dynamically switches the upstream/downstream spectrum split using software, allowing RF legs to operate in FDD mode and enabling dynamic sharing of spectrum between upstream and downstream transmissions, with techniques like FDX RBA messages and amplifier circuits to manage interference groups.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If dynamic TDD duplexing is used to increase flexibility and adaptability, then adaptability improves, but device complexity increases
Solution Approach 1:
The patent implements dynamic TDD duplexing where the network side dynamically configures uplink-downlink slot patterns based on real-time traffic conditions. The base station can flexibly adjust the proportion of uplink slots, downlink slots, and special slots in a period, transforming a static system into a dynamic one that adapts to changing traffic demands, thereby resolving the contradiction between flexibility and complexity through controlled dynamic adjustment.
Solution Approach 2:
The patent changes the parameter of slot configuration by adjusting the number and distribution of uplink slots, downlink slots, and special slots within a period. By modifying these parameters dynamically based on traffic conditions, the system achieves flexibility without requiring complete system redesign, thus managing the complexity while improving adaptability.
2Reliability
If guard periods are lengthened to accommodate dynamic slot switching, then reliability improves, but transmission efficiency deteriorates
Solution Approach 1:
The patent applies different slot configurations to different time resources within a period. By locally optimizing slot assignments based on specific traffic conditions in different time slots, the system provides necessary guard periods only where interference protection is needed, rather than uniformly across all slots, thus maintaining reliability while improving overall transmission efficiency.
Solution Approach 2:
The patent organizes slots into periodic structures where uplink slots, downlink slots, and special slots are arranged in repeating patterns. This periodic organization allows the system to efficiently manage guard periods by concentrating them in specific slot positions rather than distributing them throughout, reducing the total time lost to guard periods while maintaining necessary interference protection.
3Adaptability or versatility
If random access resources are increased to support more devices, then adaptability improves, but resource waste increases when resources are not fully utilized
Solution Approach 1:
The patent makes special slots serve multiple functions: they can act as downlink slots for data transmission, as guard periods for interference protection, and as random access opportunities for device connectivity. By enabling this multi-functionality, the system supports more devices accessing the network without requiring dedicated random access resources for each device, thus improving adaptability while reducing resource waste through unified resource utilization.
Data Source
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Figure 2A~2B
Figure 3A
AI summary
In one embodiment, systems and methods for implementing a soft-duplex architecture utilizing a shared spectrum that may selectively and alternately be used to communicate upstream and downstream signals, and where one subscriber may receive a downstream signal from a device over the shared spectrum while another subscriber may deliver an upstream signal to the same device over the shared spectrum.