D2D User Terminal Resource Allocation
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Solution Overview
Problem
Current D2D communication systems in LTE networks face challenges in efficiently managing resource allocation for D2D proximity services, particularly in scenarios where user terminals are out of cell coverage, leading to interference and reduced reception quality due to power leak-in and in-band emissions.
Innovation Solution
The system employs a UE-driven assignment mode (Mode 2) where user terminals select their control and data resources from a predetermined pool, using pseudo-random sequences to randomize data resource allocation, reducing overlap and improving reception quality by avoiding designated resource areas.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If base station-driven assignment mode (Mode 1) is used to allocate control and data resources, then resource allocation is centralized and controlled, but user terminals out of cell coverage cannot access base station resources, leading to communication failure
Solution Approach 1:
The patent segments resource allocation into two modes: Mode 1 for in-coverage terminals (base station-driven) and Mode 2 for out-of-coverage terminals (terminal-driven). This segmentation allows the system to adapt to different coverage scenarios by selecting the appropriate mode, ensuring both centralized control when available and autonomous operation when needed.
Solution Approach 2:
The patent introduces dynamic mode selection capability where user terminals can switch between Mode 1 and Mode 2 based on their coverage status. The system dynamically adjusts the resource allocation mechanism according to real-time conditions, enabling seamless adaptation to changing network environments and maintaining communication reliability across all scenarios.
2Adaptability or versatility
If user terminal-driven assignment mode (Mode 2) is used to select control and data resources from a predetermined pool, then out-of-coverage terminals can autonomously communicate, but resource overlap and interference increase due to random selection
Solution Approach 1:
The patent changes the selection parameters from completely random to pseudo-random based on terminal identifiers. This parameter change maintains the autonomy needed for out-of-coverage operation while significantly reducing resource overlap by ensuring that terminals with different IDs select different resources systematically, thereby reducing interference.
Solution Approach 2:
The patent introduces pseudo-random sequences as an intermediary mechanism between terminal identifiers and resource selection. This intermediary transforms terminal-specific information into distributed resource selections, ensuring both autonomy for out-of-coverage terminals and reduced interference through systematic distribution of resources.
3Reliability
If the same control information (SA) is retransmitted using different resources, then reception reliability improves, but resource consumption increases and power leak-in effects worsen
Solution Approach 1:
The patent applies local quality by making retransmission behavior context-dependent. Instead of uniform retransmission across all scenarios, the system selectively performs retransmissions based on local conditions such as coverage status and interference levels. This localized approach maintains reliability where needed while minimizing energy consumption and power leak-in effects where retransmission is unnecessary.
Data Source
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AI summary
A user terminal according to one embodiment supports D2D communication. The user terminal includes a controller configured to perform repetition of same control information using first and second control resources allocated continuously or discontinuously in a time direction, in a control region having a predetermined time length and a predetermined frequency bandwidth. The controller is configured to determine positions of the first and second control resources in the time direction such that the second control resource does not overlap with a control resource of another user terminal in the time direction, even if the first control resource overlaps with the control resource of the another user terminal in the time direction.