D2D Synchronization Hierarchical Structure Algorithm
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Solution Overview
Problem
In device-to-device (D2D) communication networks, achieving accurate time and frequency synchronization is challenging due to the slower rate of synchronization signal broadcasting by user equipment (UEs) and the impact of distance from WWAN-connected UEs on timing accuracy.
Innovation Solution
A distributed algorithm constructs and maintains a hierarchical structure for D2D synchronization by assigning UEs a hop count based on their distance to the closest WWAN-connected UE, allowing them to update their synchronization levels and states dynamically, and includes additional algorithms for handling network dynamics and reliability indicators to avoid loops in the hop count.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If UEs broadcast synchronization signals at a slower rate to reduce energy consumption, then energy efficiency is improved, but timing synchronization accuracy deteriorates
Solution Approach 1:
The system segments UEs into different synchronization roles: WWAN-connected UEs act as primary synchronization sources while non-WWAN UEs act as secondary sources. This segmentation allows the network to maintain synchronization accuracy by having dedicated reference points while other UEs consume less energy by broadcasting at slower rates.
Solution Approach 2:
WWAN-connected UEs serve as intermediary synchronization sources between the WWAN network and non-WWAN UEs. These intermediary UEs receive synchronization signals from WWAN and relay them to other UEs, enabling accurate timing synchronization across the D2D network without requiring every UE to broadcast continuously.
2Device complexity
If UEs synchronize based on signals from other UEs without a hierarchical structure, then device complexity is reduced, but synchronization reliability deteriorates due to distance impact and potential loops
Solution Approach 1:
The system segments the D2D network into hierarchical levels based on WWAN connectivity. Level 0 contains WWAN-connected UEs that serve as root synchronization sources, while Level 1+ contains non-WWAN UEs that synchronize to their nearest lower-level UE. This segmentation prevents synchronization loops by establishing a clear directional flow from higher to lower levels.
Solution Approach 2:
The system adds a hierarchical dimension to the synchronization structure by introducing levels based on WWAN connectivity distance. Instead of flat peer-to-peer synchronization, UEs are organized in layers where each level synchronizes to the level below it, creating a tree-like structure that eliminates loops and improves reliability.
3Measurement precision
If a hierarchical structure with hop count is implemented to improve synchronization accuracy, then timing precision is improved, but device complexity increases
Solution Approach 1:
Each UE autonomously determines its own synchronization level and selects its parent UE based on simple criteria: non-WWAN UEs select the nearest UE at level l-1 as their parent. This self-service approach allows distributed implementation without centralized control, maintaining timing precision while keeping individual UE complexity manageable through localized decision-making.
Solution Approach 2:
The system implements feedback through the hop count mechanism, where each UE knows its distance from the WWAN network boundary. This feedback information is used to determine synchronization level and parent selection, enabling accurate timing synchronization while providing a simple metric that reduces algorithmic complexity compared to continuous distance calculations.
Data Source
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AI summary
A method, an apparatus, and a computer program product for wireless communication are provided. The apparatus may be a UE. The UE determines timing information associated with a synchronization signal to be transmitted. The timing information includes a hop count and a reliability indicator associated with the synchronization signal. The reliability indicator is independent of the hop count and indicates one of reliable or unreliable. The UE broadcasts the timing information with the synchronization signal. The hop count may be a number of hops the synchronization signal is from a base station synchronization signal received from a base station.