D2D Terminal Common Time Reference Synchronization
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In emergency situations where the cellular network is damaged or unavailable, device-to-device (D2D) wireless communication terminals face challenges in acquiring a common time reference, leading to increased power consumption and inefficient discovery processes due to the lack of synchronization with a base station.
Innovation Solution
A D2D terminal autonomously provides a common time reference through a D2D synchronization signal, which is distinct from the base station's synchronization signal, allowing it to synchronize with other terminals and maintain communication even without a functioning cellular network. This involves transmitting the D2D synchronization signal in specific time and frequency resources, enabling terminals to operate independently and reduce power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If D2D terminals continuously monitor discovery signals without common time reference, then they can detect neighboring terminals, but power consumption increases significantly
Solution Approach 1:
The patent applies preliminary action by having D2D terminals pre-synchronize their time references before the discovery process begins. Terminals acquire a common time reference from available sources (base station or other D2D terminals) in advance, allowing them to know precisely when neighboring terminals will transmit discovery signals. This eliminates the need for continuous monitoring, as terminals can enter low-power states between predetermined discovery signal transmission times.
2Measurement precision
If D2D terminals rely on base station for common time reference, then synchronization is accurate, but communication fails when cellular network is unavailable
Solution Approach 1:
The patent introduces an intermediary mechanism where D2D terminals themselves become time reference sources for other terminals when the base station is unavailable. A terminal that has acquired a common time reference (either from base station or previously from another terminal) can share this reference with neighboring terminals through dedicated synchronization signals. This intermediary approach maintains time synchronization accuracy without requiring direct base station connection for all terminals.
Solution Approach 2:
The patent segments the time reference provision function into hierarchical levels: base station provides reference to covered terminals, and those terminals in turn provide reference to other D2D terminals outside base station coverage. This segmentation allows the system to maintain accurate time references across the entire D2D network even when parts are disconnected from the cellular infrastructure.
3Measurement precision
If D2D terminals use base station synchronization signal, then time reference is provided, but interference occurs with existing data scheduling
Solution Approach 1:
The patent applies local quality by making the synchronization signal transmission characteristics specific to D2D communication needs rather than using the base station's downlink synchronization signal format. D2D terminals transmit synchronization signals with parameters (time, frequency, power, sequence) optimized for device-to-device scenarios, which are locally adapted to minimize interference with uplink data scheduling while maintaining time reference accuracy.
Solution Approach 2:
The patent moves the synchronization function to another dimension by having D2D terminals transmit synchronization signals in dedicated resource elements and time slots that are separate from both base station downlink synchronization signals and data transmission resources. This dimensional separation in the time-frequency domain allows simultaneous operation of data scheduling and D2D synchronization without mutual interference.
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A method by a terminal in a communication system comprises attempting to acquire synchronization information from a cell. The method comprises attempting to acquire synchronization information from another terminal in a case that the synchronization information from the cell is not acquired after attempting to acquire the synchronization information from the cell. The method comprises acquiring synchronization information by the terminal itself in a case that the synchronization information from the cell is not acquired and the synchronization information from the another terminal is not acquired. The method comprises transmitting the synchronization information acquired by the terminal itself on a subframe identified based on preconfigured information.