D2D Synchronization Source Selection and Power Management
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Solution Overview
Problem
User terminals in mobile communication systems face challenges in effectively utilizing Device-to-Device (D2D) proximity services when out of network coverage, as existing solutions do not efficiently manage synchronization signals and resource monitoring, leading to unnecessary power consumption and communication disruptions.
Innovation Solution
A user terminal is designed to select a D2D synchronization source from other user terminals, both within and out of network coverage, and dynamically manage radio resources to synchronize and transmit signals, optimizing power usage by monitoring only necessary resource pools based on signal strength and coverage status.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If user terminals transmit D2D synchronization signals continuously when out of network coverage, then synchronization reliability is improved, but power consumption increases
Solution Approach 1:
The patent implements periodic transmission of D2D synchronization signals instead of continuous transmission. User terminals transmit synchronization signals at predetermined intervals (e.g., every frame or every other frame) when out of network coverage, which maintains synchronization reliability while significantly reducing power consumption compared to continuous transmission.
Solution Approach 2:
The patent enables user terminals to autonomously select synchronization sources and manage their own synchronization state without network assistance. When out of coverage, terminals independently determine whether to transmit or monitor synchronization signals based on their battery status and detected signal conditions, eliminating the need for network-controlled transmission scheduling.
2Reliability
If user terminals monitor all D2D communication resource pools, then communication reliability is improved, but power consumption increases
Solution Approach 1:
The patent implements selective monitoring where user terminals monitor only specific D2D communication resource pools based on their synchronization state and coverage condition. Terminals out of coverage monitor only the second resource pool designated for out-of-coverage operations, while terminals in coverage monitor the first resource pool, avoiding unnecessary monitoring of all resource pools and reducing power consumption.
Solution Approach 2:
The patent makes the monitoring behavior dynamic based on real-time conditions. User terminals adapt their monitoring strategy according to whether they are in or out of network coverage, their battery status, and the presence of detectable synchronization signals, transitioning between different monitoring modes to optimize the balance between communication reliability and power consumption.
3Reliability
If multiple user terminals transmit D2D synchronization signals simultaneously, then synchronization availability is improved, but signal interference increases
Solution Approach 1:
The patent implements feedback mechanisms where user terminals detect and measure the strength of D2D synchronization signals from other terminals. Based on this feedback, terminals adjust their transmission behavior - selecting stronger signals as synchronization sources and avoiding simultaneous transmission with selected sources, thereby reducing interference while maintaining synchronization availability.
Solution Approach 2:
Instead of having all terminals transmit synchronization signals simultaneously, the patent inverts the approach by having terminals selectively receive and synchronize to signals from others. Terminals out of coverage that detect sufficient synchronization signals from other terminals will stop transmitting their own synchronization signals and instead monitor and synchronize to the detected signals, reducing overall interference.
Data Source
AI summary
A user terminal supports a D2D proximity service enabling a direct device-to-device communication without passing through a network. The user terminal includes a controller configured to select one of a plurality of other user terminals as a D2D synchronization source and to synchronize to a D2D synchronization signal transmitted by the D2D synchronization source, when the user terminal receives D2D synchronization signals transmitted by the plurality of other user terminals in a case where the user terminal is out of network coverage. The controller stops transmission of a predetermined D2D synchronization signal in response to selecting the other user terminal as the D2D synchronization source, when the user terminal is transmitting the predetermined D2D synchronization signal in a case where the user terminal is out of network coverage.