Inter-Cell D2D Discovery via Uplink Relay
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Solution Overview
Problem
In mobile communication systems, Device-to-Device (D2D) proximity services face challenges with inter-cell discovery when user terminals in different cells operate on different frequencies, as the discovery signal cannot be received due to frequency mismatches, hindering effective D2D communication.
Innovation Solution
User terminals use radio resources of a secondary frequency, exclusively allocated for uplink, to transmit discovery signals, synchronized with the primary cell's frequency, allowing for successful inter-cell discovery even when frequencies differ between cells.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a user terminal transmits a discovery signal on the frequency of its serving cell, then the transmission is simple and follows standard procedures, but the discovery signal cannot be received by terminals in cells with different frequencies
Solution Approach 1:
The patent introduces a base station as an intermediary that bridges frequency differences between cells. The base station receives discovery signals from user terminals on its serving frequency, processes them, and forwards discovery information to other base stations serving cells with different frequencies, enabling indirect inter-cell discovery across frequency boundaries
Solution Approach 2:
The patent combines cellular network infrastructure with D2D discovery functionality. By integrating the base station into the discovery process, it merges the reliability of network infrastructure with the directness of D2D communication, allowing discovery signals to be effectively transmitted and received across frequency boundaries through the network's coordinated effort
2Productivity
If different cells operate on different frequencies to increase system capacity and reduce interference, then resource allocation is optimized, but inter-cell D2D discovery becomes impossible due to frequency mismatches
Solution Approach 1:
The base station is赋予 multi-functionality: it serves both as a traditional cellular base station for its own frequency and as a discovery relay for other frequencies. This universal role allows the network to maintain multiple frequency operations for capacity while enabling cross-frequency discovery through the base station's coordinated forwarding capability
Solution Approach 2:
The patent establishes a feedback mechanism where base stations exchange discovery signal information through the network. When a base station receives a discovery signal, it provides feedback to other base stations about the discovered terminal, enabling other cells to be aware of and communicate with terminals in different frequency cells
Data Source
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AI summary
A user terminal exists in a first cell operating at a first frequency, in a mobile communication system that supports a D2D proximity service. The user terminal includes a transmitter configured to transmit a discovery signal for discovering a proximal terminal that exists in a second cell different from the first cell by using radio resources of a second frequency different from the first frequency. The radio resources of the second frequency are radio resources used exclusively for an uplink.