Cellular Feedback Multiplexing in D2D Subframes
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Solution Overview
Problem
In 3GPP LTE-A systems, device-to-device (D2D) communication performance is degraded due to prioritization of cellular feedback over D2D signals, leading to performance loss in D2D communications when uplink cellular feedback conflicts with D2D transmissions.
Innovation Solution
Cellular feedback is multiplexed with D2D signals in the same subframe, using a symbol initially kept as a D2D gap, allowing continuous D2D transmission without interrupting cellular feedback, thus avoiding performance degradation in both D2D and cellular communications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If cellular feedback is prioritized over D2D signals, then cellular communication reliability is improved, but D2D communication performance deteriorates
Solution Approach 1:
The uplink subframe is segmented into multiple regions: D2D signal transmission regions and cellular feedback transmission regions. This segmentation allows both D2D signals and cellular feedback to coexist in the same subframe without mutual interference, resolving the contradiction by providing dedicated resources for each function.
Solution Approach 2:
The patent introduces a new dimension for resource allocation by utilizing previously unused or underutilized resources in the uplink subframe. Specifically, it employs resources that were traditionally left blank or used for other purposes, thereby adding capacity for cellular feedback without encroaching on D2D signal resources.
2Loss of time
If D2D transmission is interrupted for cellular feedback, then cellular feedback timing is maintained, but D2D communication continuity deteriorates
Solution Approach 1:
The patent performs preliminary allocation of resources by designating specific regions within the uplink subframe for cellular feedback transmission in advance. This preliminary action ensures that cellular feedback can be transmitted at the required timing without interrupting ongoing D2D transmissions, as the feedback resources are pre-configured and do not conflict with D2D signal resources.
Solution Approach 2:
The patent enables continuous D2D transmission by ensuring that D2D signal resources remain continuously available throughout the uplink subframe. Meanwhile, cellular feedback is transmitted in dedicated regions without disrupting the continuous flow of D2D communications, thus maintaining the continuity of useful action for both functions.
3Reliability
If separate resources are allocated for cellular feedback and D2D signals, then transmission conflicts are avoided, but resource utilization efficiency deteriorates
Solution Approach 1:
The patent creates a multi-functional uplink subframe structure that can simultaneously support both D2D signal transmission and cellular feedback transmission. By designing the subframe to serve multiple functions concurrently through regional division, it achieves universal resource allocation that avoids transmission conflicts while maintaining high overall resource utilization.
Solution Approach 2:
The patent merges D2D signal transmission and cellular feedback transmission into the same uplink subframe by allocating different regions within it. This merging approach allows both functions to operate simultaneously in a coordinated manner, avoiding the need for separate dedicated subframes and thereby improving resource utilization efficiency while preventing transmission conflicts.
Data Source
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Figure 4B
AI summary
This disclosure generally relates to cellular feedback transmission for the user equipments enabling D2D communications. In one embodiment, the cellular uplink feedback and the D2D signals may be multiplexed in the same D2D subframe. For example, the feedback may be transmitted using a symbol that is not used to carry the D2D signal. In one embodiment, the feedback may be transmitted in the symbol that is kept as gap in the D2D subframe. By multiplexing the cellular feedback with the D2D signals, the cellular feedback can be transmitted to the BS without breaking off the D2D transmission.