D2D Resource Selection in Exception Idle State for Coverage Transition
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Solution Overview
Problem
Current D2D communication systems face discontinuity issues when a terminal transitions from outside to inside network coverage, as mode 2 operations are only allowed in the RRC-connected state, leading to potential service disruptions and stability concerns, especially in public safety networks that require continuous communication.
Innovation Solution
A method allowing mode 2 operations in an exceptional state, where the terminal can select resources from a pool to transmit D2D signals even in the RRC idle state by determining network coverage and receiving specific resource information, ensuring continuous D2D communication.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If mode 2 operation is allowed only in RRC-connected state, then resource management is simplified and network control is maintained, but D2D communication continuity is disrupted when terminal enters network coverage
Solution Approach 1:
The patent introduces dynamic state classification, dividing RRC idle state into two sub-states: normal idle state and exception idle state. This dynamic classification allows the system to adaptively apply different mode 2 operation rules based on whether the terminal is in coverage, thereby maintaining D2D communication continuity while managing RRC states efficiently.
Solution Approach 2:
The patent changes the operational parameters by introducing a coverage-based exception state flag. When a terminal enters coverage from out-of-coverage, the exception state is activated, allowing mode 2 operations in RRC idle state. This parameter change enables continuous D2D communication without requiring RRC connection establishment, thus resolving the contradiction between reliability and complexity.
2Reliability
If terminal switches to RRC-connected state for mode 2 operation, then D2D communication can continue, but service disruption occurs during state transition
Solution Approach 1:
The patent enables mode 2 operations to be prepared and maintained in the exception idle state before RRC connection is established. By allowing resource selection and D2D signal transmission in advance during the exception idle state, the system eliminates the need for state transition before D2D communication, thereby preventing service disruption and reducing transition time.
Solution Approach 2:
The patent ensures continuous D2D communication by maintaining mode 2 operation capability throughout the exception idle state. The terminal can continuously select resources from the resource pool and transmit D2D signals without interruption, ensuring the useful action of D2D communication remains continuous even when entering network coverage.
3Adaptability or versatility
If mode 2 operation is restricted to RRC-connected state, then network control over D2D resources is maintained, but D2D service availability is reduced in public safety networks
Solution Approach 1:
The patent applies local quality by introducing special exception state rules specifically for terminals entering coverage from out-of-coverage. This localized approach allows mode 2 operations in RRC idle state only for these specific terminals in the exception state, while other terminals continue to follow standard RRC state management rules, thus increasing D2D service availability without overwhelming system complexity.
Solution Approach 2:
The patent segments the RRC idle state into normal idle state and exception idle state, allowing different D2D operation rules to apply to each segment. This segmentation enables targeted relaxation of RRC state requirements for mode 2 operations in the exception state, improving D2D service availability for public safety networks while maintaining standard control for other scenarios.
Data Source
AI summary
Provided are a D2D (device-to-device) signal transmitting method implemented by a terminal in a wireless communication system, and a terminal using the method. The method is characterized by the operations of: receiving information showing whether a mode 2 operation is allowed in an exceptional state; determining whether the exceptional state is in effect; and when the exceptional state is determined to be in effect, implementing the mode 2 operation, wherein in the mode 2 operation, the terminal selects a certain resource from a resource pool, and the selected resource is used to transmit the D2D signal.