D2D PDCP State Variable Synchronization via Explicit Signaling
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Solution Overview
Problem
Current D2D communication systems lack an efficient method for transmitting explicit signals of layer-2 state variables, which can lead to synchronization issues and communication failures between devices.
Innovation Solution
The transmission of explicit configuration messages containing initial values of RLC and PDCP state variables from the transmitter to the receiver, allowing for robust initialization and synchronization of state variables, such as VR(UH) and VR(UR) for RLC, and RX_HFN and Next_PDCP_RX_SN for PDCP, to ensure correct packet ordering and deciphering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If D2D communication systems transmit data without explicit signaling of layer-2 state variables, then the device complexity and signaling overhead are reduced, but synchronization reliability and communication stability deteriorate
Solution Approach 1:
The patent applies preliminary action by transmitting explicit configuration messages containing initial values of layer-2 state variables (such as PDCP sequence numbers, RLC sequence numbers, and HARQ process identifiers) before actual data transmission begins. This pre-signaling ensures that both transmitting and receiving devices initialize their state variables consistently, preventing synchronization issues during subsequent communication without requiring continuous complex signaling.
2Loss of information
If D2D communication systems use implicit state variable initialization, then the signaling overhead is reduced, but packet ordering accuracy and deciphering reliability worsen
Solution Approach 1:
The patent introduces an intermediary explicit configuration message that carries initial state variable values between transmitting and receiving devices. This intermediate signaling layer provides the necessary synchronization information without requiring excessive ongoing signaling, acting as a mediator that establishes initial conditions for accurate packet ordering and deciphering while minimizing overall information loss.
3Loss of time
If D2D devices initialize state variables without explicit signaling, then the communication setup time is reduced, but the risk of packet discarding and communication failure increases
Solution Approach 1:
The patent applies preliminary action by establishing initial state variable values through explicit configuration messages during the connection setup phase. This preliminary synchronization prevents subsequent packet discarding and communication failures by ensuring both devices start with consistent state variables, without significantly extending initialization time beyond standard connection establishment procedures.
Data Source
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AI summary
A method for a User Equipment, UE, operating in a wireless communication system is proposed, which comprises: transmitting, by a transmitting Packet Data Convergence Protocol, PDCP, entity of the UE to a receiving PDCP entity of a peer UE, first PDCP variables via a direct interface between the UE and the peer UE; transmitting, by the transmitting PDCP entity of the UE to the receiving PDCP entity of the peer UE, a first PDCP data unit via the direct interface; transmitting, by the transmitting PDCP entity of the UE to the receiving PDCP entity of the peer UE, second PDCP variables via the direct interface; and transmitting, by the transmitting PDCP entity of the UE to the receiving PDCP entity of the peer UE, a second PDCP data unit via the direct interface, wherein the first PDCP variables are used for deciphering the first PDCP data unit by the peer UE, and the second PDCP variables are used for deciphering the second PDCP data unit by the peer UE.