Dynamic PDCP Reordering Window for Sidelink Duplication
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Solution Overview
Problem
In wireless communication systems, particularly in sidelink communication for V2X, the existing methods face challenges in reliable packet duplication and reordering, leading to potential packet loss and increased latency due to the PDCP reordering window management, especially when the first received PDCP PDU is outside the reordering window.
Innovation Solution
The proposed solution involves updating the lower edge of the PDCP reordering window when the first received PDCP PDU is not associated with PDCP SN 0, and using state variables like Last_Submitted_PDCP_RX_SN and Next_PDCP_RX_SN to manage packet reordering and duplication, ensuring that packets are not incorrectly discarded and maintaining reliable communication.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the PDCP reordering window is used to manage packet reception, then packet reordering capability is improved, but packet loss occurs when the first received PDCP PDU is outside the reordering window
Solution Approach 1:
The reordering window lower edge is made dynamic by updating it to the PDCP SN of the first received PDCP PDU when that PDU is outside the original reordering window. This dynamic adjustment allows the window to adapt to the actual reception situation, preventing packet loss while maintaining reordering capability for subsequent packets.
Solution Approach 2:
The patent changes the parameter of the reordering window lower edge position based on the PDCP SN of the first received PDCP PDU. By modifying this parameter dynamically, the system resolves the contradiction between maintaining a fixed reordering window for reliability and adapting to variable packet arrival patterns to prevent loss.
2Ease of operation
If the first received PDCP PDU is outside the reordering window, then reordering management becomes complex, but latency increases due to incorrect packet discarding
Solution Approach 1:
The patent performs preliminary action by updating the reordering window lower edge to the PDCP SN of the first received PDCP PDU before processing subsequent packets. This preliminary adjustment prevents incorrect discarding of packets and avoids the latency that would result from reordering management complexity and packet discarding.
3Reliability
If packet duplication is implemented for sidelink communication, then reliability is improved, but packet loss occurs due to reordering window management issues
Solution Approach 1:
By making the reordering window lower edge dynamic and updating it based on the first received PDCP PDU's PDCP SN, the system resolves the contradiction between implementing packet duplication for reliability and preventing packet loss during reordering management.
Data Source
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AI summary
Methods and apparatuses for improving initialization of sidelink duplication reception in a wireless communication system are disclosed herein. In one method, a User Equipment, UE, receives a first Packet Data Convergence Protocol, PDCP, Protocol Data Unit, PDU, on a logical channel associated with a sidelink radio bearer, SLRB, (1005). The UE initializes a first state variable based on a partial Reordering_Window and a PDCP Sequence Number, SN, of the first received PDCP PDU, wherein the first state variable indicates the PDCP SN of a last PDCP Service Data Unit, SDU, delivered to the upper layers by a PDCP entity created for the SLRB, and the partial Reordering Window is less than a Reordering Window (1010). The UE performs a re-ordering procedure for the first PDCP PDU using the initialized first state variable (1015).