Electronic Device PDCP Sequence Number Synchronization
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Solution Overview
Problem
In 5G communication systems, there is a significant mismatch between the sequence numbers of packet data convergence protocol (PDCP) PDUs transmitted by user equipment (UE) and expected by the network, leading to discarding of packets, which affects data transmission efficiency.
Innovation Solution
An electronic device is configured to receive a message indicating the PDCP state from the network, identify the first missing count, compare it with the scheduled transmission count, and adjust the count accordingly to prevent packet discarding by transmitting a PDCP control PDU with recovery request information when conditions are met.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the UE transmits PDCP PDUs with sequence numbers based on its local count, then the UE can maintain continuous data transmission, but the sequence numbers may significantly differ from those expected by the network, causing packets to be discarded as out of window
Solution Approach 1:
The network sends PDCP status reports to the UE containing the first missing count (FMC), which indicates the sequence number the network expects to receive. The UE uses this feedback to adjust its transmission count and synchronize with the network's expected sequence numbers, preventing packet discarding while maintaining continuous transmission.
Solution Approach 2:
The UE dynamically changes its transmission count parameter based on the received FMC value. When the network indicates a missing count, the UE adjusts its count to match the network's expected sequence number, resolving the mismatch between UE-generated and network-expected sequence numbers.
2Measurement precision
If the network discards PDCP PDUs with sequence numbers outside the expected window, then the network can maintain receiving accuracy, but data transmission efficiency deteriorates due to frequent packet discarding and retransmission
Solution Approach 1:
The network performs preliminary actions by sending PDCP status reports containing the FMC before the UE transmits out-of-window packets. This allows the UE to adjust its count in advance, preventing the transmission of packets that would otherwise be discarded, thereby maintaining both verification accuracy and transmission efficiency.
3Reliability
If the UE maintains a large counting window to accommodate sequence number variations, then packet delivery reliability improves, but the complexity of sequence number management increases
Solution Approach 1:
The PDCP status report with FMC acts as an intermediary mechanism that simplifies sequence number management. Instead of the UE maintaining a large counting window to handle all possible sequence number variations, the network provides precise feedback about the expected sequence number, allowing the UE to use a smaller, more manageable window while maintaining high delivery reliability.
Data Source
AI summary
According to an embodiment, an electronic device comprises: at least one processor, wherein the at least one processor may be configured to: receive a first message indicating a packet data convergence protocol (PDCP) state of a network from the network, identify a first missing count (FMC) of the network based on the first message, identify a count of a message scheduled to be transmitted by the electronic device, compare the count of the message scheduled to be transmitted with the FMC, and adjust the count of the message scheduled to be transmitted based on a result of the comparison.