LTE WLAN Aggregation PDCP Sequence Number Synchronization
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Solution Overview
Problem
In LTE and WLAN aggregation systems, the LLC layer in the WLAN link is unable to provide necessary feedback information to the PDCP layer, such as successfully delivered sequence numbers, leading to synchronization issues and inefficient data stream management.
Innovation Solution
A WLAN termination (WT) is designed to receive data from the PDCP layer, process it, and transmit it to the LLC layer, while also feeding back sequence number information to the PDCP layer, ensuring that only valid sequence numbers are used and indicating any transmission failures, thereby maintaining data stream synchronization and detecting link failures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the LLC layer transmits data without feedback mechanism, then the transmission speed is fast and simple, but the PDCP layer cannot detect data loss and synchronization is lost
Solution Approach 1:
The patent implements a feedback mechanism where the LLC layer sends status information (including sequence numbers of transmitted and acknowledged data) back to the PDCP layer. This feedback enables the PDCP layer to detect data loss, maintain synchronization, and request retransmission when necessary, thereby improving transmission reliability without excessive complexity.
Solution Approach 2:
The patent introduces an adaptation layer as an intermediary between the PDCP layer and the LLC layer. This adaptation layer handles the complex feedback and acknowledgment mechanisms, shielding the PDCP layer from direct complexity while ensuring reliable data transmission through proper sequence number management and loss detection.
2Productivity
If sequence numbers are continuously incremented without validation, then data transmission is continuous and fast, but sequence numbers may exceed valid range causing synchronization errors
Solution Approach 1:
The patent implements preliminary validation of sequence numbers before data transmission. The system checks whether the sequence number is within the valid range (using variables like t-FirstValidSN and t-LastValidSN) before allowing transmission, preventing synchronization errors from occurring in the first place while maintaining continuous data flow.
Solution Approach 2:
The feedback mechanism provides continuous monitoring of sequence number validity. The receiving end sends acknowledgments with valid sequence number ranges, and the transmitting end adjusts its sequence number generation accordingly, ensuring sequence numbers remain within valid ranges while maintaining high transmission efficiency.
3Reliability
If the system uses simple transmission without link failure detection, then the operation is simple and fast, but transmission failures go undetected and data loss occurs
Solution Approach 1:
The patent implements feedback mechanisms including acknowledgments and status reports that enable the system to detect link failures. When the PDCP layer does not receive expected acknowledgments or detects sequence number gaps, it can identify link failures and trigger appropriate recovery procedures, improving reliability while maintaining operational simplicity through automated detection.
Solution Approach 2:
The system implements self-diagnosis capabilities where the PDCP layer automatically detects transmission issues through sequence number validation and feedback analysis, and autonomously initiates retransmission or link recovery procedures without requiring complex external intervention, thereby improving reliability while keeping operations simple.
Data Source
AI summary
A data processing method and apparatus for LTE and WLAN aggregation and a communications system. The data processing method includes: receiving, by a WLAN termination in a WLAN link, data transmitted by a PDCP layer in an LTE link, and transmitting the data transmitted by the PDCP layer to an LLC layer in the WLAN link after processing; and feeding back highest successfully delivered PDCP sequence number information and/or unsuccessfully delivered PDCP sequence number information to the PDCP layer in the LTE link. Hence, a problem that an LLC layer is unable to provide transmission status indication necessary to a PDCP layer may be effectively solved.