PDCP Packet Order Maintenance During Wireless Handover
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Solution Overview
Problem
In wireless communication systems, maintaining the order of data units during handover procedures is challenging, particularly in UMTS networks, where data packets may arrive out of sequence, leading to desynchronization and errors.
Innovation Solution
Incorporating sequence numbers into packet data convergence protocol (PDCP) units and using a mechanism to detect and correct sequence number errors, ensuring that only in-sequence packets are delivered to higher layers, with a timer or explicit indication from base stations to manage packet delivery during handover.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If data packets are transmitted during handover between base stations, then data transmission continuity is maintained, but packets may arrive out of sequence causing desynchronization and errors
Solution Approach 1:
The source base station performs preliminary actions by determining the last transmitted packet's sequence number before handover and forwarding this information to the target base station. This allows the target base station to pre-configure its transmission sequence, ensuring continuous and ordered packet delivery during handover without waiting for post-handover synchronization.
Solution Approach 2:
The mechanism implements feedback by having the source base station report the last transmitted packet's sequence number to the target base station during handover. This feedback information enables the target base station to adjust its transmission behavior and maintain proper packet sequencing, preventing out-of-order delivery and desynchronization.
2Manufacturing precision
If sequence numbers are used to maintain packet order, then packet delivery accuracy is improved, but processing complexity and overhead increase
Solution Approach 1:
The invention extracts only the essential sequence number information (specifically the last transmitted packet's sequence number) from the complete packet data and transmits this extracted information during handover. This selective extraction maintains packet delivery accuracy while minimizing the amount of additional data that needs to be processed and transmitted, thereby reducing protocol overhead and processing complexity.
3Duration of action of stationary object
If handover is performed rapidly to maintain connection continuity, then connection stability is improved, but packet sequence synchronization may be lost
Solution Approach 1:
The source base station performs preliminary action by determining and forwarding the last transmitted packet's sequence number to the target base station before the handover is complete. This advance preparation ensures that when the rapid handover occurs, the target base station already has the synchronization information needed to maintain packet sequence order, thus preserving reliability despite the speed of handover.
Data Source
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AI summary
The present invention relates to maintaining an order of received data units during a handover procedure in a wireless communication system. The present invention includes receiving a plurality of data units from a source base station according to a sequence prior to handover to a target base station, wherein each data unit includes a sequence number, receiving at least one data unit having a sequence number after handover from a target base station, and delivering to a higher layer all data units received from the source base station prior to handover and having sequence numbers smaller than a sequence number of the at least one data unit received from the target base station after handover.