FMS and Bitmap Control Message for LTE Handover Reliability
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Solution Overview
Problem
In next-generation mobile communication systems like LTE, there is a need for efficient reception and transmission of reception information to prevent packet losses and unnecessary retransmissions during handovers, as existing methods lack effective mechanisms to indicate whether data units have been received.
Innovation Solution
A method and apparatus that generate and transmit a First Missing Sequence Number (FMS) and a bitmap to indicate non-received data units, allowing for efficient retransmission by distinguishing between out-of-sequence and non-received data units, thereby preventing unnecessary packet transmission and loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional PDCP status report methods are used during handover, then handover continuity is maintained, but packet losses and unnecessary retransmissions occur due to inability to accurately indicate received data units
Solution Approach 1:
The reception status report is segmented into two parts: FMS (First Missing Sequence Number) indicating the first missing data unit, and a bitmap indicating reception status of subsequent data units. This segmentation allows precise indication of which data units were received and which were lost, resolving the information loss problem while maintaining reliability.
Solution Approach 2:
The patent implements a feedback mechanism where the receiving end sends back a status report containing FMS and bitmap information to the transmitting end. This feedback loop enables the transmitting end to accurately identify missing packets and retransmit only those specific packets, improving reliability while preventing unnecessary retransmissions of already received data.
2Reliability
If all data units are retransmitted during handover, then packet loss is prevented, but transmission efficiency decreases due to unnecessary retransmissions
Solution Approach 1:
The patent extracts only the necessary information (FMS and bitmap) needed to identify missing data units, rather than retransmitting all data units. This allows the system to achieve lossless handover by retransmitting only the specific missing packets identified through the extracted status information, thereby maintaining reliability while improving transmission efficiency.
Solution Approach 2:
Instead of retransmitting all data units (excessive action), the patent uses FMS and bitmap to identify and retransmit only the partial set of missing data units. This partial action approach prevents packet loss while avoiding the inefficiency of redundant retransmissions, thus balancing reliability and productivity.
3Reliability
If detailed reception status information is transmitted, then packet loss prevention is improved, but control message size and processing complexity increase
Solution Approach 1:
The patent changes the parameter representation from transmitting detailed status for each data unit to using FMS (a single sequence number) and a compact bitmap. This parameter transformation maintains high reception status accuracy while significantly reducing control message size and processing complexity, as the bitmap efficiently encodes the status of multiple data units in a compact form.
Data Source
AI summary
A method and an apparatus for processing a control message for a request of retransmission are provided. The method includes generating a First Missing Serial number (FMS) describing a serial number of a data unit having a lowest serial number among data units which are not received, determining whether a data unit having a serial number greater than the serial number described in the FMS exists due to an out of sequence among data units which are previously received, generating a bitmap indicating a reception of a plurality of data units having a serial number greater than the FMS, if a data unit which is out of sequence exists, and connecting and transmitting the FMS and the bitmap.