Bi-casting Sequence Number Slip for Mobile Handover
Solution Overview
Problem
During handover from one Node-B to another in a mobile system, real-time data packets experience interruptions due to misinterpreted sequence number wrap-around, leading to erroneous deciphering and loss of data, especially in HS-DSCH services like VoIP, as the user equipment incorrectly interprets received sequence numbers.
Innovation Solution
A method of bi-casting real-time data packets where a different sequence number is associated with each packet sent to the new Node-B compared to the old Node-B, preventing misinterpreted sequence number wrap-around by introducing a sequence number slip, ensuring continuous data flow and correct deciphering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the same sequence number is used for real-time data packets sent to both old Node-B and new Node-B during handover, then the system complexity is reduced, but the user equipment misinterprets sequence number wrap-around leading to erroneous deciphering and data loss
Solution Approach 1:
The sequence number space is segmented into two distinct ranges: one for packets sent to the old Node-B and another for packets sent to the new Node-B. This segmentation prevents the user equipment from misinterpreting sequence number wrap-around during handover, as the sequence numbers from different segments do not overlap or conflict.
Solution Approach 2:
The system changes the sequence number parameter dynamically based on the destination Node-B. When switching from old Node-B to new Node-B, a new sequence number range is introduced, effectively changing the parameter value to avoid wrap-around misinterpretation while maintaining the same underlying data packet sequence.
2Reliability
If bi-casting is implemented with different sequence numbers for old and new Node-B, then data reliability during handover is improved, but the system complexity and processing overhead increase
Solution Approach 1:
The sequence number slip is applied in advance before packet transmission to the new Node-B. By pre-configuring different sequence number ranges for old and new Node-B, the system eliminates the need for complex real-time sequence number adjustment during handover, reducing processing overhead while maintaining reliability.
Solution Approach 2:
The sequence number acts as an intermediary parameter that bridges the old and new Node-B transmissions. By introducing a sequence number slip, the system creates a clear distinction between packets from different sources, allowing the user equipment to correctly identify and process packets without complex handover management.
3Measurement precision
If sequence number slip is introduced to prevent wrap-around misinterpretation, then data interpretation accuracy is improved, but the processing time and computational overhead increase
Solution Approach 1:
The sequence number slip is applied in advance during packet preparation rather than during reception or processing. This preliminary assignment of distinct sequence number ranges eliminates the need for complex real-time verification and interpretation logic at the user equipment, maintaining low processing time while ensuring accurate data interpretation.
Data Source
AI summary
A method is provided for bi-casting real time data packets in a mobile system that includes a first Node-B and a second Node-B for communication with a user equipment. The method includes associating a first sequence number with a first real time data packet when sending the first real time data packet to the first Node-B and transmitting the first real time data packet associated with the first sequence number to the first Node-B. The method also includes associating a second sequence number with a second real time data packet when sending the first real time data packet to the second Node-B. wherein the second sequence number is different from the first sequence number and transmitting the first real time data packet associated with the second sequence number to the second Node-B.