RLP Personality Switch Buffering for HRPD Handover
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Solution Overview
Problem
Current wireless communication systems face challenges in performing seamless handovers between different revisions of air interface standards, leading to data loss and deleterious effects due to missing packets and corrupted data during personality changes, especially during handovers from Rev A to Rev 0 BTSs in HRPD systems.
Innovation Solution
The solution involves a personality switch mechanism that includes sending specific messages such as AttributeUpdateRequest, ConnectionClose, and TrafficChannelAssignment to manage the transition, and storing a buffer of data from the source BTS to ensure continuous data transmission to the terminal without purging unsent data, thereby avoiding RTO expiration and data loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a handover is performed between base stations implementing different revisions of air interface standard, then the terminal can maintain communication coverage and mobility, but data loss and packet corruption occur due to personality changes in the radio link protocol
Solution Approach 1:
The source base station transmits a buffer of data containing unsent and partially sent packets to the target base station before the handover is completed. This preliminary action ensures that when the terminal switches to the target base station, the data transmission can continue seamlessly without loss, as the target base station already has the necessary data in its buffer.
Solution Approach 2:
The patent introduces an intermediary data buffer mechanism that mediates between the source and target base stations during handover. The buffer acts as a temporary storage intermediary, holding data packets that need to be transferred from the source to the target base station, ensuring data continuity and preventing corruption during the personality change transition.
2Adaptability or versatility
If the radio link protocol instance is reset during personality change, then the protocol can adapt to the new revision, but packets are missed and data corruption occurs
Solution Approach 1:
The source base station performs preliminary action by transmitting the data buffer to the target base station before the protocol reset occurs. This ensures that when the radio link protocol instance is reset during personality change, the target base station already has the necessary data to continue transmission without causing packet loss or information corruption.
Solution Approach 2:
The patent implements a copying mechanism where the source base station creates a copy of the data buffer containing unsent and partially sent packets and transfers it to the target base station. This copying ensures that the data is preserved and available at the target base station even though the protocol instance is being reset during the personality change.
3Productivity
If data buffer is purged at source base station during handover, then memory resources are freed, but data loss occurs and RTO expiration is triggered
Solution Approach 1:
The source base station performs preliminary action by transmitting the data buffer to the target base station before purging its own buffer. This sequence ensures that data is safely transferred and stored at the target base station before the source base station frees its memory resources, preventing both data loss and RTO expiration while maintaining memory resource efficiency.
Solution Approach 2:
The patent applies the extraction principle by removing the data buffer from the source base station's memory only after it has been successfully transferred to the target base station. This extraction of the buffer contents to the target station enables the source to free its memory resources while ensuring data continuity, thus resolving the contradiction between memory efficiency and transmission reliability.
Data Source
AI summary
Techniques to support handover of a terminal from a source base station to a target base station are described. In one design, a determination is made whether a change in personality is requested by the terminal. If the answer is ‘Yes’, then the personality of the terminal may be switched by sending one or more appropriate messages. The connection and RLP for the terminal may be reset due to the change in personality. A buffer of data reported by the source base station as being served to the terminal (e.g., no NAK was sent) may be saved by a BSC/PCF. The buffer of data may be sent to the target base station when handover occurs. New data may thereafter be sent to the target base station. This buffer of duplicate data may avoid both loss of data and retransmission timeout by TCP during the handover.