Handover Control System Alternative Cell Investigation
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Solution Overview
Problem
In mobile communication systems, the handover process generates extra signaling due to concentration of signaling on a single control entity, leading to increased time requirements and potential failures, especially when relay stations are used, resulting in out-of-synchronization issues.
Innovation Solution
A handover control system where a target control apparatus investigates and autonomously notifies the source control apparatus of alternative cells that can accept a handover, reducing the need for retransmissions and extra signaling by including information on cells that can accept the handover in the acknowledge response.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the handover request is transmitted to a single target cell, then the handover control is simplified, but the handover fails when the target cell cannot accept the handover, requiring extra signaling and time for retransmission
Solution Approach 1:
The target control apparatus performs preliminary investigation of multiple candidate cells before the handover is executed. When the source control apparatus sends a handover request, the target control apparatus proactively identifies and prepares alternative target cells in advance, so that if the originally requested cell cannot accept the handover, the source can immediately switch to an alternative without additional signaling rounds.
2Reliability
If the source control apparatus retransmits the handover request when the first target cell cannot accept it, then the handover can succeed, but extra signaling and time are consumed
Solution Approach 1:
Alternative target cells are identified and prepared in advance by the target control apparatus before the handover execution phase. This preliminary action eliminates the need for time-consuming retransmission cycles, as the source control apparatus can immediately initiate handover to an alternative cell when the primary target is unavailable.
3Reliability
If multiple handover destination candidates are investigated, then the handover reliability improves, but the signaling load on the control apparatus increases
Solution Approach 1:
The target control apparatus acts as an intermediary that performs the investigation of multiple handover destination candidates on behalf of the source control apparatus. Instead of the source having to query multiple cells directly (which would increase source processing load), the target control apparatus centrally manages the investigation and selection, reducing the signaling and processing burden on the source control apparatus while still achieving reliable handover.
Data Source
Figure 1~2A
Figure 2B~3A
Figure 3B
AI summary
A second control apparatus (1B) is configured to be able to investigate handover possibilities of a plurality of cells including cells (41B, 42A, and 42C) in response to receipt of a handover request message transmitted from a first control apparatus (1A). The second control apparatus (1B) is configured to transmit an acknowledge response message indicating handover acknowledgment to the first control apparatus (1A) when at least one of the plurality of cells can accept a handover of a mobile station (3). As a result, extra signaling related to a handover procedure can be reduced.