Synchronizing Circuit-Switched and Packet-Switched Handovers

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Solution Overview

Problem

In Dual Transfer Mode (DTM) handovers, there is a significant service interruption issue due to the lack of synchronization between MSCs and SGSNs during PS handovers, resulting in excessive delays, particularly in cases where there is no direct connection between MSCs and SGSNs, leading to inefficiencies in resource handover.

Innovation Solution

A new mechanism is introduced to synchronize the handover of PS and CS resources to the same target cell by ensuring the Target Cell Identifier is known to the SGSN, with the BSS sending either a single preferred target cell ID or a list, depending on network mode and interface support, to facilitate coordinated handovers between MSC and SGSN.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the BSS sends a list of target BSSs to the MSC for CS handover selection, then the MSC can choose an appropriate target BSS based on network conditions, but the SGSN lacks knowledge of the target BSS chosen by the MSC, causing PS handover synchronization issues and service interruption

Engineering Contradiction:

Improvehandover synchronizationVSAvoidservice interruption

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The patent introduces the target BSS as an intermediary that receives information from both the MSC and SGSN. The target BSS acts as a mediator to synchronize the handover process by receiving the target cell identifier from the MSC and the target BSS identifier from the SGSN, ensuring both networks coordinate on the same target for seamless DTM handover

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent merges the CS and PS handover processes by ensuring both the MSC and SGSN select the same target BSS. This is achieved by the target BSS combining information from both networks and coordinating the handover execution, effectively merging what were previously separate independent handover procedures into a synchronized unified process

Inventive Principle:

Principle #5Merging (Combining)

2Adaptability or versatility

If there is no direct connection between MSC and SGSN, then network architecture flexibility is improved, but information exchange between MSC and SGSN cannot occur, preventing efficient and seamless handover

Engineering Contradiction:

Improvenetwork architecture flexibilityVSAvoidtarget cell information exchange

Core Design Contradiction:

Adaptability or versatilityVSLoss of information

Solution Approach 1:

The target BSS serves as an intermediary that enables information exchange between the MSC and SGSN without requiring a direct connection between them. The target BSS receives the target cell identifier from the MSC and the target BSS identifier from the SGSN, facilitating coordinated handover information exchange through this intermediate node

Inventive Principle:

Principle #24Intermediary (Mediator)

Data Source

PatentEP1864542B1Utilizing a same target cell during circuit-switched and packet switched handover

Publication Date: 2014.09.03 QUALCOMM INC

Figure 1
Figure 2A~2B
Figure 3

AI summary

In case of both circuit-switched and a packet-switched connection handover from a source (200) to a target (510) radio access network or base station subsystem a new target ID indication message (415.1; 415.2) is sent to a core network node (422) either from a core network element (215) or from the target radio access network or base station subsystem, depending on whether there is an interface (Gs) between the core network element and the core network node. In one embodiment, in contrast to the prior art, the new target ID indication message is mandated to only identify one target base station or target radio access network.