Circuit-Switched Fallback Delay Mitigation in LTE Networks
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Circuit-switched fallback (CSFB) delays occur in Evolved Packet System (EPS) networks, leading to unintended delays and poor quality of service when transitioning from Long Term Evolution (LTE) to Second Generation/Third Generation (2G/3G) networks for circuit-switched services, due to factors like weak signal strength and excessive processing times.
Innovation Solution
A method and system that mitigates CSFB delay by initiating a timer upon sending a request for CSFB, selecting an algorithm to connect to a 2G/3G network if no response is received within a predetermined time, and utilizing signal strength measurements to implement inter-RAT cell reselection and Public Land Mobile Network selection for seamless service access.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the UE waits for a response message from the packet-switched network before initiating connection to the circuit-switched network, then the network can confirm resource allocation, but the service access delay increases significantly
Solution Approach 1:
The UE performs preliminary actions by starting a timer concurrently with sending the CSFB request message and proactively initiating connection to the circuit-switched network upon timer expiration without receiving a response. This preliminary action prevents the UE from idle waiting, thereby reducing service access delay while maintaining resource allocation confirmation through the timer mechanism.
Solution Approach 2:
The UE autonomously manages the fallback process by self-monitoring the timer status and self-initiating the circuit-switched network connection when the timer expires without response. This self-service approach eliminates the need for continuous network confirmation waiting, reducing delay while ensuring resource allocation is handled through the pre-configured timer-based mechanism.
2Loss of time
If the UE proactively initiates connection to the circuit-switched network without waiting for network response, then the service access delay is reduced, but the risk of connection failure due to unallocated resources increases
Solution Approach 1:
The network performs preliminary resource allocation confirmation before the UE initiates the CSFB request. The UE sends the request only after receiving this preliminary confirmation, ensuring resources are allocated while still allowing proactive initiation upon timer expiration without complete network response, thus balancing delay reduction with connection success.
3Reliability
If the UE implements traditional CSFB procedure waiting for network response, then resource allocation is confirmed, but the quality of service deteriorates due to excessive waiting time
Solution Approach 1:
The network performs preliminary resource allocation confirmation before the UE initiates CSFB. The UE then uses a timer-based mechanism to proactively initiate connection without waiting for the complete network response, thus maintaining resource allocation confirmation while significantly improving service access efficiency by eliminating idle waiting time.
Solution Approach 2:
The UE autonomously manages the fallback timing by self-monitoring the timer and self-initiating connection when appropriate. This self-service approach eliminates unnecessary waiting while ensuring resources are allocated through the pre-configured timer mechanism, thereby improving service access efficiency without sacrificing resource allocation confirmation.
4Reliability
If the UE uses signal strength measurements for cell reselection, then the service access reliability is improved, but the processing time and complexity increase
Solution Approach 1:
The UE performs signal strength measurements of candidate circuit-switched network cells in advance before initiating the CSFB connection. This preliminary measurement ensures the UE selects an appropriate target cell with sufficient signal strength, improving service access reliability while managing complexity through advance preparation rather than complex real-time decision-making.
Data Source
Figure 1
Figure 2
Figure 3
AI summary
System and methods for mitigating circuit-switched fallback delay. A user equipment may initiate connection of the user equipment to a packet-switched network. A request may be sent by the user equipment to the packet-switched network to access a circuit-switched service. A timer may be started to determine elapsed duration between sending the request and receiving a response from the packet-switched network that confirms resource allocation to access the circuit-switched service. The user equipment may select in response to timer expiration, indicating absence of response to the request, a particular algorithm when implemented initiates connection of the user equipment to a particular circuit-switched network to access the circuit-switched service.