CSFB Scan-List Filtering for Load Management
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Solution Overview
Problem
The process of circuit switched fallback (CSFB) in cellular wireless networks is inefficient due to the time-consuming scanning for CDMA coverage areas by wireless communication devices (WCDs), which can result in unnecessary delay and signaling when these areas are threshold loaded, leading to unproductive channel searches.
Innovation Solution
Implementing a method where the LTE network omits threshold-loaded CDMA coverage areas from the CSFB scan-list provided to WCDs, preventing them from scanning these areas and reducing unnecessary signaling and delay by filtering out high-load coverage areas from the list.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If WCDs scan all CDMA coverage areas for CSFB setup, then coverage availability is improved, but latency and signaling overhead increase due to scanning threshold-loaded areas
Solution Approach 1:
The network performs preliminary actions by determining the load status of CDMA coverage areas before providing the scan-list to the WCD. Coverage areas that are threshold-loaded are identified and excluded from the scan-list in advance, preventing the WCD from wasting time scanning these areas. This preliminary filtering resolves the contradiction by maintaining coverage availability through selective scanning while reducing latency by avoiding pre-loaded areas.
Solution Approach 2:
The patent applies local quality by providing different scan-lists to different WCDs based on their specific location and the local load conditions of CDMA coverage areas. Each WCD receives a customized scan-list that excludes only the threshold-loaded areas relevant to its location, rather than a universal exclusion. This resolves the contradiction by maintaining reliability for each local area while optimizing latency based on local conditions.
2Reliability
If WCDs scan threshold-loaded CDMA coverage areas, then comprehensive coverage search is performed, but unnecessary signaling and channel searches occur
Solution Approach 1:
The patent extracts and removes threshold-loaded CDMA coverage areas from the scan-list provided to WCDs. By taking out these problematic areas from the list of areas to be scanned, the system maintains comprehensive coverage search for all non-loaded areas while eliminating unnecessary signaling and channel searches for threshold-loaded areas. This directly resolves the contradiction by improving productivity without compromising coverage search completeness.
3Adaptability or versatility
If the scan-list includes all CDMA coverage areas, then complete coverage options are provided to WCDs, but network signaling overhead increases
Solution Approach 1:
The patent extracts threshold-loaded CDMA coverage areas from the complete list and removes them from the scan-list provided to WCDs. This extraction maintains adaptability by providing all viable coverage options while reducing signaling overhead by excluding areas that would result in unsuccessful scanning. The network still has complete information about all coverage areas, but only transmits the relevant subset to WCDs, resolving the contradiction between versatility and signaling overhead.
Data Source
AI summary
Disclosed is a method and system to help manage latency and reduce unnecessary signaling in setup of fallback communications, such as circuit switched fallback calls for instance, by taking into account the load in various fallback coverage areas. When the load of a fallback coverage area is threshold high, signaling may pass to a serving network to cause that fallback coverage area to be filtered out of a list of fallback coverage areas that a base station of the serving network would provide to a served device, so as to help avoid having the device scan for coverage of that fallback coverage area.