CDMA Access Screening Using Pilot Strength Thresholds
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Solution Overview
Problem
In CDMA networks, a significant number of origination access failures and drops occur due to low active pilot strength, with existing echo screening methods failing to effectively redirect mobile units to stronger pilots, leading to inefficient call handling and increased call drops.
Innovation Solution
A method for access screening in CDMA networks that compares the strength of a reference pilot in an origination message to upper and lower pilot strength thresholds, redirecting mobile units if the reference pilot is weak and determining if additional pilots are stronger, thereby optimizing pilot selection and reducing unnecessary redirections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If screening is performed based solely on the Echo of the primary or reference pilot, then the screening process is simple, but a higher number of calls are redirected without a significant increase in performance
Solution Approach 1:
The patent changes the screening parameters from using only reference pilot Echo to a multi-parameter approach that includes reference pilot strength, additional pilot strengths, and comparison against multiple thresholds (UPST and LPST). This parameter expansion resolves the contradiction by improving call handling performance through more informed screening decisions while maintaining manageable system complexity through structured threshold comparisons.
Solution Approach 2:
The patent segments the screening process into distinct decision stages: first comparing reference pilot strength against thresholds, then conditionally evaluating additional pilot strengths. This segmentation allows the system to achieve better performance by evaluating multiple factors while keeping the overall process organized and computationally efficient through a hierarchical decision structure.
2Reliability
If mobile units are redirected more frequently to stronger pilots, then access failure reduction is improved, but network overhead and redirection signaling increase
Solution Approach 1:
The patent introduces threshold parameters (UPST and LPST) that define specific conditions for redirection. By changing from frequent unconditional redirection to threshold-based conditional redirection, the system reduces access failures only when necessary, thereby minimizing unnecessary redirection signaling and network overhead while maintaining improved access reliability.
Solution Approach 2:
The patent implements a feedback mechanism where the system evaluates current pilot strength conditions against predefined thresholds before initiating redirection. This feedback-based approach ensures redirection occurs only when performance degradation is detected, optimizing the balance between access failure reduction and network overhead by avoiding unnecessary redirection signaling.
3Measurement precision
If the system evaluates additional pilot strengths, then pilot selection accuracy is improved, but processing complexity increases
Solution Approach 1:
The patent segments the pilot evaluation process into a two-stage approach: first evaluating reference pilot strength against thresholds, then conditionally evaluating additional pilot strengths only when needed. This segmentation improves pilot selection accuracy by considering multiple pilots while controlling processing complexity through a hierarchical structure that avoids unnecessary evaluations.
Solution Approach 2:
The patent applies partial action by evaluating additional pilot strengths only in specific conditions (when reference pilot strength exceeds LPST but fails to exceed UPST). This partial evaluation approach improves pilot selection accuracy when needed while avoiding the processing complexity of evaluating all pilots in all scenarios, achieving optimal balance through conditional processing.
Data Source
AI summary
Provided are system and method for performing access screening in a CDMA network. In one embodiment, the method comprises comparing a strength of a reference pilot specified in an origination message (“ORM”) received from the mobile unit to at least one of an upper pilot strength threshold (“UPST”) and a lower pilot strength threshold (“LPST”); responsive to the reference pilot strength failing to exceed the LPST, redirecting the mobile unit; responsive to the reference pilot strength exceeding the LPST but failing to exceed the UPST, determining whether an additional pilot is reported having a strength greater than that of the reference pilot; and responsive to a determination that no additional pilot is reported having a strength greater than that of the reference pilot, redirecting the mobile unit.