UE Cell Selection for Asymmetric Uplink Downlink Range Mismatch
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Solution Overview
Problem
User equipment (UE) with asymmetric uplink and downlink communication capabilities, particularly those with high gain antennas, often experience transmit failures and radio link failures due to mismatched reception and transmission ranges, leading to suboptimal cell selection and increased dropped calls when near international borders or in densely configured PLMN areas.
Innovation Solution
The UE identifies asymmetric conditions by determining the difference between its downlink reception range and uplink transmission range, or by monitoring transmit failures and GPS coordinates, and modifies cell selection parameters to switch from a less favorable public land mobile network (PLMN) to a more suitable visitor or visited PLMN, ensuring better connectivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If a UE with high gain antenna uses standard cell selection rules, then the UE can receive downlink signals over a greater range, but the UE experiences transmit failures and radio link failures due to limited uplink transmission range
Solution Approach 1:
The patent modifies cell selection parameters (q-RxLevMinimum, q-QualMinimum, cellReselectionOffset) based on detected uplink transmission failures. When failures are detected, the UE adjusts these parameters to prefer cells with more favorable uplink conditions, thereby resolving the contradiction between extended downlink range and reliable uplink transmission
Solution Approach 2:
The UE monitors uplink transmission success/failure rates and uses this feedback to dynamically adjust cell selection behavior. When transmit failures exceed a threshold, the UE modifies its cell selection criteria to avoid cells where the downlink is strong but uplink is weak, thus improving uplink reliability while maintaining the benefit of high gain antenna reception
2Stability of the object's composition
If the UE remains on the current PLMN cell with strong downlink signal, then the UE maintains stable downlink reception, but the UE experiences transmit failures due to mismatched uplink range
Solution Approach 1:
The patent implements dynamic cell selection parameter adjustment based on real-time uplink transmission performance. Instead of static cell selection, the UE continuously monitors uplink failures and adapts its selection criteria, allowing it to switch from a cell with stable downlink but poor uplink to a more balanced cell when failures are detected
Solution Approach 2:
The UE changes cell selection parameters (q-RxLevMinimum, q-QualMinimum, cellReselectionOffset) when uplink failures are detected, modifying the evaluation criteria to favor cells with better uplink characteristics, thereby improving uplink transmission success rate while maintaining acceptable downlink stability
3Device complexity
If the UE uses standard cell selection criteria near PLMN borders, then the UE can maintain simple selection logic, but the UE fails to identify more favorable VPLMN cells due to asymmetric UL/DL capabilities
Solution Approach 1:
The UE autonomously detects its own uplink transmission failures and self-adjusts its cell selection parameters without requiring complex network assistance or additional signaling. This self-service approach maintains relatively simple selection logic while improving cell selection appropriateness for asymmetric UL/DL scenarios
Solution Approach 2:
The UE performs preliminary monitoring of uplink transmission success rates before making cell selection decisions. By detecting asymmetric UL/DL conditions in advance through failure rate monitoring, the UE can proactively adjust its selection criteria to favor suitable cells, improving selection appropriateness without significantly increasing complexity
Data Source
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AI summary
Method and apparatus are described for wireless communication. A user equipment (UE) located at a public land mobile network (PLMN) border area may modify cell selection parameters in order to leave a current PLMN for a more favorable visited PLMN (VPLMN). The UE may, for example, identify the border area by monitoring GPS coordinates, identifying a mobile country code (MCC) of a network, searching for a background PLMN after experiencing a number of uplink transmit failures, or by detecting a high block error rate (BLER). Additionally or alternatively, the UE may have certain physical or environmental constraints that create a mismatch between the Downlink (DL) reception range and the Uplink (UL) transmission range, and this mismatch may be a basis for, or may be accounted for, in modifying cell selection parameters.