GERAN to UTRAN Cell Reselection with RSCP Threshold
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Solution Overview
Problem
Current 2G to 3G cell reselection in mobile communication systems lacks a minimum acceptable UTRAN CPICH RSCP threshold, leading to inadequate reselection behavior, where mobile stations may choose unsuitable UTRAN cells, resulting in uplink failures or inability to access loaded cells.
Innovation Solution
A method for cell reselection by a mobile station from a GERAN to a UTRAN network, involving the use of a stored UTRAN RSCP suitability threshold with an offset, allowing for flexible reselection criteria that include a hysteresis value or power capabilities, to ensure reliable uplink and downlink operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the Ec/No threshold is set low to allow aggressive reselection, then the mobile station can reselect UTRAN cells more freely, but uplink failures occur when the mobile is too far from the target cell
Solution Approach 1:
The patent introduces a new parameter (RSCP threshold) in addition to the existing Ec/No threshold to control reselection. By changing the parameter set used for reselection decisions, the system can independently control both downlink quality (Ec/No) and uplink capability (RSCP), resolving the contradiction between aggressive reselection and uplink reliability
Solution Approach 2:
The network pre-configures both Ec/No thresholds and RSCP thresholds for reselection. The mobile station performs preliminary evaluation of both parameters before initiating reselection, ensuring that both downlink quality and uplink capability are satisfied before the mobile moves to the target cell, thus preventing uplink failures
2Reliability
If the Ec/No threshold is set high to guarantee uplink access, then uplink reliability is improved, but the mobile station cannot access loaded UTRAN cells or must go far closer to the target site
Solution Approach 1:
The patent decouples the control of uplink reliability and downlink quality by introducing separate thresholds: Ec/No for downlink quality and RSCP for uplink capability. This allows the system to set Ec/No high for reliability while setting RSCP appropriately to enable access to loaded cells, resolving the contradiction
Solution Approach 2:
The reselection criterion is segmented into two independent parts: Ec/No threshold for downlink evaluation and RSCP threshold for uplink evaluation. This segmentation allows independent optimization of each parameter, enabling the system to guarantee uplink access while maintaining flexibility to access loaded cells
3Device complexity
If no RSCP threshold is signaled in GSM, then the reselection procedure is simpler, but it is impossible to apply aggressive reselection behavior with proper hysteresis
Solution Approach 1:
The network pre-signalizes both Ec/No thresholds and RSCP thresholds to the mobile station in advance. This preliminary provision of parameters enables the mobile to perform aggressive reselection with proper hysteresis control without increasing procedural complexity during the actual reselection process
Solution Approach 2:
The RSCP threshold acts as an intermediary parameter that mediates between the mobile's desire for aggressive reselection and the network's need for controlled behavior. By introducing this intermediate control parameter, the system achieves fine-grained control over reselection behavior without complicating the overall procedure
Data Source
AI summary
This invention describes a method for a cell reselection by a mobile station from a serving GERAN cell supported by a GSM/EDGE (global system for mobile communications/enhanced data rates for GSM evolution) radio access network (GERAN) to a UTRAN cell supported by a universal terrestrial radio access network (UTRAN). According to a first embodiment of the invention, the intended intersystem reselection behavior is reached without signaling changes. This can be a preferred mode for early implementations because signaling changes always take a longer time to reach the products on the field (both mobile and network updates are normally required). According to a second embodiment of the invention, the flexibility of signaling changes is used for an advantage.