Radio Network Controller Target Cell Selection Using Scrambling Codes
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Solution Overview
Problem
Legacy UEs in wireless communication systems face difficulties in disambiguating target cells, especially in heterogeneous networks, due to limited information and high reuse of Primary Scrambling Codes (PSCs) among CSG cells, leading to incorrect relocation attempts.
Innovation Solution
The method involves providing neighbor cell information that includes scrambling codes and timing differences to disambiguate multiple neighbor cells, allowing for accurate target cell selection and handover, even when legacy UEs cannot report cell identifications, by utilizing reports from non-legacy UEs to enhance the Neighbor Relation Table (NRT) and prevent relocation to inaccessible CSG cells.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If Primary Scrambling Codes are reused among CSG cells to increase network capacity, then the number of accessible CSG cells increases, but the ability to disambiguate target cells deteriorates
Solution Approach 1:
The patent introduces timing difference information as an additional dimension to distinguish between CSG cells that share the same PSC. Instead of relying solely on PSC for cell identification, the system now uses a combination of PSC and timing difference parameters, effectively moving from one-dimensional to two-dimensional cell identification. This allows the network to support more CSG cells with reused PSCs while maintaining accurate target cell identification during handover.
2Reliability
If neighbor cell information is enhanced with timing differences to improve target cell selection, then handover accuracy improves, but signaling traffic and processing complexity increase
Solution Approach 1:
The patent applies preliminary action by having the serving RNC pre-calculate and store timing difference information for all neighbor CSG cells in the Neighbor Relation Table before handover is needed. When a handover is initiated, the UE simply reports the timing difference it measures, and the RNC performs a straightforward lookup and comparison to identify the target cell. This eliminates the need for complex real-time processing during the actual handover event, reducing signaling traffic and processing complexity while maintaining high handover accuracy.
3Adaptability or versatility
If legacy UEs are supported without CSG proximity indication capability, then device compatibility improves, but target cell disambiguation capability deteriorates
Solution Approach 1:
The patent introduces timing difference information as an intermediary parameter that enables legacy UEs to provide sufficient information for target cell identification without requiring CSG proximity indication capability. The timing difference acts as a mediator that, when combined with PSC reporting, allows the RNC to uniquely identify the target CSG cell even when the UE cannot provide CSG-specific measurements. This maintains device compatibility while restoring target cell disambiguation accuracy.
Data Source
AI summary
A method of operating a radio access network may include providing neighbor cell information identifying neighbor cells of a source cell and respective neighbor scrambling codes of the neighbor cells. A report may be received from a wireless terminal through the source cell with the report identifying a reported scrambling code of a reported cell and at least one detected scrambling code of at least one detected cell other than the reported cell. One of the neighbor cells may be selected as a target cell based on the reported scrambling code, the at least one detected scrambling code, and the neighbor cell information.