Uplink Scrambling Code Determination for Handover Detection
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Solution Overview
Problem
The introduction of a large number of pico-cells in 3G systems complicates handover processes due to the need for extensive neighbor lists, shared pilot signal scrambling codes causing ambiguity and increased interference, leading to inefficient resource usage and management challenges.
Innovation Solution
A CDMA cellular communication system that determines a unique set of uplink scrambling codes based on a remote station's identity, allowing for efficient handover detection and reduced interference by limiting handover attempts to registered access points, using shared pilot signal scrambling codes while maintaining backwards compatibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If individual pilot signal scrambling codes are assigned to each underlay cell, then handover target identification is unique, but neighbour lists become excessively large and resource usage increases
Solution Approach 1:
Multiple underlay cells share a common pilot signal scrambling code, reducing the number of unique codes in neighbour lists. The system combines the identification of the shared code with additional cell-specific information to uniquely identify target cells, thereby reducing neighbour list size while maintaining identification accuracy.
Solution Approach 2:
The common pilot signal scrambling code serves multiple underlay cells simultaneously, allowing a single code to represent multiple cells in the neighbour list. This universal code reduces the quantity of codes required while the cells' relationship to the macro-cell provides additional identification context.
2Quantity of substance
If shared pilot signal scrambling codes are used for underlay cells, then neighbour list size is reduced, but handover target identification becomes ambiguous
Solution Approach 1:
The system adds an additional dimension to cell identification by combining the shared pilot signal scrambling code with cell-specific parameters such as cell ID or geographic location. This multi-dimensional identification approach allows unique target cell identification despite code sharing, resolving the ambiguity while keeping neighbour lists compact.
3Reliability
If each underlay cell transmits pilot signals, then handover support is provided, but system interference increases significantly
Solution Approach 1:
Multiple underlay cells combine their pilot signal transmissions using a shared scrambling code, reducing the total number of distinct pilot signals in the system. This merging approach maintains handover support capability while reducing pilot signal interference through code reuse and coordinated transmission.
4Adaptability or versatility
If large neighbour lists are configured for macro-cells, then all potential underlay cells are identified, but mobile station measurement performance slows down
Solution Approach 1:
The system merges multiple underlay cells under a shared pilot signal scrambling code, reducing the number of individual measurements required by mobile stations. This approach maintains comprehensive handover target coverage while improving measurement speed by reducing the total number of distinct codes to evaluate.
Data Source
AI summary
A base station (101) supports a remote station (117) making uplink transmissions using an uplink scrambling code in a first cell. A controller (119) determines a set of uplink scrambling codes from an identity of the remote station (117) and selects the used code therefrom. An access point (111) determines the group of remote stations registered at the access point. A measurement code processor (205) determines the uplink scrambling codes potentially used by the remote stations. A measurement unit (207, 209) then monitors for received signals using these codes and a handover detection processor (211) generates a potential handover detection for the remote station (117) in response to a detection of a received signal using the uplink scrambling code of the remote station (117).