Mobile Communication System CSG Cell Access Control
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Solution Overview
Problem
In mobile communication systems, the installation of a large number of closed subscriber group (CSG) cells in locations like apartment buildings and schools leads to radio wave interference, causing control delays and inefficiencies in radio resource utilization due to endless cell searches by user equipment (UEs) within the reach of multiple CSG cells, especially when UEs lack access registration with these cells.
Innovation Solution
A mobile communication system where user equipment (UEs) use orthogonal frequency division multiplexing (OFDM) for downlink and single carrier frequency division multiple access (SC-FDMA) for uplink, with base stations managing specific and non-specific subscriber cells, employing access allowance information for UEs to access specific subscriber cells, and a radio network controller manages tracking areas to optimize cell selection and resource allocation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If a large number of CSG cells are installed in locations like apartment buildings and schools, then coverage is improved, but radio wave interference increases causing control delays and inefficiencies
Solution Approach 1:
The patent segments the cell search process into two distinct phases: intra-frequency cell search and inter-frequency cell search. This segmentation allows the UE to first complete the intra-frequency search (which includes CSG cells) and only proceed to inter-frequency search if necessary, thereby reducing unnecessary searching and control delays while maintaining comprehensive coverage.
2Measurement precision
If UEs perform endless cell searches within the reach of multiple CSG cells, then cell selection accuracy might improve, but control delays and power consumption increase
Solution Approach 1:
The patent implements preliminary action by requiring UEs to complete intra-frequency cell search (which identifies CSG cells) before proceeding to inter-frequency cell search. This preliminary step allows the network to determine whether the UE has successfully found a suitable CSG cell, preventing unnecessary inter-frequency searches and reducing both power consumption and control delays while maintaining cell selection accuracy.
3Adaptability or versatility
If UEs search for CSG cells without access registration, then coverage availability increases, but radio resource utilization efficiency decreases
Solution Approach 1:
The patent implements feedback mechanisms where the network monitors whether UEs have successfully completed cell search and obtained access to CSG cells. Based on this feedback, the network can determine whether inter-frequency cell search is necessary, thereby optimizing radio resource allocation and preventing wasteful searches by UEs that have already found suitable cells, thus improving radio resource utilization efficiency while maintaining coverage availability.
Data Source
AI summary
A closed subscriber group (CSG) cell is a cell that allows use of subscribers. In order to receive the service by the CSG cell, a CSG-ID is required to be notified to a user equipment, which cannot be obtained in a situation outside the reach of radio waves from a non-CSG cell. In a mobile communication system including base stations respectively provided to a CSG cell and a non-CSG cell in which access is made to the CSG cell with the use of a CSG-ID issued in a case where use of the CSG cell is allowed, the base station provided in the CSG cell refers to the notified identification information of a user equipment and then transmits a tracking area update request from the user equipment to a core network, and the core network determines whether the user equipment is allowed to use the CSG cell and, in the case where the use is allowed, transmits a signal for allowing assignment of radio resources to the user equipment and the CSG-ID. The user equipment accesses the CSG cell with the use of the CSG-ID.