Femto Base Station Identification Using CRC Masks for Access Control
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Solution Overview
Problem
Current wireless communication systems face challenges in distinguishing and accessing femtocell base stations, particularly in differentiating between open-access and closed-subscriber-group femtocells, which affects handover operations and user authorization.
Innovation Solution
The system employs cyclic redundancy check (CRC) masks and scrambling sequences to identify and differentiate between macro base stations, open-access femtocell base stations, and closed-subscriber-group femtocell base stations, allowing mobile stations to determine access authorization and perform handovers accordingly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional cell search methods are used in broadband wireless communication systems, then the system can operate with multiple carriers, but the mobile station cannot efficiently distinguish between macro base stations and femtocell base stations or determine access authorization
Solution Approach 1:
The patent applies the principle of 'Color changes' by using different CRC masks as unique identifiers for different base station types. Just as colors can distinguish different objects, the CRC masks (different bit patterns) serve as visual identifiers that allow mobile stations to quickly distinguish between macro base stations, open-access femtocells, and closed-subscriber-group femtocells without complex additional signaling.
2Reliability
If the system implements access control for femtocell base stations, then user authorization can be managed, but the complexity of access determination increases
Solution Approach 1:
The patent applies 'Preliminary action' by pre-configuring mobile stations with lists of authorized femtocell CRC masks before they enter the coverage area. When a mobile station receives a broadcast channel, it can immediately check the CRC mask against its pre-stored list to determine access authorization, eliminating the need for complex real-time authentication procedures and reducing access determination complexity.
3Loss of information
If the broadcast channel includes detailed base station type information, then mobile stations can accurately identify femtocell types, but the broadcast channel overhead increases
Solution Approach 1:
The patent applies 'Universality (Multi-functionality)' by designing the CRC mask to serve multiple functions simultaneously: it provides error detection for the broadcast channel, identifies the base station type (macro, open-access femtocell, or closed-subscriber-group femtocell), and indicates access authorization status. This multi-functional approach eliminates the need for separate signaling fields, thereby reducing broadcast channel overhead while maintaining complete base station type information.
Data Source
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AI summary
A system and method for identifying the accessibility of femto base stations in a communication system. The system and method includes a plurality of macro base stations, open-access femto base stations and femto base stations with different subscriber groups. At least one of the base stations includes a transmitter configured to apply a base station identifier, such as a closed subscription group identifier, as a cyclic redundancy check (CRC) mask to XOR (exclusive OR) the CRC of a broadcast channel communication or an input to generate a scrambling sequence to the broadcast channel communication.