Femtocell Scrambling Code Selection via Value Tag Differentiation
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Solution Overview
Problem
In cellular communication systems, when a mobile network operator allocates a small number of scrambling codes to femtocell basestations, there is a high probability that adjacent basestations will share the same code, leading to interference and issues with call completion, as user equipment may fail to perform necessary location updates due to identical System Information Block value tags.
Innovation Solution
A method where a femtocell basestation identifies a desired scrambling code, detects the Information Block value tags broadcast by neighboring basestations using the same code, and sets its own value tags to differ, ensuring unique identification and preventing interference by forcing location updates even when basestations share the same scrambling code.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a small number of scrambling codes are allocated to femtocell basestations, then network resource allocation is simplified and cost is reduced, but interference between adjacent basestations increases and call completion reliability deteriorates
Solution Approach 1:
The patent changes the Information Block value tag parameter to differentiate between basestations using the same scrambling code. When a femtocell basestation detects that adjacent basestations are using the same scrambling code, it modifies its Information Block value tag to a different value, forcing user equipment to perform location updates and preventing call completion failures.
2Adaptability or versatility
If the same scrambling code is reused by adjacent femtocell basestations, then the number of available scrambling codes is effectively increased, but user equipment fails to perform location updates and interference increases
Solution Approach 1:
The patent introduces the Information Block value tag as an intermediary parameter that mediates between basestations using the same scrambling code. This value tag acts as a secondary identifier that allows user equipment to distinguish between different basestations even when scrambling codes are identical, enabling proper location updates and preventing interference issues.
3Quantity of substance
If femtocell basestations use identical Information Block value tags, then broadcasting overhead is reduced, but user equipment cannot distinguish between adjacent basestations and call handovers fail
Solution Approach 1:
The patent modifies the Information Block value tag parameter to enable basestation differentiation. By setting unique value tags for each basestation (especially when scrambling codes are reused), the system ensures that user equipment can properly identify and handover between basestations while maintaining minimal broadcasting overhead through the efficient use of this single parameter.
Data Source
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AI summary
In a femtocell basestation of a cellular communications network, there is a potential difficulty that the basestation may be unable to select a scrambling code for its transmissions, without the risk of interference with other basestations using the same scrambling code. The femtocell basestation receives from a management system a list comprising at least one allowed scrambling code for femtocell basestations, and also detects, in information broadcast by at least one macrocell basestation, at least one allowed scrambling code available in an area containing the basestation. If it is determined that use of each scrambling code that is allowed and is available in an area containing the basestation would cause interference with another femtocell basestation, a parameter is set to ensure that a user equipment would perform a location update when moving between the coverage areas of said basestation and the other femtocell basestation. The parameter may be a MIB and/or SIB value tag.