Femtocell Scrambling Code Selection and Clash Avoidance
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Solution Overview
Problem
In cellular communication networks, the limited number of scrambling codes shared among basestations, particularly in femtocell access points, leads to complex scrambling code selection issues, especially in dense deployments where network planning is absent, resulting in potential clashes and interference.
Innovation Solution
A method for allocating identifying codes to basestations, where each basestation selects a code to avoid neighbors' codes, resolves clashes by determining unused codes and calculating a 'freedom of selection' parameter to minimize interference, allowing for the reuse of codes while ensuring unique combinations and minimizing overlap in coverage areas.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If each femtocell access point autonomously selects scrambling codes without network planning, then deployment flexibility and ease of operation are improved, but the risk of code clashes and interference between neighbouring basestations increases
Solution Approach 1:
The system performs preliminary actions by having each basestation proactively monitor neighbouring basestations' codes before completing its own selection, and by calculating freedom of selection parameters in advance to predict potential clashes before they occur
Solution Approach 2:
The system implements continuous feedback loops where basestations monitor their neighbours' code selections, detect clashes when they occur, and dynamically adjust their own code choices based on the freedom of selection parameter calculated from neighbour configurations
2Productivity
If the number of scrambling codes is limited and shared among all basestations, then network resource efficiency is improved, but the complexity of code allocation and the difficulty of detecting and measuring code availability increases
Solution Approach 1:
Each basestation autonomously performs code selection, monitoring of neighbours, clash detection, and self-adjustment based on calculated freedom of selection parameters, eliminating the need for centralized code allocation management
Solution Approach 2:
The system dynamically changes the freedom of selection parameter based on the number of available codes and neighbour configurations, allowing basestations to adapt their code selection strategy to current network conditions
3Area of stationary object
If femtocell access points are deployed in dense networks within small areas, then network coverage and service quality are improved, but the probability of scrambling code clashes and interference increases
Solution Approach 1:
The system applies local quality by having each basestation independently calculate its freedom of selection parameter based on its specific local environment and neighbour configurations, allowing differentiated code selection strategies tailored to each location's interference conditions
Data Source
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AI summary
A basestation forms part of a group of basestations within a cellular communications network, and selects an identifying code for use in identifying transmissions from the basestation. The basestation receives from a management node a first list of identifying codes and a second list of identifying codes, wherein the identifying codes of the first list can appear in neighbour cell lists of basestations outside said group, and wherein the identifying codes of the second list can not appear in neighbour cell lists of basestations outside said group. The basestation determines whether there is at least one identifying code either in the first list of identifying codes or the second list of identifying codes that is not used by any other basestation in said group. If there is at least one identifying code in the first list of identifying codes and at least one identifying code in the second list of identifying codes that are not used by any other basestation in said group, an identifying code from the first list of identifying codes is selected in preference to an identifying code from the second list of identifying codes.