Femtocell Synchronization via Mobile Device Assistance
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Solution Overview
Problem
Existing synchronization methods for femtocell access points with macrocell base stations in wireless communication networks suffer from low accuracy, coverage issues, and high costs.
Innovation Solution
Mobile devices assist access points by providing information over out-of-band wireless links to facilitate coarse and fine synchronization with macrocell base stations, using methods such as transferring timing information, sniffing uplink transmissions, and performing network measurements to adjust for clock drift.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional synchronization methods are used for femtocell access points, then synchronization can be established, but the accuracy is low and costs are high
Solution Approach 1:
The patent introduces mobile devices as intermediary elements that facilitate synchronization between femtocell access points and macrocell base stations. Mobile devices capture timing information from macrocell base stations and relay it to femtocell access points, enabling accurate synchronization without requiring direct line-of-sight or expensive dedicated synchronization infrastructure. This intermediary approach resolves the contradiction by achieving high synchronization accuracy through mobile device assistance while avoiding the high costs of traditional methods.
Solution Approach 2:
The patent enables mobile devices to perform multiple functions: they serve as both user communication devices and as synchronization assistance nodes. By utilizing the existing cellular connectivity and timing capabilities of mobile devices for synchronization purposes, the system achieves reliable and accurate synchronization without requiring dedicated synchronization hardware, thereby reducing costs while maintaining high accuracy and reliability.
2Measurement precision
If mobile devices are used to assist synchronization, then costs are reduced and accuracy is improved, but device complexity increases
Solution Approach 1:
The patent implements a self-service synchronization mechanism where mobile devices automatically capture timing information from macrocell base stations and relay it to femtocell access points without requiring manual configuration or complex coordination protocols. The mobile devices utilize their existing cellular stack and timing measurement capabilities, performing synchronization assistance as a transparent service. This approach improves synchronization accuracy while minimizing added complexity, as the process leverages existing device functionalities rather than introducing complex new systems.
3Measurement precision
If out-of-band wireless links are used for synchronization information transfer, then synchronization accuracy is improved, but use of energy increases
Solution Approach 1:
The patent combines synchronization information transfer with existing out-of-band wireless communication channels (such as WiFi or Bluetooth) that mobile devices already utilize for other purposes. By merging synchronization data transmission with these existing communication pathways, the system achieves accurate synchronization without requiring separate dedicated synchronization channels, thereby minimizing additional energy consumption while maintaining high synchronization accuracy.
Data Source
AI summary
A mobile device provides first information to an access point over an out-of-band wireless link. The access point uses the first information to coarsely synchronize with a macrocell base station. The access point transmits a low power pilot signal that is formed using a pseudo-random noise (PN) sequence. The mobile device uses the out-of-band wireless link to provide second information to the access point that indicates a PN phase of the pilot signal with respect to a reference time point. The access point uses the second information to finely synchronize with the macrocell base station. The mobile device communicates with a mobile operator core network through the access point using an in-band wireless link to the access point. The mobile device compensates for propagation delay when obtaining time information. The mobile device provides additional information to the access point, which the access point uses to adjust for continued clock drift.