NB-IoT Modem Synchronization for Small Cells
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Solution Overview
Problem
Existing synchronization techniques for small base stations in heterogeneous networks, such as GNSS, IEEE 1588 v2, and Network Listening, are expensive and inaccurate, especially in indoor scenarios with high propagation delays and multi-hop synchronization, leading to errors and reduced accuracy.
Innovation Solution
A method and system using an NB-IoT modem to synchronize small cells with macro cells by detecting synchronization signals containing cell identifier information and residual time offsets, enabling accurate frequency and timing synchronization even in deep indoor environments with high coupling loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If GNSS, IEEE 1588 v2, or Network Listening techniques are used for synchronization, then synchronization capability is provided, but cost and accuracy deteriorate in indoor scenarios with high propagation delays
Solution Approach 1:
The patent introduces an NB-IoT modem as an intermediary device between the small cell and macro cell for synchronization. The modem detects synchronization signals from the macro cell and provides timing reference information to the small cell, mediating the synchronization process to overcome high propagation delays and coupling losses in indoor environments that render traditional methods ineffective
Solution Approach 2:
The patent changes the synchronization approach by utilizing NB-IoT's narrowband characteristics and extended coverage parameters. By detecting NB-IoT synchronization signals which are designed for deep indoor coverage, the system adapts to high coupling loss environments (up to 164 dB) where traditional LTE synchronization signals would fail
2Area of stationary object
If small cells are deployed in deep indoor environments, then coverage is extended, but synchronization accuracy deteriorates due to high coupling loss
Solution Approach 1:
The NB-IoT modem serves as a mediator that can reliably detect synchronization signals even in deep indoor environments with coupling loss up to 164 dB. It extracts timing information from macro cell signals and provides accurate synchronization to small cells, enabling coverage extension without sacrificing synchronization precision
Solution Approach 2:
The patent employs a low-cost NB-IoT modem instead of expensive synchronization equipment. The modem uses narrowband technology specifically designed for cost-effective deployment in IoT applications, providing reliable synchronization capability at lower cost while maintaining performance in challenging RF environments
3Reliability
If traditional synchronization methods are used, then synchronization is achieved, but cost and power consumption increase
Solution Approach 1:
The patent replaces expensive, power-hungry traditional synchronization equipment with a low-cost NB-IoT modem. The modem leverages NB-IoT's power-saving features including extended discontinuous reception (eDRX) and power save mode, achieving reliable synchronization with significantly reduced power consumption suitable for battery-operated small cells
Solution Approach 2:
The system changes from traditional LTE-band synchronization to NB-IoT narrowband synchronization. This parameter change enables the use of power-efficient NB-IoT modems that can operate in low-power modes while maintaining synchronization reliability, addressing both cost and energy consumption concerns
Data Source
AI summary
System and method for synchronizing at least one small cell with at least one macro cell in a heterogeneous network. The method comprises the at least one small cell triggering an NB-IoT modem for a clock reference signal. The NB-IoT modem detects a first synchronization signal and a second synchronization signal, the first synchronization signal and the second synchronization signal being transmitted by at least one NB-IoT cell connected to the at least one macro cell. The NB-IoT modem synchronizes the at least one small cell with the at least one macro cell based on at least one of the first synchronization signal and the second synchronization signal.