Frame Timing Acquisition in Multi-Cell Communication Systems
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Solution Overview
Problem
Conventional communication systems fail to accurately acquire initial frame timing when signals from multiple base stations with different segment numbers are simultaneously received at a terminal located at the cell edge, as the auto-correlation method loses its repeating characteristic in a multi-cell environment.
Innovation Solution
An apparatus and method that include a normalizer, cross power calculator, divider, and peak-value detector to calculate a normalized window power and window cross power, and determine the starting point of a frame by finding the sample with the maximum ratio of cross powers between delayed and non-delayed samples, effectively addressing the challenge of multi-cell signal reception.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If auto-correlation method is used for frame timing acquisition, then timing acquisition is successful in single-cell environment, but timing acquisition fails when signals from multiple base stations are simultaneously received
Solution Approach 1:
The patent segments the received signal into multiple hypotheses corresponding to different base stations. Each hypothesis represents a potential frame timing from a different base station. By evaluating multiple hypotheses separately and selecting the best match, the system adapts to multi-cell environments where signals from multiple base stations are simultaneously received.
Solution Approach 2:
The patent changes the parameter being measured from simple auto-correlation to a more comprehensive metric that considers cross-correlation between received signal and multiple preamble hypotheses. This parameter change enables the system to distinguish between signals from different base stations and successfully acquire frame timing in multi-cell environments.
2Measurement precision
If conventional auto-correlation method is used, then device complexity is low, but measurement precision of frame timing deteriorates in multi-cell environments
Solution Approach 1:
The patent performs preliminary action by pre-defining multiple preamble hypotheses corresponding to different base stations before processing the received signal. This preparation allows the system to efficiently evaluate multiple potential frame timings without excessive computational complexity during the actual measurement process.
Solution Approach 2:
The patent creates multiple copies of the expected preamble patterns (hypotheses) for different base stations. By comparing the received signal against these pre-generated copies, the system achieves high measurement precision without requiring complex real-time calculations, thus balancing accuracy and computational complexity.
Data Source
AI summary
Disclosed is an apparatus for acquiring initial frame timing in a communication system having a normalizer that calculates a normalized window power from powers of samples of received signal during a monitoring period, a cross power calculator that calculates a window cross power from cross powers of the samples during the monitoring period, and each cross power corresponds to multiplication of two of the samples, a divider that divides the window cross power by the normalized window power and outputs a metric for a sample corresponding to the monitoring period, and a peak-value detector that searches a sample having the maximum value among metrics for the samples of the received signals during a predetermined period, and the metrics are calculated by shifting the monitoring period, with a sample next to the sample searched by the peak-value detector being determined as a starting point of a frame.