Synchronization Channel Signal Correlation for Handover Measurements
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Solution Overview
Problem
Intra- and inter-frequency handover measurements in OFDMA systems pose challenges due to the need for Fast Fourier Transform (FFT) for both data detection and measurements, leading to lower throughput, synchronization requirements, and increased chip area costs in user equipment.
Innovation Solution
The method utilizes the synchronization channel (SCH) for time synchronization, eliminating the need for FFT in signal strength estimation for neighboring cells, and reduces pilot overhead by transmitting pilot signals with constant power, allowing for efficient handling of handover measurements without requiring synchronization of base stations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If FFT is used for both data detection and intra- and inter-frequency measurements in OFDMA systems, then measurements can be performed, but throughput decreases due to interruption of data reception
Solution Approach 1:
The patent segments the measurement function by using dedicated synchronization channels (SCH) for neighboring cell measurements, separating it from the data detection path. This allows measurements to occur on specific resource elements without requiring FFT of the entire data signal, thus maintaining throughput while enabling measurements.
Solution Approach 2:
The patent introduces synchronization channels as an intermediary carrier for measurement information. Instead of using FFT to extract measurement data from data signals, the system uses pre-defined SCH sequences transmitted on specific resource blocks, which can be correlated directly to obtain signal strength without interrupting data reception.
2Measurement precision
If two FFTs are used for SC detection and NB cell measurements, then both functions can be performed, but chip area cost increases
Solution Approach 1:
The patent extracts the measurement function from the FFT processing path by utilizing dedicated synchronization channel sequences. Instead of requiring a second FFT for NB cell measurements, the system extracts measurement information by correlating received SCH sequences with known local sequences, eliminating the need for dual FFT processors.
Solution Approach 2:
The patent uses copying of known SCH sequences stored in the UE for correlation-based measurement. By having local copies of synchronization sequences and correlating them with received signals, the system obtains measurement data without requiring additional FFT hardware, thus reducing chip area while maintaining measurement capability.
3Measurement precision
If pilot signals are transmitted in all resource blocks for HO measurements, then accurate measurements can be obtained, but system capacity decreases due to increased overhead
Solution Approach 1:
The patent applies local quality by transmitting pilot signals only in specific resource blocks dedicated to synchronization channels, rather than uniformly across all resource blocks. This localized approach provides sufficient measurement accuracy for handover decisions while minimizing overhead and maximizing system capacity.
Solution Approach 2:
The patent uses partial action by transmitting pilot signals only where necessary for measurements - specifically in synchronization channel resource blocks - rather than in all resource blocks. This partial deployment of pilot signals is sufficient for handover measurements while reducing overall overhead and increasing available capacity for data transmission.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enhances throughput and reduces costs by eliminating the need for FFT in neighboring cell measurements and minimizing pilot signal transmission, thereby increasing capacity in cellular telecommunications systems.
Implementation Method 1
only a correlation between the known SCH signal and the received sequence is needed
Data Source
AI summary
A method and apparatus that utilizes the synchronization channel (SCH) by the user equipment (UE) to obtain time synchronization information and to perform cell search. In order to perform the SCH detection, only a correlation between the known SCH signal and the received sequence is needed, hence the FFT is not involved in the synchronization step. Typically the SCH and pilot symbols are transmitted with a constant power which is the same for all base stations. Hence, based on the serving cell (SC) SCH and pilot symbols, the power relation between these signals is estimated and the ratio applied when performing time synchronization to other cells (i.e. correlation the received sequence with the SCH from that particular NC) to estimate the pilot signal strength for the NB cell.