Terminal Time Delay Measurement in OFDM Cluster Systems
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Solution Overview
Problem
In wireless communication systems, especially in cluster systems, terminal time delays lead to reduced signal strength and demodulation success rates due to unsynchronized terminal signals, and existing methods are complex and only suitable for base station processing, failing to provide timely automatic time delay adjustments for group calling services.
Innovation Solution
A method for measuring time delay in OFDM cluster systems that transforms received signals to the frequency domain, performs channel estimation, calculates angular velocity, and compensates for frequency deviation to improve time delay estimation accuracy, enabling terminal-side automatic time delay adjustments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If base station measures time delay and notifies terminal for TA adjustment, then terminal signal synchronization is improved, but cluster system cannot provide timely TA adjusting orders to group members due to resource constraints
Solution Approach 1:
The terminal performs self-estimated air interface time delay measurement based on downlink signals without requiring base station intervention. The terminal autonomously measures time delay, estimates phase rotation, and compensates for TA adjustment timing losses, enabling self-service synchronization in cluster systems where base station resources are constrained.
2Ease of operation
If existing time delay measurement methods are used, then base station processing is simplified, but terminal side automatic time delay adjustment is not enabled and operations remain complex
Solution Approach 1:
The terminal autonomously performs time delay measurement and compensation without base station processing involvement. The terminal measures time delay using downlink signals, calculates phase rotation, and executes automatic TA adjustment, achieving both simplicity and automation at the terminal side.
Solution Approach 2:
Instead of the base station measuring and controlling time delay, the terminal performs the measurement and compensation in reverse. The terminal measures air interface time delay and proactively adjusts its transmission timing, inverting the traditional base station-controlled approach.
3Extent of automation
If only self-estimated air interface time delay is considered for phase time delay compensation, then terminal side processing is enabled, but measurement accuracy is insufficient without combined terminal processing
Solution Approach 1:
The terminal changes the measurement parameter from simple time delay to time delay combined with phase rotation estimation. By measuring both time delay and phase rotation characteristics of the air interface, the terminal achieves higher measurement accuracy while maintaining terminal-side autonomous processing.
Data Source
AI summary
A method for measuring a time delay of an OFDM cluster system includes steps of: transforming a received signal to a frequency-domain; providing channel estimation to a corresponding carrier position based on RS; providing frequency-domain interpolation channel estimation; processing the carriers of the same frequency-domain between different symbols with frequency deviation estimation, so as to obtain an angular velocity; calculating an average angular velocity; after the linear interpolation, transforming RS symbols to a time-domain, so as to obtain a crude time delay; and compensating based on the angular velocity, so as to obtain a fine time delay. For the cluster system adopting the method, the accuracy of the terminal side system time delay detection is improved, in such a manner that the availability of the terminal side automatic time delay adjustment is greatly increased, and the TA adjustment under the group calling service of the cluster system is sufficiently compensated.