Frequency Deviation Pre-Correction for Handover Signal Stability
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Solution Overview
Problem
In mobile communication systems, frequency deviation during cell handover leads to performance degradation in user equipment, especially in high-speed movements, where existing frequency deviation pre-calibration methods are ineffective for broadcast channels and result in significant demodulation issues due to Doppler frequency shifts.
Innovation Solution
A method and device for frequency deviation pre-calibration in a base station that estimates and adjusts the uplink frequency deviation value of user equipment, using a current pre-calibration value closer to the estimated value than historical values, to minimize frequency deviation impact by transmitting signals at a frequency closer to the cell frequency, thereby stabilizing the signal reception for the user equipment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If frequency deviation pre-calibration is applied at the base station, then the demodulation performance of user equipment is improved, but the complexity of the base station increases
Solution Approach 1:
The base station performs frequency deviation pre-calibration by estimating the Doppler frequency shift fd and adjusting the downlink transmission frequency to fc-fd in advance, so that the user equipment receives the signal at frequency fc without significant frequency deviation impact
Solution Approach 2:
The base station estimates the uplink frequency deviation from the uplink channel and uses this feedback information to adjust the downlink transmission frequency, creating a closed-loop system that continuously optimizes frequency alignment
2Stability of the object's composition
If the user equipment tracks frequency through AFC after handover, then the frequency stability is maintained, but the frequency deviation increases to maximum value of 2fd due to AFC delay
Solution Approach 1:
The base station adjusts the downlink transmission frequency to fc-fd before the user equipment completes AFC tracking after handover, so that even with AFC delay the user equipment receives the signal at the correct frequency fc without experiencing maximum frequency deviation of 2fd
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 effectively reduces frequency deviation-induced performance degradation during cell handover, improving signal detection performance by aligning the user equipment's frequency with the base station's operating frequency, thus enhancing network performance despite increased base station complexity.
Implementation Method 1
the base station transmits a signal at the frequency fc, and the user equipment receives the signal at a frequency of fc+Δf over a channel, where Δf is a Doppler frequency shift
Data Source
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AI summary
A method and device for frequency deviation pre -correction are provided. The method includes: estimating an uplink frequency deviation value of a terminal, and obtaining a historic value of the uplink frequency deviation pre -correction that has been used for the frequency deviation pre -correction of the terminal; according to the historic value of the uplink frequency deviation pre-correction, determining a current value of the uplink frequency deviation pre-correction of the terminal, the current value of the uplink frequency deviation pre-correction being closer to the uplink frequency deviation value than the historic value of the uplink frequency deviation pre-correction; by using the current value of the uplink frequency deviation pre-correction, pre -correcting the frequency deviation of the terminal, thereby the signal detection performance of the terminal can be effectively improved.