Uplink Doppler Compensation Using UE Frequency Retuning
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Solution Overview
Problem
Existing communication systems face challenges in accurately estimating and compensating for uplink frequency offsets in high-speed UE scenarios, leading to increased demodulation pressure on base station receivers due to inaccurate Doppler frequency offset estimation and differing UE speeds under the base station.
Innovation Solution
A method and apparatus that involve demodulating a random access message to obtain an initial Doppler frequency offset, delivering it to the terminal, and estimating a residual Doppler frequency offset to adjust the uplink transmission frequency, reducing the demodulation pressure on the base station by performing uplink compensation at the UE.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the base station processes the Doppler frequency offset compensation in the receiver, then the uplink transmission can be received, but the demodulation pressure on the base station receiver increases significantly
Solution Approach 1:
Instead of having the base station receiver compensate for the large Doppler frequency offset (which increases demodulation pressure), the patent inverts the approach by having the UE transmitter compensate for the frequency offset before transmission. The base station estimates the initial Doppler frequency offset from the random access message and delivers it to the UE, which then adjusts its transmission frequency accordingly, transforming the heavy processing burden from the receiver to the transmitter.
Solution Approach 2:
The patent applies preliminary action by performing frequency offset compensation before the actual uplink data transmission. The base station estimates the initial Doppler frequency offset during the random access phase and delivers this information to the UE before the UE transmits uplink data. This preliminary frequency adjustment ensures that the uplink signal arrives at the base station with minimized frequency offset, reducing the demodulation pressure during actual data reception.
2Measurement precision
If the base station uses accurate frequency offset estimation algorithms, then the frequency offset can be compensated, but the estimation accuracy remains insufficient for high-speed UE scenarios
Solution Approach 1:
The patent segments the frequency offset compensation process into two distinct stages: (1) initial frequency offset estimation during the random access phase using a simple algorithm with large estimation range and low accuracy requirements, and (2) frequency offset compensation during the connected mode data transmission phase using the estimated value. This segmentation allows the system to use simple estimation algorithms initially and then apply compensation, achieving accurate frequency offset handling without requiring complex real-time estimation algorithms during high-speed transmission.
3Manufacturing precision
If the UE compensates for the Doppler frequency offset, then the uplink transmission frequency can be adjusted accurately, but the UE needs to process the frequency offset information from the base station
Solution Approach 1:
The patent implements feedback by having the base station estimate the initial Doppler frequency offset from the random access message and deliver this information back to the UE. The UE then uses this feedback information to adjust its transmission frequency. This feedback mechanism enables the UE to compensate for frequency offset accurately without requiring the UE to perform complex estimation algorithms itself, as the base station provides the necessary frequency offset information.
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 improves demodulation performance at the base station by reducing the need for complex frequency offset estimation and compensation algorithms, allowing for accurate frequency adjustments based on individual UE speeds, thus enhancing reception capabilities.
Implementation Method 1
a frequency offset is introduced in the downlink and uplink of the wireless communication, and the higher the speed, the larger the frequency offset
Implementation Method 2
the UE locks the downlink transmission frequency point f DL of the base station in the downlink. Actually the UE is always moving, the actually locked downlink transmission frequency of the base station is f DL + Δ by considering the influence of the Doppler frequency offset
Data Source
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AI summary
Disclosed are a method and apparatus for processing an uplink frequency offset of a communication system. The method on a base station side includes: demodulating a random access message sent by a terminal to obtain an initial Doppler frequency offset of the terminal and delivering the initial Doppler frequency offset to the terminal; receiving an uplink subframe signal sent by the terminal, estimating a residual Doppler frequency offset of the terminal on an uplink, obtaining a frequency retuning amount according to the residual Doppler frequency offset and delivering the frequency retuning amount to the terminal. The method on a terminal side includes: receiving an initial Doppler frequency offset sent by a base station, obtaining an initial uplink transmission frequency according to an initial downlink transmission frequency and the initial Doppler frequency offset and sending an uplink subframe signal; and receiving a frequency retuning amount sent by the base station, and obtaining a transmission frequency of a next uplink transmission according to the frequency retuning amount.