Downlink sampling frequency offset estimation and compensation method for low-earth-orbit satellite multi-carrier communication system

A technology of multi-carrier communication and sampling frequency offset, applied in the direction of modulated carrier system, multi-frequency code system, transmission system, etc. Partial estimation range is limited and other issues, to achieve a high range of demodulated signal-to-noise ratio, reduce implementation complexity, and reduce the effect of the range

Active Publication Date: 2020-02-14
成都天奥集团有限公司
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  • Application Information

AI Technical Summary

Problems solved by technology

[0008] In order to solve the low-orbit satellite multi-carrier communication system, the traditional sampling frequency offset estimation method based on the received signal has limited frequency offset estimation range, low estimation accuracy, and cannot

Method used

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  • Downlink sampling frequency offset estimation and compensation method for low-earth-orbit satellite multi-carrier communication system
  • Downlink sampling frequency offset estimation and compensation method for low-earth-orbit satellite multi-carrier communication system
  • Downlink sampling frequency offset estimation and compensation method for low-earth-orbit satellite multi-carrier communication system

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specific example

[0048] refer to figure 2 , the specific example of the downlink sampling frequency offset estimation and compensation method is as follows:

[0049] Step 1: The gateway station estimates the frequency offset of the downlink common Doppler sampling based on the ephemeris, and uses the estimated value of the downlink common Doppler sampling frequency offset to precompensate the downlink transmitted signal. Specifically, the gateway station calculates the Doppler sampling frequency offset of the downlink feeder link according to the ephemeris information, the location of the gateway station, and the carrier frequency of the downlink feeder link. refer to Figure 4 , the downlink feeder link Doppler sampling frequency offset f s,feeder is calculated as:

[0050]

[0051] in, is the connection direction between the satellite and the gateway station, is the velocity vector of the satellite, c is the speed of light, f s is the sampling frequency of the multi-carrier syste...

Embodiment 1

[0071] The altitude of the satellite is 1175km, and the speed of the satellite is 7.2km / s. The elevation angle of the gateway station to the satellite is 5°, the maximum elevation angle between the common reference point of the user link and the satellite is 30°, and the sampling frequency f s is 491.52MHz. Calculate the frequency offset by Doppler sampling formula The gateway station can calculate from the ephemeris that the Doppler sampling frequency offset of the common part of the downlink user link is 4.7kHz; the downlink Doppler sampling frequency offset of the feeder link is 9.8kHz.

[0072] The width of the satellite beam is 3°, and the Doppler frequency deviation of the user link of the cell edge user is calculated as 13.6 kHz by the above Doppler frequency deviation calculation formula. Therefore, the user's residual Doppler frequency offset is 14.5kHz-13.6kHz=900Hz. The sampling frequency deviation caused by the user and the satellite crystal oscillator is 50Hz....

Embodiment 2

[0074] Gateway station-satellite-ground channel Gaussian white noise channel, using 8PSK modulation, the code rate is 0.891, and the receiving signal-to-noise ratio is 10dB. Assuming that the initial sampling frequency offset is 5000 Hz, without pre-compensation in step 1, the sampling frequency offset is estimated only by segment correlation in step 2. Simulation results such as Figure 6 As shown, the estimated root mean square error obtained through simulation is 32.4 Hz. It can be seen that this method has high accuracy in estimating the residual sampling frequency offset. As shown in the simulation results, in this simulation scenario, the sampling frequency offset will cause a performance loss of about 2.6dB to the system, but after being estimated and compensated by the algorithm of the present invention, the link performance is compared with the ideal link without sampling frequency offset The performance loss is within 0.02dB, and the performance has been improved by...

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Abstract

The invention designs a downlink sampling frequency offset estimation and compensation method for a low-earth-orbit satellite multi-carrier communication system, and belongs to the field of wireless communication. A downlink refers to a transmission link which is transmitted by a gateway station, forwarded by a satellite and received by a user terminal. The specific method comprises the followingsteps that: a gateway station estimates downlink common Doppler sampling frequency offset based on ephemeris, and pre-compensates a downlink transmitting signal by using a downlink common Doppler sampling frequency offset estimation value and changing the sampling frequency of a sampling crystal oscillator or using a resampling digital filter; and a user terminal estimates a downlink residual sampling frequency offset by using the downlink synchronization signal and a segmentation correlation algorithm, and compensates a downlink receiving signal in a frequency domain by using a downlink residual sampling frequency offset estimation value. The downlink sampling frequency offset can be compensated with lower complexity and higher precision under the condition that the user terminal has noephemeris and only the gateway station has ephemeris, and the demodulation requirement of multi-carrier communication under the large sampling frequency offset of a low-earth-orbit satellite is met.

Description

technical field [0001] The invention belongs to the field of wireless communication, and in particular relates to a downlink sampling frequency offset estimation and compensation method in low-orbit satellite multi-carrier communication. [0002] technical background [0003] With the development of communication requirements, in order to meet the high-speed data transmission in remote areas without base station coverage, in the future mobile communication, it has become an important issue to achieve communication coverage for remote areas through low-orbit satellites. A typical low-orbit satellite communication system such as figure 1 As shown, the system components include: (1) gateway station, (2) satellite, (3) user terminal. (2) The satellite is only responsible for transparent forwarding, that is, it only performs frequency shift forwarding processing on the received signal, and does not perform signal modulation and demodulation. The link between the gateway station ...

Claims

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Application Information

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IPC IPC(8): H04L27/26H04B7/185
CPCH04L27/2657H04L27/2684H04B7/1851
Inventor 张毅刘田马松袁田夏彬徐元浩
Owner 成都天奥集团有限公司
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