WO2016082606A1

WO2016082606A1 - Frequency offset correction method and apparatus

Info

Publication number: WO2016082606A1
Application number: PCT/CN2015/090037
Authority: WO
Inventors: 袁晓超; 霍燚
Original assignee: 中兴通讯股份有限公司
Priority date: 2014-11-24
Filing date: 2015-09-18
Publication date: 2016-06-02
Also published as: CN105704076A

Abstract

Disclosed are a frequency offset correction method and apparatus. The method comprises: demodulating a received uplink signal of a user equipment; performing calculation based on a demodulation result and according to a Doppler frequency shift formula to obtain a downlink Doppler frequency shift value; and during transmission of a downlink signal, performing frequency offset correction in advance according to the downlink Doppler frequency shift value. By means of the present invention, a problem in the prior art that in a scenario of high-speed movement, a relatively large Doppler frequency shift occurs, causing a failure of synchronization in a downlink and a failure of a soft handover, and further causing a call drop is resolved, thereby improving downlink coverage, improving a success rate of seamless handovers, and reducing a call drop rate.

Description

Frequency offset correction method and device

Technical field

The present invention relates to the field of communications, and in particular to a frequency offset correction method and apparatus.

Background technique

At present, with the gradual expansion of the construction scale of China's high-speed railway and the gradual improvement of the operating speed, a new topic has been proposed for the third-generation mobile communication system. The high penetration loss caused by the high-speed rail closed compartment and the high-speed movement of the user equipment UE are not common in the current high-speed rail scene.

In view of the high penetration loss caused by the high-speed rail closed compartment, in the current third-generation mobile communication system, the base station site configuration is adopted in the place where the high-speed rail track is close.

In view of the problem that the site coverage and handover are not timely due to the high-speed movement of the user equipment UE in the high-speed rail scenario, the distance between the base station sites is relatively close in the current third-generation mobile communication system, and the coverage and handover of the base station is countered by the MRRU scenario. Not timely.

However, this high-speed rail scene still has certain problems, mainly because the speed of the high-speed rail has reached a speed of more than 300km/h, and the Doppler shift is far greater under the high motion state of the user equipment UE. The Doppler shift in the general urban scene is simply by reducing the distance between the base stations and adopting the MRRU scene and not completely resisting the Doppler shift in the high-speed moving state. In the current third-generation mobile communication system, the Doppler shift for this high-speed scene has not been processed in the downlink transmission signal, so that the terminal is receiving downlink in the high-speed railway scenario. There is a risk of downlink performance degradation when the signal is transmitted, resulting in downlink signal synchronization, coverage and seamless handover performance degradation.

In the high-speed mobile scenario in the related art, a large Doppler shift occurs in the downlink signal, which causes the downlink to be incapable of synchronization, and the soft handover fails, which may lead to the problem of dropped calls. Currently, an effective solution has not been proposed.

Summary of the invention

In the scenario of the high-speed mobile in the related art, a large Doppler shift occurs in the downlink signal, and the downlink cannot be synchronized, and the soft handover fails, which may cause a call drop. The embodiment of the present invention provides a frequency offset. The calibration method and device are used to solve the above technical problems.

According to an aspect of the embodiments of the present invention, the present invention provides a frequency offset correction method, wherein the method includes: demodulating an uplink signal of a received user equipment; and based on a demodulation result, according to a Doppler frequency shift The formula calculates the downlink Doppler shift value; when performing the downlink signal transmission, the frequency offset correction is performed in advance according to the downlink Doppler shift value.

Optionally, the demodulation result is an uplink Doppler shift value and a phase value of the user equipment.

Optionally, the Doppler shift formula includes: an upward Doppler shift formula:

Wherein, the uplink Doppler shift fd value, V is the running speed of the user equipment, C is the speed of light, f is _the frequency of the uplink of the user equipment, [theta] is the phase value of the user equipment; downlink multiple Puller frequency shift formula:

Where f is _the frequency of the downlink of the user equipment, the downlink fd is the Doppler shift value.

Optionally, calculating, according to the demodulation result of the uplink signal, the downlink Doppler frequency shift value according to the Doppler frequency shift formula, including: based on the uplink Doppler frequency shift value and the phase value, according to the The uplink Doppler shift formula calculates the running speed of the user equipment; and based on the operating speed of the user equipment, calculates the downlink Doppler shift value according to the downlink Doppler shift formula.

According to another aspect of the present invention, the present invention further provides a frequency offset correction apparatus, wherein the apparatus comprises: a signal demodulation module configured to demodulate an uplink signal of a received user equipment; and a calculation module And being set to calculate a downlink Doppler shift value according to the Doppler shift formula based on the demodulation result; the frequency offset correction module is configured to advance according to the downlink Doppler shift value when performing downlink signal transmission Perform frequency offset correction.

Optionally, the demodulation result is an uplink Doppler shift value and a phase value.

Optionally, the calculating module includes: a first calculating unit, configured to calculate the user equipment according to the uplink Doppler frequency shift formula based on the uplink Doppler frequency shift value and the phase value The running speed of the second computing unit is set to calculate the downlink Doppler shift value according to the downlink Doppler shift formula based on the running speed of the user equipment.

The beneficial effects of the embodiments of the present invention are as follows:

The invention can achieve better downlink signal synchronization by correcting the Doppler frequency shift of the downlink signal in advance in the high-speed railway scenario, thereby improving downlink coverage, improving the success rate of seamless handover, and reducing the dropped call rate.

The above description is only an overview of the technical solutions of the present invention, and the above-described and other objects, features and advantages of the present invention can be more clearly understood. Specific embodiments of the invention are set forth below.

DRAWINGS

The drawings described herein are intended to provide a further understanding of the invention, and are intended to be a part of the invention. In the drawing:

1 is a flow chart of a frequency offset correction method according to an embodiment of the present invention;

2 is a flowchart of a method for improving downlink coverage and improving seamless handover success rate according to an embodiment of the present invention;

3 is a block diagram showing the structure of a frequency offset correction apparatus according to an embodiment of the present invention.

detailed description

In order to solve the problem that in the high-speed mobile scenario in the prior art, a large Doppler shift occurs in the downlink signal, the downlink cannot be synchronized, the soft handover fails, and the call may be dropped, the present invention provides a frequency offset. Correction Method and Apparatus The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It is understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

This embodiment provides a frequency offset correction method, which can be implemented on the network side, and is mainly applied to high-speed mobile scenes such as high-speed rail. 1 is a flow chart of a frequency offset correction method according to an embodiment of the present invention. As shown in FIG. 1, the method includes the following steps (step S102 - step S106):

Step S102: The network side demodulates the received uplink signal of the user equipment.

Step S104, the network side calculates a downlink Doppler shift value according to the Doppler shift formula based on the demodulation result. The demodulation result is an uplink Doppler shift value and a phase value.

Step S106: The baseband processing unit on the network side performs frequency offset correction in advance according to the downlink Doppler frequency shift value when performing downlink signal transmission.

With the embodiment, in the high-speed mobile scenario in the prior art, a large Doppler frequency shift occurs in the downlink signal, and the downlink cannot be synchronized, and the soft handover fails, which may cause a call drop problem, and the downlink is improved. Coverage improves the success rate of seamless switching and reduces the call drop rate.

In this embodiment, the above Doppler shift formula includes:

Upward Doppler shift formula:

Wherein, the uplink Doppler shift fd value, V is the running speed of the user equipment, C is the speed of light, f is _the frequency of the uplink user equipment, [theta] is the phase value of the user equipment;

Downstream Doppler shift formula:

Where f is _the frequency of the user equipment downlink, the downlink fd is the Doppler shift value.

In the above step S104, the network side calculates the downlink Doppler shift value according to the Doppler shift formula based on the demodulation result, including: the uplink Doppler shift value and the phase value obtained by demodulating the uplink signal, According to the uplink Doppler shift formula, the running speed of the user equipment is calculated; based on the running speed of the user equipment, the downlink Doppler shift value is calculated according to the downlink Doppler frequency shift formula. This provides data support for subsequent frequency offset correction.

The specific calculation process of the embodiment of the present invention is introduced below.

The invention provides a method for improving the downlink coverage of high-speed rail and the success rate of seamless handover, comprising the following steps:

In the first step, the network side receives the uplink signal of the user equipment UE, performs frequency offset estimation and phase estimation on the uplink signal, and obtains an uplink Doppler frequency shift value (also referred to as a frequency offset value) and a phase value of the uplink signal. .

In the second step, considering that in the high-speed rail scenario, the frequency offset of the uplink signal is mainly caused by the Doppler shift, the frequency offset value of the uplink signal can be expressed by the following formula:

Where f _d is the uplink Doppler shift, V is the operating speed of the user equipment UE, C is the speed of light, f _is the uplink frequency of the user equipment UE, and θ is the phase value of the user equipment UE.

After the network side receiving the uplink signal from the user equipment can demodulate _the value f _D and θ, while _the uplink frequency f C with the speed of light is a known value, it is possible to (1) calculate the user equipment UE in accordance with the above formula The speed of operation V.

Similarly, since there is a Doppler shift of the uplink signal, there is also a Doppler shift of the downlink signal. The formula of the Doppler shift of the downlink is calculated according to formula (1) as follows:

V is the running speed of the user equipment UE, C is the speed of light, f is _the frequency of the user equipment UE downlink, [theta] is the phase value of the user equipment UE.

The values of V and θ can be directly used as the values of the upward Doppler shift formula (1). Here, it is mainly considered that the network side performs demodulation, frequency offset estimation, phase estimation after receiving the uplink signal, and then the time interval between the modulation and transmission of the downlink signal is very short, which is generally calculated in units of slots. In such a short period of time, the V and θ values received based on the uplink signal can be directly used to estimate the downlink Doppler shift value.

In the third step, after the network side calculates the downlink Doppler shift value according to formula (2), the baseband processing unit performs the Doppler shift correction of the downlink signal in advance, so that the downlink transmit signal and the user on the high-speed rail have The same Doppler shift achieves better downlink signal synchronization, improves downlink coverage, improves seamless handover success rate, and reduces dropped calls.

The preferred embodiments of the present invention are described in detail below with reference to the accompanying drawings.

FIG. 2 is a flowchart of a method for improving downlink coverage and improving seamless handover success rate according to an embodiment of the present invention. As shown in FIG. 2, the method includes the following steps:

Step S201: The network side performs uplink signal demodulation, frequency offset estimation, and phase estimation according to the received uplink signal of the user equipment UE.

Step S202: The network side reversely derives the operating speed of the user equipment UE according to the frequency offset estimation value and the phase estimation value of the uplink signal obtained in step S101 by using the Doppler frequency shift formula (1).

Step S203: The network side extracts the downlink Doppler frequency shift value according to the Doppler frequency shift formula (2) according to the operating speed, phase estimation value, downlink frequency, and light speed of the user equipment UE obtained in step S102.

Step S204: The baseband processing unit on the network side performs frequency correction in advance according to the downlink Doppler frequency shift value calculated in step S103 when performing downlink signal transmission, and improves the synchronization success rate of the downlink signal.

In step S201, the frequency offset estimation value obtained by demodulating the uplink signal on the network side is also the uplink Doppler frequency shift value, because in the high-speed rail scenario, the frequency offset estimation value of the uplink signal is mainly due to Doppler frequency. Move caused.

In step S203, the downlink Doppler shift value is estimated in advance on the network side, and the operation speed and the phase estimation value of the user equipment UE in step S202 are directly calculated in the calculation, mainly considering that the network side is in the uplink signal. Demodulation processing to downlink signal transmission, the baseband processing unit on the network side has a short time in this part, and is calculated in units of slots. In such a short time, the operating speed and phase of the user equipment UE are basically unchanged. Therefore, it can be directly used to estimate the Doppler shift value of the downlink signal.

In step S204, the network side performs the Doppler shift correction of the downlink signal in advance in the baseband processing unit, so that the downlink transmission signal has the same Doppler frequency shift as the user on the high-speed rail, so as to achieve better downlink signal synchronization. Improve downlink coverage, improve seamless switching success rate, and reduce dropped calls.

Corresponding to the frequency offset correction method introduced in the above embodiment, the embodiment provides a frequency offset correction device, which can be disposed on the network side to implement the above embodiment. FIG. 3 is a structural block diagram of a frequency offset correction apparatus according to an embodiment of the present invention. As shown in FIG. 3, the apparatus includes a signal demodulation module 10, a calculation module 20, and a frequency offset correction module 30. The structure is described in detail below.

The signal demodulation module 10 is configured to demodulate the received uplink signal of the user equipment;

The calculation module 20 is connected to the signal demodulation module 10, and is configured to calculate a downlink Doppler shift value according to the Doppler shift formula based on the demodulation result; wherein the demodulation result is an uplink Doppler shift value And phase values.

The frequency offset correction module 30 is connected to the calculation module 20 and configured to perform frequency offset correction in advance according to the downlink Doppler shift value when performing downlink signal transmission.

In this embodiment, the Doppler shift formula includes:

Upward Doppler shift formula:

Downstream Doppler shift formula:

Based on the above two formulas, the calculation module 20 includes: a first calculating unit configured to calculate an operating speed of the user equipment according to an uplink Doppler shift formula based on an uplink Doppler shift value and a phase value; The calculating unit is configured to calculate a downlink Doppler shift value according to a running Doppler frequency shift formula based on a running speed of the user equipment. The foregoing embodiment has been described in the specific calculation process, and details are not described herein again.

The device provided by the embodiment of the invention improves the downlink coverage by correcting the downlink Doppler frequency in advance, and improves the seamless handover success rate. Specifically, it may be a base station.

In summary, the network side receives the uplink signal demodulation of the user equipment UE to obtain the frequency offset estimation value and the phase estimation value, and the baseband processing unit inversely derives the downlink Doppler frequency shift value according to the Doppler frequency shift formula, thereby The network side can make correction for the downlink Doppler shift in advance. The invention can extract and correct the downlink Doppler frequency shift in the high-speed mobile scene, thereby improving the synchronization success rate of the downlink signal, improving the downlink coverage, improving the seamless handover success rate, and reducing the call drop rate.

While the preferred embodiments of the present invention have been disclosed for purposes of illustration, those skilled in the art will recognize that various modifications, additions and substitutions are possible, and the scope of the invention should not be limited to the embodiments described above.

Industrial applicability

Claims

A frequency offset correction method includes:

Demodulating the received uplink signal of the user equipment;

Based on the demodulation result, the downlink Doppler shift value is calculated according to the Doppler shift formula;

When downlink signal transmission is performed, frequency offset correction is performed in advance according to the downlink Doppler shift value.
The method of claim 1 wherein said demodulating result is an uplink Doppler shift value and a phase value of said user equipment.
The method of claim 2 wherein said Doppler shift formula comprises:

Upward Doppler shift formula:
Wherein, the uplink Doppler shift fd value, V is the speed of the user equipment, C is the speed of light, f is the frequency of the uplink of the user equipment, [theta] is the phase value of the user equipment;

Downstream Doppler shift formula:
Where f is the frequency of the downlink of the user equipment, the downlink fd is the Doppler shift value.
The method according to claim 3, wherein, based on the demodulation result, the downlink Doppler shift value is calculated according to the Doppler shift formula, including:

Calculating an operating speed of the user equipment according to the uplink Doppler shift formula according to the uplink Doppler shift value and the phase value;

The downlink Doppler shift value is calculated according to the downlink Doppler shift formula based on the operating speed of the user equipment.
A frequency offset correction device includes:

a signal demodulation module configured to demodulate an uplink signal of the received user equipment;

a calculation module, configured to calculate a downlink Doppler shift value according to a Doppler shift formula based on the demodulation result;

The frequency offset correction module is configured to perform frequency offset correction according to the downlink Doppler shift value in advance when performing downlink signal transmission.
The apparatus of claim 5 wherein said demodulation result is an uplink Doppler shift value and a phase value of said user equipment.
The apparatus of claim 6 wherein said Doppler shift formula comprises:

Upward Doppler shift formula:
Wherein, the uplink Doppler shift fd value, V is the speed of the user equipment, C is the speed of light, f is the frequency of the uplink of the user equipment, [theta] is the phase value of the user equipment;

Downstream Doppler shift formula:
Where f is the frequency of the downlink of the user equipment, the downlink fd is the Doppler shift value.
The apparatus of claim 7 wherein said computing module comprises:

a first calculating unit, configured to calculate, according to the uplink Doppler frequency shift formula, an operating speed of the user equipment according to the uplink Doppler frequency shift value and the phase value;

The second calculating unit is configured to calculate the downlink Doppler shift value according to the downlink Doppler shift formula based on the operating speed of the user equipment.