CN101547062B - Method and device for correcting frequency deviation - Google Patents

Abstract

The embodiment of the invention discloses a frequency offset correction method and equipment, belonging to the communication field. The method includes: receiving current packet data, obtaining frequency domain data and pilot data of the user in the current packet data according to the received current packet data; The frequency offset correction result of the user in the packet data that has undergone frequency offset correction is obtained to obtain the frequency offset estimation result of the user in the current packet data; and the frequency offset estimation result of the user in the current packet data is obtained according to the frequency offset estimation result frequency domain data for frequency offset correction. The device includes: a receiving module, an obtaining module and a frequency offset correcting module. The frequency offset correction result of the user in the current packet data is obtained by using the frequency offset correction result feedback of the user in the packet data that has undergone frequency offset correction, which greatly reduces the complexity of the AFC.

Description

Frequency offset correction method and device

technical field

The invention relates to the communication field, in particular to a frequency offset correction method and equipment.

Background technique

In 3GPP (3rd Generation Partnership Project, 3rd Generation Partnership Project), LTE (Long Term Evolution, long-term evolution) project is the largest new technology research and development project launched by 3GPP in the past two years. This kind of OFDM (Orthogonal Frequency Division Multiple Access , Orthogonal Frequency Division Multiple Access)/FDMA (Frequency Division Multiple Access, Frequency Division Multiple Access) as the core technology can be regarded as "quasi-4G" technology.

OFDM is a type of MCM (Multi-Carrier Modulation, multi-carrier modulation). The main idea is: divide the channel into several orthogonal sub-channels, convert high-speed data signals into parallel low-speed sub-data streams, and modulate them on each sub-channel for transmission. Orthogonal signals can be separated by using correlation techniques at the receiving end, which can reduce the mutual interference between sub-channels. The signal bandwidth on each sub-channel is smaller than the correlation bandwidth of the channel, so each sub-channel can be regarded as flat fading, so that inter-symbol interference can be eliminated. And since the bandwidth of each sub-channel is only a small part of the original channel bandwidth, channel equalization becomes relatively easy. OFDM can combine diversity, space-time coding, interference and inter-channel interference suppression, and smart antenna technology to maximize system performance. However, OFDM is sensitive to frequency offset, and frequency offset will cause phase rotation of time-domain samples, causing phase deviation between different OFDM symbols, and destroying the orthogonality between subcarriers of OFDM system. Thereby deteriorating the demodulation performance. Therefore, an estimation of the frequency offset is required.

The AFC (Automatic Frequency Correction, automatic frequency offset correction) method in the prior art uses a method of CP (Cyclic Prefix, cyclic prefix) frequency offset estimation combined with a pilot reference signal frequency offset estimation method to estimate the frequency offset. Among them, the CP in the time domain separates the user's frequency domain signal through DFT (Discrete Fourier Transform, Discrete Fourier Transform), and the phase between the frequency domain data of the FFT (FastFourier Transform, Fast Fourier Transform) symbol part of the user's OFDM symbol The corresponding frequency offset can be calculated by the difference. Since the CP is a partial repetition of the data FFT symbol, and the time interval between the CP part and the data repetition part is not large, a larger frequency offset range can be covered by using this repetition characteristic.

In the process of realizing the present invention, the inventors have found that the above-mentioned prior art has at least the following disadvantages:

It is necessary to save the CP signal in the time domain, and additionally perform DFT processing on the CP, which has high complexity;

Moreover, the CP in the time domain is more affected, and the timing deviation will shorten the effective length of the CP. The CP contains signals of multiple users, especially the CP is not a complete FFT symbol, so the CP signal is transformed into the frequency domain of different users. Signal interference occurs. Therefore, the accuracy of estimating the frequency offset using the CP is poor, and even if it is estimated in combination with the pilot reference signal, the error probability is still relatively high.

Contents of the invention

In order to reduce the complexity of frequency offset correction and ensure reliable and safe operation of the system, embodiments of the present invention provide a frequency correction method and device. Described technical scheme is as follows:

A frequency offset correction method, comprising:

receiving the current packet data, and obtaining frequency domain data and pilot data of the user in the current packet data according to the received current packet data;

Obtain a frequency offset estimation result of the user in the current packet data according to the pilot data of the user in the current packet data and the frequency offset correction result of the user in the packet data that has undergone frequency offset correction;

performing frequency offset correction on frequency domain data of the user in the current packet data according to the frequency offset estimation result;

Wherein, the obtaining the frequency offset estimation result of the user in the current packet data specifically includes:

Obtaining an estimated frequency offset value of the user in the current packet data according to the pilot data of the user in the current packet data;

Obtaining a candidate frequency offset estimation result of the user in the current packet data according to the frequency offset estimation value of the user in the current packet data;

According to the frequency offset correction result of the user in the packet data that has undergone frequency offset correction, the frequency offset estimation result of the user in the current packet data is selected from the candidate frequency offset estimation results.

A network side device, comprising:

A receiving module, configured to receive current packet data, and obtain frequency domain data and pilot data of the user in the current packet data according to the received current packet data;

An obtaining module, configured to obtain the frequency offset of the user in the current packet data according to the pilot data of the user in the current packet data and the frequency offset correction result of the user in the packet data that has undergone frequency offset correction estimated results;

a frequency offset correction module, configured to perform frequency offset correction on the frequency domain data of the user in the current packet data according to the frequency offset estimation result obtained by the obtaining module;

Wherein, the obtaining module specifically includes:

a frequency offset estimation value obtaining unit, configured to obtain an estimated frequency offset value of the user in the current packet data according to the pilot data of the user in the current packet data;

A candidate frequency offset estimation result obtaining unit, configured to obtain a candidate frequency offset estimation result of the user in the current packet data according to the frequency offset estimation value of the user in the current packet data;

A frequency offset estimation result obtaining unit, configured to select the frequency offset of the user in the current packet data from the candidate frequency offset estimation results according to the frequency offset correction result of the user in the packet data that has undergone frequency offset correction Estimated results.

In the technical solution provided by the embodiment of the present invention, a more accurate frequency offset estimation result is obtained by combining the frequency offset correction result of the user in the packet data that has undergone frequency offset correction and the pilot data of the user in the current packet data, and according to the obtained The frequency offset correction result performs frequency offset correction on the user's frequency domain data in the current packet data. The technical solutions provided by the embodiments of the present invention have less computational complexity and can ensure reliable and effective work of the system.

Description of drawings

FIG. 1 is a flowchart of a frequency correction method provided by Embodiment 1 of the present invention;

FIG. 2 is a schematic diagram of a signal received by a receiving end provided in Embodiment 1 of the present invention;

FIG. 3 is a flowchart of a frequency correction method provided by Embodiment 2 of the present invention;

FIG. 4 is a schematic diagram of division of frequency offset intervals provided by Embodiment 2 of the present invention;

FIG. 5 is a schematic diagram of sub-interval division of the frequency offset interval provided by Embodiment 2 of the present invention;

FIG. 6 is a schematic structural diagram of a network-side device provided in Embodiment 3 of the present invention;

FIG. 7 is a schematic structural diagram of an acquisition module provided by Embodiment 3 of the present invention;

Fig. 8 is a schematic structural diagram of a candidate frequency offset estimation result unit provided by Embodiment 3 of the present invention.

Detailed ways

In order to make the object, technical solution and advantages of the present invention clearer, the implementation manner of the present invention will be further described in detail below in conjunction with the accompanying drawings.

Embodiment one

Referring to Fig. 1, an embodiment of the present invention provides a frequency offset correction method, which mainly includes:

101: Receive the current packet data, and acquire frequency domain data and pilot data of the user in the current packet data according to the received current packet data;

Referring to Fig. 2, each group may consist of several OFDM symbols, pilot data is allocated in a few OFDM symbols, and the nearest two OFDM symbols containing pilot data are separated by P OFDM symbols.

102: Obtain a frequency offset estimation result of the user in the current packet data according to the pilot data of the user in the current packet data and the frequency offset correction result of the user in the packet data that has undergone frequency offset correction;

The packet data that has undergone frequency offset correction may include: any group of packet data received before receiving the current packet data, each user in the packet data is respectively Frequency offset correction.

The frequency offset correction result may include CRC (Cyclic Redundancy Check, Cyclic Redundancy Check) feedback, or other results that can identify whether the frequency offset corrected data is correct or not.

103: Correct the frequency offset of the user's frequency domain data in the current packet data according to the frequency offset estimation result.

In the embodiment of the present invention, a relatively accurate frequency offset estimation result is obtained by combining the frequency offset correction result of the user in the packet data that has undergone frequency offset correction with the user's pilot data in the current packet data, and according to the obtained frequency offset correction result Frequency offset correction is performed on the frequency domain data of the user in the current packet data. The technical solutions of the embodiments of the present invention have less computational complexity and can ensure reliable and effective work of the system.

Embodiment two

The embodiment of the present invention provides a frequency offset correction method, taking the mobile terminal as the sending end and the base station as the receiving end as an example, see Figure 3, the method includes:

301: The base station receives time-domain data sent by the mobile terminal through multiple orthogonal subcarriers;

What needs to be explained here is that the base station receives the high-speed serial data stream modulated on a single carrier by the mobile terminal, divides it into multiple low-speed data streams, and modulates the time-domain data sent in parallel on multiple orthogonal sub-carriers.

The time-domain data sent by each subcarrier received by the base station is sent in units of packets. Each group can be composed of several OFDM symbols, pilot data is allocated in a small number of OFDM symbols, and the nearest two OFDM symbols containing pilot data are separated by P OFDM symbols;

Wherein, one OFDM symbol is composed of CP and FFT samples. The length of the CP is N _cp , the number of FFT samples is N _FFT , and the length of one OFDM symbol=N _cp +N _FFT . The advantage of sending time-domain data in units of packets is that the amount of data in each group is relatively small. Compared with continuously sending all OFDM symbols, when the base station performs frequency offset correction in units of a group, the amount of processed data will decrease. At the same time, the base station performs frequency offset correction in units of one group, and the frequency offset correction result of each group can prompt and help the frequency offset correction of the next group, reducing the need for continuous correction of all OFDM Timing errors caused by symbols.

302: Obtain frequency domain data and pilot data of each user in the current packet data;

In this step, the base station receives the time-domain data sent by the mobile terminal in units of packets, takes out the CP in the received time-domain data of the current group and discards it, performs FFT transformation and user separation on the FFT samples, and obtains each A user's frequency domain data and pilot data in the current packet data.

It should be noted that taking out and discarding the CP in the time-domain data of the current packet received can greatly reduce the computational complexity of the entire frequency offset estimation process; using FFT samples for FFT transform user separation can properly reduce multi-user interference between them.

This embodiment takes the frequency domain data and pilot data of the mth user in the current group as an example.

Wherein, the frequency domain data in the rth OFDM symbol in the kth subcarrier on the frequency domain received by the base station is represented as R(k, r);

If the n-th OFDM symbol in the k-th subcarrier in the frequency domain includes pilot data, the pilot data can be expressed as R _RS (k, n), where k=0, 1,  … K-1, where K is the total number of pilot data.

303: Estimate the channel impulse response coefficient on the pilot data of the current group of the mth user, and obtain the estimated value of the channel impulse response coefficient;

The embodiment of the present invention takes the LS (Least Square, least squares) method to obtain the estimated value of the channel impulse response coefficient as an example. In addition, methods such as maximum likelihood estimation and DFT transform domain channel estimation can also be used to obtain the channel impulse response coefficient. , the process is basically the same as that of LS estimation, and will not be repeated here.

The estimated value H _LS (k, n) of the channel impulse response coefficient of the pilot data in the nth OFDM symbol in the kth subcarrier can be expressed as:

${\mathrm{<span\; class="notranslate">\; h</span>}}_{\mathrm{<span\; class="notranslate">\; LS</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; RS</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; )</span>{\mathrm{<span\; class="notranslate">\; S</span>}}_{\mathrm{<span\; class="notranslate">\; RS</span>}}^{<span\; class="notranslate">\; *</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; )</span>}{{<span\; class="notranslate">\; |</span>{\mathrm{<span\; class="notranslate">\; S</span>}}_{\mathrm{<span\; class="notranslate">\; RS</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; |</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0,1</span>}<span\; class="notranslate">\; ,</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span>\mathrm{<span\; class="notranslate">\; K</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}$

Wherein, S _RS (k, n) refers to the pilot reference signal sent by the mobile terminal without channel impact. For the base station and the mobile terminal, S _RS (k, n) is known to both parties. S ^* _RS (k,n) represents the conjugate of _SRS (k,n).

Since the pilot reference signal sent by the mobile terminal generally has |S _RS (k, n)| ² =1, the above formula can be simplified as:

${\mathrm{<span\; class="notranslate">\; h</span>}}_{\mathrm{<span\; class="notranslate">\; LS</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; RS</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; )</span>{\mathrm{<span\; class="notranslate">\; S</span>}}_{\mathrm{<span\; class="notranslate">\; RS</span>}}^{<span\; class="notranslate">\; *</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0,1</span>}<span\; class="notranslate">\; ,</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span>\mathrm{<span\; class="notranslate">\; K</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}$

304: Acquire the estimated frequency offset value of the current group of the mth user according to the estimated values of the channel impulse response coefficients of the two closest adjacent pilot data in the current group;

Specifically, since there is a difference of (P-1) OFMD symbols between the serial number of the OFDM symbol where the previous pilot data is located and the serial number of the OFDM symbol where this pilot data is located, when the channel impact of the previous pilot data When the LS estimation result of the response coefficient is H _LS (k, n), the LS estimation result of the channel impulse response coefficient of the nearest adjacent pilot data is H _LS (k, n+P-1). The phase difference between them is:

$\mathrm{<span\; class="notranslate">\; \&theta;</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; the\; angle</span>}<span\; class="notranslate">\; \{</span>\underset{\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0</span>}}{\overset{\mathrm{<span\; class="notranslate">\; K</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}{\mathrm{<span\; class="notranslate">\; h</span>}}_{\mathrm{<span\; class="notranslate">\; LS</span>}}^{<span\; class="notranslate">\; *</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; h</span>}}_{\mathrm{<span\; class="notranslate">\; LS</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; P</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; \}</span>$

What needs to be explained here is that the $\mathrm{\&Gamma;}=\underset{k=0}{\overset{K-1}{\mathrm{\&Sigma;}}}{h}_{\mathrm{LS}}^{*}(k,\mathrm{no})\&Center\; Dot;h_{\mathrm{LS}}(k,\mathrm{no}+P-1),$ Then θ=angle{Γ} can be specifically expressed as θ=arctan (imaginary part of Γ/real part of Γ).

Secondly, according to the phase difference θ, calculate the estimated value of the fractional frequency offset of the actual frequency offset value of the mth user's current group. The method of the bias estimation value is basically similar to the method of the fractional frequency offset estimation value, and will not be described in detail here.

Specifically, the fractional frequency offset estimation value can be calculated according to the following formula:

${\stackrel{<span\; class="notranslate">\; ^</span>}{\mathrm{<span\; class="notranslate">\; \&epsiv;</span>}}}_{\mathrm{<span\; class="notranslate">\; RS</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; \&theta;</span>}<span\; class="notranslate">\; \&CenterDot;</span>{\mathrm{<span\; class="notranslate">\; N</span>}}_{\mathrm{<span\; class="notranslate">\; FFT</span>}}}{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; \&pi;</span>}<span\; class="notranslate">\; \&CenterDot;</span>\mathrm{<span\; class="notranslate">\; P</span>}<span\; class="notranslate">\; \&Center\; Dot;</span><span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; N</span>}}_{\mathrm{<span\; class="notranslate">\; FFT</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; N</span>}}_{\mathrm{<span\; class="notranslate">\; CP</span>}}<span\; class="notranslate">\; )</span>}$

What needs to be explained here is that due to the fact that within a group, the nearest two adjacent pilot data are separated by P-1 OFDM symbols, and the interval is relatively large, the frequency offset range of the pilot frequency estimation is small, which is not enough to cover the actual Frequency offset range. Therefore, the actual frequency offset value of the current group of the mth user needs to be further processed through the estimated frequency offset value obtained by the pilot estimation.

305: Obtain a candidate frequency offset estimation result of the current group of the m-th user within the actual frequency offset range according to the estimated frequency offset value of the current group of the m-th user estimated by the pilot;

In this step, the frequency offset estimation range of the pilot frequency estimation is used as the size of a frequency offset interval, and the actual frequency offset range of the user is divided into multiple frequency offset intervals, and the fractional frequency offset estimation value calculated in 304 is used among them The position in the frequency offset interval to which it belongs, obtains the candidate frequency offset estimation result of the current group of the m-th user in the same position as the fractional frequency offset estimation value in the frequency offset interval.

Specifically, the division of the frequency offset interval may include:

1) The base station calculates the actual frequency offset range that the uplink system may reach according to the carrier frequency F of the uplink system and the moving speed V of the mobile terminal relative to the base station, where the frequency offset is proportional to the carrier frequency F of the system and the movement of the mobile terminal relative to the base station speed v.

其中，C表示光速；那么，该上行系统可能达到实际的最大频偏范围可以表示为

Specifically, the maximum frequency offset range that the actual frequency offset can achieve is

Among them, C represents the speed of light; then, the actual maximum frequency deviation range that the uplink system may reach can be expressed as

2) calculate the frequency offset range of the pilot frequency estimation;

那么

其中N_RS是两个包含导频数据的OFMD符号之间相隔的时域样点个数，Δf是子载波之间的频率间隔。Since the uplink system is known, the frequency offset range of the pilot estimation between the mobile terminal and the base station is known. Let the frequency offset range of pilot frequency estimation be

So

Where N _RS is the number of time-domain samples separated between two OFMD symbols containing pilot data, and Δf is the frequency spacing between subcarriers.

Correspondingly, the frequency offset estimation range of the pilot frequency estimation is

将该上行系统可能达到的实际频偏范围ε_max划分为多个频偏区间；3) Using the frequency offset estimation range of pilot frequency estimation

The actual frequency offset range ε _max that the uplink system may achieve is divided into multiple frequency offset intervals;

Specific division methods may include:

的值向上取整进行计算，当U的计算值为偶数时，实际的U值需要加1。According to ε _zone , ε _max is divided into U frequency offset intervals, starting from the position where the frequency offset is zero as the center point of the first frequency offset interval, and proceeding to the two directions of negative frequency offset and positive frequency offset respectively Division of frequency offset intervals. The divided frequency offset intervals are marked with 1, 2, . . . , U respectively. Wherein, due to the division method of the frequency offset interval, all the frequency offset intervals are symmetrical with respect to the first frequency offset interval, so the value of U is an odd number. The value of U can be changed by setting

The value of is rounded up for calculation. When the calculated value of U is an even number, the actual value of U needs to be added by 1.

第二个频偏区间位于第一个频偏区间的负向，范围是

第三个频偏区间位于第一个频偏区间的正向，范围是 $(\frac{{\mathrm{\&epsiv;}}_{\mathrm{zone}}}{2},\frac{{\mathrm{\&epsiv;}}_{\max }}{2}].$ For example, assuming that U is 3, the division of intervals can be shown in Figure 4. The range of the first frequency offset interval is

The second frequency offset interval is located in the negative direction of the first frequency offset interval, and the range is

The third frequency offset interval is located in the positive direction of the first frequency offset interval, and the range is $(\frac{{\mathrm{\&epsiv;}}_{\mathrm{zone}}}{2},\frac{{\mathrm{\&epsiv;}}_{\max }}{2}].$

For example, assuming that the actual frequency offset range of the user is [-10, 10], and the frequency offset estimation range of the pilot estimation is [-3, 3], the actual frequency offset range of the user is calculated by using the frequency offset estimation range of the pilot estimation For division of frequency offset intervals, the divided frequency offset intervals may be expressed as [-10, -9], [-9, -3], [-3, 3], [3, 9], [9, 10]. Assume that the fractional frequency offset value of the current group of the mth user estimated by the pilot is 1, which falls within the frequency offset interval of [-3, 3]. According to the position of 1 in the current frequency offset interval, the frequency offset interval The left endpoint is 4 larger and 2 smaller than the right endpoint of the frequency offset interval, and the estimated frequency offset value of the current group of the mth user within the actual frequency offset range is obtained in the entire frequency offset interval, namely: [-10, -9], [9, 10] There is no such frequency offset estimate in the two frequency offset intervals, the frequency offset estimate in the [-9, -3] frequency offset interval is -5, [3, 9] in the frequency offset interval The frequency offset estimate is 7.

306: According to the frequency offset correction result of the packet data that has undergone frequency offset correction, select the candidate frequency offset estimation result of which frequency offset interval to use as the frequency offset estimation result;

Wherein, the frequency offset correction result of the packet data that has undergone frequency offset correction can be CRC feedback, and CRC feedback specifically refers to: the frequency offset correction result of the packet data that has undergone frequency offset correction is subjected to CRC after demodulation and decoding to obtain CRC feedback.

If the CRC feedback of the frequency offset correction result of the packet data that has undergone frequency offset correction is an error, it means that the frequency offset estimation result used by the packet data that has undergone frequency offset correction is not the actual frequency offset value of the mth user, and has The frequency offset interval of the frequency offset estimation result used by the offset-corrected packet data is not the frequency offset interval of the mth user's actual frequency offset value, so the frequency offset estimation used by the packet data that has been frequency offset corrected is used As a result, the candidate frequency offset estimation results of different frequency offset intervals are used as the frequency offset estimation results of the current packet data, and continue to perform frequency offset estimation on the packet data; There may be multiple frequency offset intervals with different frequency offset intervals where the result is located. When selecting, different frequency offset intervals may be randomly selected, or may be selected one by one in a certain order.

If the CRC feedback of the frequency offset correction result of the frequency offset corrected packet data is correct, it means that the frequency offset estimation result adopted by the frequency offset corrected packet data is the actual frequency offset value of the mth user, correspondingly, The frequency offset interval where the frequency offset estimation result is located is also the frequency offset interval to which the actual frequency offset value belongs, so continue to use the frequency offset interval where the frequency offset estimation result of the packet data that has undergone frequency offset correction belongs, and use the frequency offset interval that has been corrected. Candidate frequency offset estimation results in the same frequency offset interval as the frequency offset estimation results adopted by the packet data are used as the frequency offset estimation results of the current packet data.

It should be noted that: when the CRC feedback is correct, the base station will request the mobile terminal to retransmit the original packet data, so as to correct the frequency offset of all the packet data with the actual frequency offset value.

It should also be noted here that when performing frequency offset correction on the first group of packet data, since there is no CRC feedback of the frequency offset correction result of the packet data that has undergone frequency offset correction, the frequency offset value can be set to an optimal Possible values, or initialized to zero, i.e. assuming no frequency offset.

307: Perform frequency offset correction on the frequency domain data of the current group of the mth user according to the frequency offset value of the current group of the mth user;

308: Demodulate and decode the frequency offset corrected data, and use the demodulated and decoded data as the frequency offset correction result to provide reference for other packet data to select the frequency offset estimation result from the candidate frequency offset estimation results .

Here, the frequency offset correction result may be CRC feedback, that is, performing CRC on the demodulated and decoded data to obtain CRC feedback.

Further, in order to ensure that the correctness of the actual frequency offset value is not affected when the estimated frequency offset value jumps, each frequency offset interval can be further divided:

A) Each frequency offset interval is further divided into a boundary subinterval and a non-boundary subinterval.

Of course, the non-boundary sub-interval may also be divided into multiple non-boundary sub-intervals, and the frequency range of each sub-interval is not smaller than the jitter range of the frequency offset. Here, the jitter range refers to the minimum value of frequency offset variation.

Referring to FIG. 5 , assuming U=3, each frequency offset interval can be divided into three subintervals A, B, and C, wherein subinterval A belongs to the non-boundary subinterval, and subintervals B and C belong to the boundary subinterval.

It should be noted that there are no strict regulations on the division of subintervals. The interval can be divided into thirds, or the proportion of non-boundary subintervals in the entire interval can be higher than that of boundary subintervals. Of course, the non-boundary subintervals can also be further divided, that is, the frequency offset interval can be divided into 4, 5 ... subintervals, including 2 boundary subintervals and multiple non-boundary subintervals.

落在哪个已划分好的频偏区间中的子区间；B) Judging the estimated value of decimal frequency offset

Which sub-interval falls in the divided frequency offset interval;

As shown in Figure 5, assume that the estimated The X1 position in the A1 subinterval of the first frequency offset interval, correspondingly, the X2 position in the A2 subinterval of the second frequency offset interval, and the X3 position in the A3 subinterval of the third frequency offset interval are both the mth user The candidate frequency offset estimation results of the current group.

Specifically, referring to Fig. 5, it is assumed that the actual frequency offset value is initially in the subinterval A2 in frequency offset interval 2. After several groups, the actual frequency offset value may have changed to a certain position of C2, since C2 still belongs to the frequency range 2, so this value can still be used as the actual frequency offset value, but if the actual frequency offset continues to change to B3, then the calculated fractional frequency offset estimated value can be one of B1, B2, and B3, but if at this time Locking still considers that the actual frequency offset value is in the frequency offset interval 2, so there is a deviation from the actual frequency offset value, so it is necessary to track the frequency offset interval, which can provide a reference value for future frequency offset estimation. The specific method is as follows:

C) Track the actual frequency offset value of each group. When the actual frequency offset value changes from one boundary subinterval to another boundary subinterval, the frequency offset interval needs to be changed to a frequency offset adjacent to the boundary subinterval before the change Interval, so as to complete the interval change and effectively prevent the jitter in the frequency offset interval.

Of course, if the CRC has continuous errors after the frequency offset interval is determined, it is necessary to re-search the frequency offset interval until the CRC feedback is correct.

(A1)作为频偏估计结果，其中

(A1)是A1子区间的频偏估计值，经过解调及译码后，得到CRC反馈，如果收到的CRC反馈为错误，则第2个分组可以采用

(A2)作为A2子区间的频偏估计结果，以此类推，直至收到的CRC反馈为正确。当然，也可以只采用一个分组进行自动频偏纠正，即按照一定的顺序，用不同的频偏区间中的候选频偏估计结果对同一个分组中第m个用户的频域数据进行频偏纠正，直至收到的CRC反馈为正确。Specifically, assuming that starting from the A1 subinterval, the first group uses

(A1) As the frequency offset estimation result, where

(A1) is the estimated frequency offset value of the A1 sub-interval. After demodulation and decoding, the CRC feedback is obtained. If the received CRC feedback is wrong, the second group can use

(A2) as the frequency offset estimation result of the A2 sub-interval, and so on until the received CRC feedback is correct. Of course, only one group can be used for automatic frequency offset correction, that is, according to a certain order, use the candidate frequency offset estimation results in different frequency offset intervals to perform frequency offset correction on the frequency domain data of the mth user in the same group , until the received CRC feedback is correct.

It should be noted that the method provided by the embodiment of the present invention can be used in systems other than OFDM. As long as the frequency offset estimation range of the reference signal is small and the actual frequency offset is large, the frequency offset can be corrected by this method. . It only needs to use the frequency offset period estimated by the reference signal as the interval, divide the actual frequency offset into several intervals, and then perform interval search and interval tracking on the basis of feedback CRC, so as to lock the frequency offset interval and obtain a more accurate frequency offset estimated value.

In the embodiment of the present invention, the actual frequency offset range that the user may reach is divided into several frequency offset intervals, and the frequency offset estimation is performed in combination with the user's pilot data in the current packet data, and the frequency offset is corrected by the user in the packet data that has been corrected. The frequency offset correction result of the user can be obtained to obtain a relatively accurate frequency offset estimation result of the user in the current group, so as to achieve the effect of effectively correcting the frequency offset of the user in the current group data. Moreover, the reliability and stability of frequency tracking are guaranteed through effective interval division technology, and interval jitter will not occur. The technical solutions of the embodiments of the present invention have less computational complexity, are less affected by timing errors and multi-user interference, and can ensure reliable and effective work of the system.

Embodiment three

Referring to Figure 6, an embodiment of the present invention provides a network side device, including:

The receiving module 601 is configured to receive the current packet data, and obtain frequency domain data and pilot data of the user in the current packet data according to the received current packet data;

An obtaining module 602, configured to obtain a frequency offset estimation result of the user in the current packet data according to the pilot data of the user in the current packet data and the frequency offset correction result of the user in the packet data that has undergone frequency offset correction;

The frequency offset correction module 603 is configured to perform frequency offset correction on the user's frequency domain data in the current packet data according to the frequency offset estimation result obtained by the obtaining module 602 .

It should be noted here that when no frequency offset correction is performed on all packet data, the obtaining module 602 is further configured to: set the frequency offset estimation result of the user in the current packet data to zero.

Wherein, referring to the corresponding description of the previous method embodiment, referring to FIG. 7, the obtaining module 602 may include:

A frequency offset estimation value obtaining unit 602A, configured to obtain an estimated frequency offset value of the user in the current packet data according to the pilot data of the user in the current packet data;

The candidate frequency offset estimation result obtaining unit 602B is configured to obtain the candidate frequency offset estimation result of the user in the current packet data according to the frequency offset estimation value of the user in the current packet data;

The frequency offset estimation result obtaining unit 602C is configured to select the user's frequency offset estimation result in the current packet data from the candidate frequency offset estimation results according to the user's frequency offset correction result in the frequency offset corrected packet data.

Specifically, referring to the corresponding descriptions of the foregoing method embodiments, the frequency offset estimation value obtaining unit 602A may include:

The coefficient estimation subunit is used to obtain the estimated value of the channel impulse response coefficient of the pilot data;

The obtaining subunit is configured to obtain the estimated frequency offset value of the user's current group according to the estimated values of the channel impulse response coefficients of the two closest adjacent pilot signals obtained in the coefficient estimation subunit.

Specifically, referring to the corresponding description of the previous method embodiment, referring to FIG. 8, the candidate frequency offset estimation result unit 602B may include:

The frequency offset interval division subunit 602B1 is used to divide the predicted actual frequency offset range of the user into multiple frequency offset intervals;

The obtaining subunit 602B2 is configured to obtain a plurality of candidate frequency offset estimation results with the same position in multiple frequency offset intervals according to the position of the frequency offset estimation value of the user in the current packet data within the frequency offset interval to which it belongs.

Wherein, referring to the corresponding description of the foregoing method embodiments, the frequency offset interval division subunit 602B1 is used to:

The frequency offset estimation range of the pilot frequency estimation is taken as the size of a frequency offset interval, and the position where the frequency offset is zero is taken as the midpoint of the first frequency offset interval, and the frequency offset is positive and the frequency offset is negative respectively. The predicted actual frequency offset range of the user is divided into multiple frequency offset intervals.

It should be noted that when the frequency offset correction result of the user in the packet data that has undergone frequency offset correction is: when the user performs the CRC feedback after frequency offset correction in the packet data that has undergone frequency offset correction , the frequency offset estimation result obtaining unit 602C is used to:

If the user's CRC feedback after frequency offset correction of the packet data that has undergone frequency offset correction is an error, select the frequency offset between the user's candidate frequency offset estimation results in the current packet data and the user's frequency offset corrected packet data The candidate frequency offset estimation results whose estimation results belong to different frequency offset intervals are used as the frequency offset estimation results of the current group;

If the user's CRC feedback after frequency offset correction of the packet data that has undergone frequency offset correction is correct, select the frequency offset between the user's candidate frequency offset estimation results in the current packet data and the user's frequency offset corrected packet data The candidate frequency offset estimation results whose estimation results belong to the same frequency offset interval are used as the frequency offset estimation results of the current group.

Further, referring to the corresponding description of the foregoing method embodiments, the candidate frequency offset estimation result unit 602B may further include:

The sub-interval is divided into sub-units, and each frequency offset interval is divided into a boundary sub-interval and a non-boundary sub-interval;

Then the obtaining subunit 602B2 can also be used for:

When the frequency offset estimation value changes from one boundary subinterval to another boundary subinterval within the frequency offset interval to which it belongs, use the frequency offset estimation value in the frequency offset interval adjacent to the boundary subinterval before the change as the current group frequency offset value.

It should be noted that, the network side device in this embodiment may specifically be a base station.

The network side device provided by the embodiment of the present invention obtains a relatively accurate frequency offset estimation result by combining the frequency offset correction result of the user in the packet data that has undergone frequency offset correction and the pilot data of the user in the current packet data, and according to The obtained frequency offset correction result performs frequency offset correction on the user's frequency domain data in the current packet data. Furthermore, the embodiment of the present invention divides the actual frequency offset range that the user may reach into several frequency offset intervals, so as to ensure the reliability and stability of frequency tracking and avoid interval jitter. The technical solutions of the embodiments of the present invention have less computational complexity, are less affected by timing errors and multi-user interference, and can ensure reliable and effective work of the system.

The embodiment of the present invention can be realized by software, and the corresponding software program can be stored in a readable storage medium, for example, a hard disk, cache or optical disc of a router.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included in the protection of the present invention. within range.

Claims (12)

1. A frequency offset correction method, characterized in that, comprising: receiving the current packet data, and obtaining frequency domain data and pilot data of the user in the current packet data according to the received current packet data; Obtain a frequency offset estimation result of the user in the current packet data according to the pilot data of the user in the current packet data and the frequency offset correction result of the user in the packet data that has undergone frequency offset correction; performing frequency offset correction on frequency domain data of the user in the current packet data according to the frequency offset estimation result; Wherein, the obtaining the frequency offset estimation result of the user in the current packet data specifically includes: Obtaining an estimated frequency offset value of the user in the current packet data according to the pilot data of the user in the current packet data; Obtaining a candidate frequency offset estimation result of the user in the current packet data according to the frequency offset estimation value of the user in the current packet data; According to the frequency offset correction result of the user in the packet data that has undergone frequency offset correction, the frequency offset estimation result of the user in the current packet data is selected from the candidate frequency offset estimation results. 2. The method for correcting frequency offset according to claim 1, characterized in that, when no frequency offset correction has been performed on all packet data, the frequency offset estimation result of the user in the current packet data is set to zero. 3. The frequency offset correction method according to claim 1, wherein said obtaining the estimated frequency offset of the user in the current packet data according to the pilot data of the user in the current packet data comprises: Acquiring an estimated value of the channel impulse response coefficient of the pilot data; The estimated value of the frequency offset of the current group of the user is obtained according to the estimated values of the channel impulse response coefficients of the two closest adjacent pilot signals. 4. The frequency offset correction method according to claim 1, wherein the frequency offset estimation result of the user in the current packet data is obtained according to the frequency offset estimation value of the user in the current packet data ,include: dividing the predicted actual frequency offset range of the user into a plurality of frequency offset intervals, and according to the position of the estimated frequency offset value of the user in the current packet data within the frequency offset interval to which it belongs, the frequency offset in the plurality of frequency offset intervals is A plurality of candidate frequency offset estimation results identical to the position are obtained in the interval. 5. The frequency offset correction method according to claim 4, wherein the frequency offset correction result of the user in the packet data that has undergone frequency offset correction is: the frequency offset correction result of the user in the packet data that has undergone frequency offset correction Cyclic redundancy check CRC feedback after frequency offset correction in Then, according to the frequency offset correction result of the user in the packet data that has undergone frequency offset correction, selecting the frequency offset estimation result of the current group from the candidate frequency offset estimation results includes: If the user's CRC feedback after frequency offset correction of the packet data that has undergone frequency offset correction is an error, select the candidate frequency offset estimation result of the user in the current packet data that is the same as that of the user that has undergone frequency offset correction The frequency offset estimation results of the grouped data belong to the candidate frequency offset estimation results of different frequency offset intervals as the frequency offset estimation results of the current group; If the user's CRC feedback after frequency offset correction of the packet data that has undergone frequency offset correction is correct, select the candidate frequency offset estimation result of the user in the current packet data that is the same as that of the user that has undergone frequency offset correction The frequency offset estimation results of the grouped data belong to the candidate frequency offset estimation results of the same frequency offset interval as the frequency offset estimation results of the current group. 6. The frequency offset correction method according to claim 4, wherein the method further comprises: dividing each of the frequency offset intervals into boundary subintervals and non-boundary subintervals; Then when the estimated frequency offset value changes from one boundary subinterval to another boundary subinterval within the frequency offset interval to which it belongs, use the estimated frequency offset value in the frequency offset interval adjacent to the boundary subinterval before the change as the frequency offset value of the current group. 7. A network side device, characterized in that the device comprises: A receiving module, configured to receive current packet data, and obtain frequency domain data and pilot data of the user in the current packet data according to the received current packet data; An obtaining module, configured to obtain the frequency offset of the user in the current packet data according to the pilot data of the user in the current packet data and the frequency offset correction result of the user in the packet data that has undergone frequency offset correction estimated results; a frequency offset correction module, configured to perform frequency offset correction on the frequency domain data of the user in the current packet data according to the frequency offset estimation result obtained by the obtaining module; Wherein, the obtaining module specifically includes: a frequency offset estimation value obtaining unit, configured to obtain an estimated frequency offset value of the user in the current packet data according to the pilot data of the user in the current packet data; A candidate frequency offset estimation result obtaining unit, configured to obtain a candidate frequency offset estimation result of the user in the current packet data according to the frequency offset estimation value of the user in the current packet data; A frequency offset estimation result obtaining unit, configured to select the frequency offset of the user in the current packet data from the candidate frequency offset estimation results according to the frequency offset correction result of the user in the packet data that has undergone frequency offset correction Estimated results. 8. The network side device according to claim 7, wherein when all packet data has not undergone frequency offset correction, the obtaining module is further configured to: set the frequency offset estimation result of the user in the current packet data to be zero. 9. The network side device according to claim 7, wherein the frequency offset estimation value obtaining unit comprises: a coefficient estimation subunit, configured to obtain an estimated value of the channel impulse response coefficient of the pilot data; The obtaining subunit is configured to obtain the estimated frequency offset value of the current group of the user according to the estimated channel impulse response coefficient values of the two closest adjacent pilot signals obtained in the coefficient estimation subunit. 10. The network side device according to claim 7, wherein said candidate frequency offset estimation result obtaining unit comprises: a frequency offset interval division subunit, configured to divide the predicted actual frequency offset range of the user into a plurality of frequency offset intervals; The obtaining subunit is used to obtain a plurality of candidate frequency offsets that are the same as the position in the plurality of frequency offset intervals according to the position of the estimated frequency offset value of the user in the current packet data within the frequency offset interval to which it belongs. biased estimates. 11. The network side device according to claim 7, wherein the frequency offset correction result of the user in the packet data that has undergone frequency offset correction is: the frequency offset correction result of the user in the packet data that has undergone frequency offset correction Cyclic redundancy check CRC feedback after frequency offset correction; Then the frequency offset estimation result obtaining unit is used for: If the user's CRC feedback after frequency offset correction of the packet data that has undergone frequency offset correction is an error, select the candidate frequency offset estimation result of the user in the current packet data that is the same as that of the user that has undergone frequency offset correction The frequency offset estimation results of the grouped data belong to the candidate frequency offset estimation results of different frequency offset intervals as the frequency offset estimation results of the current group; If the user's CRC feedback after frequency offset correction of the packet data that has undergone frequency offset correction is correct, select the candidate frequency offset estimation result of the user in the current packet data that is the same as that of the user that has undergone frequency offset correction The frequency offset estimation results of the grouped data belong to the candidate frequency offset estimation results of the same frequency offset interval as the frequency offset estimation results of the current group. 12. The network side device according to claim 10, wherein the unit for obtaining the candidate frequency offset estimation result further comprises: The sub-interval is divided into sub-units, and each frequency offset interval is divided into a boundary sub-interval and a non-boundary sub-interval; Then the obtaining subunit is also used for: When the estimated frequency offset value changes from one boundary subinterval to another boundary subinterval within the frequency offset interval to which it belongs, the estimated frequency offset value in the frequency offset interval adjacent to the boundary subinterval before the change is used as The frequency offset value of the current group.

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