CN101854322B - Frequency tracking method and system and frequency discriminator - Google Patents

Abstract

The present invention provides a frequency tracking method, system and frequency discriminator. The method includes: respectively detecting the frequency offset between the user equipment and the network equipment through the first frequency discrimination algorithm and the second frequency discrimination algorithm, and obtaining the first frequency offset Estimation results and second frequency offset estimation results; if the smoothed value of the obtained first frequency offset estimation results converges within the frequency discrimination range of the second frequency discrimination algorithm, then the currently obtained second frequency offset estimation As a result, the adjustment step length is reset, and the adjusted second frequency offset estimation result is used to perform frequency correction. Through the method, system and frequency discriminator of the embodiment of the present invention, not only the frequency offset capture range can be guaranteed, but also the tracking precision can be guaranteed.

Description

A frequency tracking method, system and frequency discriminator

technical field

The invention relates to the communication field, in particular to a frequency tracking method, system and frequency discriminator.

Background technique

The 3GPP (The 3rd Generation Partnership Project) long-term evolution (LTE, Long Term Evolution) project is the largest new technology research and development project launched by 3GPP in the past two years. Division Multiplexing)/FDMA (Frequency Division Multiple Access, Frequency Division Multiple Access) as the core technology can be regarded as "quasi-4G" technology, which has broad application prospects. However, the LTE system is the same as other wireless communication systems. Since the user equipment UE (User Equipment) and the crystal oscillator of the base station cannot be located at the same frequency accurately, there is a frequency offset in the communication system, which needs to be corrected by frequency tracking.

The LTE protocol requires that the accuracy of the carrier frequency offset must be within ±0.1PPM in an observation area of 1 ms in a sub-frame. That is to say, the center frequency of the lowest carrier frequency 746MHz stipulated in the agreement only allows the frequency deviation to be within ±75Hz, which puts forward very high requirements for frequency tracking. Frequency tracking is generally completed through an AFC (Auto Frequency Control, automatic frequency control) loop. The loop structure is shown in Figure 1. Among them, the frequency discriminator is used to detect the frequency offset between the UE and the base station, which is the core of the loop tracking Part, its performance is related to the frequency offset estimation algorithm used; the loop filter is used to smooth the estimated value, usually using a first-order loop or a second-order loop; the voltage-controlled oscillator is used to adjust the frequency.

在初始频偏为1500Hz(ε＝0.1)，载频为746MHz，信噪比SNR为0dB，带宽为1.4MHz，子载波间隔为15kHz的仿真条件下，由于实际频偏超过鉴频算法的有效估计范围，频率跟踪环路始终无法收敛到稳态。The inventor found in the process of realizing the present invention that, in the prior art, the frequency discrimination algorithm TDPD_CP (TDPD: Time Domain Phase Difference, time domain phase cross product; CP: CyclicPrefix, cyclic prefix) is used as the AFC tracking of the frequency discriminator The loop has the problem of insufficient estimation accuracy, and the residual frequency offset in the loop steady state is difficult to meet the requirements of the agreement 0.1ppm. The schematic diagram of the residual frequency offset simulation result (10000ms) shown in Figure 2. The offset is 1500Hz (ε=0.1, ε is the normalized frequency offset, which is defined as the ratio of the actual frequency offset to the subcarrier spacing), the carrier frequency is 746MHz, the SNR is 0dB, the bandwidth is 1.4MHz, and the subcarrier spacing is Under the simulation condition of 15kHz, the residual frequency deviation exceeds 0.1ppm in most cases. However, the AFC tracking loop using the frequency discrimination algorithm FDPD_RS (FDPD: Frequency Domain Phase Difference, frequency domain phase cross product; RS: ReferenceSignal, reference signal) as the frequency discriminator has the problem that the effective range of frequency discrimination is too small, as shown in the figure The schematic diagram of the residual frequency offset simulation result (10000ms) shown in 3, which is an example of the LTE system OFDM symbol data length N = 2048, and its time slot length N _slot = 15360, from which the frequency offset estimation can be obtained

Under the simulation conditions where the initial frequency offset is 1500Hz (ε=0.1), the carrier frequency is 746MHz, the signal-to-noise ratio SNR is 0dB, the bandwidth is 1.4MHz, and the subcarrier spacing is 15kHz, since the actual frequency offset exceeds the effective estimation of the frequency discrimination algorithm range, the frequency tracking loop can never converge to a steady state.

Contents of the invention

In order to solve the problems of insufficient steady-state accuracy and too small frequency offset capture range of the frequency tracking method in the prior art, embodiments of the present invention provide a frequency tracking method, system and frequency discriminator.

The above object of the embodiments of the present invention is achieved through the following technical solutions:

A frequency tracking method, the method comprising: respectively detecting a frequency offset between a user equipment and a network equipment through a first frequency discrimination algorithm and a second frequency discrimination algorithm, and obtaining a first frequency offset estimation result and a second frequency offset estimation result ; Wherein, compared with the second frequency discrimination algorithm, the frequency discrimination range of the first frequency discrimination algorithm is larger and the accuracy is lower; if the smoothed value of the obtained first frequency offset estimation result converges to the second Within the frequency discrimination range of the frequency discrimination algorithm, the currently obtained second frequency offset estimation result is adjusted to reset the step size, and the adjusted second frequency offset estimation result is used to perform frequency correction.

A frequency discriminator, the frequency discriminator includes: a first frequency discrimination unit, configured to detect a frequency offset between a user equipment and a network device through a first frequency discrimination algorithm, and obtain a first frequency offset estimation result; a second frequency discrimination unit A frequency unit, configured to detect a frequency offset between the user equipment and the network device through a second frequency discrimination algorithm, and obtain a second frequency offset estimation result; wherein, relative to the second frequency discrimination algorithm, the first frequency discrimination algorithm The frequency discrimination range is relatively large, and the precision is low; the outer loop locks the judgment unit, which is used to judge whether the smooth value of the obtained first frequency offset estimation result converges within the frequency discrimination range of the second frequency discrimination algorithm; An estimation result output unit, configured to output the second frequency offset estimation result to the loop filter when the obtained smoothed value of the first frequency offset estimation result converges within the frequency discrimination range of the second frequency discrimination algorithm and reset the adjustment step size of the second frequency offset estimation result through the loop filter, and then use the adjusted second frequency offset estimation result to perform frequency correction through the voltage controlled oscillator.

A frequency tracking system includes a loop filter, a voltage controlled oscillator and the aforementioned frequency discriminator.

The frequency tracking method, system, and frequency discriminator of the embodiments of the present invention propose a scheme that combines two frequency discrimination algorithms for frequency tracking. Through the method, system, and frequency discriminator of the embodiments of the present invention, both It can also guarantee the tracking steady-state accuracy.

Description of drawings

The drawings described here are used to provide further understanding of the present invention, constitute a part of the application, and do not limit the present invention. In the attached picture:

Figure 1 is a schematic diagram of the loop structure of the automatic frequency control system;

Figure 2 is a schematic diagram of the simulation results of the time-domain phase cross-product algorithm;

Fig. 3 is the schematic diagram of simulation result of frequency domain phase cross product algorithm;

4 is a flowchart of a frequency tracking method according to an embodiment of the present invention;

Fig. 5 is a schematic diagram of the CP repetition structure of the OFDM system;

FIG. 6A is a schematic diagram of normal CP downlink RS mapping in an LTE system;

FIG. 6B is a schematic diagram of extended CP downlink RS mapping of the LTE system;

7 is a flowchart of a frequency tracking method according to another embodiment of the present invention;

FIG. 8 is a flowchart of a frequency tracking method according to another embodiment of the present invention;

FIG. 9 is a schematic diagram of a frequency offset simulation result of an experiment using an embodiment of the present invention;

FIG. 10 is a structural block diagram of a frequency discriminator according to an embodiment of the present invention;

Fig. 11 is a block diagram of a frequency tracking system according to an embodiment of the present invention.

Detailed ways

In order to make the purpose, technical solutions and advantages of the embodiments of the present invention more clear, the embodiments of the present invention will be further described in detail below in conjunction with the embodiments and the accompanying drawings. Here, the exemplary embodiments and descriptions of the present invention are used to explain the present invention, but not to limit the present invention.

Embodiment one

An embodiment of the present invention provides a frequency tracking method, which will be described in detail below with reference to the accompanying drawings.

Fig. 4 is the method flowchart of this embodiment, please refer to Fig. 4, the frequency tracking method of this embodiment mainly includes:

401: Detect the frequency offset between the user equipment and the network equipment by using the first frequency discrimination algorithm and the second frequency discrimination algorithm, and obtain a first frequency offset estimation result and a second frequency offset estimation result;

Wherein, compared with the second frequency discrimination algorithm, the frequency discrimination range of the first frequency discrimination algorithm is larger, and the precision is lower.

In this embodiment, the first frequency discrimination algorithm is TDPD_CP (TDPD: Time Domain Phase Difference, time domain phase cross product; CP: Cyclic Prefix, cyclic prefix) algorithm.

In this embodiment, the second frequency discrimination algorithm is an FDPD_RS (FDPD: Frequency Domain Phase Difference, frequency domain phase cross product; RS: Reference Signal, reference signal) algorithm.

402: Judging whether the obtained smoothed value of the first frequency offset estimation result converges within the frequency discrimination range of the second frequency discrimination algorithm;

Wherein, the smoothing value of the obtained first frequency offset estimation results can be realized by taking the average value of the current and previously obtained multiple first frequency offset estimation results, or by averaging the current and previously obtained multiple first frequency offset estimation results. The partial estimation result is filtered and then compared with a threshold value, which is not limited in this embodiment. In addition, the average value of the multiple first frequency offset estimation results here may be the average value of all the first frequency offset estimation results obtained within a certain period, or may be the average value of the first frequency offset estimation results of a preset predetermined number of times. The average value is not limited by the embodiments of the present invention.

403: If the smoothed value of the obtained first frequency offset estimation result converges within the frequency discrimination range of the second frequency discrimination algorithm, perform an adjustment step reset on the currently obtained second frequency offset estimation result, Frequency correction is performed by using the adjusted second frequency offset estimation result.

404: If the smoothed value of the obtained first frequency offset estimation result exceeds the frequency discrimination range of the second frequency discrimination algorithm, then adjust the currently obtained first frequency offset estimation result with a decreasing step size, and use the adjustment Perform frequency correction on the last first frequency offset estimation result.

In this embodiment, it is judged whether the smoothed value of the obtained first frequency offset estimation result converges within the frequency discrimination range of the second frequency discrimination algorithm, by evaluating the current and previously obtained multiple times of the first frequency offset estimation The results are accumulated and averaged or compared with a threshold value after filtering to avoid misjudgment caused by an inaccurate frequency offset estimation result, but this embodiment is not limited by this.

If the result of judgment is that the smoothed value of the obtained first frequency offset estimation result converges within the frequency discrimination range of the second frequency discrimination algorithm, it indicates that the frequency discrimination range has been reduced, and the second frequency discrimination range with a relatively small frequency discrimination range can be used. The frequency discrimination algorithm detects the second frequency offset estimation result obtained by detecting the current frequency offset to perform frequency correction.

The loop filter receives the second frequency offset estimation result, adjusts the step size of the second frequency offset estimation result, and outputs the processed second frequency offset estimation result to the voltage-controlled oscillator, and the voltage-controlled oscillation The processor uses the processed second frequency offset estimation result to perform frequency correction. Wherein, the operation of the loop filter and the voltage controlled oscillator are the same as those of the prior art, and will not be repeated here.

In this embodiment, the first frequency discrimination algorithm with relatively large frequency discrimination range and relatively low frequency discrimination accuracy can be TDPD_CP (TDPD: Time Domain Phase Difference, time domain phase cross product; CP: Cyclic Prefix, cyclic prefix) Algorithm, but this embodiment of the present invention is not limited by this, TDPD_CP will be described below.

θ∈{-π～π}，频偏估计结果为

ε∈{-0.5～0.5}，其中，ε是指归一化频偏，定义为实际频偏

(单位：Hz)与子载波间隔Δf(单位：Hz)的比值。Please refer to Figure 5, since the OFDM system usually has a cyclic prefix CP (Cyclic Prefix), wherein the length of the data part is N, that is, z ₀ , z ₁ , ... z _N-1 , the length of the CP is L, and the data part is repeated z _NL , z _N-L+1 ,...z _N-1 , assuming the received signal is γ(n), the starting position of the symbol is n ₀ , and the phase cross product is performed using CP repeatability,

θ∈{-π～π}, the frequency offset estimation result is

ε∈{-0.5～0.5}, where ε refers to the normalized frequency offset, which is defined as the actual frequency offset

(unit: Hz) and the ratio of the subcarrier spacing Δf (unit: Hz).

In this embodiment, the second frequency discrimination algorithm with relatively small frequency discrimination range and relatively high frequency discrimination accuracy can be FDPD_RS (FDPD: Frequency Domain Phase Difference, frequency domain phase cross product; RS: Reference Signal, reference signal) Algorithm, but this embodiment of the present invention is not limited by this, and the FDPD_RS will be described below.

其中，N_slot表示时隙长度。Please refer to Figure 6A and Figure 6B. From the LTE system downlink RS mapping in Figure 6A and 6B, it can be seen that for 1, 2 transmit antennas, the position of the subcarrier of the RS symbol will be repeated after a time slot interval, and the phase cross product is defined as follows, $\mathrm{\θ}=\∠\left(\underset{k\∈\mathrm{\Γ}}{\mathrm{\Σ}}({(Z_k\left({\mathrm{no}}_{\mathrm{the\; s}}\right)\&Center\; Dot;P_k^{*}\left({\mathrm{no}}_{\mathrm{the\; s}}\right))}^{*}\&Center\; Dot;(Z_k\left({\mathrm{no}}_{\mathrm{the\; s}}\right)\&Center\; Dot;P_k^{*}({\mathrm{no}}_{\mathrm{the\; s}}+1)))\right)$ θ∈{-π～π}, where Z _k (n _s ) is the n _sth time slot, the symbol received at the kth subcarrier, P _k (n _s ) is the n _sth time slot, the kth subcarrier RS symbols are generated locally at the carrier, then the frequency offset estimation result is

Wherein, N _slot represents the length of the time slot.

If the judged result is that the smoothed value of the obtained first frequency offset estimation result exceeds the frequency discrimination range of the second frequency discrimination algorithm, it means that the frequency discrimination range is still very large, and the second frequency discrimination with a relatively small frequency discrimination range is not applicable. Frequency algorithm, at this time, output the currently obtained first frequency offset estimation result to the loop filter, after decreasing the adjustment step size through the loop filter, output the processed first frequency offset estimation result to the voltage controlled oscillator , the voltage controlled oscillator continues to use the processed first frequency offset estimation result to perform frequency correction.

According to this embodiment, in order to achieve a better tracking effect, the loop filter used can be a first-order loop with a variable adjustable step size, so that a large step size can be used at the beginning of the tracking, and a small step size can be used in a steady state. The initial steady-state transition step size is decremented to the configured low value.

The embodiment of the present invention adopts the method of combining two kinds of frequency discrimination algorithms. Firstly, the frequency offset is detected by the first frequency discrimination algorithm with relatively large frequency discrimination range and relatively low frequency discrimination accuracy, and then the frequency deviation is detected by the relatively small frequency discrimination range and the The relatively high-precision second frequency discrimination algorithm detects the frequency offset, which can not only ensure the frequency offset capture range, but also ensure the tracking accuracy.

Embodiment two

An embodiment of the present invention also provides a frequency tracking method, which will be described in detail below with reference to the accompanying drawings.

Figure 7 is a flow chart of the method of this embodiment, please refer to Figure 7, this embodiment is based on the first embodiment, in the process of using the second frequency discrimination algorithm, that is, the second frequency offset estimation result is used for frequency In the process of correction, a preferred embodiment of the frequency tracking method, as shown in Figure 7, the method of this embodiment mainly includes:

701: Judging whether the obtained smoothed value of the second frequency offset estimation result meets the protocol requirements;

702: If the obtained smoothed value of the second frequency offset estimation result satisfies the requirements of the protocol, perform adjustment step size reduction on the currently obtained second frequency offset estimation result, and use the adjusted second frequency offset estimation result to perform frequency correction ;

703: If the smoothed value of the obtained second frequency offset estimation result does not meet the protocol requirements, reset the adjustment step size for the currently obtained second frequency offset estimation result, and use the adjusted second frequency offset estimation result to perform frequency correction.

In this embodiment, judging whether the smoothed value of the obtained second frequency offset estimation result meets the protocol requirements can also be performed by accumulating and averaging multiple times of the current and previously obtained second frequency offset estimation results or by filtering It is implemented by comparing with another threshold value, so as to avoid misjudgment caused by the possible inaccuracy of the first frequency offset estimation result, but this embodiment is not limited by this.

If the result of the judgment is that the smoothed value of the obtained second frequency offset estimation result meets the protocol requirements, it means that the frequency offset at this time is within the acceptable range of the user. At this time, the currently obtained second frequency offset estimation result can be output to Loop filter, through the loop filter, the step size of the loop filter is decremented, and the processed second frequency offset estimation result is obtained, which is output to the voltage-controlled oscillator, and the voltage-controlled oscillator can use the processed second frequency offset Frequency correction is performed on the partial estimation results.

If the result of the judgment is that the smoothed value of the obtained second frequency offset estimation result does not meet the agreement requirements, it means that the frequency offset at this time still cannot meet the requirements. At this time, the currently obtained second frequency offset estimation result can be output to The loop filter resets the loop filter adjustment step size through the loop filter, and obtains the processed second frequency offset estimation result, which is output to the voltage controlled oscillator, and the voltage controlled oscillator can use the processed first frequency offset estimation result. Frequency correction is performed on the results of the second frequency offset estimation.

According to this embodiment, in order to achieve a better tracking effect, the loop filter used can be a first-order loop with a variable adjustable step size, so that a large step size can be used at the beginning of the tracking, and a small step size can be used in a steady state. The initial steady-state transition step size is decremented to the configured low value.

The embodiment of the present invention adopts the method of combining two kinds of frequency discrimination algorithms. Firstly, the frequency offset is detected by the first frequency discrimination algorithm with relatively large frequency discrimination range and relatively low frequency discrimination accuracy, and then the frequency deviation is detected by the relatively small frequency discrimination range and the The relatively high-precision second frequency discrimination algorithm detects the frequency offset, which can not only ensure the frequency offset capture range, but also ensure the tracking accuracy.

Embodiment three

An embodiment of the present invention also provides a frequency tracking method, which will be described in detail below with reference to the accompanying drawings.

Figure 8 is a flow chart of the method of this embodiment, please refer to Figure 8, this embodiment is based on Embodiment 1 and or Embodiment 2, in the process of using the second frequency discrimination algorithm, that is, the second frequency In the process of performing frequency correction on the partial estimation result, another preferred embodiment of the frequency tracking method, as shown in Figure 8, the method of this embodiment mainly includes:

801: Judging whether the obtained smoothed value of the first frequency offset estimation result exceeds the frequency discrimination range of the second frequency discrimination algorithm;

802: If the smoothed value of the obtained first frequency offset estimation result exceeds the frequency discrimination range of the second frequency discrimination algorithm, reset the adjustment step size for the currently obtained first frequency offset estimation result, and use the adjustment performing frequency correction on the final first frequency offset estimation result;

803: If the smoothed value of the obtained first frequency offset estimation result does not exceed the frequency discrimination range of the second frequency discrimination algorithm, then adjust the currently obtained second frequency offset estimation result with decreasing step size, and use the adjustment Perform frequency correction on the last second frequency offset estimation result.

In this embodiment, it is judged whether the smoothed value of the obtained first frequency offset estimation result exceeds the frequency discrimination range of the second frequency discrimination algorithm, or by analyzing the first frequency offset estimation results obtained multiple times at present and before Averaging after accumulation or comparison with another threshold value after filtering is implemented to avoid misjudgment caused by a possible inaccurate frequency offset estimation result, but this embodiment is not limited by this.

If the result of judgment is that the smoothed value of the obtained first frequency offset estimation result exceeds the frequency discrimination range of the second frequency discrimination algorithm, it means that the second frequency discrimination algorithm is not applicable at this time. At this time, the currently obtained first The frequency offset estimation result is output to the loop filter, and the loop filter step size is reset through the loop filter to obtain the processed first frequency offset estimation result, which is output to the voltage-controlled oscillator, and the voltage-controlled oscillator is sufficient Frequency correction is performed by using the processed first frequency offset estimation result.

If the result of the judgment is that the smoothed value of the obtained first frequency offset estimation result does not exceed the frequency discrimination range of the second frequency discrimination algorithm, it means that the second frequency discrimination algorithm is still applicable. At this time, the currently obtained second frequency offset The estimation result is output to the loop filter, and the loop filter step size is decremented through the loop filter to obtain the processed second frequency offset estimation result, which is output to the voltage-controlled oscillator, and the voltage-controlled oscillator can use this processing Perform frequency correction on the last second frequency offset estimation result.

In this embodiment, it may also be judged at the same time whether the obtained smoothed value of the second frequency offset result satisfies the protocol requirement. The determination of whether the obtained second frequency offset estimation result satisfies the protocol requirements has been described in Embodiment 2, and will not be repeated here.

According to this embodiment, in order to achieve a better tracking effect, the loop filter used can be a first-order loop with a variable adjustable step size, so that a large step size can be used at the beginning of the tracking, and a small step size can be used in a steady state. The initial steady-state transition step size is decremented to the configured low value.

Fig. 9 is a schematic diagram of the simulation result of the frequency tracking experiment done by using the frequency tracking method of the embodiment of the present invention. In the experiment shown in Fig. 9, the simulation conditions are: the initial frequency deviation is 1500Hz (ε=0.1); the carrier frequency is 746MHz; the signal-to-noise ratio SNR is 0dB; the transmission bandwidth is 1.4MHz; the subcarrier spacing is 15kHz, according to the residual frequency offset simulation result (10000ms) shown in Figure 9, it can be known that by the method of the embodiment of the present invention, the frequency offset Fast acquisition and very good locking performance in steady state.

The embodiment of the present invention adopts the method of combining two kinds of frequency discrimination algorithms. Firstly, the frequency offset is detected by the first frequency discrimination algorithm with relatively large frequency discrimination range and relatively low frequency discrimination accuracy, and then the frequency deviation is detected by the relatively small frequency discrimination range and the The relatively high-precision second frequency discrimination algorithm detects the frequency offset, which can not only ensure the frequency offset capture range, but also ensure the tracking accuracy.

Embodiment four

An embodiment of the present invention also provides a frequency discriminator, which will be described in detail below with reference to the accompanying drawings.

Fig. 10 is a composition block diagram of the frequency discriminator of this embodiment, please refer to Fig. 10, the frequency discriminator of this embodiment mainly includes:

The first frequency discrimination unit 101 is configured to detect a frequency offset between the user equipment and the network equipment through a first frequency discrimination algorithm, and obtain a first frequency offset estimation result;

The second frequency discrimination unit 102 is configured to detect a frequency offset between the user equipment and the network equipment through a second frequency discrimination algorithm, and obtain a second frequency offset estimation result;

Wherein, the frequency between the user equipment and the network equipment is received by the radio frequency receiving unit, which is the content of the prior art and will not be repeated here.

The outer loop locking decision unit 103 is used to judge whether the smoothed value of the obtained first frequency offset estimation result converges in the frequency discrimination range of the second frequency discrimination algorithm, and send the result of the judgment to the frequency offset estimation result output unit 104 ;

A frequency offset estimation result output unit 104, configured to output the currently obtained second frequency offset estimation result to the loop when the smoothed value of the obtained first frequency offset estimation result converges within the frequency discrimination range of the second frequency discrimination algorithm A loop filter is used to reset the adjustment step size of the second frequency offset estimation result through the loop filter, and then frequency correction is performed by using the adjusted second frequency offset estimation result through the voltage controlled oscillator.

In this embodiment, the frequency offset estimation result output unit 104 is also configured to convert the currently obtained first frequency offset to The estimation result is output to the loop filter, and the step size of the first frequency offset estimation result is adjusted by the loop filter, and then the frequency is adjusted by using the adjusted first frequency offset estimation result through the voltage controlled oscillator. Correction.

According to this embodiment, the frequency discriminator may further include:

Inner-loop loss-of-lock judging unit 105, configured to judge whether the smoothed value of the obtained second frequency offset estimation result satisfies protocol requirements, and send the judgment result to the frequency offset estimation result output unit 104 .

The frequency offset estimation result output unit 104 is also configured to output the currently obtained second frequency offset result to the loop filter when the smoothed value of the obtained second frequency offset estimation result meets the protocol requirements, and pass through the loop filter The filter adjusts the second frequency offset estimation result in decreasing steps, and then uses the adjusted second frequency offset estimation result to perform frequency correction through the voltage-controlled oscillator; and after smoothing the obtained second frequency offset estimation result When the value does not meet the protocol requirements, the currently obtained second frequency offset estimation result is output to the loop filter, and the second frequency offset estimation result is adjusted by the loop filter to reset the step size, and then passed The voltage controlled oscillator uses the adjusted second frequency offset estimation result to perform frequency correction.

According to this embodiment, the frequency discriminator may further include:

Outer-loop loss-of-lock judging unit 106, used for judging whether the smoothed value of the obtained first frequency offset estimation result exceeds The frequency discrimination range of the second frequency discrimination algorithm, and the judgment result is sent to the frequency offset estimation result output unit 104 .

The frequency offset estimation result output unit 104 is also used to output the currently obtained first frequency offset estimation result to the loop when the smoothed value of the obtained first frequency offset estimation result exceeds the frequency discrimination range of the second frequency discrimination algorithm. loop filter, and reset the adjustment step size of the first frequency offset estimation result through the loop filter, and then use the adjusted first frequency offset estimation result to perform frequency correction through the voltage controlled oscillator; and When the smoothed value of the obtained first frequency offset estimation result does not exceed the frequency discrimination range of the second frequency discrimination algorithm, the currently obtained second frequency offset estimation result is output to the loop filter, and passed through the loop The filter adjusts the second frequency offset estimation result by decreasing step size, and then uses the adjusted second frequency offset estimation result to perform frequency correction through the voltage-controlled oscillator.

Wherein, the loop filter may be a first-order loop with a variable adjustment step size.

The functions of the various components of the frequency discriminator in this embodiment are the functions used to realize the steps of the frequency tracking method in Embodiment 1-Embodiment 3. Since Embodiment 1-Embodiment 3 have described each function in detail, I won't repeat them here.

Through the frequency discriminator of the embodiment of the present invention, the combination of two frequency discrimination algorithms is used for frequency tracking, which can not only realize fast acquisition of frequency offset, but also obtain very good locking performance in a steady state.

Embodiment five

An embodiment of the present invention also provides a frequency tracking system, which will be described in detail below with reference to the accompanying drawings.

FIG. 11 is a block diagram of the frequency tracking system of this embodiment. As shown in FIG. 11 , the frequency tracking system of this embodiment includes a frequency discriminator 111, a loop filter 112, and a voltage-controlled oscillator 113 in Embodiment 3. in:

The frequency discriminator 111 of this embodiment applies the frequency tracking method of Embodiment 1 to Embodiment 3, and realizes frequency detection and tracking from user equipment to network equipment, such as a base station. The specific implementation process has been described in Embodiment 1 and Embodiment It has been described in the second and third embodiments, and will not be repeated here.

The loop filter 112 of this embodiment is used to adjust the variable adjustment step size according to the frequency offset estimation result of the frequency discriminator 111, and obtain an adjustment amount of the frequency offset estimation result and output it to the voltage-controlled oscillator. Its working principle and process are the same as The prior art is the same and will not be repeated here. The loop filter 112 can be a first-order loop with a variable adjustable step size. In this way, a large step size can be used at the beginning of tracking, a small step size can be used at a steady state, and the step size is gradually reduced to a configured low value in the initial transition to a steady state.

The voltage-controlled oscillator 113 of this embodiment is used to perform frequency correction according to the adjustment amount of the frequency offset estimation result output by the loop filter 112 , and its working principle and process are the same as those of the prior art, and will not be repeated here.

Through the frequency tracking system of the embodiment of the present invention, since the frequency discriminator 111 uses a combination of two frequency discrimination algorithms for frequency tracking, it can not only realize fast acquisition of frequency offset, but also obtain very good locking performance in a steady state.

The specific embodiments described above have further described the purpose, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above descriptions are only specific embodiments of the present invention and are not intended to limit the scope of the present invention. Protection scope, within the spirit and principles of the present invention, any modification, equivalent replacement, improvement, etc., shall be included in the protection scope of the present invention.

Claims (13)

1. a frequency tracking method is characterized in that, said method comprises:

Detect the frequency deviation between the subscriber equipment and the network equipment respectively through the first frequency discrimination algorithm and the second frequency discrimination algorithm, obtain first frequency offset estimation result and second frequency offset estimation result; Wherein, with respect to the said second frequency discrimination algorithm, the frequency discrimination scope of the said first frequency discrimination algorithm is bigger, and precision is lower;

If the smooth value of acquired first frequency offset estimation result converges in the frequency discrimination scope of the said second frequency discrimination algorithm; Then said second frequency offset estimation result of current acquisition is adjusted step-length and reset, utilize adjusted second frequency offset estimation result to carry out frequency correction.

2. method according to claim 1 is characterized in that, said method also comprises:

Whether the smooth value of judging acquired second frequency offset estimation result meets the demands;

If the smooth value of acquired second frequency offset estimation result meets the demands, then said second frequency offset estimation result of current acquisition is adjusted step-length and successively decrease, utilize adjusted second frequency offset estimation result to carry out frequency correction.

3. method according to claim 2 is characterized in that:

If the smooth value backlog demand of acquired second frequency offset estimation result is then adjusted step-length to said second frequency offset estimation result of current acquisition and reset, utilize adjusted second frequency offset estimation result to carry out frequency correction.

4. method according to claim 1 and 2 is characterized in that, said method also comprises:

If the smooth value of acquired first frequency offset estimation result exceeds the frequency discrimination scope of the said second frequency discrimination algorithm; Then said first frequency offset estimation result of current acquisition is adjusted step-length and reset, utilize adjusted first frequency offset estimation result to carry out frequency correction.

5. method according to claim 1 is characterized in that:

The said first frequency discrimination algorithm is a time domain phase place cross product algorithm, and the said second frequency discrimination algorithm is a frequency domain phase place cross product algorithm.

6. method according to claim 1 is characterized in that, said adjustment step-length is reset and adopted variable adjustment step-length single order ring to realize.

7. a frequency discriminator is characterized in that, said frequency discriminator comprises:

The first frequency discrimination unit is used for detecting the frequency deviation between the subscriber equipment and the network equipment through the first frequency discrimination algorithm, obtains first frequency offset estimation result;

The second frequency discrimination unit is used for detecting the frequency deviation between the subscriber equipment and the network equipment through the second frequency discrimination algorithm, obtains second frequency offset estimation result; Wherein, with respect to the said second frequency discrimination algorithm, the frequency discrimination scope of the said first frequency discrimination algorithm is bigger, and precision is lower;

Outer shroud locking decision unit is used to judge whether the smooth value of acquired first frequency offset estimation result converges in the frequency discrimination scope of the said second frequency discrimination algorithm;

The frequency offset estimation result output unit; When being used in the frequency discrimination scope that smooth value in acquired first frequency offset estimation result converges on the said second frequency discrimination algorithm; Second frequency offset estimation result of current acquisition is outputed to loop filter; And through said loop filter said second frequency offset estimation result is adjusted step-length and reset, utilize adjusted second frequency offset estimation result to carry out frequency correction through voltage-controlled oscillator (VCO) then.

8. frequency discriminator according to claim 7 is characterized in that, said frequency discriminator also comprises:

In ring losing lock decision unit, be used for said second frequency offset estimation result being outputed to the process of loop filter at said frequency offset estimation result output unit, judge whether the smooth value of acquired second frequency offset estimation result meets the demands;

Said frequency offset estimation result output unit also is used for when the smooth value of acquired second frequency offset estimation result meets the demands; Second frequency offset estimation result of current acquisition is outputed to loop filter; And through said loop filter said second frequency offset estimation result is adjusted step-length and successively decrease, utilize adjusted second frequency offset estimation result to carry out frequency correction through voltage-controlled oscillator (VCO) then.

9. frequency discriminator according to claim 8 is characterized in that:

Said frequency offset estimation result output unit also is used for when the smooth value backlog demand of acquired second frequency offset estimation result; Second frequency offset estimation result of current acquisition is outputed to loop filter; And through said loop filter said second frequency offset estimation result is adjusted step-length and reset, utilize adjusted second frequency offset estimation result to carry out frequency correction through voltage-controlled oscillator (VCO) then.

10. frequency discriminator according to claim 7 is characterized in that, said frequency discriminator also comprises:

Outer shroud losing lock decision unit; Be used for said second frequency offset estimation result being outputed to the process of loop filter, judge whether the smooth value of acquired first frequency offset estimation result exceeds the frequency discrimination scope of the said second frequency discrimination algorithm at said frequency offset estimation result output unit;

Said frequency offset estimation result output unit also is used for when the smooth value of acquired first frequency offset estimation result exceeds the frequency discrimination scope of the said second frequency discrimination algorithm; First frequency offset estimation result of current acquisition is outputed to loop filter; And through said loop filter said first frequency offset estimation result is adjusted step-length and reset, utilize adjusted first frequency offset estimation result to carry out frequency correction through voltage-controlled oscillator (VCO) then.

11., it is characterized in that according to each described frequency discriminator of claim 7-10:

The said first frequency discrimination unit adopts time domain phase place cross product algorithm to detect the frequency between the subscriber equipment and the network equipment;

The said second frequency discrimination unit adopts frequency domain phase place cross product algorithm to detect the frequency between the subscriber equipment and the network equipment.

12. a frequency-tracking system is characterized in that, said frequency-tracking system comprises each described frequency discriminator of loop filter, voltage-controlled oscillator (VCO) and claim 7-10.

13. frequency-tracking according to claim 12 system is characterized in that: said loop filter adopts variable adjustment step-length single order ring adjustment step-length to reset or the adjustment step-length is successively decreased.

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