CN102413543A

CN102413543A - Initial AGC (automatic gain control) method and equipment of LTE (long term evolution) system

Info

Publication number: CN102413543A
Application number: CN2011103913681A
Authority: CN
Inventors: 张国松; 李亚辉; 胡剑锋; 莫勇; 任江涛; 吴齐发; 唐相国
Original assignee: HEFEI DONGXIN COMMUNICATION CO Ltd
Current assignee: HEFEI DONGXIN COMMUNICATION CO Ltd
Priority date: 2011-11-30
Filing date: 2011-11-30
Publication date: 2012-04-11
Anticipated expiration: 2031-11-30
Also published as: CN102413543B

Abstract

The invention discloses an initial AGC (automatic gain control) method and equipment of an LTE (long term evolution) system. The method comprises the following steps of: measuring and sending an average power of receiving signals according to a first preset time interval; calculating the bias between the average power and a preset target power to obtain a gain error; smoothing the gain error according to a first smoothing factor to obtain a smoothing gain error; updating the current AGC gain value by use of the smoothing gain error; and converting the updated AGC gain value to obtain an AGC control word, and sending the AGC control word according to a second preset time interval. In the invention, the quick measurement and quick adjustment of the initial AGC can be realized through the processes, and finally the aims of improving the signal quality for cell search and improving the sensitivity of the cell search are achieved.

Description

Initial AGC method and equipment of LTE system

Technical Field

The present invention relates to the field of communications technologies, and in particular, to a method and a device for initial AGC (Automatic Gain Control) of an LTE (Long term evolution) system

Background

Currently, for the development of communication technology, the 3G era has been shifted to the 4G era, and the LTE (Long Term Evolution) system is widely considered as a 4G wireless communication system. The physical layer of LTE adopts OFDM (Orthogonal Frequency division multiplexing) technology. After the LTE terminal device is turned on, an AGC process of the terminal device is executed to control the power of a received signal, prevent signal saturation, and reduce quantization noise in each signal processing process, thereby improving the signal-to-noise ratio in the receiver, and the working process of the terminal device is as shown in fig. 1, and the AGC process includes the following steps:

step S11, performing cell search, mainly including obtaining information such as cell ID (IDentity, cell number), timing synchronization information, duplex mode (FDD/TDD), CP (Cyclic Prefix) mode (normal CP/extended CP), and the like; step S12, acquiring System Information, which mainly consists of receiving MIB (master Information block) and SIB (System Information block) Information; step S13, executing random access, mainly referring to the process that the terminal accesses the cell and acquires the RNTI (radio network temporary identifier) and more system information; step S14, normal service is executed. The four steps are divided according to the working process of AGC (Automatic Gain Control), step S11 is an initial AGC stage, and step S12, step S13, and step S14 are AGC tracking stages. In the AGC process, frame timing information and frame structure information (including a duplex mode, a CP mode, an uplink and downlink ratio) which cannot be obtained at an initial AGC stage are known at an AGC tracking stage, so that in the whole AGC process, only a precise and representative time domain or frequency domain signal can be obtained to perform AGC measurement and AGC control adjustment until the AGC tracking stage is executed.

Because the control quality of the initial AGC stage directly affects the sensitivity and the search time of the terminal receiver cell search, the performance and the user experience of the terminal are directly affected. Therefore, in the prior art, the problem of initial AGC is generally solved by using a slow-tuning manner as shown in fig. 2, that is, averaging the power of a received signal for a long time (power measurement unit 205), if the power is greater than 10ms, obtaining the measured power of the current received signal, comparing the measured power with a preset target reference power of the received signal to obtain a gain error (gain error calculation unit 206), and converting the gain error into an AGC adjustment control word to be fed back to a radio frequency device so as to adjust the operating gain of a power control device such as LNA/VGA (AGC control word generation unit 207). In fig. 2, 201 is an LNA/VGA unit, 202 is an analog-to-digital conversion unit, 203 is a low-pass filtering unit, and 204 is an FFT (Fast Fourier transform) unit.

However, in the existing TD-LTE (TD-LTE is a technology of TDD (Time Division duplex) version of LTE) system, each radio frame contains uplink and downlink subframes, as shown in table 1.

Table 1:

since, in the initial AGC stage, the terminal device is always in the receiving mode, that is, the signal in the uplink subframe time is received and processed by the terminal device. At this time, when the initial AGC solution in the prior art is used to measure the received signal power, the received signal power in the uplink subframe time is counted. In this process, if the received Signal power in the uplink subframe is large, if other terminals nearby are transmitting uplink, the AGC will cause the data (including PSS (Primary Synchronization Signal)/SSS (secondary Synchronization Signal)) of the downlink subframe used for cell search to be small; or if the received signal power in the uplink subframe is small, this will cause the AGC to adjust the data (including PSS/SSS) of the downlink subframe used for cell search to be large until saturation.

The above problems occur when the prior art is adopted to solve the initial AGC, which may ultimately result in directly reducing the signal quality for cell search and reducing the sensitivity of cell search.

Disclosure of Invention

In view of this, the present invention provides an initial AGC method and device for an LTE system, so as to overcome the problem that in the prior art, when a terminal device is always in a receiving mode, the received signal power cannot be accurately measured, thereby reducing the cell search signal quality and the cell search sensitivity.

In order to achieve the purpose, the invention provides the following technical scheme:

a method for initial Automatic Gain Control (AGC) of a Long Term Evolution (LTE) system comprises the following steps:

measuring and transmitting an average power of a received signal at a first preset time interval;

calculating the deviation between the average power and a preset target power to obtain a gain error;

smoothing the gain error according to a first smoothing factor to obtain a smooth gain error;

updating the current automatic gain control AGC gain value by using the smoothing gain error;

and converting the updated AGC gain value to obtain an AGC control word and sending the AGC control word according to a second preset time interval.

Preferably, the process of measuring and transmitting the average power of the received signal at the first preset time interval includes:

calculating the average power P of the sampled time domain sampling points in the first preset time interval;

the amplitude value of the time domain sampling point is as follows: s_i＝I_i+j*Q_iWherein S is_iThe time domain sampling point acquisition method is characterized in that the time domain sampling point acquisition method is a complex signal and is divided into two paths I and Q, wherein I is 0, 1, and N is-1, and N is the number of the captured time domain sampling points; the average power

And converting the average power P into a dB value, and transmitting according to the first preset time interval.

sampling time domain sampling points in the first preset time interval, and calculating the power of each time domain sampling point by point;

according to a second smoothing factor, using

Continuously smoothing the power of each time domain sampling point to obtain an average power P;

wherein beta is a second smoothing factor, and the value of beta comprises 1/128, P₀Taking the initial average power value as 0 and P for each sample point passing through₀Is updated to the value of P; the amplitude value of the time domain sampling point is as follows: s_i＝I_i+j*Q_iWherein S is_iThe time domain sampling point is a complex signal and is divided into two paths I and Q, I is 0, 1, N is-1, and N is the number of the captured time domain sampling points,

Preferably, the number N of the time domain samples includes all the samples in a first preset time interval;

or, continuously or intermittently selecting the number of partial sample points in the first preset time interval, wherein the value range of the number of partial sample points is as follows: the power of 2.

Preferably, the smoothing of the gain error according to a preset smoothing factor, and the process of obtaining the smoothed gain error includes:

obtaining the first smoothing factor, and receiving the gain error;

based on

Obtaining the smoothed gain error;

wherein G is_errorIn order to be able to determine the gain error,and alpha is the first smoothing factor for the smoothing gain error, and the value range of the alpha is 0.1-0.5.

Preferably, the process of updating the current AGC gain value with the smoothed gain error comprises:

obtaining a gain error obtained after smoothing the gain error and a current AGC gain value;

the initial value of the current AGC gain value is 0, and the process of updating the current AGC gain value is as follows;

when the smoothing gain error is larger than zero, reducing the current AGC gain value, wherein the reduced value is the smoothing gain error;

when the smoothing gain error is less than zero, increasing the current AGC gain value, wherein the increased value is the absolute value of the smoothing gain error;

when the smoothing gain error is equal to zero, maintaining the current AGC gain value unchanged.

Preferably, the value of the first time interval includes a time length of one OFDM symbol;

the value of the second predetermined time interval includes a time length of one OFDM symbol.

An apparatus of initial automatic gain control, AGC, of a long term evolution, LTE, system, comprising:

a signal power measuring unit for measuring an average power of a received signal at a first preset time interval and transmitting the average power at the first preset time interval;

the gain error calculation unit is used for calculating the deviation between the average power and a preset target power to obtain a gain error;

the gain error smoothing unit is used for smoothing the gain error according to a first smoothing factor to obtain a smooth gain error;

the AGC control word generating unit is used for updating the current automatic gain control AGC gain value by using the smooth gain error, converting the updated AGC gain value, generating an AGC control word corresponding to the AGC gain value and sending the AGC control word according to a second preset time interval;

and the AGC control unit is used for outputting a first preset time interval to the signal power measuring unit, outputting a preset target power to the gain error calculating unit, outputting a first smoothing factor to the gain error smoothing unit and outputting a second preset time interval for sending an AGC control word to the AGC control word generating unit.

Preferably, the signal power measuring unit includes:

the sampling unit is used for sampling time domain sampling points in the first preset time interval;

the calculating unit is used for calculating the average power of the time domain sampling points;

and the conversion unit is used for converting the average power into a dB value and transmitting the dB value according to the first preset time interval.

Preferably, the signal power measuring unit includes:

the smoothing unit is used for calculating the power of each time domain sampling point by point and continuously smoothing the power of each time domain sampling point according to a second smoothing factor to obtain average power; the second smoothing factor is output by the AGC control unit;

Compared with the prior art, the invention discloses an initial AGC method and equipment of an LTE system. And performing related power measurement and gain error calculation and smoothing by sampling time domain sampling points in a time interval, finally generating and sending an AGC control word at the time interval, and maintaining the data of a downlink subframe used for cell search in a normal state according to the AGC control word. Namely, the purposes of improving the signal quality for cell search and improving the sensitivity of cell search are finally achieved through a mode of rapid measurement and rapid adjustment.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the provided drawings without creative efforts.

Fig. 1 is a flowchart illustrating an LTE terminal device according to the prior art;

FIG. 2 is a diagram illustrating an apparatus corresponding to an initial AGC mechanism in the prior art;

fig. 3 is a flowchart of an initial AGC method of an LTE system according to an embodiment of the present invention;

fig. 4 is a flowchart of an initial AGC method of an LTE system according to an embodiment of the present invention;

fig. 5 is a flowchart of an initial AGC method of an LTE system according to a second embodiment of the present invention;

fig. 6 is a schematic diagram of an initial AGC device of an LTE system according to an embodiment of the present invention;

fig. 7 is a schematic diagram of an initial AGC device of another LTE system according to an embodiment of the present invention.

Detailed Description

For the sake of reference and clarity, the descriptions, abbreviations or abbreviations of the technical terms used hereinafter are summarized as follows:

LTE: long Term Evolution system, Long Term Evolution system;

AGC: automatic Gain Control;

OFDM: orthogonal Frequency Division Multiplexing.

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

It can be known from the background art that the terminal device is always in the receiving mode at the initial AGC stage, and the slow modulation method in the prior art is adopted to measure the received signal power of the initial AGC, so that the received signal power in the uplink subframe time is counted, and the problems of directly reducing the signal quality for cell search and reducing the sensitivity of cell search due to too large or too small received signal power are easily caused.

Therefore, the embodiment of the invention discloses an initial AGC method and equipment of an LTE system. As shown in fig. 3, the initial AGC process disclosed in the embodiment of the present invention mainly includes the following steps:

step S101, measuring the average power of the received signal and according to a first preset time interval T_estAnd (5) sending.

Step S102, calculating the average power and a preset target power P_normalDeviation therebetween, resulting in a gain error G_error。

Step S103, according to the first smoothing factor alpha, the gain error G is corrected_errorSmoothing to obtain a smoothed gain error

Step S104, utilizing the smooth gain error

And updating the current AGC gain value.

Step S105, converting the updated AGC gain value to obtain an AGC control word and setting the AGC control word according to the second preset time interval T_adjAnd (5) sending.

That is, the AGC control word is finally generated and transmitted at time intervals through the above-mentioned processes of performing related power measurement, calculation and smoothing of gain error based on the time domain samples within the sampling time interval, and data of the downlink subframe used for cell search is maintained in a normal state according to the AGC control word. Ultimately, the signal quality for cell search is improved, and the sensitivity of cell search is improved. For the sake of clarity, the following examples are given in detail.

Example one

On the basis of the technical solution disclosed in the embodiment of the present invention, please refer to fig. 4, which is a flowchart of a method for initial AGC of an LTE system specifically disclosed in the embodiment of the present invention, and the method mainly includes the following steps:

step S201, measuring average power P of received signal and according to first preset time interval T_estAnd (5) sending.

In the process of executing the above step S201, according to a first preset time interval T_estMeasuring the average power P of the received signal and according to the first predetermined time interval T_estThe average power P is transmitted. In order to perform the fast-tuning function of the AGC more quickly, in the first embodiment of the disclosure, the shorter time interval is selected, that is, the first predetermined time interval T is selected_estThe time length of one OFDM symbol specified in the LTE protocol includes, but is not limited to, 71 microseconds, and preferably 71 microseconds.

In the first embodiment disclosed in the present invention, step S201 specifically includes the following steps:

step S2011, countCalculating the first preset time interval T_estThe average power P of the time domain samples N within.

In the process of executing step S2011, based on the selected time-domain sample point, the average power P of the time-domain sample point N is calculated by using formula (1):

in this equation (1), the amplitude values of the time domain samples are used: s_i＝I_i+j*Q_i(ii) a Wherein S is_iThe time domain sampling method is a complex signal and comprises two paths of I and Q, wherein I is 0, 1, N-1 and N is the number of the sampled time domain sampling points.

It should be noted that the number N of the sampled time domain samples may be a first preset time interval T_estThe number of all samples in the sample container can be continuously or intermittently selected from the first preset time interval T_estThe number of partial samples in. In the embodiment disclosed, the power of 2 is taken as a reference, and the first preset time interval T is_estThe number of the selected sampling points is continuous or interval. However, the value of N is not limited to the value disclosed in the embodiments of the present invention, and may be taken according to specific needs.

Step S2012, converting the time domain samplesThe average power P is dB and is marked as P_dB。

Step S2013, according to the first preset time interval T_estSending the converted P_dB。

In the process of executing step S2012, conversion is performed using formula (2), and P is acquired_dB：

P_dB＝10*log₁₀(P) (2)

Wherein, P is the average power of the number N of time domain samples. As shown in step S2011, the first predetermined time interval T is set_estTime domain samples are selected, preferably based on power of 2, in the first predetermined time interval T_estThe number of the sampling points selected continuously or at intervals can effectively reduce the calculated amount in the formula (1), and further, the power measurement of the received signal can be realized more quickly.

Step S202, calculating the average power P_dBAnd a preset target power P_normalDeviation therebetween, resulting in a gain error G_error。

In step S202, the average power P is expressed by the formula (2)_dBThe dB value for the average power P is used for the calculations thereafter. I.e. obtaining said average power P_dBAnd a preset target power P_normalThe process of deviation therebetween is shown in equation (3):

G_error＝P_dB-P_normal (3)

wherein the target power P is preset_normalThe physical meaning of (1) is the input signal power value expected by the system, and the value can be preset and adaptively adjusted according to the specific use scene and the performance requirement of specific terminal equipment. P_dBIs the average power P converted to dB value.

The gain error G_errorIn relation to the current AGC gain valueThe physical meaning is as follows: if G is_errorIf the current time domain signal power is greater than the target power, the current gain of the AGC needs to be reduced; if G is_errorIf the current time domain signal power is less than the target power, the current gain of the AGC needs to be increased; if G is_errorAnd 0, the current time domain signal power is equal to the target power, and the current gain of the AGC is maintained unchanged.

Step S203, according to the first smoothing factor alpha, the gain error G is corrected_errorSmoothing to obtain a smoothed gain error

The step S203 of using the first smoothing factor α to correct the gain error G is executed_errorSmoothing is performed, and in the embodiment disclosed in the present invention, smoothing is performed in a manner as shown in formula (4):

<math> <mrow> <msub> <mover> <mi>G</mi> <mo>&OverBar;</mo> </mover> <mi>error</mi> </msub> <mo>=</mo> <msub> <mover> <mi>G</mi> <mo>&OverBar;</mo> </mover> <mi>error</mi> </msub> <mo>×</mo> <mrow> <mo>(</mo> <mn>1</mn> <mo>-</mo> <mi>α</mi> <mo>)</mo> </mrow> <mo>+</mo> <msub> <mi>G</mi> <mi>error</mi> </msub> <mo>×</mo> <mi>α</mi> <mo>-</mo> <mo>-</mo> <mo>-</mo> <mrow> <mo>(</mo> <mn>4</mn> <mo>)</mo> </mrow> </mrow> </math>

wherein,

the smoothed gain error has an initial value of 0; alpha is a first smoothing factor, which is generally the caseThe value range is more than or equal to 0 and less than or equal to 1.

In the first embodiment disclosed in the present invention, the preferable value range is: alpha is more than or equal to 0.1 and less than or equal to 0.5, and the first smoothing factor alpha in the range can realize the fast-tuning function of the initial AGC.

Step S204, utilizing the smooth gain error

Updating the current AGC gain value G₀And obtaining the updated AGC gain.

Step S204 is executed to update the current AGC gain value G₀The method mainly comprises the following steps:

step S2041, obtaining the gain error G_errorGain error after smoothing

And the current AGC gain value G₀。

In step S2041, the current AGC gain value G₀Is 0.

Step S2042, the initial value of the current AGC gain value is 0, the magnitude of the smoothing gain error is determined, and if the smoothing gain error is greater than zero, step S2043 is executed; if the smoothing gain error is less than zero, executing step S2044; if the smoothing gain value is equal to zero, step S2045 is performed.

Step S2043, reducing the current AGC gain value G₀The reduced value is the smoothed gain error.

Step S2044, increasing the current AGC gain value G₀The increased value is the absolute value of the smoothing gain error.

Step S2045, maintaining the current AGC gain value G₀And is not changed.

In particular for the current AGC gain value G₀Concrete updates that increase or decreaseThe latter AGC gain value is denoted as G, as shown in equation (5):

<math> <mrow> <mi>G</mi> <mo>=</mo> <msub> <mi>G</mi> <mn>0</mn> </msub> <mo>-</mo> <msub> <mover> <mi>G</mi> <mo>&OverBar;</mo> </mover> <mi>error</mi> </msub> <mo>-</mo> <mo>-</mo> <mo>-</mo> <mrow> <mo>(</mo> <mn>5</mn> <mo>)</mo> </mrow> </mrow> </math>

step S205, converting the updated AGC gain value to obtain AGC control words and setting the AGC control words according to the second preset time interval T_adjAnd (5) sending.

Step S205 is executed to convert the updated current AGC gain value G into a control word recognizable by the rf AGC module in the LTE system (the specific conversion process may refer to the manual of the rf chip of the LTE terminal device), and according to a second preset time interval T_adjAnd feeding back to the radio frequency AGC module. In the first embodiment of the present disclosure, the second predetermined time interval T_adjAnd selecting a shorter time interval to realize a faster AGC fast-tuning function. Preferably 71 microseconds, which is the time length of one OFDM symbol specified in the LTE protocol. However, the second predetermined time interval T_adjIncluding but not limited to 71 microseconds.

Through the above process, based on the time domain sampling points in the sampling time interval, the related power measurement, and the calculation and smoothing process of the gain error are performed, finally, the AGC control word is generated and sent at the time interval, and the data of the downlink subframe used for cell search is maintained in a normal state according to the AGC control word. Ultimately, the signal quality for cell search is improved, and the sensitivity of cell search is improved.

Example two

On the basis of the technical solution disclosed in the above embodiment of the present invention, please refer to fig. 5, which is a flowchart of an initial AGC method of an LTE system specifically disclosed in the second embodiment of the present invention, and mainly includes the following steps:

step S301, measuring average power P of received signal and according to first preset time interval T_estAnd (5) sending.

The first preset time interval T is set during the execution of the above step S301_estThe value range of (a) is the same as the range disclosed in the first embodiment, and details are not repeated herein.

The process of specifically acquiring the average power in step S301 is different from the process disclosed in the first embodiment, and specifically includes the following steps:

step S3011, sampling the first preset time interval T_estAnd calculating the power of each time domain sampling point by the time domain sampling point N in the time domain sampling point.

Step S3012, continuously smoothing the power of each time domain sample point N according to a second smoothing factor β, and obtaining an average power P.

The process of performing step S3012 to smooth the power of each time-domain sample point N is shown in formula (6):

wherein, P₀Is the initial average power, with an initial value of 0, P for each sample point smoothing₀Is updated to the value of P; the amplitude value of the time domain sampling point is as follows: s_i＝I_i+j*Q_iWherein S is_iThe time domain sampling method is a complex signal and is divided into two paths I and Q, where I is 0, 1, and N-1, N is the number of sampled time domain sampling points, and the process of sampling the time domain sampling points N is the same as the process disclosed in the first embodiment, and is not described here again. Beta is a second smoothing factor, and generally has a value range of 0-1, and preferred values of beta include, but are not limited to 1/128. In the second embodiment of the present disclosure, the fast-tuning function of the initial AGC can be realized by using the second smoothing factor β in the range.

Step S3013, converting the average power P to a dB value, which is denoted as P_dBAnd according to the first preset time interval T_estTransmitting the average power P_dB。

In the process of executing step S3013, conversion is performed using formula (7), and P is acquired_dB：

P_dB＝10*log₁₀(P) (7)

And P is the average power obtained after smoothing the power of each time domain sampling point N.

Step S302, calculating the average power P_dBAnd a preset target power P_normalDeviation therebetween, resulting in a gain error G_error。

Step S303, according to the first smoothing factor alpha, the gain error G is corrected_errorSmoothing to obtain a smoothed gain error

Step S304, utilizing the smoothed gain errorUpdating the current AGC gain value G₀And obtaining the updated AGC gain G.

Step S305, converting the updated AGC gain value to obtain an AGC control word and setting the AGC control word according to the second preset time interval T_adjAnd (5) sending.

The specific execution process of the steps S302 to S305 is consistent with the steps S202 to S205 in the first embodiment disclosed above, and may be referred to each other, which is not described herein again.

Through the above process, the related power measurement, and the calculation and smoothing of the gain error are performed based on the time domain samples within the sampling time interval, and finally, the AGC control word can be generated and transmitted at the time interval, and the data of the downlink subframe used for cell search can be maintained in a normal state according to the AGC control word. The purposes of improving the signal quality for cell search and improving the sensitivity of cell search are achieved.

The above embodiments of the present disclosure describe in detail a method for initial AGC of an LTE system, and the above method disclosed by the present disclosure can be implemented by various types of devices, so the present disclosure also discloses a device for initial AGC of an LTE system corresponding to the above method, and the following specific embodiments are described in detail.

Referring to fig. 6, an AGC device of a long term evolution LTE system disclosed in the embodiment of the present invention mainly includes: signal power measuring unit 305, gain error calculating unit 306, gain error smoothing unit 307, AGC control word generating unit 308, and AGC control unit 309.

The LNA/VGA unit 301, the analog-to-digital conversion unit 302, the low-pass filtering unit 303, and the FFT unit 304 in fig. 6 are reception side portions of the LTE system.

A signal power measurement unit 305 for measuring T at a first preset time interval_estAverage power of received signal, and according to the first presetInterval T_estAnd transmitting the average power.

A gain error calculation unit 306 for calculating the average power and a preset target power P_normalDeviation therebetween, resulting in a gain error G_error。

For the implementation process of the gain error calculation unit 306, reference may be made to the description of the gain error calculation in the first embodiment and the second embodiment of the disclosure, and details are not repeated here.

A gain error smoothing unit 307 for smoothing the gain error G according to a first smoothing factor_errorSmoothing to obtain a smoothed gain error

For the implementation process of the gain error smoothing unit 307, reference may be made to the process of gain error smoothing described in the first embodiment and the second embodiment of the disclosure of the present invention, and details are not described here.

An AGC control word generation unit 308 for utilizing said smoothed gain errorUpdating the current AGC gain value, converting the updated AGC gain value, generating an AGC control word corresponding to the AGC gain value and setting a second preset time interval T_adjAnd (5) sending.

For the implementation process of the AGC control word generating unit 308, reference may be made to the process of generating the AGC control word described in the first embodiment and the second embodiment of the disclosure, and details are not repeated here.

An AGC control unit 309 for outputting a first preset time interval T to the signal power measurement unit 305_estOutputs a preset target power P to the gain error calculation unit 306_normalOutputs a first smoothing factor alpha to the gain error smoothing unit 307, andthe AGC control word generating unit 308 outputs a second predetermined time interval T for transmitting AGC control words_adj。

The received signal is power-measured in the signal power measurement unit 305, and the average power of the received signal is obtained. Two specific structures are included in the power measurement unit 305 to obtain the average power.

As shown in fig. 6, the power measurement unit 305 mainly includes: a sampling unit 3051, a calculation unit 3052 and a conversion unit 3053.

A sampling unit 3051 for sampling said first predetermined time interval T_estTime domain samples N.

A calculating unit 3052, configured to calculate an average power P of the time-domain samples.

A conversion unit 3053, configured to convert the average power P to a dB value according to the first predetermined time interval T_estAnd (5) sending.

The execution process of each unit described above may specifically refer to the records in step S2011 to step S2013 in the first embodiment disclosed in the present disclosure, and therefore, details are not repeated here.

As shown in fig. 7, the power measurement unit 405 mainly includes: a sampling unit 4051, a smoothing unit 4052, and a conversion unit 4053.

A sampling unit 4051 for sampling the first preset time interval T_estTime domain sample points N;

a smoothing unit 4052, configured to calculate the power of each time domain sample point N point by point, and continuously smooth the power of each time domain sample point N to obtain an average power P;

a converting unit 4053, configured to convert the average power into a dB value according to the first preset time interval T_estAnd (5) sending.

The execution processes in the above units are the same as the descriptions in step S3011 to step S3013 in the second embodiment of the disclosure, and reference may be made to these descriptions, which are not repeated herein.

It should be noted that, in fig. 7, the LNA/VGA unit 401, the analog-to-digital conversion unit 402, the low-pass filtering unit 403 and the FFT unit 404 are the same as 301 to 304 in fig. 6 for the receiving end portion of the LTE system, and are not described again here; the gain error calculation unit 406, the gain error smoothing unit 407, the AGC control word generation unit 408, and the AGC control unit 409 in fig. 7 are the same as the processes performed by the gain error calculation unit 306, the gain error smoothing unit 307, the AGC control word generation unit 308, and the AGC control unit 309 in fig. 6, and can be referred to, and are not described again here.

In summary, the following steps:

according to the embodiment of the invention, the related power measurement, the gain error calculation and the smoothing are performed based on the time domain sampling points in the sampling time interval, and finally, the AGC control word is generated and sent at the time interval, and the data of the downlink subframe used for cell search is maintained in a normal state according to the AGC control word. Namely, the purposes of improving the signal quality for cell search and improving the sensitivity of cell search are finally achieved through a mode of rapid measurement and rapid adjustment.

The embodiments in the present description are described in a progressive manner, each embodiment focuses on differences from other embodiments, and the same and similar parts among the embodiments are referred to each other. The device disclosed by the embodiment corresponds to the method disclosed by the embodiment, so that the description is simple, and the relevant points can be referred to the method part for description.

The steps of a method or algorithm described in connection with the embodiments disclosed herein may be embodied directly in hardware, in a software module executed by a processor, or in a combination of the two. A software module may reside in Random Access Memory (RAM), memory, Read Only Memory (ROM), electrically programmable ROM, electrically erasable programmable ROM, registers, hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art.

The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for initial Automatic Gain Control (AGC) of a Long Term Evolution (LTE) system is characterized by comprising the following steps:

2. The method of claim 1, wherein the step of measuring and transmitting the average power of the received signal at the first predetermined time interval comprises:

3. The method of claim 1, wherein the step of measuring and transmitting the average power of the received signal at the first predetermined time interval comprises:

according to a second smoothing factor, using

4. A method according to claim 2 or 3, wherein the number N of time domain samples comprises the number of all samples in a first predetermined time interval;

5. The method according to any one of claims 1 to 3, wherein smoothing the gain error according to a preset smoothing factor to obtain a smoothed gain error comprises:

obtaining the first smoothing factor, and receiving the gain error;

based on

Obtaining the smoothed gain error;

wherein G is_errorIn order to be able to determine the gain error,

for the smoothing gain error, alpha is a first smoothing factor, and the value range of alpha is0.1～0.5。

6. The method according to any one of claims 1-3, wherein updating the current AGC gain value with the smoothed gain error comprises:

7. The method according to any one of claims 1 to 3, wherein the value of the first time interval comprises a time length of one OFDM symbol;

8. An apparatus for initial Automatic Gain Control (AGC) in a Long Term Evolution (LTE) system, comprising:

9. The apparatus of claim 8, wherein the signal power measurement unit comprises:

10. The apparatus of claim 8, wherein the signal power measurement unit comprises: