CN100550698C - The auto gain control method of mobile digital multi-media broadcast and device - Google Patents

Abstract

The invention relates to the field of mobile digital multimedia broadcasting, in particular to an automatic gain control technology of mobile digital multimedia broadcasting. Embodiments of the present invention provide an automatic gain control method and device for mobile digital multimedia broadcasting, which are used to improve the receiving effect of mobile digital multimedia broadcasting. In each designated time slot of mobile digital multimedia broadcasting, the average power of the received signal is periodically adjusted according to the automatic gain control cycle, and in each automatic gain control cycle, the average power of the received signal is detected according to the signal power detection cycle; and when the automatic gain When the last detected average power of the received signal in the control cycle is greater than the maximum value of the target range, reduce the average received signal power; when the last detected value in the automatic gain control cycle is smaller than the minimum value of the target range, increase the average received signal power , the automatic gain control period, target range and signal power detection period are determined according to the received signal quality.

Description

Automatic gain control method and device for mobile digital multimedia broadcasting

technical field

The invention relates to the field of mobile digital multimedia broadcasting, in particular to an automatic gain control technology of mobile digital multimedia broadcasting.

Background technique

Mobile digital multimedia broadcasting is a broadcasting system covering a wide range of user terminals. Through satellite and terrestrial wireless broadcasting, it provides small screen, small size, mobile and portable user terminals, such as mobile phones, personal digital assistants (Personal Digital Assistant, PDA), MP3, MP4, digital cameras, notebook computers, etc., receive multimedia broadcasting programs and information services anytime and anywhere.

China Mobile Multimedia Broadcasting (CMMB) is a technical standard for mobile digital multimedia broadcasting proposed by China. The following takes the CMMB system as an example to introduce the receiving system of mobile digital multimedia broadcasting. The length of a radio frame in the CMMB system is 1s, and a radio frame is divided into several equal-length time slots, for example, 40 time slots. When a user terminal receives a multimedia broadcast program, it only needs to turn on a few designated time slots in all time slots, and turn off the system in non-designated time slots to save power consumption. As shown in Figure 1, it is a schematic diagram of a CMMB receiving system. The received radio frequency (Radio Frequency, RF) signal is converted into a baseband signal through a tuner (Tuner), and the output baseband signal is expressed in a differential manner. The baseband signal in the horizontal direction is represented by The signal difference between I+ and I- is determined, the baseband signal in the vertical direction is determined by the signal difference between Q+ and Q-, the radio frequency signal and the baseband signal are both analog signals; the baseband signal passes through the analog-digital converter controller (Analog-Digital Converter, ADC) is converted into a digital signal that can be demodulated by a demodulator (Demodulator), and the average power of the received signal can be obtained by cumulatively averaging the digital signal within a certain time range; the demodulator (Demodulator) decodes the digital signal Adjust and restore to get the original data transmitted on the wireless channel, and the ADC and Demodulator can be combined and set; the original data is sent to the application processor (Application Processor, AP) through the data transmission bus, where the data transmission bus uses the service provider interface ( ServiceProvider Interface, SPI) bus as an example, in which SPI_CS, SPI_CLK is the control bus, SPI_SDO, SPI_SDI is the data bus, and transmits the original data; after the AP receives the original data, it decodes the audio data, video data or other application data, and sends the video The data plays the video image through the Liquid Crystal Display (LCD), and the audio data is sent to the speaker (Speaker) through the codec (Coder-Decoder, CODEC) for sound.

In the actual environment of mobile digital multimedia broadcasting, the average power of the received signal will change in different physical areas or in different time domains of the same physical area, especially in the fast fading channel (Fast Fading Channel) environment, the change of the average power of the received signal The amplitude is very large, which affects the effect of multimedia playback. In order to achieve an ideal multimedia playback effect, it is necessary to perform automatic gain control (Automatic Gain Control, AGC) on the digital signal input to the demodulator. Automatic gain control is a method of controlling the power of the received signal. According to the change of the average power of the received signal Control in the opposite direction to ensure that the average power of the received signal is stable within a certain range.

If the automatic gain control is performed in all time slots according to the existing technology, then in the non-designated time slots when the system is closed, since the received signal is 0 when the system is closed, the average power of the received signal will continuously increase under the action of the automatic gain control In some cases, the value of the automatic gain control is out of control; and when the adjustment step of the automatic gain control (Step) is relatively small, the adjustment of the automatic gain control cannot keep up with the fast fading signal changes in the fast fading channel, and when the automatic gain control When the Step is relatively large, the accuracy of the automatic gain control will be relatively poor.

Contents of the invention

The invention provides an automatic gain control method and device for mobile digital multimedia broadcasting, which are used to improve the receiving effect of mobile digital multimedia broadcasting.

The invention provides an automatic gain control method for mobile digital multimedia broadcasting. In each designated time slot for receiving a mobile digital multimedia broadcasting program, the average power of the received signal is periodically adjusted according to the automatic gain control cycle, and each automatic gain control In the cycle, the average power of the received signal is detected according to the signal power detection cycle, wherein an automatic gain control cycle includes several signal power detection cycles; and

When the received signal average power detection value of the last signal power detection cycle in the automatic gain control cycle is greater than the maximum value of the target range, reduce the received signal average power;

When the received signal average power detection value of the last signal power detection cycle in the automatic gain control cycle is less than the minimum value of the target range, increase the received signal average power, the automatic gain control cycle, target range and signal power detection cycle according to the received signal Signal quality determination;

The detection value of the received signal average power detected in one signal power detection cycle is: the average value of all received signal powers sampled in one signal power detection cycle.

Among them, the method for reducing the average power of the received signal includes: setting at least one level of down-regulation step size and the down-regulation error range corresponding to each level of down-regulation step size, and each level of down-regulation step size decreases in turn, and each time it is determined to reduce the received When the signal average power:

Judging whether the difference between the average power detection value of the received signal in the last signal power detection cycle and the maximum value of the target range satisfies the first down-regulation error range, if yes, then reduce the average power of the received signal according to the first-level down-regulation step; if not , then judge whether the difference meets the second down-regulation error range, and if so, reduce the average power of the received signal according to the second-level down-regulation step; and so on, when the difference does not meet the penultimate down-down error range , to reduce the average power of the received signal according to the step size of the last level of down-regulation.

Methods to increase the average power of the received signal include:

Set at least one level of upward adjustment step size and the upward adjustment error range corresponding to each level of upward adjustment step size, and each level of upward adjustment step size decreases in turn, and each time it is determined to increase the average power of the received signal:

Judging whether the difference between the minimum value of the target range and the received signal average power detection value in the last signal power detection cycle satisfies the first upward adjustment error range, and if so, increases the received signal average power according to the first level upward adjustment step;

If not, it is judged whether the difference meets the second upward adjustment error range, and if so, the average power of the received signal is increased according to the second level upward adjustment step;

By analogy, when the difference does not meet the penultimate upward adjustment error range, the average power of the received signal is increased according to the last level of upward adjustment step.

The specified time slot is determined by detecting the time slot number of the mobile digital multimedia broadcasting.

Preferably, a security protection period is set before the first designated time slot of the mobile digital multimedia broadcasting, and the automatic gain control is performed during the security protection period.

Among them, the specific methods for determining the automatic gain control period, the target range and the signal power detection period according to the quality of the received signal include:

determining at least two sets of parameter values, each set of parameter values including an automatic gain control period, a target range and a signal power detection period;

Each group of parameter values is used to simulate the automatic gain control, and a group of parameter values with the best received signal quality is selected.

The quality of the received signal is judged according to at least one performance parameter of the received signal, the performance parameter of the received signal includes a bit error rate of the received signal, and the optimal quality of the received signal means that the bit error rate of the received signal is the lowest; or,

The received signal performance parameters include received signal sensitivity, and the optimal received signal quality refers to the highest received signal sensitivity; or,

The performance parameters of the received signal include the bit error rate of the received signal and the sensitivity of the received signal, and the optimal quality of the received signal means that the sum of the reciprocal of the bit error rate of the received signal and the sensitivity of the received signal is the highest; or,

The received signal performance parameters include the received signal bit error rate and the received signal sensitivity, and the optimal received signal quality means that the sum of the reciprocal of the received signal sensitivity and the received signal bit error rate is the lowest; or,

The performance parameters of the received signal include the bit error rate of the received signal and the sensitivity of the received signal, and the optimal quality of the received signal means that the reciprocal of the bit error rate of the received signal and the sensitivity of the received signal are respectively multiplied by the set weight value and the sum is the highest; or,

The received signal performance parameters include received signal bit error rate and received signal sensitivity, and the optimal received signal quality means that the sum of the reciprocal of received signal sensitivity and received signal bit error rate multiplied by the set weight value is the lowest.

The invention provides an automatic gain control device for mobile digital multimedia broadcasting, comprising:

Parameter storage unit: used to store the automatic gain control cycle, signal power detection cycle and target range determined according to the received signal quality, wherein one automatic gain control cycle includes several signal power detection cycles;

Signal power detection unit: used to detect the average power of the received signal according to the signal power detection cycle;

Automatic gain control unit: used to periodically adjust the average power of the received signal according to the automatic gain control cycle at each designated time slot for receiving mobile digital multimedia broadcasting programs, when the signal power detection unit outputs in the automatic gain control cycle When the received signal average power detection value of the last signal power detection cycle is greater than the maximum value of the target range, reduce the received signal average power; when the received signal average power detection value of the last signal power detection cycle in the automatic gain control cycle is less than When the target range is at the minimum value, the average power of the received signal is increased.

Preferably, the device also includes:

Down-regulation information storage unit: used to store at least one level of down-regulation step size and the down-regulation error range corresponding to each level of down-regulation step size, and the down-regulation step size of each level decreases in turn;

Each time the automatic gain control unit determines to reduce the average power of the received signal, it judges whether the difference between the detected value of the average power of the received signal in the last signal power detection cycle and the maximum value of the target range satisfies the first lowering error range, if If yes, reduce the average power of the received signal according to the first-level down-regulation step; if no, then judge whether the difference meets the second down-regulation error range, and if so, reduce the average power of the received signal according to the second-level down-regulation step;

By analogy, when the difference does not meet the penultimate down-regulation error range, the average power of the received signal is reduced according to the last level of down-regulation step.

The unit also includes:

Up-regulation information storage unit: used to store at least one level of up-adjustment step size and the up-adjustment error range corresponding to each level of up-adjustment step size, and the up-adjustment step size of each level decreases in turn;

Each time the automatic gain control unit determines to increase the average power of the received signal, it judges whether the difference between the minimum value of the target range and the detected value of the average power of the received signal in the last signal power detection cycle satisfies the first upward adjustment error range, if If yes, increase the average power of the received signal according to the step size of the first step;

If not, it is judged whether the difference meets the second upward adjustment error range, and if so, the average power of the received signal is increased according to the second level upward adjustment step;

By analogy, when the difference does not meet the penultimate upward adjustment error range, the average power of the received signal is increased according to the last level of upward adjustment step.

The automatic gain control method and device for mobile digital multimedia broadcasting provided by the present invention determine the automatic gain control period, target range and signal power detection period by using the quality of received signals, and determine the automatic gain control period, target range and signal power detection period in each designated time slot of mobile digital multimedia broadcasting. The gain control cycle periodically adjusts the received signal; in each automatic gain control cycle, when the average power detection value of the received signal detected in the last signal power detection cycle is outside the target range, the average power of the received signal is adjusted to achieve The purpose of controlling the average power of the received signal within the determined target range effectively improves the peak-to-average ratio of the received signal in the fast fading channel, and improves the receiving effect of the mobile digital multimedia broadcasting.

Description of drawings

Fig. 1 is the schematic diagram of receiving system of CMMB in the prior art;

FIG. 2 is a schematic diagram of a specified time slot cycle of automatic gain control in an embodiment of the present invention;

3 is a flowchart of an automatic gain control method for mobile digital multimedia broadcasting in an embodiment of the present invention;

4 is a block diagram of an automatic gain control device for mobile digital multimedia broadcasting in an embodiment of the present invention;

Fig. 5 is the block diagram of the automatic gain control device of CMMB system in the embodiment of the present invention;

Fig. 6 is a flow chart of the automatic gain control method of the CMMB system in the embodiment of the present invention.

Detailed ways

The embodiment of the present invention provides an automatic gain control method and device for mobile digital multimedia broadcasting. According to the characteristics of the receiving system of mobile digital multimedia broadcasting, by performing automatic gain control in designated time slots, the received signal in each designated time slot is finally The average power is accurately controlled within a certain range, and the purpose of improving the receiving effect of the mobile digital multimedia broadcasting is achieved.

In order to perform reasonable and efficient automatic gain control, three parameters are firstly introduced, namely automatic gain control period, signal power detection period and target range, where:

The automatic gain control period is the period for adjusting the average power of the received signal, which reflects the speed of the automatic gain control. The larger the automatic gain control period, the fewer times the automatic gain control is performed in a specified time slot, that is, the slower the speed; The smaller the automatic gain control period, the more times the automatic gain control is performed in a specified time slot, that is, the faster the speed;

The signal power detection cycle is the cumulative average calculation cycle of the average power of the received signal. The detection value of the average power of the received signal is to accumulate and average the power values of all received signals sampled in a signal power detection cycle. The average power of the received signal is The sampling frequency is set according to the needs; an automatic gain control cycle includes several signal power detection cycles, and several detection values of the average power of the received signal can be obtained, but only according to the detection value of the last signal power detection cycle in the automatic gain control cycle Adjust the average power of the received signal;

The target range is the optimal power range to which the average power of the received signal is finally adjusted through the automatic gain control, and a better multimedia playback effect can be achieved within this range.

As shown in Figure 2, it is a schematic diagram of the designated time slot cycle of automatic gain control, in each designated time slot of mobile digital multimedia broadcasting, it includes N automatic gain control cycles, and each automatic gain control cycle includes M signal power detection cycles ; In each automatic gain control cycle, detect the average power of the received signal according to the signal power detection cycle, and obtain a detection value of the average power of the received signal in each signal power detection cycle; according to the detection of the last signal power detection cycle in the automatic gain control cycle The value adjusts the received signal average power.

The automatic gain control period, target range and signal power detection period are the key parameters for automatic gain control, which can be determined according to the quality of the received signal through simulation tests. The specific determination method includes steps:

A. Determine at least two groups of parameter values, each group of parameter values includes automatic gain control period, target range and signal power detection period;

B. Use each set of parameter values to simulate the automatic gain control, and select a set of parameter values with the best received signal quality.

The basis for judging the received signal quality may be at least one received signal performance parameter, and there may be many kinds of received signal performance parameters, such as received signal bit error rate, received signal sensitivity, etc., and the received signal quality is judged to be optimal according to the selected received signal performance parameter The principles can be:

The performance parameters of the received signal include the bit error rate of the received signal, and the optimal quality of the received signal means the lowest bit error rate of the received signal; or,

The received signal performance parameters include received signal sensitivity, and the optimal received signal quality refers to the highest received signal sensitivity; or,

The performance parameters of the received signal include the bit error rate of the received signal and the sensitivity of the received signal, and the optimal quality of the received signal means that the sum of the reciprocal of the bit error rate of the received signal and the sensitivity of the received signal is the highest; or,

The received signal performance parameters include the received signal bit error rate and the received signal sensitivity, and the optimal received signal quality means that the sum of the reciprocal of the received signal sensitivity and the received signal bit error rate is the lowest; or,

Received signal performance parameters include received signal bit error rate and received signal sensitivity, and the optimal received signal quality means that the sum of the reciprocal of received signal bit error rate and received signal sensitivity multiplied by the set weight value is the highest; or,

The received signal performance parameters include received signal bit error rate and received signal sensitivity, and the optimal received signal quality means that the sum of the reciprocal of the received signal sensitivity and the received signal bit error rate multiplied by the set weight value is the lowest; etc.

Those skilled in the art can select other received signal performance parameters to specifically judge the received signal quality, and the corresponding optimal received signal quality principle can also be flexibly set according to the selected received signal performance parameters, which will not be listed here.

Based on the automatic gain control period, target range and signal power detection period determined according to the quality of the received signal, the embodiment of the present invention provides an automatic gain control method for mobile digital multimedia broadcasting, in each designated time slot of mobile digital multimedia broadcasting , periodically adjust the average power of the received signal according to the automatic gain control period, and each automatic gain control period, as shown in Figure 3, includes the following steps:

S301. Detect the average power of the received signal according to the signal power detection cycle;

S302. When the average received signal power detection value in the last signal power detection cycle in the automatic gain control cycle is outside the target range, adjust the average received signal power;

The specific adjustment method is:

When the received signal average power detection value of the last signal power detection cycle is greater than the maximum value of the target range, reduce the received signal average power;

When the received signal average power detection value in the last signal power detection cycle is smaller than the minimum value of the target range, increase the received signal average power.

Each time the average power of the received signal is reduced or increased, it can be adjusted according to a fixed step size for down-regulation or step-up for up-regulation.

Preferably, the method for reducing the average power of the received signal may include:

Set at least one level of down-adjustment step size and the down-adjustment error range corresponding to each level of down-adjustment step size, and each level of down-regulation step size decreases in turn, and each time it is determined to reduce the average power of the received signal:

Judging whether the difference between the received signal average power detection value of the last signal power detection cycle and the maximum value of the target range satisfies the first down-regulation error range, and if so, reduces the received signal average power according to the first-level down-regulation step;

If not, it is judged whether the difference satisfies the second down-regulation error range, and if so, the received signal average power is reduced according to the second-level down-regulation step;

By analogy, when the difference does not meet the penultimate down-regulation error range, the average power of the received signal is reduced according to the last level of down-regulation step.

Preferably, the method for increasing the average power of the received signal may include:

Set at least one level of upward adjustment step size and the upward adjustment error range corresponding to each level of upward adjustment step size, and each level of upward adjustment step size decreases in turn, and each time it is determined to increase the average power of the received signal:

Judging whether the difference between the minimum value of the target range and the received signal average power detection value in the last signal power detection cycle satisfies the first upward adjustment error range, and if so, increases the received signal average power according to the first level upward adjustment step;

If not, it is judged whether the difference meets the second upward adjustment error range, and if so, the average power of the received signal is increased according to the second level upward adjustment step;

By analogy, when the difference does not meet the penultimate upward adjustment error range, the average power of the received signal is increased according to the last level of upward adjustment step.

Of course, it is also possible to use a fixed step-down step when reducing the average power of the received signal and at least one step-up method when increasing the average power of the received signal; or, use a fixed step-up step when increasing the average power of the received signal When reducing the average power of the received signal, at least one step reduction method is adopted, which will not be listed one by one.

Use at least one down-adjustment step size or up-adjustment step size to reduce or increase the average power of the received signal. The difference between the detected value of the average power of the received signal and the target range can be used to determine whether it is a coarse adjustment or a fine adjustment. If the difference is large It can quickly adjust the average power of the received signal to the predetermined target range to adapt to the change of the received signal in the fast fading channel environment; when the difference is small, it can ensure stable and accurate adjustment of the received signal.

And preferably, the safety protection period can be set before the first designated time slot of the mobile digital multimedia broadcasting, and the automatic gain control is performed during the safety protection period. Setting the safety protection time can ensure the power of the received signal in the designated time slot It is in a basically stable state, thereby further improving the sensitivity and stability of the received signal of the mobile digital multimedia broadcasting.

An embodiment of the present invention provides an automatic gain control device for mobile digital multimedia broadcasting, as shown in FIG. 4 , including:

Parameter storage unit 401: used to store the automatic gain control period, signal power detection period and target range determined according to the received signal quality;

Signal power detection unit 402: used to detect the average power of the received signal according to the signal power detection cycle;

Automatic gain control unit 403: used to periodically adjust the average power of the received signal according to the automatic gain control period in each designated time slot of the mobile digital multimedia broadcasting, when the last signal output by the signal power detection unit in the automatic gain control period When the average power detection value of the received signal in the power detection cycle is greater than the maximum value of the target range, reduce the average power of the received signal; when the average power detection value of the received signal in the last signal power detection cycle in the automatic gain control cycle is smaller than the minimum value of the target range When , increase the average power of the received signal.

The embodiment of the present invention can flexibly set at least one level of downward adjustment step size or upward adjustment step size to reduce or increase the average power of the received signal, so the device may further include:

Down-regulation information storage unit 404: used to store at least one level of down-regulation step size and the down-regulation error range corresponding to each level of down-regulation step size, and the down-regulation step size of each level decreases in turn;

When the automatic gain control unit 403 determines to reduce the average power of the received signal each time, it judges whether the difference between the detected value of the average power of the received signal in the last signal power detection cycle and the maximum value of the target range satisfies the first lowering error range, and if so Then reduce the average power of the received signal according to the step size of the first level down;

If not, it is judged whether the difference satisfies the second down-regulation error range, and if so, the received signal average power is reduced according to the second-level down-regulation step;

By analogy, when the difference does not meet the penultimate down-regulation error range, the average power of the received signal is reduced according to the last level of down-regulation step.

Further may include:

The upward adjustment information storage unit 405: used to store at least one level of upward adjustment step size and the upward adjustment error range corresponding to each level of upward adjustment step size, and the upward adjustment step size of each level decreases in turn;

The automatic gain control unit 403 determines whether the difference between the minimum value of the target range and the detected value of the received signal average power of the last signal power detection cycle satisfies the first upward adjustment error range when determining to increase the average power of the received signal each time, if yes Then increase the average power of the received signal according to the first-level upward adjustment step;

If not, it is judged whether the difference meets the second upward adjustment error range, and if so, the average power of the received signal is increased according to the second level upward adjustment step;

By analogy, when the difference does not meet the penultimate upward adjustment error range, the average power of the received signal is increased according to the last level of upward adjustment step.

The automatic gain control solution provided by the embodiment of the present invention will be described in detail below by taking the CMMB system as an example. Based on the characteristics of the CMMB system receiving by time slots, it is only necessary to perform automatic gain control in the N specified time slots. At the same time, in order to improve the sensitivity and stability of the CMMB system, it can be advanced for a period of time (for example, several ms, or one or Several time slots) open the receiving system for automatic gain control, and the period of automatic gain control in advance is called the safety protection period, which is used to ensure that the power of the received signal in the specified time slot is in a basically stable state.

In the CMMB system, the three parameters of automatic gain control are introduced:

The automatic gain control period can generally be selected between 10us and 10ms, and an optimal parameter value can be obtained according to the simulated test environment in the laboratory or the test in the real test environment;

The signal power detection period is much shorter than the automatic gain control period, which is generally set on the order of ns;

The target range is the best working range of the Demodulator. According to the simulated test environment of the CMMB receiving system in the laboratory, fading channel (fading) and additive white Gaussian noise (Additive White Gaussian) can be added in the simulated test environment for accurate test results. Noise, AWGN) channel test, or determined by testing in a real test environment.

The general method for detecting the average power of the received signal is to perform cumulative average calculation within a fixed time range. In such a case, if you want to expand the dynamic range of the ADC, there is only one parameter that can be adjusted when performing automatic gain control, that is, the automatic gain control period, but it is difficult to achieve a very ideal effect with this adjustment. In order to achieve a more ideal effect, the embodiment of the present invention provides a method for determining the automatic gain control period, the signal power detection period and the target range according to the quality of the received signal. The channel, and the real test environment are simulated and determined. The specific process is as follows:

a. Fix the automatic gain control period and target range, adjust the signal power detection period, and obtain a set of parameter values;

b. Change the automatic gain control cycle, repeat the operation of step a, and obtain several groups of parameter values;

c. Fix the signal power detection period and target range, adjust the automatic gain control period, and obtain a set of parameter values;

d. Change the signal power detection cycle, repeat the operation of step c, and obtain several sets of parameter values;

E, according to several groups of parameter values obtained in steps a to d, select a group of parameter values with optimal received signal quality when the simulation carries out automatic gain control, and this group of parameter values determines the signal power detection cycle and the automatic gain control cycle;

f. Fix the signal power detection period and automatic gain control period, adjust the target range, and obtain a set of parameter values;

g, repeat step f, obtain several groups of parameter values;

h, according to some groups of parameter values obtained in step g, select a group of parameter values with optimal received signal quality when the simulation carries out automatic gain control, and this group of parameter values determines the target range;

i. By repeating the above steps several times, a set of parameter values with optimal received signal quality can be determined, that is, automatic gain control cycle, signal power detection cycle, and target range can be determined.

Judging the received signal quality of each group of parameter values is judged according to the received signal performance parameters. An important received signal performance parameter is to observe the received signal sensitivity corresponding to the set of parameter values in the case of accelerated fading and AWGN channels. The higher the received signal sensitivity is, the It is considered that the more ideal this group of parameter values is, the better the corresponding received signal quality is; another important received signal performance parameter is to observe the bit error rate of the received signal corresponding to this group of parameter values under the condition of accelerated fading and AWGN channel, and the received signal The lower the bit error rate is, the more ideal the value of this group of parameters is, and the better the corresponding received signal quality is; of course, there are other received signal performance parameters, which can be comprehensively considered according to actual needs. When there are more than two received signal performance parameters, test the test data of each group of parameter values corresponding to different received signal performance parameters, obtain a test standard value corresponding to the group of parameter values according to each test data, and determine the quality of the received signal according to the test standard value An optimal set of parameter values. It is also possible to assign weights to each received signal performance parameter according to system requirements. The test data of each received signal performance parameter is multiplied by the corresponding weight to obtain a test standard value corresponding to the set of parameter values, so that the reception can be determined according to the test standard value. A set of parameter values for optimal signal quality.

An example is given to illustrate the calculation method of the test standard value for assigning weights to each received signal performance parameter. There are two sets of parameter values x(a1, b1, c1) and y(a2, b2, c2), where a1 and a2 represent the automatic gain control cycle, b1 and b2 represent the signal power detection cycle, c1 and c2 represent the target range ; Set two received signal performance parameters for each group of parameter values, which are the bit error rate of the received signal and the sensitivity of the received signal, and the weights of the two evaluation criteria are α and β respectively. In the simulated test environment and the real test environment of the laboratory, the two sets of parameter values are tested respectively. The test data of the first set of parameter values corresponding to the bit error rate of the received signal is m _x , and the test data corresponding to the sensitivity of the received signal is n _x . Let the test standard value ξ _x corresponding to this group of parameter values = α/m _x + βn _x ; similarly, the test data of the second group of parameter values corresponding to the bit error rate of the received signal is m _y , and the test data corresponding to the sensitivity of the received signal is n _y , let the test standard value ξ _y corresponding to this group of parameter values = α/m _y + βn _y ; according to ξ _x and ξ _{y ,} it is determined that the received signal quality corresponding to a group of parameter values with the highest test standard value is the best; or,

Let the test standard value ξ _x corresponding to the first group of parameter values = αm _x + β/n _x ; let the test standard value ξ y corresponding to the second group of parameter values ξ _y = αm _y + β/n _y ; according to ξ _x and ξ _y It is determined that the received signal quality corresponding to a group of parameter values with the lowest test standard value is the best.

Using a set of parameter values determined by the above method to perform automatic gain control on the received signal can make the speed of automatic gain control more reasonable, which can not only follow the fast fading signal changes, so as to achieve a relatively ideal effect; and can be adjusted at the same time The signal power detection period and the automatic gain control period achieve an optimal effect of extending the dynamic range of the ADC.

After determining the three parameters of the automatic gain control: the automatic gain control period, the signal power detection period and the target range, the automatic gain control can be performed according to each parameter value. As shown in Figure 5, adding an automatic gain control device between the tuner and the analog-to-digital conversion controller in the CMMB receiving system can stabilize the average power of the received signal of the demodulator in the best working range, thereby improving the quality of mobile digital multimedia. The reception effect of broadcasting, in which:

The automatic gain control period register, the signal power detection period register and the target range register form a parameter storage unit for storing the automatic gain control period, signal power detection period and target range determined according to the quality of the received signal respectively;

The signal average power detector, the horizontal signal strength register, and the vertical signal strength register form a signal power detection unit, which is used to detect the average power of the received signal according to the parameter value stored in the signal power detection cycle register;

The pulse width modulation controller is an automatic gain control unit, which is used to periodically adjust the average power of the received signal according to the parameter values stored in the automatic gain control period register and the target range register in each specified time slot of the CMMB system, and according to the automatic gain In the control cycle, the average power of the received signal is adjusted by the detection value of the average power of the received signal in the last signal power detection cycle, so that it is adjusted within the target range.

Based on the automatic gain control device added in the CMMB receiving system, the embodiment of the present invention provides an automatic gain control method for the CMMB system, which is described by setting the three-level adjustment step as an example, as shown in Figure 6, the specific implementation process as follows:

S601, after the system is powered on, start the timer of the automatic gain control period, and the initial value of the timer is zero;

S602. Detect the time slot serial number of the CMMB system;

S603. Set the state of the automatic gain control according to the time slot number, if it is a designated time slot, set the automatic gain control to be on, and if it is a non-designated time slot, set the automatic gain control to be off;

S604. Detect the average power of the received signal according to the determined signal power detection cycle;

S605. The timing value of the timer reaches the time length of the determined automatic gain control cycle;

S606, judging whether the current automatic gain control is on, if yes, execute S607, if otherwise, execute S615;

S607. Judging whether the average power detection value of the received signal in the current signal power detection cycle is within the determined target range, if yes, execute S614, and if not, execute S608;

S608. Determine the difference between the detection value and the target range. When the detection value is greater than the maximum value of the target range, the difference between the detection value and the target range refers to the difference between the detection value and the maximum value of the target range. When the When the detection value is less than the minimum value of the target range, the difference between the detection value and the target range refers to the difference between the minimum value of the target range and the detection value;

S609, judging whether the difference between the detection value and the target range satisfies the set first error range, if yes, execute S610, if not, execute S611;

S610. Roughly adjust the average power of the received signal according to the first-level adjustment step. If the detection value is greater than the maximum value of the set target range, reduce the average power of the received signal according to the first-level adjustment step; if the detection value is less than When the target range is the minimum value, increase the average power of the received signal according to the first-level adjustment step, for example, the first error range is greater than or equal to 5dB, and the first-level adjustment step is 5dB each time, or 4.5dB, etc.;

S611. Judging whether the difference between the detected value and the target range satisfies the set second error range, if yes, execute S612, and if not, execute S613;

S612. Fine-tune the average power of the received signal according to the second-level adjustment step. If the detection value is greater than the maximum value of the set target range, reduce the average power of the received signal according to the second-level adjustment step; if the detection value is less than When the minimum value of the target range is reached, the average power of the received signal is increased according to the second-level adjustment step. For example, the second error range is greater than or equal to 1dB and less than 5dB, and the second-level adjustment step is 1dB each time, or 1.5dB, etc. wait;

S613. Fine-tune the average power of the received signal according to the third-level adjustment step. If the detection value is greater than the maximum value of the set target range, reduce the average power of the received signal according to the third-level adjustment step; if the detection value is less than When the minimum value of the target range is reached, the average power of the received signal is increased according to the third-level adjustment step. For example, the third error range is greater than 0dB and less than 1dB, and the third-level adjustment step is 0.1dB or 0.2dB each time. wait;

S614, reset the timer of the automatic gain control period to zero, and return to execute 602;

S615. The automatic gain control is not performed, the timer of the automatic gain control cycle is reset to zero, and the execution returns to S602.

The automatic gain control method provided by the embodiment of the present invention, in the CMMB system, has gone through a large number of laboratory tests and real environment tests, and has achieved the following effects after testing and verification: a group of relatively ideal parameter values has been obtained; time slot number and perform automatic gain control in the specified time slot; the difference between the average power detection value of the received signal in the last signal power detection cycle and the target range can be used to determine whether it is coarse adjustment or fine adjustment; the average power of the received signal can be quickly adjusted to within the predetermined target range.

The automatic gain control method of the CMMB system provided by the embodiment of the present invention performs the automatic gain control of the specified time slot in the CMMB system, adjusts the average power of the received signal quickly and accurately, and can adapt to the change of the received signal in the fast fading channel environment, It can stably receive CMMB signals affected by channel burst fading in the specified time slot; and when receiving CMMB signals, it effectively controls the bit error rate of received data and improves the peak-to-average ratio of received signals in fast fading channels. It can enable users to watch CMMB video programs continuously and smoothly, and improves the receiving effect of mobile digital multimedia broadcasting.

Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalent technologies, the present invention also intends to include these modifications and variations.

Claims (11)

1. An automatic gain control method of mobile digital multimedia broadcasting, in each appointed time slot of receiving mobile digital multimedia broadcasting program, periodically adjusting the average power of received signal according to automatic gain control period, in each automatic gain control period, detecting the average power of received signal according to signal power detection period, wherein one automatic gain control period includes several signal power detection periods; and are

When the average power detection value of the received signal of the last signal power detection period in the automatic gain control period is larger than the maximum value of the target range, reducing the average power of the received signal;

when the average power detection value of the received signal of the last signal power detection period in the automatic gain control period is smaller than the minimum value of a target range, increasing the average power of the received signal, wherein the automatic gain control period, the target range and the signal power detection period are determined according to the quality of the received signal;

the average power detection value of the received signals detected in the signal power detection period is as follows: the average of all received signal powers sampled in one signal power detection period.

2. The automatic gain control method of claim 1 wherein said method of reducing the average power of the received signal comprises:

setting at least one stage of down-regulation step length and a down-regulation error range corresponding to each stage of down-regulation step length, wherein each stage of down-regulation step length is reduced in sequence, and when the average power of a received signal is reduced each time:

judging whether the difference value of the average power detection value of the received signal in the last signal power detection period and the maximum value of the target range meets a first down-regulation error range, and if so, reducing the average power of the received signal according to a first-stage down-regulation step length;

if not, judging whether the difference value meets a second down-regulation error range, and if so, reducing the average power of the received signal according to a second down-regulation step length;

and the like, when the difference does not meet the range of the next to last down regulation error, reducing the average power of the received signal according to the down regulation step of the last stage.

3. The automatic gain control method of claim 1 or 2, wherein the method of increasing the average power of the received signal comprises:

setting at least one level of up-regulation step length and an up-regulation error range corresponding to each level of up-regulation step length, wherein the up-regulation step lengths at all levels are sequentially reduced, and when the average power of a received signal is determined to be increased each time:

judging whether the difference value between the minimum value of the target range and the average power detection value of the received signal in the last signal power detection period meets a first up-regulation error range, and if so, increasing the average power of the received signal according to the first-stage up-regulation step length;

if not, judging whether the difference value meets a second up-regulation error range, and if so, increasing the average power of the received signal according to the second-stage up-regulation step length;

and the like, when the difference value does not meet the range of the last second up-regulation error, the average power of the received signals is increased according to the last stage up-regulation step length.

4. The automatic gain control method of claim 1, wherein the designated time slot is determined by detecting a time slot number of a mobile digital multimedia broadcasting.

5. The automatic gain control method of claim 1, further comprising:

setting a safety protection period before the first appointed time slot of the mobile digital multimedia broadcasting, and performing the automatic gain control in the safety protection period.

6. The automatic gain control method of claim 1, wherein the specific method for determining the automatic gain control period, the target range and the signal power detection period according to the quality of the received signal comprises:

determining at least two groups of parameter values, wherein each group of parameter values comprises an automatic gain control period, a target range and a signal power detection period;

and respectively utilizing each group of parameter value simulation to carry out automatic gain control, and selecting a group of parameter values with the optimal received signal quality.

7. The automatic gain control method of claim 6, wherein the received signal quality is determined based on at least one received signal performance parameter.

8. The automatic gain control method of claim 7,

the performance parameter of the received signal comprises the error rate of the received signal, and the optimal quality of the received signal refers to the lowest error rate of the received signal; or,

the performance parameters of the received signals comprise the sensitivity of the received signals, and the optimal quality of the received signals means that the sensitivity of the received signals is the highest; or,

the performance parameters of the received signals comprise the bit error rate and the sensitivity of the received signals, and the optimal quality of the received signals means that the sum of the reciprocal of the bit error rate and the sensitivity of the received signals is the highest; or,

the performance parameters of the received signals comprise the bit error rate and the sensitivity of the received signals, and the optimal quality of the received signals means that the sum of the reciprocal of the sensitivity of the received signals and the bit error rate of the received signals is the lowest; or,

the received signal performance parameters comprise a received signal error rate and a received signal sensitivity, and the optimal received signal quality means that the sum of the reciprocal of the received signal error rate and the received signal sensitivity is the highest after being multiplied by a set weight value respectively; or,

the performance parameters of the received signals comprise the error rate of the received signals and the sensitivity of the received signals, and the optimal quality of the received signals means that the sum of the reciprocal of the sensitivity of the received signals and the error rate of the received signals multiplied by a set weight value is the lowest.

9. An automatic gain control apparatus for mobile digital multimedia broadcasting, comprising:

a parameter storage unit: the device comprises a storage unit, a power detection unit and a control unit, wherein the storage unit is used for storing an automatic gain control period, a signal power detection period and a target range which are determined according to the quality of a received signal, and one automatic gain control period comprises a plurality of signal power detection periods;

a signal power detection unit: detecting the average power of the received signal according to the signal power detection period;

an automatic gain control unit: the device comprises a signal power detection unit, a target range detection unit, a signal power detection unit and a control unit, wherein the signal power detection unit is used for detecting the average power of a received signal in the last signal power detection period output by the signal power detection unit in the automatic gain control period; and when the average power detection value of the received signal of the last signal power detection period in the automatic gain control period is smaller than the minimum value of the target range, increasing the average power of the received signal.

10. The apparatus of claim 9, further comprising:

a down-regulation information storage unit: the down-regulation error range is used for storing at least one stage of down-regulation step length and the down-regulation error range corresponding to each stage of down-regulation step length, and each stage of down-regulation step length is reduced in sequence;

the automatic gain control unit judges whether the difference value of the average power detection value of the received signal in the last signal power detection period and the maximum value of the target range meets a first down-regulation error range or not when determining to reduce the average power of the received signal every time, and if so, the average power of the received signal is reduced according to a first-stage down-regulation step length;

if not, judging whether the difference value meets a second down-regulation error range, and if so, reducing the average power of the received signal according to a second down-regulation step length;

and the like, when the difference does not meet the range of the next to last down regulation error, reducing the average power of the received signal according to the down regulation step of the last stage.

11. The apparatus of claim 9 or 10, further comprising:

an up information storage unit: the device is used for storing at least one level of up-regulation step length and an up-regulation error range corresponding to each level of up-regulation step length, and the up-regulation step lengths of all levels are reduced in sequence;

the automatic gain control unit judges whether the difference value between the minimum value of the target range and the average power detection value of the received signal in the last signal power detection period meets a first up-regulation error range or not when the average power of the received signal is determined to be increased every time, and if so, the average power of the received signal is increased according to the first-stage up-regulation step length;

if not, judging whether the difference value meets a second up-regulation error range, and if so, increasing the average power of the received signal according to the second-stage up-regulation step length;

and the like, when the difference value does not meet the range of the last second up-regulation error, the average power of the received signals is increased according to the last stage up-regulation step length.

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