CN100550698C - The auto gain control method of mobile digital multi-media broadcast and device - Google Patents
The auto gain control method of mobile digital multi-media broadcast and device Download PDFInfo
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Abstract
The present invention relates to the mobile digital multi-media broadcast field, relate in particular to a kind of automatic gain control of mobile digital multi-media broadcast.The embodiment of the invention provides a kind of auto gain control method and device of mobile digital multi-media broadcast, is used to improve the reception of mobile digital multi-media broadcast.At each assigned timeslot of mobile digital multi-media broadcast, according to the automatic gain control cycle to received signal average power carry out periodicity and adjust, in each automatic gain control cycle, detect the received signal average power according to the signal power sense cycle; And, reduce the received signal average power when last received signal average power detection value in the automatic gain control cycle during greater than the maximum of target zone; When last detected value in the automatic gain control cycle during less than the minimum value of target zone, increase the received signal average power, automatic gain control cycle, target zone and signal power sense cycle are determined according to received signal quality.
Description
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
Mobile Digital multimedia broadcasting is a very wide broadcasting system covering user terminals, and is used for small-screen, small-size, mobile and portable user terminals, such as mobile phones, Personal Digital Assistants (PDAs), MP3, MP4, Digital cameras, notebook computers, and the like, to receive multimedia broadcasting programs, information services, and other services anytime and anywhere in a satellite and terrestrial wireless broadcasting manner.
China Mobile Multimedia Broadcasting (CMMB) is a technical standard of Mobile digital Multimedia Broadcasting proposed by China, and a receiving system of the Mobile digital Multimedia Broadcasting is introduced below by taking a CMMB system as an example. In the CMMB system, the length of a radio frame is 1s, and the radio frame is divided into a plurality of equal-length slots, for example, 40 slots. When receiving the multimedia broadcast program, the user terminal only needs to open several appointed time slots in all time slots, and the system is closed in the non-appointed time slots, so as to save power consumption. As shown in fig. 1, which is a schematic diagram of a CMMB receiving system, a received Radio Frequency (RF) signal is converted into a baseband signal by a Tuner (Tuner), the output baseband signal is represented in a differential manner, the baseband signal in the horizontal direction is determined by a signal difference between I + and I-, the baseband signal in the vertical direction is determined by a signal difference between Q + and Q-, and both the Radio Frequency signal and the baseband signal are analog signals; the baseband signal is converted into a Digital signal which can be demodulated by a demodulator (demodulator) through an Analog-Digital Converter (ADC), and the average power of the received signal can be obtained by carrying out accumulative average calculation on the Digital signal within a certain time range; the demodulator (demodulator) demodulates and restores the digital signal to obtain original data transmitted on a wireless channel, and the ADC and the demodulator can be combined; the original data is sent to an Application Processor (AP) through a data transmission bus, where the data transmission bus takes a Service Provider Interface (SPI) bus as an example, where SPI _ CS and SPI _ CLK are control buses, SPI _ SDO and SPI _ SDI are data buses, and the original data is transmitted; the AP decodes audio data, video data or other application data after receiving the original data, plays a video image through a Liquid Crystal Display (LCD) by the video data, and sends the audio data to a Speaker (Speaker) for sounding through a Coder-Decoder (CODEC).
In an actual environment of mobile digital multimedia broadcasting, the average power of received signals changes in different physical areas or in different time domains of the same physical area, and especially in a fast fading Channel (fast fading Channel) environment, the change range of the average power of the received signals is very large, which affects the effect of multimedia playing. In order to achieve an ideal multimedia playing effect, Automatic Gain Control (AGC), which is a method for controlling the power of a received signal, is required to be performed on a digital signal input to a demodulator, and the AGC is performed in the reverse direction according to the change of the average power of the received signal, so as to ensure that the average power of the received signal is stabilized within a certain range.
If automatic gain control is performed in all time slots according to the prior art, in a non-designated time slot of system shutdown, because a system shutdown received signal is 0, the situation of continuously increasing the average power of the received signal will occur under the action of automatic gain control, so that the value of automatic gain control is out of control; when the Step size (Step) of the automatic gain control is smaller, the adjustment of the automatic gain control cannot keep up with the signal change of the fast fading in the fast fading channel, and when the Step size (Step) of the automatic gain control is larger, the accuracy of the automatic gain control is poorer.
Disclosure of Invention
The invention provides an automatic gain control method and device for mobile digital multimedia broadcasting, which are used for improving the receiving effect of the mobile digital multimedia broadcasting.
The invention provides an automatic gain control method of mobile digital multimedia broadcasting, which comprises the steps of periodically adjusting the average power of a received signal according to an automatic gain control period in each appointed time slot for receiving a mobile digital multimedia broadcasting program, and detecting the average power of the received signal according to a signal power detection period in each automatic gain control period, wherein one automatic gain control period comprises a plurality of 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.
The method for reducing the average power of the received signal comprises the following steps: 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.
The method for increasing the average power of the received signal comprises the following steps:
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.
The designated 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.
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 the following steps:
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.
The quality of the received signal is judged according to at least one received signal performance parameter, the received signal performance parameter comprises a received signal error rate, and the optimal received signal quality means that the received signal error rate is the lowest; 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.
The invention provides an automatic gain control device of 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.
Preferably, the apparatus further comprises:
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.
The device also includes:
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.
The invention provides an automatic gain control method and a device for mobile digital multimedia broadcasting.A received signal quality is utilized to determine an automatic gain control period, a target range and a signal power detection period, and a received signal is periodically adjusted according to the determined automatic gain control period in each appointed time slot of the mobile digital multimedia broadcasting; in each automatic gain control period, when the average power detection value of the received signal detected in the last signal power detection period is out of the target range, the average power of the received signal is adjusted, the purpose of controlling the average power of the received signal in the determined target range is achieved, the peak-to-average ratio of the received signal under a fast fading channel is effectively improved, and the receiving effect of the mobile digital multimedia broadcasting is improved.
Drawings
FIG. 1 is a diagram of a CMMB receiving system according to the prior art;
FIG. 2 is a diagram illustrating an assigned slot cycle for AGC in an embodiment of the present invention;
FIG. 3 is a flowchart illustrating an automatic gain control method for mobile digital multimedia broadcasting according to an embodiment of the present invention;
FIG. 4 is a block diagram of an automatic gain control apparatus for mobile digital multimedia broadcasting according to an embodiment of the present invention;
FIG. 5 is a block diagram of an automatic gain control apparatus of the CMMB system according to an embodiment of the present invention;
FIG. 6 is a flowchart of an automatic gain control method of the CMMB system according to the embodiment of the invention.
Detailed Description
The embodiment of the invention provides an automatic gain control method and device for mobile digital multimedia broadcasting, which can accurately control the average power of a received signal in each appointed time slot within a certain range finally by carrying out automatic gain control in the appointed time slot according to the characteristics of a receiving system of the mobile digital multimedia broadcasting, thereby achieving the purpose of improving the receiving effect of the mobile digital multimedia broadcasting.
For reasonably efficient automatic gain control, three parameters are introduced first, namely an automatic gain control period, a signal power detection period, and a target range, where:
the automatic gain control period is a period for adjusting the average power of the received signal, which reflects the speed of automatic gain control, and the larger the automatic gain control period is, the less the times of automatic gain control in a specified time slot is, namely the slower the speed is; the smaller the automatic gain control period is, the more times of automatic gain control in a specified time slot is, namely the faster the speed is;
the signal power detection period is an accumulated average calculation period of the average power of the received signals, the detection value of the average power of the received signals is obtained by accumulating the power values of all the received signals sampled in one signal power detection period and then averaging, and the sampling frequency of the average power of the received signals is set according to the requirement; one automatic gain control period comprises a plurality of signal power detection periods, a plurality of detection values of the average power of the received signals can be obtained, but the average power of the received signals is adjusted only according to the detection value of the last signal power detection period in the automatic gain control period;
the target range is the optimal power range to which the average power of the received signal is finally adjusted through automatic gain control, and a better multimedia playing effect can be realized in the range.
As shown in fig. 2, a schematic diagram of the assigned slot cycle of the agc, which includes N agc cycles in each assigned slot of the mobile dmb, each agc cycle including M signal power detection cycles; in each automatic gain control period, detecting the average power of the received signal according to a signal power detection period, and obtaining a detection value of the average power of the received signal in each signal power detection period; and adjusting the average power of the received signal according to the detection value of the last signal power detection period in the automatic gain control period.
The automatic gain control period, the target range and the signal power detection period are key parameters for automatic gain control, and can be determined according to the quality of a received signal through a simulation test, and the specific determination method comprises the following steps:
A. 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;
B. 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.
The criterion for judging the quality of the received signal may be at least one received signal performance parameter, the received signal performance parameters may be various, such as a received signal error rate, a received signal sensitivity, and the like, and the principle for judging the quality of the received signal to be optimal according to the selected received signal performance parameter may be:
the performance parameters of the received signals comprise the error rate of the received signals, and the optimal quality of the received signals means that the error rate of the received signals is the lowest; 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 quality of the received signal means that the sum of the reciprocal of the received signal error rate and the received signal sensitivity is the highest after the reciprocal of the received signal error rate and the received signal sensitivity are multiplied by a set weight value respectively; 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 sensitivity and the received signal error rate after being multiplied by a set weight value respectively is the lowest; and so on.
Those skilled in the art can select other performance parameters of the received signal to specifically determine the quality of the received signal, and the corresponding received signal quality optimization principle can also be flexibly set according to the selected performance parameters of the received signal, which are not listed here.
Based on the agc period, the target range and the signal power detection period determined according to the quality of the received signal, an embodiment of the present invention provides an agc method for mobile digital multimedia broadcasting, where in each designated timeslot of the mobile digital multimedia broadcasting, the average power of the received signal is periodically adjusted according to the agc period, and in each agc period, as shown in fig. 3, the method includes the following steps:
s301, detecting the average power of the received signal according to the signal power detection period;
s302, when the average power detection value of the received signal of the last signal power detection period in the automatic gain control period is out of the target range, adjusting the average power of the received signal;
the specific adjusting method comprises the following steps:
when the average power detection value of the received signal in the last signal power detection period is larger than the maximum value of the target range, reducing the average power of the received signal;
and when the average power detection value of the received signal in the last signal power detection period is smaller than the minimum value of the target range, increasing the average power of the received signal.
Each time the average power of the received signal is reduced or increased, the adjustment may be made according to a fixed down step or up step.
Preferably, the method for reducing the average power of the received signal may comprise:
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.
Preferably, the method for increasing the average power of the received signal may comprise:
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.
Of course, a method of using a fixed down step when reducing the average power of the received signal and using at least one level of up step when increasing the average power of the received signal may also be used; or, a fixed up-regulation step size is adopted when the average power of the received signal is increased, and at least one stage of down-regulation step size is adopted when the average power of the received signal is reduced, which are not listed.
The method of reducing or increasing the average power of the received signal by at least one stage of down-regulation step length or up-regulation step length is adopted, the coarse regulation or the fine regulation can be determined according to the difference value of the average power detection value of the received signal and the target range, and the average power of the received signal can be quickly regulated to the predetermined target range when the difference value is larger, so that the method is suitable for the change of the received signal under the fast fading channel environment; when the difference is small, the stable and accurate adjustment of the received signal can be ensured.
And preferably, a safety protection period can be set before the first appointed time slot of the mobile digital multimedia broadcasting, automatic gain control is carried out in the safety protection period, and the setting of the safety protection period can ensure that the power of a received signal in the appointed time slot is in a basically stable state, so that the sensitivity and the stability of the received signal of the mobile digital multimedia broadcasting are further improved.
An embodiment of the present invention provides an automatic gain control apparatus for mobile digital multimedia broadcasting, as shown in fig. 4, including:
parameter storage unit 401: for storing an automatic gain control period, a signal power detection period and a target range determined according to the quality of a received signal;
signal power detection unit 402: detecting the average power of the received signal according to the signal power detection period;
automatic gain control unit 403: the device comprises a signal power 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 each appointed time slot of the mobile digital multimedia broadcast according to an 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.
The embodiment of the invention can flexibly set at least one stage of down-regulation step length or up-regulation step length to reduce or increase the average power of the received signal, therefore, the device can further comprise:
down information storage unit 404: 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 403 determines whether the difference between the average power detection value of the received signal in the last signal power detection period and the maximum value of the target range satisfies the first down-regulation error range each time the average power of the received signal is determined to be reduced, and if so, reduces the average power of the received signal according to the first 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.
Further, the method can also comprise the following steps:
the up information storage unit 405: 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 403 judges whether the difference 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 satisfies a first up-regulation error range each time the average power of the received signal is determined to be increased, and if so, increases the average power of the received signal according to the first level 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.
The following describes the automatic gain control scheme provided by the embodiment of the present invention in detail by taking a CMMB system as an example. Based on the characteristic that the CMMB system receives signals in time slots, it only needs to perform automatic gain control in N designated time slots, and in order to improve the sensitivity and stability of the CMMB system, the receiving system may be turned on in advance for performing automatic gain control for a period of time (e.g., several ms, or one or several time slots), where the period of time in advance for performing automatic gain control is referred to as a safety protection period to ensure that the power of the received signal is in a substantially stable state in the designated time slots.
In the CMMB system, three parameters of automatic gain control are described:
the automatic gain control period can be generally selected from 10us to 10ms, and an optimal parameter value can be obtained according to a simulated test environment in a laboratory or a test under a real test environment;
the signal power detection period is far shorter than the automatic gain control period and is generally set on the order of ns;
the target range is the best working range of the demodulator, and can be determined by adding a fading channel (fading) channel test and an Additive White Gaussian Noise (AWGN) channel test in the simulated test environment or by testing in a real test environment for accurate test results according to the simulated test environment of the CMMB receiving system in a laboratory.
A common method for detecting the average power of the received signal is to perform a cumulative average calculation in a fixed time range. In such a case, if it is desired to extend the dynamic range of the ADC, only one parameter can be adjusted during the agc, i.e. the agc period, and it is difficult to achieve a very desirable effect by such an adjustment. In order to achieve a more ideal effect, embodiments of the present invention provide a method for determining an automatic gain control period, a signal power detection period, and a target range according to received signal quality, which needs to perform simulation tests and determination in a laboratory simulation test environment, such as additive fading and AWGN channels, and a real test environment, and the specific process is as follows:
a. fixing the automatic gain control period and the target range, and adjusting the signal power detection period to obtain a group of parameter values;
b. changing the automatic gain control period, and repeating the operation of the step a to obtain a plurality of groups of parameter values;
c. fixing a signal power detection period and a target range, and adjusting an automatic gain control period to obtain a group of parameter values;
d. changing the signal power detection period, and repeating the operation of the step c to obtain a plurality of groups of parameter values;
e. selecting a group of parameter values with optimal received signal quality when carrying out automatic gain control simulation according to a plurality of groups of parameter values obtained in the steps a to d, wherein the group of parameter values determines a signal power detection period and an automatic gain control period;
f. fixing a signal power detection period and an automatic gain control period, and adjusting a target range to obtain a group of parameter values;
g. repeating the step f to obtain a plurality of groups of parameter values;
h. selecting a group of parameter values with optimal received signal quality when simulation is carried out on automatic gain control according to the plurality of groups of parameter values obtained in the step g, wherein the group of parameter values determines a target range;
i. repeating the above steps for several times, a group of parameter values with the best quality of the received signal can be determined, namely, an automatic gain control period, a signal power detection period and a target range are determined.
Judging the received signal quality of each group of parameter values according to the received signal performance parameters, wherein one important received signal performance parameter is the received signal sensitivity corresponding to the group of parameter values under the condition of accelerating fading and AWGN channels, and the higher the received signal sensitivity is, the more ideal the group of parameter values is considered, and the better the corresponding received signal quality is; another important performance parameter of the received signal is that the error rate of the received signal corresponding to the group of parameter values is observed under the condition of accelerating fading and AWGN channels, and the lower the error rate of the received signal is, the more ideal the group of parameter values is considered, and the better the quality of the corresponding received signal is; of course, there are other performance parameters of the received signal, which can be considered comprehensively according to actual needs. When more than two received signal performance parameters exist, testing data of each group of parameter values corresponding to different received signal performance parameters, obtaining a testing standard value corresponding to the group of parameter values according to each testing data, and determining a group of parameter values with optimal received signal quality according to the testing standard value. Or according to the system requirement, distributing weight to each received signal performance parameter, and multiplying the test data of each received signal performance parameter by the corresponding weight to obtain a test standard value corresponding to the group of parameter values, thereby determining a group of parameter values with optimal received signal quality according to the test standard value.
The method for calculating the test standard value for assigning a weight to each received signal performance parameter will be described by way of example. Two sets of parameter values x (a1, b1, c1) and y (a2, b2, c2) are provided, wherein a1 and a2 represent automatic gain control periods, b1 and b2 represent signal power detection periods, and c1 and c2 represent target ranges; and setting two performance parameters of the received signals, namely the bit error rate and the sensitivity of the received signals, for each group of parameter values, wherein the weights of the two judgment standards are respectively alpha and beta. Simulated test environment and real test environment in laboratoryThen, two groups of parameter values are respectively tested, and the test data of the first group of parameter values corresponding to the error rate of the received signal is mxThe test data corresponding to the sensitivity of the received signal is nxMaking the testing standard value xi corresponding to the group of parameter valuesx＝α/mx+βnx(ii) a Similarly, the second set of parameter values corresponds to the test data of the error rate of the received signal as myThe test data corresponding to the sensitivity of the received signal is nyMaking the testing standard value xi corresponding to the group of parameter valuesy＝α/my+βny(ii) a According to xixAnd xiyDetermining that the received signal quality corresponding to a group of parameter values with the highest test standard value is optimal; or,
making the testing standard value xi corresponding to the first group of parameter valuesx＝αmx+β/nx(ii) a Making the testing standard value xi corresponding to the second group of parameter valuesy＝αmy+β/ny(ii) a According to xixAnd xiyAnd determining that the received signal quality corresponding to the group of parameter values with the lowest test standard value is optimal.
The method determines a group of parameter values to carry out automatic gain control on the received signals, so that the speed of the automatic gain control is reasonable, the automatic gain control can follow the signal change of fast fading, and an ideal effect is achieved; and the signal power detection period and the automatic gain control period can be adjusted simultaneously, so that an optimal effect of expanding the dynamic range of the ADC is achieved.
Three parameters of automatic gain control are determined: and after the automatic gain control period, the signal power detection period and the target range, performing automatic gain control according to each parameter value. As shown in fig. 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 operating range, thereby improving the receiving effect of the mobile digital multimedia broadcasting, wherein:
the automatic gain control period register, the signal power detection period register and the target range register form a parameter storage unit which is used for respectively storing the automatic gain control period, the signal power detection period and the target range which are determined according to the quality of the received signal;
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 for detecting the average power of the received signals according to the parameter values stored by the signal power detection period register;
the pulse width modulation controller is an automatic gain control unit and is used for periodically adjusting the average power of the received signals according to parameter values stored in an automatic gain control period register and a target range register in each appointed time slot of the CMMB system, and adjusting the average power of the received signals to be within a target range according to the average power detection value of the received signals in the last signal power detection period in the automatic gain control period.
Based on an automatic gain control device added in a CMMB receiving system, an embodiment of the present invention provides an automatic gain control method of a CMMB system, which is described by taking setting of three-level adjustment step lengths as an example, and as shown in fig. 6, the specific implementation process is as follows:
s601, after the system is powered on, starting a timer of an automatic gain control period, wherein the initial value of the timer is zero;
s602, detecting a time slot serial number of the CMMB system;
s603, setting the state of automatic gain control according to the time slot serial number, if the time slot is designated, setting the automatic gain control to be in an open state, and if the time slot is not designated, setting the automatic gain control to be in a closed state;
s604, detecting the average power of the received signal according to the determined signal power detection period;
s605, the time length of the timing value of the timer reaching the determined automatic gain control period;
s606, judging whether the current automatic gain control is in an open state, if so, executing S607, otherwise, executing S615;
s607, judging whether the average power detection value of the received signal in the current signal power detection period is in the determined target range, if so, executing S614, otherwise, executing S608;
s608, determining a difference between the detection value and the target range, wherein when the detection value is larger than the maximum value of the target range, the difference between the detection value and the target range is the difference between the detection value and the maximum value of the target range, and when the detection value is smaller than the minimum value of the target range, the difference between the detection value and the target range is the difference between the minimum value of the target range and the detection value;
s609, judging whether the difference value between the detection value and the target range meets a set first error range, if so, executing S610, otherwise, executing S611;
s610, roughly adjusting the average power of the received signal according to the first-stage adjusting step length, and reducing the average power of the received signal according to the first-stage adjusting step length if the detection value is larger than the maximum value of the set target range; if the detected value is smaller than the minimum value of the target range, increasing the average power of the received signal according to a first-stage adjustment step length, for example, the first error range is greater than or equal to 5dB, the first-stage adjustment step length is 5dB or 4.5dB per adjustment, and the like;
s611, judging whether the difference value between the detection value and the target range meets a set second error range, if so, executing S612, otherwise, executing S613;
s612, fine-adjusting the average power of the received signal according to a second-stage adjustment step length, and reducing the average power of the received signal according to the second-stage adjustment step length if the detection value is larger than the maximum value of the set target range; if the detected value is smaller than the minimum value of the target range, increasing the average power of the received signal according to a second-stage adjustment step, for example, the second error range is greater than or equal to 1dB and smaller than 5dB, the second-stage adjustment step is 1dB or 1.5dB per adjustment, and so on;
s613, finely adjusting the average power of the received signal according to a third-stage adjustment step length, and reducing the average power of the received signal according to the third-stage adjustment step length if the detection value is larger than the maximum value of the set target range; if the detection value is smaller than the minimum value of the target range, increasing the average power of the received signal according to a third-stage adjustment step length, wherein the third error range is larger than 0dB and smaller than 1dB, the third-stage adjustment step length is 0.1dB or 0.2dB and the like for each adjustment;
s614, resetting the timer of the automatic gain control period to zero, and returning to execute 602;
s615, the automatic gain control is not performed, the timer of the automatic gain control period is reset to zero, and the process returns to S602.
The automatic gain control method provided by the embodiment of the invention is subjected to a large number of laboratory tests and real environment tests in a CMMB system, and the following effects are completely achieved through test verification: obtaining a group of more ideal parameter values; the time slot serial number can be detected and automatic gain control is carried out in the appointed time slot; whether coarse adjustment or fine adjustment is performed can be determined according to the difference between the average power detection value of the received signal in the last signal power detection period and the target range; the average power of the received signal can be quickly adjusted to within a predetermined target range.
According to the automatic gain control method of the CMMB system provided by the embodiment of the invention, the automatic gain control of the appointed time slot is carried out in the CMMB system, the average power of the received signal is quickly and accurately adjusted, the method can adapt to the received signal change under the fast fading channel environment, and the CMMB signal influenced by the channel burst fading can be stably received in the appointed time slot; and when receiving CMMB signals, the error rate of the received data is effectively controlled, the peak-to-average ratio of the received signals under a fast fading channel is improved, a user can continuously and smoothly watch CMMB video programs, and the receiving effect of the mobile digital multimedia broadcasting is improved.
It will be apparent to those skilled in the art that various changes and modifications may be made in the present invention without departing from the spirit and scope of the invention. Thus, if such modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include such 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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| CN101835007A (en) * | 2009-03-09 | 2010-09-15 | 中兴通讯股份有限公司 | Indication method and device of mobile multimedia broadcast signal and mobile terminal thereof |
| CN101631215B (en) * | 2009-07-31 | 2012-01-04 | 福州瑞芯微电子有限公司 | Automatic gain control method of mobile digital multimedia broadcasting receiver |
| CN102065528B (en) * | 2009-11-18 | 2015-05-06 | 联芯科技有限公司 | Automatic gain control method and device |
| CN102256084B (en) * | 2010-05-19 | 2013-03-06 | 北京创毅视讯科技有限公司 | Automatic gain control method and device |
| CN102256085B (en) * | 2010-05-21 | 2013-01-23 | 北京创毅视讯科技有限公司 | Automatic gain control method and device |
| CN101969687A (en) * | 2010-10-26 | 2011-02-09 | 三维通信股份有限公司 | Method for implementing digital GSM time slot ALC |
| CN110350948B (en) * | 2018-04-03 | 2020-12-15 | 华为技术有限公司 | Relay transmission configuration method of PLC system, relay transmission method and device |
| CN114945210B (en) * | 2022-05-06 | 2024-02-09 | 广州芯之联科技有限公司 | Radio frequency signal gain control method, system, device and medium |
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