KR101087101B1 - Apparatus and Method of Signal Acquisition in Digital Multimedia Broadcasting a Receiving Set - Google Patents

Abstract

The present invention provides a signal acquisition method of a digital multimedia broadcasting receiver, comprising: comparing whether a frequency offset of a received signal is within a range of a signal acquisition capability of a searcher; Adjusting the frequency offset of the received signal by generating a predetermined frequency when the comparison is outside the range of the signal capture capability; And generating a final lock signal to terminate the signal capturing process when the adjusted frequency offset is within the range of the signal capturing capability of the searcher.

According to the present invention, the frequency offset of the signal beyond the range of the signal acquisition capability of the searcher also has an effect of ensuring initial synchronization.

Frequency generator, frequency controlled oscillator

Description

Apparatus and Method of Signal Acquisition in Digital Multimedia Broadcasting a Receiving Set}

1 is a conceptual block diagram of a digital multimedia broadcasting receiver including the present invention.

FIG. 2 is a block diagram of a search signal acquisition using a serial frequency search in a digital multimedia broadcasting receiver according to the present invention.

3 is a flowchart of operation of the frequency generator according to the present invention.

4 is a block diagram illustrating a lock signal generator according to the present invention.

* Explanation of symbols for the main parts of the drawings

130: searcher 14 (1) ~ 14 (n): tracker

15 (1) ~ 15 (n): PN despreading + WALSH despreading 210: Matching filter part

220: correlation search unit 230: threshold comparison unit

240: synchronization signal generator 250: frequency generator

260: frequency controlled oscillator 41 (1) to 41 (n): integrator

42 (1) to 42 (n): comparator 430: logical sum

The present invention relates to a digital multimedia broadcasting receiver, and more particularly, to a signal capturing process in a searcher.

Digitalization of broadcasts has made digital multimedia broadcasting possible, encompassing data transmission and multimedia services.

Digital multimedia broadcasting can be classified into terrestrial digital multimedia broadcasting and satellite digital multimedia broadcasting.

The terrestrial digital multimedia broadcasting provides audio and video services while moving based on Orthogonal Frequency Division Multiplexing (OFDM).

The satellite digital multimedia broadcasting is based on CDM (Code Division Multiplexing), using a gap filler on the ground which is a repeater used to solve the satellite and the shadow area that does not receive radio waves directly from the satellite. To enable audio and video services on the go.

At present, the technology of the satellite digital multimedia broadcasting basically adopts a CDM transmission method, and is a new concept service of communication and broadcasting convergence, which broadcasts weather, traffic, and video information using CD (Compact Disk) level sound quality and various channels.

Among these digital multimedia broadcasts, the satellite digital multimedia broadcast has a broad coverage as a national broadcast, but the transmission channel is a wireless mobile reception channel, and the size of the received signal is not only time-varying, but also the influence of mobile reception. As a result, a Doppler shift of the received signal spectrum occurs.

In consideration of the transmission and reception in such a channel environment, the satellite digital multimedia broadcasting transmission method adopts the CDM method, and interleaves the time domain signals to correct errors occurring in the transmission channel.

In the above-described digital multimedia broadcasting receiver, the parameter related to the final acquisition depends on the frequency offset of the transceiver carrier.

Although the frequency offset estimator of the digital multimedia broadcasting receiver can compensate for the frequency offset, in order for the estimator to operate, synchronization acquisition must be prioritized, and therefore initial synchronization acquisition must be performed in a situation where a frequency offset exists.

In order for the digital multimedia broadcasting receiver to operate, a signal must be acquired. However, if the frequency offset of the received signal exceeds the signal acquisition capability range in the searcher, the received signal cannot be captured. It is an object of the present invention to provide a method and apparatus for enabling acquisition of a signal beyond a range of acquisition capability.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to provide a method and apparatus for increasing the probability of signal synchronization in a searcher in a receiving apparatus.

In order to achieve the above object, the present invention comprises the steps of comparing the frequency offset of the received signal is within the range of the searcher signal acquisition capability; Adjusting the frequency offset of the received signal by generating a predetermined frequency when the comparison is outside the range of the signal capture capability; If the adjusted frequency offset is within the range of the searcher's signal capturing capability, inputting the signal received at the searcher to the tracker for each finger; Despreading by multiplying the input signal by a pseudonoise sequence (PN), and performing a logical sum through an integrator and a comparator to generate a final lock signal; And feeding back the generated final lock signal to the searcher to terminate the signal capturing process.

The adjusting of the frequency offset may include adjusting the frequency offset by adding or subtracting the predetermined frequency to or from the frequency offset of the received signal.

The adjustment is characterized in that the frequency offset is adjusted while generating different frequencies by repeating the number of times set in the receiver.

In the step of adjusting the frequency offset, if the lock signal does not occur because it does not fall within the search capturing capability range at each adjustment step, the frequency offset is compared by feeding back until the time set in the receiving apparatus has elapsed.

When the time set in the receiving device elapses, a timeout is generated and the process proceeds to the next step to generate a new preset frequency.

In the step of terminating the signal capturing process, the final lock signal is generated by performing a logical OR of the lock signals obtained for each finger and feeding back to the searcher to terminate the signal capturing process.

The logical sum is characterized in that the final lock signal is output when the lock signal is generated from any one finger.

According to another embodiment of the present invention, the present invention compares whether the frequency offset is within the searcher's signal capturing capability range in order to capture the signal in accordance with the initial synchronization of the received signal, and compares the searcher's signal capturing capability. In this case, a frequency for generating a predetermined frequency and adjusting a frequency offset of the received signal to generate a final lock signal when the adjusted frequency offset falls within the searcher's signal capturing capability range to generate a frequency for terminating the signal capturing process. A generator; Provided is a signal capture device for a digital multimedia broadcasting receiver comprising a frequency controlled oscillator for generating a digital signal for sin, cos signal corresponding to the frequency generated by the frequency generator.

In addition, the terminology used in the present invention is a general term that is currently widely used as possible, but in certain cases, the term is arbitrarily selected by the applicant, and in this case, since the meaning is described in detail in the corresponding part of the present invention, a simple term It is to be clear that the present invention is to be understood as a meaning of terms rather than names.

Hereinafter, with reference to the accompanying drawings, preferred embodiments of the present invention that can specifically realize the above object will be described.

The operation of the signal capturing method of the digital multimedia broadcasting receiver according to the present invention configured as described above will be described in detail with reference to the accompanying drawings.

First, FIG. 1 is a conceptual block diagram of a digital multimedia broadcasting reception apparatus including the present invention.

Looking at the receiving process of the receiving device, the received signal input to the antenna is converted to the baseband (Baseband) in the tuner 100, the converted signal is a constant size of the signal input to the A / D (120) In order to maintain the signal, the A / D 120 is converted into a digital signal via an automatic gain control unit 110 that measures the power of the received signal and multiplies the calculated gain value.

In order to demodulate the signal in the CDM transmission method, the converted signal must capture a pseudo-noise sequence (PN) used for signal spreading. Enter the SEARCHER 130 function to secure within / 2 chips.

The signal found by the searcher 130 enters a tracker (TRACKER) 14 (1) to 14 (n) which functions to finely synchronize the signal. The process performed by the tracker is called signal tracking.

In the above description, the chip refers to a division unit of the pseudonoise sequence PN.

In this way, the signal that is captured and tracked and synchronized is despread by multiplying the pseudonoise sequence (PN) generated by the receiver, and the symbol of the desired CDM channel is extracted by multiplying the WALSH code used to distinguish the CDM channels. 15 (1) to 15 (n)). This process is performed in all the multiple paths searched by the searcher 130, and each is called a finger.

Here, the frequency offset estimator 200 estimates the frequency offset for each finger, synthesizes it, and feeds back the tuner 100 to correct the frequency offset.

The symbols extracted through the above-described process are synthesized by multiplying the WALSH code by the rake synthesizer 160. In this case, a method of improving reception performance may be obtained by estimating and compensating a reception channel environment.

Rake synthesis is performed on all CDM channels for demodulation. The synthesized symbols extract the timing of the frame and superframe using the pilot channel in the timing extraction circuit 170 of the frame and the superframe.

In this way, the signal sent from the rake synthesizer 160 enters the forward error correction encoder 180, which is a part of the present invention, and the forward error correction encoder 180 transmits one pilot channel and four channel data. Receive, correct the error, decode it, and display it through the A / V data decoder 190.

Referring to the searcher for capturing a signal in the above-mentioned receiver, FIG. 2 is a block diagram of signal acquisition of a searcher in the digital multimedia broadcasting receiver according to the present invention.

The block diagram includes a matched filter 210, a correlation searcher 220, a threshold comparator 230, a synchronization signal generator 240, a frequency generator 250, and a frequency controlled oscillator 260. It consists of.

Referring to the signal synchronization acquisition block diagram in the searcher 130, the signal converted from the analog signal to the digital signal in the A / D 120 is removed from the matched filter unit 210 and the baseband reception is performed. Extract the signal.                     

In order to capture this sync according to the initial frequency offset before entering the matched filter section 210, the frequency generator 250 enters the signal sync capture range at the searcher 130.

The frequency controlled oscillator 260 is a device for generating a digital signal for the sin, cos signal corresponding to the frequency generated by the frequency generator 250.

After entering the matching filter unit 210 through the above-described process, the signal extracted by removing noise from the matching filter unit 210 is input to the correlation search unit 220 to perform a synchronous search.

The synchronization search performed by the correlation search unit 220 is performed by comparing the synchronization signal generated by the synchronization signal generator 240 with the signal output from the matched filter unit 210. For the correlation search, the correlation search is performed. The unit 220 consists of a multiplier and an integrator.

The threshold comparison unit 230 compares the correlation coefficient obtained through the above process with a threshold to determine whether to acquire synchronization.

If the correlation coefficient obtained is larger than the threshold value, it is a case of synchronization acquisition, and the timing is transmitted to a tracker to perform the following process.

However, in the opposite case, the synchronization acquisition fails, and a phase shift signal is sent to the synchronization signal generator 240 to generate a phase shifted synchronization signal from the synchronization signal generator 240 for a new correlation search. Repeat the above process.

This process enables signal synchronization for multiple paths.                     

Referring to the operation of the frequency generator 250 during the signal acquisition process of the searcher 130 described above in detail, Figure 3 shows an operation flowchart of the frequency generator according to the present invention.

For the description of the operation of the frequency generator 250, it is assumed that the received signal has a frequency offset of 15 kHz, and the searcher 130 assumes that the signal capturing capability can handle a frequency offset of 6 kHz. In addition, it is assumed that predetermined frequencies, which are frequencies generated by the frequency generator 250, are 0 kHz, 10 kHz, and -10 kHz.

First, when a signal having a constant frequency offset (15 kHz) is received, the frequency generator 250 operates when a signal comes in through the A / D 120.

In step S10, the frequency generator 250 first generates a frequency of 0 kHz.

The signal thus generated, when summed with the frequency offset, becomes 15 kHz (= 15 kHz + 0 kHz).

In the step S20, signal synchronization is acquired by comparing the summed 15 kHz value with 6 kHz, which is a capturing capability. Since the 15 kHz is larger than 6 kHz, which is a capturing capability range, a lock signal does not occur. The synchronization of the signal cannot be captured. However, if the signal is captured at this stage, the signal acquisition process ends here and proceeds to the next process.

In the step S30, if the lock signal is not generated at the compared frequency, the above-described steps S10 and S20 are repeated until the time set in the receiver is passed, and when the time set in the receiver is passed, the time-out is performed. It goes beyond.

In step S40, the frequency generator 25 generates 10 kHz, which is a predetermined frequency, in order to capture synchronization of the signal.

Then, the generated frequency and the frequency offset of the received signal are summed, where the sum is 25 kHz (= 15 kHz + 10 kHz).

In step S50, a signal is captured by comparing the summed 25 kHz value with 6 kHz, which is a capturing capability. Since the 25 kHz is larger than 6 kHz, which is a capturing capability range, a lock signal does not occur and Motivation also cannot be captured. However, if a signal is acquired at this stage, the signal acquisition process ends here and proceeds to the next process.

In step S60, if the lock signal is not generated at the compared frequency as in step S30 described above, steps S40 and S50 are repeated until the time set in the receiver passes. The next step is taken.

In operation S70, the frequency generator 250 generates -10 kHz, which is a predetermined frequency, in order to capture synchronization of the signal.

Then, the generated frequency and the frequency offset of the received signal are summed, where the sum is 5 kHz (= 15 kHz -10 kHz).

In the above, generating a frequency having a negative value means subtracting it.                     

In step S80, a signal is captured by comparing the summed 5 kHz value with 6 kHz of capture capability, but since the 5 kHz is smaller than 6 kHz, which is a capture capability range, a lock signal is generated this time. The synchronization of the signal is captured.

Through the above-described process, the process of synchronizing the signal is finished, and the process proceeds to the next process.

However, if the signal is not acquired even at this stage (when the receiver does not capture the synchronization of the signal using all preset frequencies), the process proceeds to step S90 and steps S70 and S80 until the time set in the receiver has passed. After repeating and the set time passes, a timeout occurs. This time, the process proceeds to step S10 again to repeat the signal synchronization process from the beginning.

As an example of the frequency search process, an example of 0, 10, -10 kHz is given, but with a slight modification, it can be modified as 0, 10, 20, -10, -20 kHz. It is still scalable.

When the preset frequency is extended, the range of capturing the synchronization of the signal with respect to the frequency offset of the received signal is widened, but it takes a lot of time. Performs the process of capturing motivation.

The frequency controlled oscillator 260 is a device for generating a digital signal for the sin, cos signal corresponding to the frequency generated by the frequency generator 250.

As described above, the final lock signal in the frequency search process acts as a signal for controlling each process. Referring to the generation of the final lock signal, FIG. 4 illustrates a lock signal generator 400 according to the present invention. It is a block diagram.

When the synchronization of the signal is acquired through the above-described process in FIG. 3, the searcher 130 enters a tracker 14 (1) to 14 (n) for each finger, and each of these signals is PN. Despread, pass through the integrator and the comparator, enter the OR and generate the final lock signal.

The generated final lock signal is fed back to the searcher 130 and used as a control signal in the signal synchronization capturing process described above.

4 is a block diagram illustrating a lock signal generator according to an embodiment of the present invention. Since a signal captured through the above-described process of FIG. 3 may be a false alarm, a signal synchronization acquisition is performed in the searcher 130. However, do not stop the frequency search immediately after generating the final lock signal.

Therefore, it is necessary to determine whether the signal acquisition in the searcher 130 is a proper signal acquisition and stop the frequency searching process only when the signal acquisition is correct. Pilot channels are used for this purpose.

If the signal acquisition is done properly through the above-described process, a considerable amount of energy will be collected through PN despreading and integration in the integrators 41 (1) to 41 (n).

Since the pilot channel uses WALSH 0, it is not necessary to separately perform WALSH despreading.

In this case, the integral section is designed in consideration of the frequency offset.                     

If the integrators 41 (1) to 41 (n) are added as they are without dividing the integral section, if there is an offset in the received signal, the value of the equation described below becomes "0", resulting in a final lock signal. Failure to do so prevents the initial synchronization of the signal due to the offset of the received signal.

Therefore, the integrators 41 (1) to 41 (n) should be added by dividing the integral section.

If the integral period is short and the equal parts are increased, energy is not collected, and if the energy is small, the noise is relatively large, so this should be considered well.

However, the longer the integration period is affected by the frequency offset, so it should be adjusted.

To do this, first, a large frequency offset is assumed, and instead of making the integration period small, it is integrated several times to compensate for the insufficient energy. If this is expressed as an expression, it becomes as follows.

The above equation represents the equation in the integrator at one finger.

The r _k represents a received signal sampled at a chip rate, and the c _k represents a PN signal generated by the receiver.

In the above formula, the larger the N (integral interval), the more energy is gathered, but it is influenced by the frequency offset. Therefore, the M (integral number) is collected to determine whether the signal is properly captured. In other words, the purpose of the above equation is to collect MN pieces and use them for signal acquisition.

The MN is determined for each receiving apparatus in consideration of the offset and energy of the frequency.

As another example, instead of adding M integrals in the integrators 41 (1) to 41 (n) described above, the same effect may be obtained by passing a low pass filter (LPF).

The addition ("+") in the above formula is a digital meaning, and when expressed analogly, it means that the same effect is obtained by using the low pass filter.

Since the above-described process is a time-consuming process, it is difficult to perform in the searcher 130, and is performed on each finger.

The lock signal is generated by comparing the obtained value with the threshold value, and the lock signal generated by each of the fingers is ORed to obtain a final lock signal.

In the above, the logical sum means that a lock signal is generated for each finger, and when a lock signal is generated from one of the fingers, a final lock signal is generated to secure and capture the initial synchronization of the signal.

When the final lock signal is generated, the frequency search process of the frequency generator 250 is stopped. Once the initial signal synchronization is completed, the frequency offset estimator 200 is operated so that the frequency offset is reduced, so that it is no longer necessary to perform the acquisition process by performing a frequency search in the searcher 130.

The present invention is not limited to the above-described embodiments, and as can be seen in the appended claims, modifications can be made by those skilled in the art to which the invention pertains, and such modifications are within the scope of the present invention.

The effects of the signal capturing method of the digital multimedia broadcasting receiver according to the present invention described above are as follows.

According to the present invention, there is an effect of reducing the initial synchronization acquisition probability decrease due to the frequency offset of the signal received in the digital multimedia broadcasting receiver, and conversely, increasing the maximum value of the range of the acquisition capacities in the searcher for initial synchronization acquisition. It works.

Claims (8)

Comparing the frequency offset of the received signal to be within the searcher's signal acquisition capability range; Adjusting the frequency offset of the received signal by generating a predetermined frequency when the comparison is outside the range of the signal capture capability; If the adjusted frequency offset is within the range of the searcher's signal capturing capability, inputting the signal received at the searcher to the tracker for each finger; Despreading by multiplying the input signal by a pseudonoise sequence (PN), and performing a logical sum through an integrator and a comparator to generate a final lock signal; Feeding back the generated final lock signal to the searcher to terminate a signal capture process; The logical sum is a signal capturing method of a digital multimedia broadcasting receiver characterized in that a final lock signal is output when a lock signal is generated from any one finger. The method of claim 1, wherein adjusting the frequency offset comprises: And adjusting the frequency offset by adding or subtracting the predetermined frequency to or from the frequency offset of the received signal. The method of claim 2, And adjusting the frequency offset while generating different frequencies by repeating the number of times set in the receiving apparatus. The method of claim 1, wherein in adjusting the frequency offset, And if the lock signal is not generated because it is not within the capturing range of the searcher in each adjustment step, the frequency offset is compared by feeding back until the time set in the receiver is elapsed. The method of claim 4, wherein And generating a timeout when the set time has elapsed in the receiving device, and proceeding to the next step to generate a preset new frequency. delete delete In order to capture the signal according to the initial synchronization of the received signal, the frequency offset is compared to be within the searcher's signal capturing capability range, and when compared, the frequency offset of the received signal is generated by generating a predetermined frequency. And a frequency generator for generating a final lock signal to generate a frequency for terminating the signal synchronization capturing process when the adjusted frequency offset falls within the searcher's signal capturing capability range, The final lock signal is generated by ORing the lock signals obtained for each finger and feeding back to the searcher to terminate the signal acquisition process. The logical sum is a signal capturing apparatus of a digital multimedia broadcasting receiver, characterized in that the final lock signal is output when the lock signal is generated from any one finger.

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