KR20060068830A - Method and apparatus for frame sync detecting - Google Patents

Abstract

The present invention relates to an apparatus and method for detecting frame synchronization. The present invention provides a unique word matching counter for increasing or decreasing a counter value by comparing whether a signal included in a received pilot channel matches a unique word, and a maximum value for comparing the output counter value with a previous counter value and outputting a maximum value. A frame comparator comprising a value comparator, a reliability counter for measuring the reliability of the compared maximum value, and a decoder for decoding the frame number included in the next data interval of the unique word interval reliably detected through the reliability counter. It provides a detection device. Therefore, a unique word is detected from the transmitted pilot signal through a high reliability test, and the frame number is decoded using the same to generate accurate frame and superframe sync signals.

Frame Sync, Super Frame, Pilot Channel, Unique Word, Reliability Counter

Description

Method and apparatus for detecting frame sync {Method and Apparatus for frame sync detecting}

1 is a block diagram showing the configuration of an apparatus for detecting frame synchronization according to the present invention;

2 is a diagram showing the configuration of a pilot channel used in the frame synchronization detecting apparatus according to the present invention.

3 is a block diagram schematically showing the overall configuration of a satellite DMB receiver according to the present invention.

-Explanation of symbols for the main parts of the drawings-

100: unique word match counter 200: maximum value comparator

300: D frame frame counter 400: reliability counter I

500: D2 interval decoder 600: Reliability counter II

The present invention relates to frame synchronization detection, and more particularly, to a method and apparatus for detecting frame synchronization transmitted on a pilot channel in a CDM transmission scheme.                         

Hereinafter, a satellite digital multimedia broadcasting (DMB) receiver using a CDM transmission method will be described as an example.

The part related to frame synchronization in the satellite DMB receiver is not specified in the specification and is an implementation problem, so there is no specific prior art defined. Here, the satellite DMB receiver will be briefly described as follows.

Digitalization of broadcasts has made Digital Multimedia Broadcasting (DMB) possible, encompassing data transmission and multimedia services. The DMB is robust against noise and distortion on a transmission channel, has a high transmission efficiency and has an advantage of enabling a multimedia service.

The satellite DMB broadcast adopted in Korea is based on the Japanese system E system and consists of performance equipment, earth station, satellite, terrestrial relay equipment and subscriber receiver.

The satellite DMB broadcasting system transmits multimedia contents from the earth station transmission center to the satellite, and the user receives the data directly from the satellite or from a terrestrial auxiliary relay called a gap filter in a shaded area where the signal strength is weak. It will work.

In this case, the transmission channel of the satellite DMB is a wireless mobile reception channel, and the amplitude of the received signal is not only time-varying, but also the Doppler shift of the received signal spectrum occurs due to the mobile reception. .

Therefore, in consideration of the transmission and reception in such a channel environment, the satellite DMB transmission method adopts a code division multiplexing (CDM) transmission method.

The CDM transmission method is a method of multiplying a data to be transmitted by a pseudo noise signal having a data rate much faster than that of the data to spread and transmit the signal. band interface), and the receiver of the RAKE structure reduces the degradation of reception performance due to the multipath.

Satellite DMB using the CDM transmission method is a new concept service of convergence communication and broadcasting, which broadcasts weather, traffic, and video information using CD quality sound and various channels.

The satellite DMB uses frequencies in the uplink 13.824 to 13.883 GHz band and the downlink 2.630 to 2.655 GHz and the 12.21 to 12.23 GHz bands, and supports up to 64 channels (32 channels in Korea and Japan). One of the 32 channels is used as a pilot channel, and the pilot channel is a control channel and contains various information necessary for demodulation. Therefore, the pilot channel is a channel that must be demodulated, and is a non-modulated spreading channel, thereby adjusting frame synchronization using the pilot channel.

In this case, matching the frame means providing timing information necessary to decode the data channel, and thus, accurate frame synchronization is an important problem for correct information recovery.

 The present invention is to solve the above problems, the object of the present invention relates to a frame synchronization detection method and apparatus for detecting the correct frame synchronization from the pilot channel.

In order to achieve the above object, the present invention provides a unique word matching counter that increases or decreases a counter value by comparing whether a signal included in a received pilot channel matches a unique word, and compares the counter value with the previous counter value. A maximum value comparator for comparing and outputting a maximum value, a reliability counter for measuring the reliability of the compared maximum value, and a decoder for decoding the frame number included in the next data interval of the unique word interval reliably detected through the reliability counter. It provides a frame synchronization detection device configured to include.

Preferably, the frame synchronization detecting apparatus further includes a data interval frame counter for counting frames such that the unique word comparison and the maximum value comparison are performed in a data interval in a pilot channel.

It is preferably configured to further comprise a reliability counter for measuring the reliability for the decoded frame number.

The present invention provides a method for receiving a digital multimedia broadcasting, comprising: increasing or decreasing a counter value by comparing whether a signal included in a received pilot channel matches a unique word, and outputting a maximum value by comparing the counter value with a previous counter value. And a step of measuring the reliability of the compared maximum value, and decoding the frame number included in the next data section of the uniquely measured unique word section.

Therefore, according to the present invention, a unique word is detected from the transmitted pilot signal through a high reliability test, and the frame number is decoded using the same to generate an accurate frame and a superframe sync signal.

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

In addition, the terminology used in the present invention was selected as a general term widely used as possible now, but in some cases, the term is arbitrarily selected by the applicant, in which case the meaning is described in detail in the corresponding description of the invention, The present invention is to be understood as the meaning of terms rather than names.

1 is a block diagram showing the configuration of a frame synchronization detecting apparatus according to the present invention.

As shown in FIG. 1, the apparatus for detecting frame synchronization according to the present invention includes a unique word matching counter 100 that increases or decreases a counter value by comparing whether a signal included in a received pilot channel matches a unique word, and A maximum value comparator 200 for comparing the compared counter value with a previous maximum counter value so that the maximum value is immediately reflected, and a D for counting frames such that the unique word comparison and the maximum value comparison are performed in units of D intervals in the pilot channel. An interval frame counter 300, a reliability counter I 400 for measuring the reliability of the compared maximum value, and a D2 interval decoder for decoding the frame number included in the next data interval between the reliably detected unique word intervals. 500, and a reliability counter II 600 that measures the reliability of the decoded frame number.

Before examining the operation relationship of the apparatus for detecting frame synchronization configured as described above, the configuration of a pilot channel will be described first for convenience of description.

The data of the satellite DMB can be largely divided into a pilot signal and a data signal. The pilot signal includes a pilot symbol (PS), a frame synchronization signal (D1), and a super frame synchronization signal (D2) as a synchronization signal. Therefore, the frame synchronization is used to find the location of the super frame as well. This is shown in Figure 2 attached.

2 is a diagram showing the configuration of a pilot channel used in the apparatus for detecting frame synchronization according to the present invention.

As shown in FIG. 2, the pilot channel has a structure in which six frames are collected to form one super frame. The one frame is composed of pilot data represented by D1 to D51 together with a pilot symbol (PS) of 32 symbols. That is, one frame includes 51 sets of the PS section and the D section, which are composed of 32 symbols.

The D1 section of the pilot data is a section in which a unique word of 32 bits (ex, 01101010 10110101 01011001 10001010) is recorded as a frame synchronization signal. The unique word is a value known to both the transmitting end and the receiving end, that is, used for frame synchronization as a predefined pattern.

The D2 section is a section in which a frame counter value is recorded. Since one super frame is composed of six frames, the frame counter value has a value of 0 to 5, and eight frame counter values having a 4-bit size are repeatedly recorded. Therefore, the frame counter value is used for synchronization of the super frame, also referred to as a super frame synchronization signal.

D3 to D50 are used for data transmission such as information on interleaver size and convolutional coding rate in order to control hardware of a receiver, and D51 is a portion allocated for other purposes.

Using the pilot channel signal configured as described above, the FEC (Foward Error Correction) unit of the satellite DMB receiver uses the start signal of the super frame as a control signal. It is a finding.

To this end, first, the D1 section of the pilot channel signal must be found for frame synchronization. To this end, since the unique word information is loaded in the D section, the D1 section may be found by comparing whether or not the D word corresponds to the unique word for all the D sections of the transmitted pilot channel signal. That is, the section corresponding to the unique word of the section D becomes the section D1.

Therefore, the unique word matching counter 100 of FIG. 1 compares 32 symbols of each D interval and 32 unique words to increase the value of the counter by one when the match is identical, and decreases the value of the counter by one. Do this.

At this time, when detecting the D1 section at an arbitrary time point, the D section frame counter 300 is used to know the D section within one frame. The D section frame counter 300 can easily count the D section using one frame composed of 51 D sections.

As a result of the comparison, since there is one D1 section in every frame, it can be considered that the section having the highest value of the unique word match counter value within one frame is the D1 section.

Therefore, the maximum value comparator 200 is used to find the counter value that has increased the most in one frame. The maximum value comparator 200 compares the unique word counter value for every D section with a previous maximum counter value so that the maximum value is immediately reflected for each D section.

At this time, the maximum value comparator 200 stores the position of the D section at that time together with the maximum unique word matching counter value.

As a result of the comparison, when the value counted by the D section frame counter 300 is 51, that is, when all the D sections for one frame are compared with the unique word, the maximum number of parts that match the unique word is the largest. The section having the value can be estimated as the position D1.

For the estimated position of D1, the reliability counter I 400 is applied to determine the reliability of the value. The reliability counter 1 400 utilizes that the estimated position is reliable when the D section of the same position is always assumed to be the D1 section when the D1 position is detected in the same way for several frames.

To this end, the reliability counter I 400 sets an initial estimated estimated D1 section position as a reference D1 position value, and sets the value of the reliability counter to 1 when the reference D1 position is equal to the next inputted estimated D1 position. Increase it, decrease it by 1 if different. If the increased reliability counter value is equal to or greater than a predetermined reference value (reliability as required by the system), it is regarded as a reliable position and the position of D1 is determined.

When the reliable position of D1 is estimated in the pilot channel signal as described above, the D2 interval decoder 500 decodes the D2 interval. That is, since the position of D1 is estimated, the next section D will be the section D2, which is to decode the section D2.

As mentioned above, the frame number is inserted in the D2 section. Therefore, the frame number of the currently received signal can be known by decoding the D2 section.

In the D2 section, frame numbers 0 to 5 are allocated by 4 bits, and eight are repeatedly recorded. Therefore, when decoding from the upper bits to the lower bits by 4 bits in the transmission order, a frame number having a total of eight identical values can be obtained. The reason why the same value is repeatedly recorded in consideration of an error condition during transmission, and it is determined that the most frequent value among the frame numbers 0 to 5 represents the current frame number.

A reliability counter is also applied to the decoded frame number again to check reliability. To this end, the decoded frame number is verified in reliability counter II (600). The reliability counter II 600 checks the reliability by comparing the first input frame number with the next predicted frame number as a reference frame number.

That is, based on the stored reference frame number, the reliability counter is increased by 1 when the two values are the same, and decremented by 1 when it is different from the next input prediction frame number. In this case, if the increased reliability counter value is equal to or greater than a predetermined reference value, the value is regarded as a reliable value, and the current frame number is determined and output.

As such, the signal passing through the reliability counter I 400 for the interval D1 and the reliability counter II 600 for the interval D2 is a result of high reliability, which is reliable for generating the frame and super frame timing control signals. Give results.

On the other hand, Figure 3 is a block diagram showing the overall configuration of the satellite DMB receiver to which the technical idea according to the present invention is applied.

As shown in FIG. 3, the received signal input through the antenna is converted into a baseband signal through the tuner 1, and the magnitude of the signal is kept constant through the AGC (Automatic Gain Controller) unit 3. . The signal whose size is relatively constant by the AGC unit 3 is sampled by an A / D converter (Analog / Digital Converter) 5 and converted into a digital signal.

In the CDM transmission method, the acquisition of a pseudo-noise sequence used for signal spreading should be prioritized. This process is divided into signal acquisition and tracking steps.

Since the division unit of the pseudo noise sequence is called a chip, the acquisition is a process of securing signal synchronization within ± 1/2 chips at a receiver, and this process is performed by a searcher 7. The tracking of the signal finely synchronizes the captured signal, and is performed in the trackers 9 (1), ..., 9 (n).

The synchronized signal is then despread by multiplying the pseudo-noise sequences generated by the receiver in the PN despreading and WALSH despreading units 11 (1), ..., 11 (n), and used to distinguish the CDM channels. By multiplying the WALSH code, the symbol of the desired CDM channel is extracted.

This process is performed in all the multiple paths found in the searcher (7), each of which is called a finger.

Thereafter, the frequency offset estimator 13 estimates a frequency offset for each finger, synthesizes it, and feeds it back to the tuner 1 to correct the frequency offset.

The symbols extracted through this process are synthesized in the Rake synthesizer 15. In this case, a method of improving reception performance may be used by estimating and compensating a reception channel environment. The rake synthesis is performed for all CDM channels for which demodulation is desired.

Thereafter, the frame and super frame timing extracting circuit 17 extracts the timing of the frame and super frame by the method according to the embodiment of the present invention. That is, a reliable D1 section and a D2 section are detected from a pilot channel as a control channel, and a control signal for timing the frame and the super frame is generated using the frame number included in the section. The timing control signal serves to adjust the timing of the received signal such as designating a start position of channel decoding in a subsequent channel decoding process.

Subsequently, the pilot channel, which is the control channel, is demodulated through corresponding configuration blocks such as convolutional decoding and reverse interleaving, and the data channel is deinterleaved, convolutional decoded, and RS decoded through control data of the pilot channel. / V will output the data.

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 apparatus and method for detecting frame synchronization according to the present invention as described above detects a unique word from a transmitted pilot signal through a high reliability test and decodes the frame number using the same to generate an accurate frame and a superframe synchronization signal. There is.

Claims (6)

In a digital multimedia broadcasting receiver, A unique word match counter for comparing a signal included in a received pilot channel with a unique word to increase or decrease a counter value; A maximum value comparator for comparing the counter value compared and outputted with a previous counter value and outputting a maximum value; A reliability counter for measuring the reliability of the compared maximum value; And, And a decoder for decoding a frame number included in a next data section of a unique word section reliably detected through the reliability counter. The method of claim 1, And a data interval frame counter for counting frames such that the unique word comparison and the maximum value comparison are performed in a data interval in a pilot channel. The method according to claim 1 or 2, And a reliability counter for measuring the reliability of the decoded frame number. In the digital multimedia broadcasting receiving method, Increasing or decreasing the counter value by comparing whether a signal included in the received pilot channel matches a unique word; Outputting a maximum value by comparing the counter value with a previous counter value; Measuring the reliability of the compared maximum value; And decoding the frame number included in the next data section of the unique word section measured reliably. The method of claim 4, wherein And counting a frame such that the unique word comparison and the maximum value output are performed in a data section of the received pilot signal. The method according to claim 4 or 5, And measuring the reliability of the decoded frame number.

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