KR20070081384A - Method and apparatus for managing memory in digital broadcating receiver - Google Patents

Abstract

A method and an apparatus for managing a memory in a digital broadcasting receiver are provided to share a memory region required for coarse carrier recovery and data demodulation in a DVB-H(Digital Video Broadcasting-Handheld) receiver to reduce hardware of the receiver and increase an operating speed. A FFT(Fast Fourier Transform) unit fast-Fourier-transforms a received digital broadcasting signal(500). The FFT unit stores a fast-Fourier-transformed symbol required to acquire synchronization of a receiver in a memory(504). A coarse carrier recovery unit acquires synchronization by using the symbol stored in the memory(512). The FFT unit stores effective sub-carriers in the memory for channel estimation. A channel estimation/compensation unit estimates a channel by using the effective sub-carriers stored in the memory in order to demodulate data.

Description

METHOD AND APPARATUS FOR MANAGING MEMORY IN DIGITAL BROADCATING RECEIVER}

1 is a block diagram for synchronization acquisition and data demodulation in a typical DVB-H receiver;

2 is a block diagram for synchronization acquisition and data demodulation in a DVB-H receiver according to an embodiment of the present invention;

3 illustrates a method of storing symbols in a shared memory to perform a synchronization acquisition process in a DVB-H receiver according to the present invention;

4 illustrates a method of storing effective subcarriers for synchronization acquisition in a shared memory of a DVB-H receiver according to an embodiment of the present invention;

5 is a flowchart illustrating an operation of sharing a memory for synchronization acquisition and data demodulation in a DVB-H receiver according to an embodiment of the present invention.

The present invention relates to a method and apparatus for managing a memory in a receiver of a digital broadcasting system, and more particularly, to obtaining synchronization and demodulating data in a receiver of a digital video broadcasting-handheld (DVB-H) method. A method and apparatus for managing memory.

In general, a broadcast service is a service provided for the purpose of providing all users with a terminal. Such broadcast services are classified into audio broadcasting services such as radio broadcasting providing only voice, and multimedia broadcasting services including video-oriented broadcasting services such as television providing voice and video services and voice, video and data services. These broadcast services are based on the analog method, and digital broadcasting is being performed according to the rapid development of technology. In addition, the broadcasting service is a method of providing a multimedia service using a multimedia service and a satellite of a wired network that provides high quality and high speed data by wire, away from the method provided based on a conventional transmission tower, and simultaneously uses a wired and satellite. It is evolving in a variety of ways.

One of these methods is spurring commercial services to DMB (Digital Multimedia Broadcasting). The DMB method is based on digital audio broadcasting (DAB) and is based on Eureka-147 (European REserch Coordination Agency project-147), which is a technical standard of DAB in Europe.

On the other hand, in Europe, the origin of DAB technology, a group called Digital Video Broadcasting (DVB) is organized for multimedia broadcasting service, and a separate technical standardization work for mobile broadcasting is underway under the name 'DVB-H'. DVB-H (Handheld) is a digital audio broadcasting (DAB) standardization organization for digital TV broadcasting in Europe. It is used for satellite digital TV (DVB-S), digital cable TV (DVB-C), and terrestrial digital TV (DVB-T). It is a broadcasting standard under development.

The DVB Group decided that third-generation mobile communication (UMTS or IMT-2000), terrestrial digital TV, and digital audio broadcasting (DAB) could not realize mass multimedia contents such as movies and broadcasting dramas through mobile terminals. (eXtention), and then more clearly, the name DVB-H, which stands for the concept of 'mobile broadcasting'.

DVB-H is a standard for enhancing mobility in DVB-T, a European digital TV transmission standard, and is an extension of DVB-T in consideration of low power, mobility, and portability of mobile terminals and portable video devices. Thus, most of the physical layer specifications of DVB-H follow the DVB-T specifications and add some additional functions for portable / mobile reception.

The DVB-H system is based on Orthogonal Frequency Division Multiplex (OFDM), and algorithms for acquiring synchronization in a receiver include mode detection and coarse symbol timing recovery. CSTR) and Coarse Carrier Recovery (CCR).

After the CCR is completed, that is, after the synchronization acquisition is completed, the DVB-H receiver performs data demodulation including channel estimation / compensation.

In a DVB-H receiver, the CCR is obtained using the correlation of two consecutive symbols, so a Fast Fourier Transform (FFT) result is required for the current symbol and the previous symbol. Done. In addition, full OFDM symbols, including guard bands (Null Carriers) are used, so the DVB-H receiver has a minimum size (FFT size) x 2 symbols for Fourier transforming of active sub-carriers. You need memory to store].

In the DVB-H receiver, the channel measurement is estimated by using a continuous pilot having a fixed position repeated every 12 samples within a symbol and a scattered pilot repeated every 4 symbol periods. Since the channel compensation is performed using the result, the FFT result before the 4 symbols is required. In addition, since data demodulation of the DVB-H receiver uses only valid subcarriers, a memory for storing [effective subcarriers x 5 symbols] should be separately provided. Next, a memory configuration for synchronization acquisition and channel measurement in the above-described DVB-H receiver will be described with reference to FIG. 1.

1 is a block diagram for synchronization acquisition and data demodulation in a typical DVB-H receiver. As described above, in FIG. 1, the FFT operator 100 performing FFT on the current symbol and the previous symbol and the channel estimator / compensator 104 perform FFT operation for estimating a channel. A second memory 108, a channel estimator / compensator 104 and an FFT operator 100 that estimate and compensate a channel based on symbols stored in the second memory 108 to demodulate data, acquire synchronization of a receiver. That is, the first memory 106 stores two full OFDM symbols for CCR operation, and a CCR operation unit 102 for performing CCR operation from the symbols stored in the first memory 106.

 The FFT size defined in the receiver of the DVB-H system standard is 8192 long, and the memory size at which the effective number of carriers is stored is 6817. That is, the number of subcarriers present for one symbol is 8192, and the subcarriers carrying actual data excluding the guard band of the one symbol (the number of valid subcarriers are 6817).

Therefore, in the DVB-H receiver, the memory required to perform the CCR operation is a memory capable of storing two symbols (full OFDM symbols), i.e., 8192 x 2 symbols, for the current symbol including the guard band and one previous symbol. need. In addition, to estimate the channel required for data demodulation, a scattered pilot that is repeated in four symbol periods is used. In this case, a current symbol and a symbol before four symbols are needed, so a memory capable of storing 6817 x 5 symbols is required. Do. That is, referring to FIG. 1, 8192 x 2 symbols for performing the CCR operation are stored one by one symbol in bank 0 and bank 1 of the first memory 106, and 6817 x 5 symbols for data demodulation are the second memory. Each symbol is stored in an output buffer 108a consisting of five banks of 108.

As shown in FIG. 1, when the DVB-H receiver separately implements a memory for CCR operation and data demodulation, the hardware area increases. In addition, when a symbol used for CCR operation is stored in one bank and used, the calculation time required for estimating the integer frequency carrier offset may exceed the symbol interval as much as possible, thereby delaying synchronization acquisition.

 The present invention provides an apparatus and method for sharing a memory required for CCR operation and data demodulation in a DVB-H receiver.

The present invention provides a method and apparatus for minimizing the hardware area by reducing the memory size of a DVB-H receiver.

The present invention provides a method and apparatus for minimizing inter carrier frequency detection time in a DVB-H receiver.

A method for managing memory for synchronization acquisition and data demodulation in a receiver of a digital broadcasting system according to the present invention includes a process of performing fast Fourier transform on a received digital broadcast signal by a fast Fourier transform calculation unit, and Storing the fast Fourier transformed symbols necessary for synchronizing the receiver in a memory, obtaining a synchronization using a symbol stored in the memory by a coarse carrier recovery operation unit, and recovering the coarse carrier If the operation unit obtains synchronization, the fast Fourier transform unit stores the effective subcarriers in the memory for channel estimation, and the channel estimator / compensator estimates the channel using the effective subcarriers stored in the memory for data demodulation. It includes the process of doing.

An apparatus for managing a memory for synchronization acquisition and data demodulation in a receiver of a digital broadcasting system according to the present invention comprises: performing fast Fourier transform on a received digital broadcast signal for synchronization acquisition of the receiver and storing the received digital broadcast signal in a memory; A fast Fourier transform unit for storing a valid subcarrier in the memory for demodulating a digital broadcast signal, and a coarse carrier recovery for synchronizing the receiver by reading symbols converted from the fast Fourier transform unit from the memory A carrier estimation unit, a channel estimator / compensator for performing channel estimation using the effective subcarrier to perform the channel estimation, and a symbol and an effective subcarrier converted by the fast Fourier transform according to whether synchronization is obtained And the memory for setting an area.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. It should be noted that the same components in the figures represent the same numerals wherever possible. Specific details are set forth below, which are provided to aid a more general understanding of the present invention. In describing the present invention, when it is determined that description of related known functions or configurations may unnecessarily obscure the gist of the present invention, the detailed description thereof will be omitted.

2 is a block diagram for synchronization acquisition and data demodulation in a DVB-H receiver according to an embodiment of the present invention.

In describing the accompanying FIG. 2, the same reference numerals are used for the same block configurations as those of FIG. 1.

In FIG. 2, in order for the CCR calculating unit 200 and the channel estimating / compensating unit 204 to share a memory required for performing an operation, the shared memory 202 according to the present invention has five banks 202b having a depth of 6817. It is shown that the use area and the control method of the shared memory 202 according to the operation of the CCR operation unit 200 is shown.

The CCR calculating unit 200 performs an operation of finding a carrier frequency offset in the initial state of broadcast reception of the DVB-H receiver, and uses a continuous pilot repeatedly transmitted in an OFDM symbol. Since the position of the continual pilot is fixed, the DVB-H receiver estimates the position of the continual pilot and calculates the correlation of the continuous pilot carrier of successive symbols to calculate the correlation within a specific search range. Motivation is obtained by finding the peak at.

 The FFT calculator 206 performs an FFT on the current symbol and the previous symbol of a signal received through an antenna (not shown) to obtain synchronization, and then uses one symbol as shown by reference numerals 302f and 302g according to an embodiment of the present invention. A carrier corresponding to a half symbol boundary, which is 1/2 of, is copied by a search interval and stored in each bank of the first buffer 202a.

DVB-H receivers must ensure mobile reception for data demodulation. Therefore, before performing data demodulation, the channel estimation / compensation unit 204 must perform channel estimation and compensation. Therefore, the channel estimator / compensator 204 estimates and compensates for a channel estimation state by using a Scatter Pilot which is repeated in four symbol periods.

As described above, the CCR operation unit 200 requires two consecutive full OFDM symbols including a guard band to perform the CCR operation, and the current OFDM symbol including only the effective carrier and 4 to perform data demodulation. The OFDM symbol before the symbol is needed. Since data demodulation starts after the CCR operation of the CCR calculator 200 ends, it is possible for the CCR calculator 200 and the channel estimator / compensator 204 to share a single memory 202 in time.

Shared memory 202 according to an embodiment of the present invention is divided into two areas. First, each of the banks (banks 0 to 3) of the first buffer 202a has a depth of 4096 (half of 8192), which is the minimum size that the CCR operation unit 200 needs to acquire synchronization as described above. . The second buffer 202b is a minimum size necessary for demodulating the actual data, and each bank (banks 0 to 4) has a depth of 6817 respectively.

In order for the CCR calculator 200 to perform a CCR operation, the FFT calculator 206 stores the FFT-calculated data in four banks as shown by reference numeral 202a of FIG. 2, and has a half OFDM symbol in each bank. Save 2 symbols each.

On the other hand, since only valid carriers need to be stored during data demodulation, one symbol is stored in each bank of the second buffer 202b of the shared memory 202 to store all five symbols.

That is, in the conventional DVB-H receiver, as shown in FIG. 1, a memory having a depth of 8192 has to be separately provided to store a full OFDM symbol for synchronization acquisition. However, in the present invention, as shown in FIG. The four banks for storing the data are shared with the memory banks used by the channel estimator / compensator 204.

In general, since the synchronization acquisition time is closely related to the number of memory accesses, storing half OFDM symbols in two banks is more effective than storing Full OFDM symbols in one bank as in the present invention. Can be reduced. In other words, if the symbols stored in the bank are read with the same clock, the present invention can be accessed twice as fast as the conventional invention.

3 illustrates a method of storing symbols in shared memory 202 to perform a synchronization acquisition process in a DVB-H receiver in accordance with the present invention.

In FIG. 3, reference numeral 300 shows a process of searching for a continuous pilot 300d and a full OFDM symbol to perform a CCR operation for synchronization acquisition in a general DVB-H receiver. Referring to FIG. 3, in a typical DVB-H receiver, a bank capable of storing 8192 depths 300a for storing a current symbol and a previous symbol in the first memory 106 of FIG. 1 to obtain synchronization. 1 and 2 banks are separately provided in the second memory 108 of FIG. 1 because the channel estimation / compensator 104 requires the number of effective carriers as long as the reference number 6817 length 300b for demodulation of data. I had to.

However, reference numeral 302 shows a process of searching for a continuous pilot and a half OFDM symbol in order to perform synchronization acquisition and data demodulation in a DVB-H receiver according to an embodiment of the present invention. Referring to the reference numeral 302, unlike the reference numeral 300, one symbol (Full OFDM Symbol) is divided into two and stored in the first buffer 202a of the shared memory 202.

Referring to FIG. 3, in the DVB-H receiver according to the present invention, a half OFDM symbol obtained by dividing the full OFDM symbol in half is stored for each bank of the first buffer 202a. Each bank (Bank 0 to Bank 3) has 4096 (302a) and 302b sized guard bands 302c and 302d, and an effective subcarrier 302d and 302e, in addition to the m size of the shared area 302f. , 302g.

As in the present invention, a method of dividing and storing a half OFDM symbol into two banks, respectively, has the advantage of reducing operation time since two carriers can be simultaneously read in one symbol. However, the CCR operation requires as many carriers as the search range 300c for each continuous pilot 300d distributed in the symbol. When storing one symbol in half, parallel operation is not possible because the search interval for the continuous pilot located at the center of the symbol cannot be secured as shown by reference numeral 310. Therefore, each bank of the first buffer 202a must include, as well as half symbols, regions 302f and 302g corresponding to the search interval centered on the center of the symbol.

4 is a diagram illustrating a method of storing effective subcarriers for synchronization acquisition in a shared memory 202 of a DVB-H receiver according to an embodiment of the present invention. In FIG. 4, as described above with reference to FIG. 3, when the FFT calculator 206 stores the FFT result, the carrier corresponding to the half symbol boundary 310 is copied by the search period 300c and inserted into each bank.

That is, referring to the bank 0 and the bank 1 of the first buffer 202a of the shared memory 202 of FIG. 4, the bank 0 includes half symbols having a length of 4096 and half symbols stored in the bank 1 as shown by reference numeral 302a. It can be seen that as much as m 302f of the search range 400b are stored together. In Bank 1, it can be seen that m (302g), which is an area corresponding to the search range m (400a) stored in Bank 0, and as many as 4096 Half Symbols are stored. As described above, the banks 2 and 3 also store the search range in addition to the half symbol.

This ensures a search interval for the correlation of the continuous pilot located in the symbol center portion 310 so that the correlation of the continuous pilot for the first Half Symbol 302a and the second Hafl Symbol 302b can be simultaneously processed. . Each bank has at least [effective subcarrier-FFT size / 2] memory margin (440), so no additional memory is required, and two continuous pilots can be read and processed in parallel in one symbol. Therefore, the computation time is reduced to 1/2.

5 is a flowchart illustrating an operation of sharing a memory 202 for synchronization acquisition and data demodulation in a DVB-H receiver according to an embodiment of the present invention.

First, in step 500, the FFT calculator 206 first performs an FFT operation on data received through an antenna (not shown) to obtain synchronization. In operation 502, the FFT calculator 206 checks whether the CCR calculator 200 acquires the synchronization (CCR lock). If the FFT operation unit 206 has not yet acquired the synchronization, the FFT operation unit 206 proceeds to step 504. The FFT results are stored by dividing a full symbol into half symbols in two buffers of the buffer 202a.

If the FFT operator 206 finishes writing the FFT result in step 506, the write completion signal WRITE_DONE is generated to the CCR operator 200 in step 508. Upon receiving the write completion signal, the CCR calculator 200 reads the FFT result stored in the first buffer 202a of the shared memory 202 and continues to perform a CCR operation to find a continuous pilot in step 512.

On the other hand, if the synchronization is obtained after checking whether the CCR operation unit 200 acquires the synchronization (CCR lock) in step 502, that is, if the CCR is locked, the FFT operation unit 206 proceeds to step 514. As a result, the FFT result of the effective carriers is stored in the second buffer 202b of the shared memory 202 and used by the channel estimator 204 to estimate the channel.

If the FFT operator 200 completes the write operation in step 516, the FFT operator 200 proceeds to step 518 and the FFT operator 200 reads an effective subcarrier stored in the second buffer 202b of the shared memory 202 to estimate / compensate the channel. Transfer to section 204.

In operation 520, a deinterleaver and a decoder (not shown) demodulate the data using the result of channel measurement / compensation by the channel estimator / compensator 204.

In steps 504 to 512, the CCR operation unit 200 searches for a continual pilot for synchronization acquisition in the DVB-H receiver. In steps 514 to 520, the channel is estimated after the synchronization is acquired in the DVB-H receiver. It's a process.

According to the present invention, by sharing the memory area required for CCR operation and data demodulation in the DVB-H receiver, it is possible to reduce the hardware size of the receiver and to increase the computation speed.

Claims (8)

A method for managing memory for synchronization acquisition and data demodulation in a receiver of a digital broadcasting system, Performing a fast Fourier transform of the received digital broadcast signal by the fast Fourier transform calculating unit; Storing, by the fast Fourier transform calculating unit, a fast Fourier transformed symbol necessary for synchronous acquisition of the receiver in a memory; A process of acquiring synchronization using a symbol stored in the memory by a coarse carrier recovery operation unit, Storing, by the fast Fourier transform unit, valid subcarriers in the memory for channel estimation when the coarse carrier recovery operation unit obtains synchronization; And estimating, by the channel estimator / compensator, a channel using the effective subcarriers stored in the memory for data demodulation. According to claim 1, The process of storing the fast Fourier transformed symbols necessary for the synchronization acquisition in a memory, And dividing the fast Fourier transformed current symbol and the previous symbol into half symbols and adding a search interval to the half symbols to store them in the memory in order to obtain synchronization of the receiver. Memory management method. According to claim 1, The fast Fourier transform unit stores the effective subcarriers in the memory for channel estimation, And storing only effective carriers of five symbols except for a guard band among the fast Fourier transformed symbols in the memory. An apparatus for managing a memory for synchronization acquisition and data demodulation in a receiver of a digital broadcasting system, A fast Fourier transform unit for storing the received digital broadcast signal in a memory by fast Fourier transforming to obtain the synchronization of the receiver and storing an effective subcarrier in the memory for channel estimation to demodulate the received digital broadcast signal; A coarse carrier recovery operation unit for reading the symbols converted by the fast Fourier transform unit from the memory to obtain synchronization of the receiver; A channel estimator / compensator for performing channel estimation using the effective subcarrier to perform the channel estimation; And a memory configured to set an area for storing a symbol and an effective subcarrier converted by the fast Fourier transform unit according to whether to acquire the synchronization. The method of claim 4, wherein And the fast Fourier transform calculating unit divides a current symbol and a previous symbol into half symbols and adds a search period to each of the half symbols in the memory to obtain the synchronization. The method of claim 4, wherein The fast Fourier transform calculating unit stores only effective subcarriers except the guard band of the transformed symbols in the memory in order to estimate the channel. The method of claim 5, And storing the memory in four banks by adding a search interval to 4096 which is half of the current and previous symbols. The method of claim 6, And the memory stores five valid subcarriers in each bank.

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