KR100283672B1 - Strobe signal generator for extracting pilot signal from COFDM receiver - Google Patents

Abstract

The present invention relates to an apparatus for generating a strobe signal to extract a pilot signal in a COFDM receiver.

The strobe signal generator of the present invention comprises a counter 20, a TPS ROM 22, and a CPC ROM 24. The counter 20 counts the clock CLK while being enabled by the valid signal valid, and outputs a count value as a carrier number. For example, in the 2K mode, the valid signal is a high signal for a 1705 clock period and a low signal for a 855 clock period. Accordingly, the counter 20 counts the clock CLK while the valid signal valid is enabled, and outputs a count value (ie, a carrier number) from 0 to 1704. The TPS ROM 22 receives a carrier number from 0 to 1704 as an address and outputs a strobe signal for outputting a TPS pilot, and the CPC ROM 24 receives a carrier number from 0 to 1704 as an address and receives a CPC. Outputs a strobe signal for outputting a pilot.

Therefore, according to the present invention, the strobe signal for extracting the TPS pilot and the CPC pilot is very simply implemented using a ROM, thereby reducing the manufacturing cost when implementing the COFDM receiver.

Description

Apparatus for generating pilot strobe signals in a COFDM receiver

The present invention relates to a COFDM receiver, and more particularly, to an apparatus for generating a strobe signal for extracting a pilot signal in a COFDM receiver.

In general, the coded orthogonal frequency division multiplex (COFDM) method converts a sequence of symbols input in serial form into parallel data by N symbols, multiplexes the parallelized symbols with different subcarrier frequencies, and stores each of the multiplexed data. In addition, send. Here, the N parallelized symbols are regarded as one unit block, and each subcarrier of the block is orthogonal to each other so that there is no influence between subcarrier channels. Therefore, compared with the conventional single carrier transmission scheme, since the symbol period can be increased by the number of subchannels N while maintaining the same symbol rate, inter-symbol interference due to multipath fading can be reduced. In particular, when a guard interval (GI) is inserted between transmitted symbols, the inter-symbol interference can be further reduced, thereby simplifying the structure of the channel equalizer.

Meanwhile, according to the European digital terrestrial broadcasting standard using the COFDM method, a pilot signal transmitted together with data as a reference signal is distributed pilot cells (SPC), continuous pilot carriers (CPC), and transmission parameters. It is divided into a signaling pilot (TPS: Transmission Parameter Signaling pilots). These pilot signals are used for frame synchronization, frequency synchronization, time synchronization, channel estimation, transmission mode identification, and phase noise. It is also used to track.

These pilot signals are included in the COFDM frame together with the transmitted data, wherein the reference information value transmitted to the receiver is a known value. Pilot signals containing reference information are transmitted at a ″ boosted ″ power level, that is, at a power level of about 1.4 times the transmission data level.

The COFDM frame structure in which the pilot signal is transmitted as described above is as follows.

The transmission signal is formed of frames, and each frame has a period of T _F and consists of 68 COFDM symbols. In addition, the four frames are gathered to form a superframe. Each symbol is composed of K = 6817 carriers (K: number of transmission carriers) in the 8K mode or K = 1705 carriers in the 2K mode, and has a symbol period T _S.

OFDM Parameter Values According to Mode Parameter 8 K mode 2 K mode Carrier K 6817 1705 K _min carrier value 0 0 K _max carrier value 6816 1704 Inverse of the carrier spacing (T _U ) 896 μs 224 μs Carrier Spacing (1 / T _U ) 1116 Hz 4464 Hz Spacing between carrier K _min and K _max {(K-1) / T _U } 7.61 MHz 7.61 MHz

In Table 1, each symbol T _S = ΔT + T _U is composed of one portion having a period T _U corresponding to the inverse of the carrier interval and the other portion having a period ΔT corresponding to a guard interval. .

In addition, the unit symbol of the COFDM system consists of useful data and a guard interval. According to the basic specifications of the European digital terrestrial broadcasting system, the size of the valid data (2K mode or 8K mode) and the size of the protection section (1/4, 1/8, 1/16 or 1/32 of the FFT size) are selected. It corresponds to matter. In the case of the 2K mode, the effective data size is 2048, and the size of the protection interval is 512 in the case of about 1/4 of the 2K FFT size 2048. Here, the size of valid data ″ 2048 ″ means that 1705 effective carriers and 343 null carriers are added together. The guard interval is a copy of the 1536th data to the 2047th data (that is, the size of 512) which is the last part of the valid data. As a result, the symbol size 2560 of the transmission unit is the sum of the size 2048 of the valid data and the size 512 of the protection interval.

1 is a block diagram showing a configuration example of a general COFDM demodulation system. An OFDM demodulation system is a digital signal processing (DSP) chip and a field programmable gate array (FPGA) chip that are programmed to sequentially perform various synchronization (SYNC), equalization, de-mapping and deinterleaving functions. Use it and place hardware which can be used jointly outside. External hardware includes a memory (SRAM, ROM table), a complex multiplier, an FFT processor, an FEC decoder, and the like.

In FIG. 1, the COFDM demodulation system includes an A / D converter 100, a rotator 102, an FFT processor 104, a rearrangement memory 106, a synchronizer 120, a first complex multiplier 122, A phase lookup table 124, a DSP 140, an equalization and deinterleaving processor 130, a filter coefficient memory 134, a symbol memory 136, and a second complex multiplier 132.

The received COFDM signal is converted by the FFT processor 104 after passing through the A / D converter 100 and the rotator 102 and stored in the rearrangement memory 106. The rearrangement memory 106 stores data stored in a suitable form according to each synchronization progress whenever time synchronization, frequency synchronization, frame synchronization, and the like are sequentially performed. Rearrange

The synchronization unit 120 may include COARSE TIME SYNC., COARSE FREQ SYNC., FRAME SYNC., FINE FREQ SYNC., FINE TIME SYNC. SYNC.) Proceeds sequentially. In addition, a function for estimating the phase error value for phase synchronization is added. At this time, the synchronization unit 120 receives the output of the rotator 102, the output of the rearrangement memory 106, and the like and time-shares the first complex multiplier 122 and the phase lookup table 124 to synchronize the corresponding time. Process and phase error estimation process. Their control is at DSP 140.

The equalization and deinterleaving processing unit 130 performs equalization, demapping, and deinterleaving processes in order. The reference pilot signals and the symbol data obtained through the synchronizer 120 are provided to compensate for the channel-distorted signal by using an external symbol memory 136, a filter coefficient memory 134, and a second complex multiplier 132. The equalization process is performed. Subsequently, the equalized symbol is QAM de-mapped to determine the original symbol, and then symbol deinterleaving is performed to obtain the original bitstream and provide it to an external FEC decoder.

In this configuration, the decoding process is an initial step, and after brief time synchronization is performed during the synchronization process, simple frequency synchronization, frame synchronization, fine frequency synchronization, and fine time synchronization are performed. After phase noise estimation and correction are performed, symbol equalization is performed, the equalized symbol is demapped, deinterleaved, and output in a final step.

However, when the receiver of the COFDM is implemented in hardware, it is necessary to generate a strobe signal corresponding to the position of the pilot in order to extract the pilot signal included in the received symbol. At this time, the TPS pilot and the CPC pilot are received in a fixed position in units of symbols, and there is a problem in that a circuit for generating a strobe signal for extracting this is very complicated in the prior art.

Accordingly, an object of the present invention is to provide a strobe signal generator for extracting a pilot signal from a COFDM receiver, which can be configured as a simple circuit using a ROM.

In order to achieve the above object, the apparatus of the present invention, in the COFDM receiver for receiving the TPS and CPC delivered through the position of a certain carrier number in symbol units, when the valid signal is enabled, the clock is counted to count the carrier number A counter to output; A TPS ROM generating a strobe signal when a carrier number of the counter corresponds to an address corresponding to a position of a TPS pilot; And a CPC ROM generating a strobe signal if the carrier number of the counter corresponds to an address corresponding to the position of the CPC pilot.

1 is a block diagram showing the overall configuration of a COFDM receiver to which the present invention can be applied,

2 is a block diagram showing an apparatus for generating a strobe signal in accordance with the present invention;

3 is an operational waveform diagram illustrating the operation of the apparatus according to the present invention.

* Explanation of symbols for main parts of the drawings

20: counter 22: TPS ROM

24: CPC ROM

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

2 is a block diagram showing a strobe signal generator for extracting a pilot signal in a COFDM receiver according to the present invention.

2, the strobe signal generator of the present invention is composed of a counter 20, a TPS ROM 22, and a CPC ROM 24. The counter 20 counts the clock CLK while being enabled by the valid signal valid, and outputs a count value as a carrier number. For example, in the 2K mode, the valid signal is a high signal for a 1705 clock period and a low signal for a 855 clock period, as shown in FIG. 3A. Accordingly, the counter 20 counts the clock CLK while the valid signal valid is enabled, and outputs a count value (ie, a carrier number) from 0 to 1704.

The TPS ROM 22 receives a carrier number from 0 to 1704 as an address and outputs a strobe signal for outputting a TPS pilot. The CPC ROM 24 receives a carrier number from 0 to 1704 as an address and a CPC pilot. Outputs a strobe signal for outputting

According to the European Digital Television Standard, in the 2k mode, since the TPS pilot is inserted and transmitted at a predetermined position of each symbol as shown in Table 2, the TPS is counted by resetting the counter 20 after each symbol starts. When the count value of the corresponding position is reached, a TPS strobe signal is generated.

TPS 2k mode 34 50 209 346 413 569 595 688 790 901 1073 1219 1262 1286 1469 1594 1687

In order to generate a TPS strobe signal, data is stored in the TPS ROM 22 as shown in Table 3 below.

TPS ROM Address Data 0 0 One 0 2 0 3 0 To To 33 0 34 One 35 0 To To 49 0 50 One 51 0 To To

As shown in Table 3, in order to generate a strobe signal by receiving the count value corresponding to the carrier number of the 2k mode as an address, data is stored in the address as shown in Table 2, and the rest is 0 is stored.

Meanwhile, according to the European digital television standard, in the 2k mode, the CPC pilot is inserted and transmitted at a predetermined position of each symbol as shown in Table 4, so that the clock is counted after resetting the counter 20 each time each symbol starts. When the CPC reaches the count value of the corresponding position, the CPC strobe signal is generated.

CPC 2k mode 0 48 54 87 141 156 192 201 255 279 282 333 432 450 483 525 531 618 636 714 759 765 780 804 873 888 918 939 942 969 984 1050 1101 1107 1110 1137 1140 1146 1206 1269 1323 1377 1491 1683 1704

In order to generate the CPC strobe signal, data is stored in the CPC ROM 24 as shown in Table 5 below.

CPC ROM Address Data 0 One One 0 2 0 3 0 To To 47 0 48 One 49 0 To To 53 0 54 One 55 0 To To

As shown in Table 5, in order to generate a strobe signal by receiving the count value corresponding to the carrier number of the 2k mode as the address in the CPC ROM 24, 1 is stored in the address shown in Table 4, and the rest is 0. Is stored.

3A illustrates a valid signal representing a valid carrier section in a 2k mode symbol. When the valid signal is high, the counter 20 counts 1705 clocks and outputs a carrier number from 0 to 1704 as shown in FIG. 3B, and the TPS ROM 22 shows a TPS strobe signal as shown in FIG. 3C according to the carrier number. Outputs The CPC ROM 24 outputs a CPC strobe signal as shown in FIG. 3D according to the carrier number. 3E is a symbol sync signal for distinguishing symbols, and the counter resets the count value according to the symbol sync signal.

As described above, according to the present invention, the strobe signal for extracting the TPS pilot and the CPC pilot is very simply implemented using a ROM, thereby reducing the manufacturing cost when implementing the COFDM receiver.

Claims (1)

In the COFDM receiver for receiving the transmission parameter signaling pilot (TPS) and the continuous pilot carrier (CPC) delivered through the position of a certain carrier number in symbol units, A counter 20 that counts a clock and outputs a carrier number when the valid signal is enabled; A TPS ROM (22) for generating a strobe signal if the carrier number of the counter corresponds to an address corresponding to the position of the TPS pilot; And And a CPC ROM (24) for generating a strobe signal if the carrier number of the counter corresponds to an address corresponding to the position of the CPC pilot. The strobe signal generator for extracting a pilot signal from a COFDM receiver.