CN100518026C - Multicarrier transmitting system for improving receiving function and signal processing method thereof - Google Patents

Abstract

Provided are a multi-carrier system and method thereof. The multi-carrier transmission system includes: an FEC unit for performing encoding on frequency domain data so that a receiving end detects and corrects errors; a mapping unit for mapping the encoded frequency domain data by using a predetermined mapping method; A parallel conversion unit for accumulating mapped data to N times, so as to output parallel data; a first synchronous information insertion unit for inserting different first synchronous information with the same length to the parallel data; IDFT unit , for performing IDFT on the N data inserted with the first synchronization information, so as to output a time-domain OFDM signal; a guard interval insertion unit, used to insert a guard interval before the time-domain OFDM signal; and a second synchronization information insertion unit, It is used for inserting the second synchronization information before the time-domain OFDM signal, and the time-domain OFDM signal is inserted with a guard interval. Therefore, the PN sequence is inserted into the frequency domain data, thereby enabling better reception performance than conventional multi-carrier transmission systems.

Description

Multi-carrier transmission system capable of improving reception performance and signal processing method thereof

Background technique

The present invention relates to a digital broadcasting system, and more particularly, to a multi-carrier transmission system capable of improving reception performance.

Background technique

OFDM (Orthogonal Frequency Division Multiplexing) is a multicarrier modulation method that has good performance under multipath and mobile conditions.

The OFDM method uses multiple carriers with mutually orthogonal characteristics to improve frequency utilization. The OFDM method is suitable for transmission at high data rates, as is the use of multi-carrier approaches in wired or wireless channels. When using a single carrier path to transmit high-rate data with short symbol intervals on a wireless communication channel with multipath fading, the complexity at the receiving end increases significantly as the intersymbol interference becomes worse. On the other hand, since the multi-carrier approach can extend the symbol interval per subcarrier to the number of subcarriers while maintaining the data transmission rate, it is easy to solve the problem due to Channels with severe frequency fading caused by multipath.

Using multiple carriers having mutual orthogonality in the OFDM method can be modulated/demodulated at a high rate by using IFFT/FFT (Inverse Fast Fourier Transform/Fast Fourier Transform) at the transmitting/receiving side, which IFFT/FFT has the same result as performing IDFT/DFT (Inverse Discrete Fourier Transform/Discrete Fourier Transform).

The TDS-OFDM transmission system (Time Domain Synchronization-Orthogonal Frequency Division Multiplexing), which is an OFDM method, has the following characteristics, for example: the system inserts a PN (pseudo-noise) sequence into the time domain, and the PN sequence is the transmission system and the synchronization information between the receiving system.

FIG. 1 is a schematic block diagram showing a digital broadcasting system employing a TDS-OFDM method, which is a type of OFDM method.

The TDS-OFDM transmission system includes an FEC (Forward Error Correction) unit 10, which is used to encode data so that the receiving end can detect and correct errors; (Orthogonal amplitude modulation), 64QAM etc. map the coded data; 3780 point IDFT units 30, are used for frequency domain OFDM modulation to become time domain OFDM signals; guard interval insertion unit 40, for the tail ( tail) is inserted before the OFDM signal to prevent ISI (intersymbol interference) in a multipath environment; the synchronization information insertion unit 50 is used to insert the synchronization signal into the time domain, which is TDS- Features of the OFDM method; a shaping filter 60 for shaping and filtering inserted synchronization information for pulse shaping; and an RF (Radio Frequency) unit 70 for transmitting an OFDM signal on a desired frequency band.

Since the TDS-OFDM transmission system inserts synchronization information into the time domain, the receiving end must perform channel equalization and synchronization in the time and frequency domains by using only the time domain synchronization signal, thereby causing a decrease in reception performance of the receiving end.

Contents of the invention

Therefore, an object of the present invention is to solve the above-mentioned problems by providing a multi-carrier transmitting system and a signal processing method thereof, which can insert a PN sequence or general synchronization information into each frequency-domain OFDM signal. One symbol to improve the receiving performance of the receiving end.

According to an aspect of the present invention, a multi-carrier transmission system includes: an FEC unit for performing encoding on frequency-domain data so that a receiving end can detect and correct errors; a mapping unit for mapping the encoded Frequency domain data; a serial/parallel conversion unit, used to accumulate mapped data to N times, so as to output parallel data; a first synchronization information insertion unit, used to insert different first synchronization information with the same length into the parallel data respectively A synchronous information; IDFT unit, is used for carrying out IDFT to the N data that is inserted with this first synchronous information, so that output time domain OFDM signal; Guard interval inserting unit, is used for inserting guard interval before the time domain OFDM signal; And the first The second synchronization information insertion unit is configured to insert the second synchronization information before the time-domain OFDM signal, and the time-domain OFDM signal is inserted with a guard interval.

According to another aspect of the present invention, the signal processing method of the multi-carrier transmission system includes the steps of: performing encoding on the frequency domain data so that the receiving end detects and corrects errors; mapping the encoded frequency domain data by using a predetermined mapping method ; Cumulatively mapped frequency domain data, in order to output parallel data; Insert different first synchronous information with the same length into the parallel data respectively; IDFT is performed on the parallel data inserted with the first synchronous information, so that when outputting a domain OFDM signal; inserting a guard interval before the time domain OFDM signal; and inserting the second synchronization information before the time domain OFDM signal, the time domain OFDM signal having the guard interval inserted.

As mentioned above, the PN sequence is inserted into the frequency domain data, thereby making the reception performance better than that of the conventional TDS-OFDM transmission system.

Description of drawings

The present invention will be described in detail with reference to the accompanying drawings, in which like numerals represent like elements:

FIG. 1 is a schematic block diagram showing a conventional TDS-OFDM transmission system;

2 is a schematic block diagram showing a TDS-OFDM transmission system according to an embodiment of the present invention;

FIG. 3 is a block diagram showing details of the first synchronization information insertion unit 230 in FIG. 2;

Fig. 4 illustrates the flowchart of the signal processing method according to the TDS-OFDM transmission system of the present invention;

Fig. 5 is a flowchart explaining the step of inserting the first synchronous information among Fig. 4;

6a to 6e are diagrams illustrating in detail the steps of inserting first synchronization information shown in FIG. 5. Referring to FIG.

Detailed ways

FIG. 2 is a schematic block diagram showing a TDS-OFDM transmission system according to an embodiment of the present invention. An embodiment of the present invention will be described in detail below with reference to FIG. 3 .

The TDS-OFDM transmission system includes a FEC (Forward Error Correction) unit 100 and an OFDM modulator 200 .

The FEC unit 100 performs encoding in order for the receiving end to detect and correct errors.

The OFDM modulator 200 includes a mapping unit 210, a serial/parallel conversion unit 220, a first synchronization information insertion unit 230, a 3780-point IDFT unit 240, a guard interval insertion unit 250, a parallel/serial conversion unit 260, and a second synchronization information insertion unit 270 , shaping filter 280 and RF (radio frequency) unit 290 .

The mapping unit 210 maps the error-coded OFDM data onto a symbol constellation diagram such as QPSK, 16QAM and 64QAM. The symbol constellation of a common OFDM transmitting system adopts 64QAM.

The serial/parallel conversion unit 220 accumulates a predetermined number of mapped serial symbols to output parallel data. The number of data in the parallel data is determined by the length of the PN sequence inserted by the first synchronization information insertion unit 230 . For example, if the length of the PN sequence is 63( ²ⁿ -1), the parallel data has 63 serial data. Here, the data is in units of symbols, and a PN sequence of length 63 corresponds to 63 symbols.

The first synchronization information insertion unit 230 inserts 3780 a PN sequence, or synchronization information such as data to be input into the IDFT unit 240 . Here, the process of inserting the PN sequence into 3780 data will be described in more detail with reference to FIG. 3 .

The first synchronization information insertion unit 230 includes a spreader 231 , a multiplier 233 and a buffer 235 .

The spreader 231 spreads each of the 63 data from the serial/parallel conversion unit 220 to obtain a length 63 which is the length of the PN sequence, which is multiplied by the data by the multiplier 233 .

The multiplier 233 multiplies each of the 63 spread data having a length of 63 times by a different PN sequence of a length of 63, thereby inserting each PN sequence into each of the 63 data.

The buffer 235 buffers 63 pieces of data multiplied by the PN sequence up to 60 times to output 3780 (3780=63×60) pieces of data to the IDFT unit 240 .

In this embodiment, the number of data output from the serial/parallel conversion unit 220 is the same as the length of the PN sequence multiplied by each data, and the size of the buffer 235 is determined by the length of the PN sequence.

The 3780-point IDFT unit 240 modulates the 3780 data inserted with the PN sequence from the first synchronization information insertion unit 230 to output a time-domain OFDM signal. Here, the OFDM signal consists of 3780 sample data.

The parallel/serial conversion unit 250 converts parallel OFDM symbols into serial OFDM symbols.

The guard interval insertion unit 260 inserts a GI, which copies sampled data truncated from the end of the OFDM symbol, before an OFDM symbol to prevent ISI under multipath conditions. The length of GI can be 1/6, 1/9, 1/12, 1/20 or 1/30 of 3780 sample data.

According to the TDS-OFDM method, in the time domain, the second synchronization information insertion unit 270 inserts synchronization information like a PN sequence before the GI.

The shaping filter 280 performs shaping filtering on the PN sequence according to the OFDM symbols into which the PN sequence is inserted, and the RF unit 290 transmits the OFDM signal on the RF channel.

Fig. 4 shows a flowchart illustrating a signal processing method of a TDS-OFDM transmission system.

The FEC unit 100 performs channel coding so that the receiving end detects and corrects errors (S10).

The mapping unit 210 maps the encoded data onto a symbol constellation such as QPSK, 16QAM, and 64QAM (S20).

The serial/parallel conversion unit 220 accumulates a predetermined number of mapped serial symbols to output parallel symbols (S30). Here, for example, the number of parallel symbols is 63 (the length of the PN sequence).

The first synchronization information insertion unit 230 inserts a PN sequence or synchronization information into each of 3780 pieces of data to be input to the IDFT unit 240 (S40). FIG. 5 is a flowchart explaining step S40 (inserting PN sequence or first synchronization information into 3780 symbols) in detail. The steps of inserting the PN sequences PN1, PN2, etc. into 3780 symbols D1, D2, etc. will be described below with reference to Figs. 6a to 6e.

The spreader 231 spreads each of the parallel data from the serial/parallel conversion unit 220 to obtain a length as long as the PN sequence. Specifically, as shown in 6a, the serial/parallel conversion unit 220 accumulates the mapped serial data D1, D2, etc. from the mapping unit 210 to output parallel data D1, D2, etc. (S30). As shown in FIG. 6c, the spreader 231 spreads each of the 63 symbols to obtain the same length as the PN sequence. That is, the number of data in the parallel data from the serial/parallel converting section 220 is set to the same length as the PN sequence, 63. The multiplier 233 multiplies the 63 spreading symbols D1, D2, etc., each of which has a length of 63 times, by different PN sequences PN1, PN2, etc., each having a length of 63 (S43). Figure 6e shows the 63 symbols multiplied by the PN sequence respectively.

Buffer 235 buffers 63 pieces of data D1, D2, etc. multiplied by PN sequences PN1, PN2, etc. up to 60 times to output 3780 (3780=63×60) symbols to IDFT unit 240 (S45).

The 3780-point IDFT unit 240 modulates the 3780 symbols inserted with the PN sequence from the first synchronization information insertion unit 230 into time-domain OFDM symbols (or 3780 sample data) (S50).

The parallel/serial conversion unit 250 converts parallel OFDM symbols into a serial form (S60).

The guard interval inserting unit 260 inserts before the OFDM symbol a GI that copies sample data intercepted from the end of the OFDM symbol (S70).

The second synchronization information inserting unit 270 inserts synchronization information like a PN sequence before the GI (S80).

The shaping filter 280 shapes-filters the PN sequence with respect to the OFDM symbol into which the PN sequence is inserted, and the RF unit 290 transmits the OFDM signal on an RF channel (S90).

As described above, a PN sequence of a predetermined length or synchronization information is added to each frequency domain symbol. This enables improved reception performance such as synchronization acquisition and channel equalization at the receiving end.

According to the present invention, the PN sequence is inserted into multiple frequency domain symbols, thereby making the receiving performance better than that of the traditional TDS-OFDM transmitting system.

Although the present invention has been described with reference to certain preferred embodiments thereof, it will be understood by those skilled in the art that changes may be made in form and in the present invention without departing from the spirit and scope of the invention as defined by the appended claims. Various modifications in details.

The embodiments and advantages described above are exemplary only and do not limit the invention. The inventive concept can be used in other types of devices. The description of the present invention is illustrative and does not limit the scope of the claims. Many alternatives, modifications and variations will be apparent to those skilled in the art. In the claims, means-plus-function clauses are intended to include the structures described herein as performing the recited function and not only structurally equivalent means but also means equivalent to such structures.

Claims (8)

1. A multi-carrier transmission system comprising: an FEC unit for performing encoding on the frequency domain data in order to enable the receiving end to detect and correct errors; a mapping unit for mapping the encoded frequency domain data by using a predetermined mapping method; A serial/parallel conversion unit for accumulating mapped data to N times so as to output parallel data, wherein the parallel data is composed of K data, and N=KxM, where N, K and M are natural numbers; The first synchronization information insertion unit, the first synchronization information insertion unit includes a frequency spreader, a multiplier and a buffer, wherein the frequency spreader is used to spread the K data, so as to obtain the same data as the first synchronization information length, the multiplier is used to multiply the spread K data by the first synchronization information, so as to insert the first synchronization information into the K data, and the buffer is used to multiply the first synchronization information K data is buffered up to M times in order to output N data; An IDFT unit, configured to perform IDFT on the N pieces of data inserted with the first synchronization information, so as to output a time-domain OFDM signal; A guard interval insertion unit, configured to insert the guard interval before the time-domain OFDM signal; and The second synchronization information inserting unit is configured to insert the second synchronization information before the time-domain OFDM signal, and the time-domain OFDM signal is inserted with a guard interval. 2. The multi-carrier transmission system as claimed in claim 1, wherein the first synchronization information is a PN sequence, and the number K of the parallel data is equivalent to the length of the PN sequence. 3. The multi-carrier transmission system as claimed in claim 1, wherein the length of the PN sequence is ²ⁿ -1, and K is ²ⁿ -1, wherein n is a natural number. 4. The multi-carrier transmission system of claim 1, wherein N is 3780, K is 63 and M is 60. 5. A signal processing method of a multi-carrier transmission system, comprising steps: Encoding is performed on frequency-domain data so that errors are detected and corrected at the receiver: mapping the encoded frequency domain data by using a predetermined mapping method; accumulating the mapped frequency domain data so as to output parallel data, wherein the parallel data is composed of K data, and the N=KxM, where N, K and M are natural numbers; Spread spectrum on the K pieces of data, so as to obtain the same length as the first synchronization information; multiplying the spread K data by the first synchronization information, so as to insert the first synchronization information into the K data; Buffering the K data multiplied by the first synchronization information up to M times, so as to output N data; performing IDFT on the parallel data inserted with the first synchronization information, so as to output a time-domain OFDM signal; Inserting a guard interval before the time-domain OFDM signal; and Inserting the second synchronization information before the time-domain OFDM signal, the time-domain OFDM signal being inserted with a guard interval. 6. The signal processing method according to claim 5, wherein the first synchronization information is a PN sequence, and the number K of the parallel data is equivalent to the length of the PN sequence. 7. The signal processing method according to claim 5, wherein the length of the PN sequence is ²ⁿ -1, and K is ²ⁿ -1, wherein n is a natural number. 8. The signal processing method according to claim 5, wherein N is 3780, K is 63, and M is 60.

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