CN1697441A - Method for modulating digital broadcast signal by orthogonal frequency division multiplexing multicarrier and transmitter - Google Patents
Method for modulating digital broadcast signal by orthogonal frequency division multiplexing multicarrier and transmitter Download PDFInfo
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- CN1697441A CN1697441A CNA2005100750206A CN200510075020A CN1697441A CN 1697441 A CN1697441 A CN 1697441A CN A2005100750206 A CNA2005100750206 A CN A2005100750206A CN 200510075020 A CN200510075020 A CN 200510075020A CN 1697441 A CN1697441 A CN 1697441A
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L27/00—Modulated-carrier systems
- H04L27/26—Systems using multi-frequency codes
- H04L27/2601—Multicarrier modulation systems
- H04L27/2626—Arrangements specific to the transmitter only
- H04L27/2627—Modulators
- H04L27/2634—Inverse fast Fourier transform [IFFT] or inverse discrete Fourier transform [IDFT] modulators in combination with other circuits for modulation
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04J—MULTIPLEX COMMUNICATION
- H04J13/00—Code division multiplex systems
- H04J13/0007—Code type
- H04J13/0022—PN, e.g. Kronecker
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L27/00—Modulated-carrier systems
- H04L27/26—Systems using multi-frequency codes
- H04L27/2601—Multicarrier modulation systems
- H04L27/2602—Signal structure
- H04L27/26025—Numerology, i.e. varying one or more of symbol duration, subcarrier spacing, Fourier transform size, sampling rate or down-clocking
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L27/00—Modulated-carrier systems
- H04L27/26—Systems using multi-frequency codes
- H04L27/2601—Multicarrier modulation systems
- H04L27/2602—Signal structure
- H04L27/2605—Symbol extensions, e.g. Zero Tail, Unique Word [UW]
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N7/00—Television systems
- H04N7/015—High-definition television systems
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Abstract
A Method for modulating digital broadcast signal by orthogonal frequency division multiplexing OFDM multicarrier and transmitter and an OFDM transmitter are provided. The method comprises steps: according to the number of subcarriers, modulating quadrature amplitude of the transmission stream signal through forward error correction coding, generating serial elements; collecting and converting serial elements into parallel elements; executing 2<N> IFFT of parallel elements, obtaining OFDM elements from the parallel elements, wherein, N is a positive integer; inserting GI into elements processed by 2<N> IFFT, generating parallel OFDM elements of GI; converting parallel OFDM elements of GI into serial OFDM elements; inserting a PN sequence into the serial OFDM elements; pulse shaping and filtering sigals inserted with PN through a SRRC filter; doing up conversion for the signals filtered by the SRRC filter and sending out the signals. By using the transmitter and the method of the invention, the calculation required by the OFDM multicarrier modulation is reduced, the circuit design of the system is simple, the simple hardware is obtained.
Description
The application is to be that January 16, application number in 2003 are 03101802.5, are entitled as the dividing an application of patent application of " method of modulating digital broadcast signal by orthogonal frequency division multiplexing multicarrier and transmitter " applying date.
Technical field
The present invention relates to a kind of method that is used to use time-domain synchronization OFDM (OFDM) transmitter OFDM multi-carrier modulation digital broadcast signal, more particularly, the method that relates to a kind of OFDM of use transmitter OFDM multi-carrier modulation digital broadcast signal, in the method, quantity by subcarrier is set, the frequency interval between the subcarrier and be used for (roll-off) factor of roll-offing of shaping filter, can improve the spectrum efficiency of ofdm signal, so that send ofdm signal by multi-subcarrier.
Background technology
Usually, the broadcast system of a digital high-definition television (HDTV) can be decomposed into a video encoder and a modulator.Video encoder becomes the digital data compression of about 1GHz that the video source from high definition obtains 15Mbps to the data the 18Mbps.Modulator to the band-limited channel of 8MHz, sends to recipient with the numerical data of tens Mbps by 6MHz.The digital HDTV broadcast system adopts terrestrial broadcast system, and described terrestrial broadcast system is used for very high frequency (the VHF)/ultra-high frequency (UHF) of existing TV broadcasting.
The example that is used for the modulating system of this type of digital broadcasting comprises quadrature amplitude modulation (QAM) system and a residual sideband (VSB) modulating system.In Europe, advanced HDTV terrestrial broadcast system has adopted the modulating system that can obtain dual effect, described dual effect be meant unit bandwidth transmission rate raising and to the effect of preventing of disturbing and so on.
The OFDM modulating system has the signal waveform that equates with white Gauss noise.Correspondingly, the OFDM modulating system has the advantage of the interference littler than other broadcast service system, and described other broadcast service system is meant line-by-line inversion (PAL) system and order and storage color TV (SECAM) system.Similarly, the OFDM modulating system can have different modulating systems on each carrier wave, thereby can hierarchical transmission.
Usually, the frequency band that uses the OFDM transmitter of TDS transmission OFDM signal to pass through to be distributed provides service.In this case, be the frequency bandwidth of the signal allocation 8Mz such as ofdm signal.The OFDM transmitter will be rearranged about the ofdm signal that frequency axis produces along time shaft; and; to be used to suppress the protection interval (GI) of interference between signals, be inserted into along the front of the ofdm signal of time shaft formation, and the front that synchronizing information is inserted into GI.
In traditional TDS-OFDM transmitter, provide 3780 subcarriers, and the frequency interval between the subcarrier is set at 2KHz.Fig. 1 shows the traditional OFDM transmitter that adopts 3780IFFT.In order to simplify its structure and realization, and in order to handle 3780 subcarriers, traditional TDS-OFDM transmitter adopts 3780IFFT.
As shown in fig. 1, this transmitter comprises: forward error correction (FEC) coding unit 100, mapper 120, serial (S/P) transducer 140,3780 contrary fast fourier transform (IFFT) unit 160, GI insert unit 180, parallel/serial convertor (P/S) 200, the insertion of PN sequence unit 220, pulse shaping filter 240 and radio frequency (RF) up converter 260.
The 3780IFFT from the parallel TS signal of serial transducer 140 is carried out in 3780IFFT unit 160, so that obtain the subcarrier of OFDM multi-carrier modulation.
Parallel/serial convertor 200 becomes the TS signal of serial to the parallel TS conversion of signals of inserting unit 180 from GI, and the quantity of described parallel TS signal is corresponding with counting of IFFT.
The PN sequence is inserted unit 220 and the PN sequence is inserted in the ofdm signal of the GI with insertion, the PN sequence is meant the synchronizing information of the channel that is used to estimate synchronizing signal and be used to estimate the ofdm signal that received by the OFDM receiver, and described OFDM receiver receives the ofdm signal that is sent out.The PN sequence is inserted unit 200 and is produced and the corresponding pulse frequency of ofdm signal, and described ofdm signal has been inserted into the PN sequence.
RF up converter 260, the ofdm signal up conversion that shaping filter 240 shaping filters are crossed becomes the RF signal.The RF signal that is obtained sends to receiver by antenna 280.
Fig. 2 is the figure that the example of the ofdm signal multicarrier of modulating according to the OFDM transmitter of Fig. 1 is described.With reference to figure 2, for the bandwidth of OFDM broadcast allocation is 8MHz, signal bandwidth is 7.56MHz, and the extra bandwidth that can be used in the pulse shaping filter is 0.44MHz (both sides in bandwidth is respectively 0.22MHz).With the quantity of the subcarrier of the corresponding ofdm signal of effective bandwidth be ' N (=3780 ', and the frequency interval between the subcarrier be ' d ' Hz (=2kHz).
So in traditional TDS-OFDM transmitter, when 3780IFFT unit 160 was used to the TDS transmission, the calculating operation amount that is used for IFFT was very big.In this case, need to carry out the circuit of the calculating operation amount that increases.Owing to this reason, the circuit structure that traditional OFDM transmitter as shown in fig. 1 has the complexity that is used for IFFT, and, on hardware, become complicated.And the OFDM receiver that receives ofdm signal from the OFDM transmitter also becomes complicated on hardware.
And the occupied bandwidth of the broadcast singal that is used to transmit accounts for the 7.56MHz of the 8MHz that is distributed.In this case, can be used within the 8MHz that is distributed that roll-off factor in the pulse shaping filter is approximate to be lower than 0.0582.Like this, on the occupied bandwidth of 7.56MHz, pulse shaping filter 240 just need have the transmission bandwidth of the sensitivity that is lower than 0.0582 roll-off factor.If pulse shaping filter 240 is carried out the shaping filter of this sensitivity, the problem of fluctuation appears in the both sides that will be created in the signal by pulse shaping filter 240.The signal that has occurred fluctuation in signal distortion just occurred with respect to original transmission signal, and the receiver side that has received the signal of distortion just can not recover this primary signal.
Be set to too for a short time if be used for the roll-off factor of shaping filter, shake will occur, therefore destroy receptivity at the receiver side of shaping filter.
From the above, according to the quantity of subcarrier, in the traditional OFDM transmitter shown in Fig. 1, the quantity that IFFT is ordered is 3780.In the art, people know that 3780IFFT is not easy to realize with hardware and/or software, and the amount of calculation that is used for 3780IFFT is very big.Similarly, the performance of pulse shaping filter 240 can not be optimised, because the roll-off factor of pulse shaping filter can not be provided with suitably.
So, need improved OFDM transmitter a kind of high computational speed and simple in structure and that receptivity improves.
Summary of the invention
Correspondingly, main purpose of the present invention provides a kind of OFDM transmitter, and this OFDM transmitter can reduce the calculating that is used for IFFT, and can improve the performance of shaping pulse filtering.
Second purpose of the present invention provides a kind of OFDM transmitter, and by inserting the protection bandwidth, this OFDM transmitter can further improve data transmission performance.
The 3rd purpose of the present invention provides a kind of method that is used to use OFDM transmitter OFDM multi-carrier modulation digital broadcast signal, in the method, can avoid owing to the complexity that is used on the hardware that multi-carrier modulation causes with the IFFT that sends ofdm signal, and, can obtain the performance of the improvement of shaping pulse filtering.
The 4th purpose of the present invention provides a kind of method of the OFDM of being used for multi-carrier modulation digital broadcast signal, and by inserting the protection bandwidth, this method can further improve data transmission performance.
For realizing above-mentioned purpose of the present invention, a kind of method that is used to use OFDM transmitter OFDM multi-carrier modulation digital broadcast signal is provided, the method comprising the steps of: (a) according to the quantity of subcarrier, execution is through the quadrature amplitude modulation (QAM) of transport stream (TS) signal of forward error correction coding, to produce serial code element, wherein, the quantity of described subcarrier is configured to corresponding with a bandwidth that is assigned with of ofdm signal; (b) assemble described serial code element, and convert thereof into paralleled code element; (c) carry out 2
NThe contrary fast fourier transform (IFFT) of the paralleled code element of individual point, so that obtain the OFDM code element from paralleled code element, wherein, N is a positive integer; (d) will protecting at interval, (GI) is inserted into described 2
NIn the code element that IFFT handled, has the parallel OFDM code element of the GI of insertion with generation; (e) the described parallel OFDM code element that will have a GI of insertion converts the OFDM code element of serial to; (f) the PN sequence is inserted in the OFDM code element of described serial; (g) with square root raised cosine (SRRC) filter the signal that has inserted PN is carried out shaping pulse filtering; And (h) will carry out up conversion through the signal of described SRRC filtering and send, wherein, N is any one among 11,12 and 13, and the roll-off factor of described square root raised cosine filter is from 0.08 to 0.12 scope.
According to a second aspect of the invention, provide a kind of OFDM transmitter.This OFDM transmitter comprises: forward error correction (FEC) coding unit is used for the broadcast singal coding that will be sent out, so that be corrected in the mistake that occurs in the transmission; Quadrature amplitude modulation (QAM) modulating unit, be used for quantity, carry out the quadrature amplitude modulation (QAM) of FEC encoded signals, to produce serial code element according to subcarrier, wherein, the quantity of described subcarrier is configured to corresponding with a bandwidth that is assigned with of ofdm signal; The serial transducer is used to assemble described serial code element, and converts thereof into paralleled code element; 2
NThe IFFT unit is used for the described paralleled code element from described serial transducer is carried out 2
NThe IFFT of individual point, with the OFDM code element that obtains to walk abreast, wherein, N is an integer; GI inserts the unit, is used for GI is inserted into from described 2
NIn the described parallel OFDM code element of IFFT unit (300) output; Parallel/serial convertor, the parallel OFDM code element that has been used for the insertion of inserting unit (180) from described GI GI converts the OFDM code element of serial to; The PN sequence is inserted the unit, is used for the PN sequence is inserted into the OFDM code element of the described serial of the GI with insertion; Pulse shaping filter is used for according to set roll-off factor, and the OFDM code element of the serial of PN sequence with insertion is carried out shaping filter; Radio frequency (RF) up converter, be used for by described pulse shaping filter shaping filter the ofdm signal up conversion of serial become the RF signal, and give receiver by antenna transmission with it, wherein, N is any one among 11,12 and 13, and the roll-off factor of described pulse shaping filter is from 0.08 to 0.12 scope.
According to a preferred embodiment of the invention, can be by 2
NIFFT carries out the OFDM multi-carrier modulation of TS signal, like this, just can reduce the needed amount of calculation of OFDM multi-carrier modulation.In this case, the circuit of design system simply just, and obtain simple hardware.
Description of drawings
In conjunction with the drawings with reference to following detailed, many attendant advantages of the present invention become better understood and become clear easily, and wherein, same label is represented identical or similar assembly, wherein:
Fig. 1 is the block diagram that the traditional OFDM transmitter of 3780IFFT has been used in explanation;
Fig. 2 be key diagram 1 multi-carrier modulation the figure of an example of ofdm signal;
Fig. 3 A has illustrated according to a preferred embodiment of the invention application 2
NThe block diagram of the OFDM transmitter of IFFT;
Fig. 3 B has illustrated the structure of the data of having inserted the protection bandwidth in the OFDM transmitter shown in Fig. 3 A.
Fig. 4 is the flow chart of the method for the explanation OFDM transmitter OFDM multi-carrier modulation data broadcasting signal that is used to use Fig. 3 A.
Embodiment
Now, with the OFDM transmitter and the method thereof that are described in detail with reference to the attached drawings according to the OFDM of being used for multi-carrier modulation data broadcasting signal of the present invention.
Fig. 3 A is the block diagram that OFDM transmitter according to a preferred embodiment of the invention is described, this OFDM transmitter has been used and has been used to the TDS transmission and the method for OFDM multi-carrier modulation digital broadcast signal.
OFDM transmitter according to the present invention as shown in Figure 3 has similar structure to the OFDM transmitter shown in Fig. 1.With reference to figure 3A, this transmitter comprises: forward error correction (FEC) coding unit 100, mapper 120, serial (S/P) transducer 140,2
NIFFT unit 300 (there, N is an integer), GI insert unit 180, parallel/serial convertor (P/S) 200, the insertion of PN sequence unit 220, pulse shaping filter 320 and radio frequency (RF) up converter 260.
In a preferred embodiment of the invention, the example of quadrature amplitude modulation (QAM) modulating unit is a mapper 120.The QAM modulating unit according to the quantity of subcarrier, is carried out the quadrature amplitude modulation (QAM) through the TS of forward error correction coding signal, and to produce serial code element, wherein, the quantity of described subcarrier is configured to corresponding with a bandwidth that is assigned with of ofdm signal.
2
NThe 300 pairs of paralleled code elements from serial transducer 140 in IFFT unit carry out 2
NThe IFFT computing so that obtain the OFDM code element.Here, the number that is used for the point of IFFT is at least 2048 (=2
11), 4096 (=2
12) and 8192 (=2
13) among one, that is, N is that value is an integer of 11,12 or 13.People in this area know, compare with traditional 3780IFFT, and number is that the number by the handled point of IFFT of 2 integer power can make the realization of hardware and/or software I FFT simplify significantly.
Parallel/serial convertor 200 insert from GI unit 180 through 2
NThe parallel OFDM code element that IFFT handles converts the OFDM code element of serial to, and is described through 2
NThe quantity of the parallel OFDM code element that IFFT handles is corresponding with counting of IFFT.
The PN sequence is inserted in the OFDM code element of serial that unit 220 is inserted into the PN sequence GI with insertion.The PN sequence is meant the synchronizing information of the channel that is used to estimate synchronizing signal and be used to estimate the ofdm signal that received by the OFDM receiver.
The ofdm signal up conversion that RF up converter 260 is crossed shaping filter 240 shaping filters becomes the RF signal.The RF signal that is obtained sends to receiver by antenna 280.
In a preferred embodiment of the invention, 2
N IFFT unit 300 is provided for the multi-carrier modulation of TS signal, and like this, the needed calculating of OFDM multi-carrier modulation can significantly reduce.In this case, the circuit of design system simply, and can obtain simple hardware.
In the ofdm signal modulation based on multicarrier according to the present invention, the sequence of symhols that serial transducer 140 is imported the ground of serial converts the parallel data of predetermined block unit to, and with paralleled code element and different subcarrier multiplex.During this time, multicarrier has mutual orthogonality.The meaning of orthogonality is: the product of two carrier waves is ' 0 '.Correspondingly, orthogonality is necessary for multicarrier.In a preferred embodiment of the invention, the OFDM modulating system can be realized by the IFFT of transmitter and the FFT of receiver.
The signal through the OFDM multi-carrier modulation according to a preferred embodiment of the invention comprises that each all has the multi-subcarrier of little bandwidth.Entire spectrum according to the ofdm signal of the bandwidth that is assigned with has square shape.Correspondingly, OFDM multicarrier modulation system according to the present invention has frequency efficiency relatively preferably than the OFDM modulating system based on single carrier wave.
Simultaneously, in the OFDM multicarrier modulation system based on the OFDM transmitter according to an embodiment of the invention, be different from 3780 subcarriers of Fig. 1, the subcarrier that is used for IFFT here has been provided 2
NIndividual (for example 2048,4096,8192).That is to say, in an embodiment of the present invention, with the quantity of the corresponding subcarrier of bandwidth that distributes the 8MHz be used to broadcast be 2
NIndividual.
Now, the description that is used for the selection of roll-off factor according to of the present invention will be provided.
In an embodiment of the present invention, the frequency interval between the subcarrier ' d ' is arranged within the predetermined scope changeably, like this, and from 2
NIn the individual subcarrier, comprise that the quantity of subcarrier of the effective bandwidth of actual OFDM signal is used to multi-carrier modulation.
For the effective piece with subcarrier, GI insertion unit 180 is inserted into GI from 2 with an interval of 1/4,1/8,1/16 and 1/32
NIn the parallel OFDM code element of IFFT unit 300 outputs.
The sum ' N ' of supposing subcarrier is configured to 2048,4096 and 8192, frequency interval between the subcarrier is ' d ', and the roll-off factor of SRRC filter is ' r ', and the summation of the effective bandwidth of SRRC filter and extra bandwidth can be by following expression:
(d×N)+(d×N)r≤8MHz………………(1)
Roll-off factor is pressed following acquisition:
As general knowledge, frequency interval d should be greater than 0.85KHz, and like this, subcarrier just can be separated fully, and, can reduce the interference between the subcarrier.
Consider the above-mentioned analysis about frequency interval ' d ', the bandwidth of ofdm signal is assumed to be it is to the scope between the 7.4MHz, so that increase the roll-off factor of pulse shaping filter at 7.14MHz.
In the situation of OFDM transmitter with 7.14MHz bandwidth, frequency interval d is 7.14MHz/N=3.49KHz, 1.74KHz or 0.87KHz, and described 3.49KHz, 1.74KHz or 0.87KHz are corresponding with 2048,4096 and 8196 N value respectively.From formula (2) as can be seen, for three values of ' N ', the item on the right side in aforementioned equation (2) is 0.12, that is, ' r ' value that is calculated is for being less than or equal to 0.12.Its result provides as follows:
When r≤0.12,
For the SRRC filter, roll-off factor is big more, and then the distortion of SRRC filter is just more little.Similarly, the hardware complexity of filter can be simplified significantly.So use value is 0.12 roll-off factor in an embodiment of the present invention.
More particularly, owing to can reduce distorted signals in the both sides of SRRC filter 700, so, can reduce distortion by the subcarrier institute data carried by data that is positioned at two ends.Then, by RF up converter 260, be sent to wireless channel at the ofdm signal of SRRC filter 320 filtering.
And, along with the roll-off factor of SRRC filter is selected suitably, can improve the performance of SRRC filtering significantly.Also have,, just can improve the performance of unifrequency network (SFN) if use the method that is used to modulate multicarrier according to an embodiment of the invention to come the Modulation OFDM signal.This SFN is used for broadcasting a broadcast program with single-frequency.In this case, the interference meeting on a channel significantly increases.Ofdm signal based on modulating system is strong for SFN according to an embodiment of the invention.Thereby, can improve the performance of the ofdm signal under this SFN.
As another example, protection bandwidth (GB) is inserted unit 320 and is positioned at S/ P transducer 140 and 2
NBetween the IFFT unit 300.In the input data is M (＜2
N) under the situation of (there, N is an integer), S/P transducer 140 is assembled serial code element M (＜2
N), and convert thereof into paralleled code element.Paralleled code element is entering 2
NBefore the IFFT unit 300, can insert unit 320 by GB earlier.Specifically, GB inserts unit 320 and receives paralleled code element M (＜2
N), and will
Be inserted into paralleled code element M (＜2
N) both sides, 2
N IFFT unit 300 inserts unit 320 from GB and receives the paralleled code element that has inserted GB, and carry out be used to modulate 2
NIFFT.The data structure that obtains is as shown in Fig. 3 B.For example, GB provides from GB data (being generally zero) feeder (not shown).
Base band frequency (=system works frequency) is (2
N* MHz subcarrier spacing).So the PN sequence has (2
N* the chip rate of MHz subcarrier spacing).Therefore, the extra bandwidth of pulse shaping filter is less than (8-2
N* MHz subcarrier spacing).The roll-off factor of pulse shaping filter has
Scope.The roll-off factor of pulse shaping filter is big more, and hardware complexity and the distorted signals such as inter symbol interference (ISI) are just more little.As mentioned above, the scope that has of GB is GB 〉=(roll-off factor * 2
N* subcarrier spacing, it is an extra bandwidth) so that avoid the distortion of the ofdm signal that causes owing to pulse shaping filter.For example, if roll-off factor is 0.12, and N is 12, then 2
N* subcarrier spacing ≈ 7.14MHz.Subcarrier spacing approximately is 1.74KHz.In this case, the GB scope that can have is GB≤0.85MHz.By using above data, the quantity M of specified data easily.
From as can be known above-mentioned, insert GB by both sides at serial code element, Data-carrying is on the effective bandwidth of carrier wave.Therefore, the data of transmission can not lost, and this makes that the transmission of data is more reliable.
Fig. 4 is the flow chart of the method for the explanation OFDM transmitter OFDM multi-carrier modulation digital broadcast signal that is used to use Fig. 3 A.
With reference to figure 3A and Fig. 4, in step S100, FEC coding unit 100 is the broadcast singal coding that will be transmitted, so that be corrected in the mistake that occurs in the transmission.
Then, in step S110, mapper 120 will be mapped to the transport stream (TS) of the serial that comprises code element through the FEC encoded signals.Be used as in the situation of mapper 120 at the QAM modulating unit, according to the quantity of subcarrier, the TS signal of forward error correction coding carried out quadrature amplitude modulation (QAM), to produce serial code element.
In step S120, serial transducer 140 is assembled serial code elements, and converts thereof into paralleled code element, described serial code element be for error correction by FEC coding unit 100 symbols encoded.
In step S130,2
NThe 300 pairs of paralleled code elements from serial transducer 140 in IFFT unit carry out 2
NThe IFFT computing of individual point is to obtain the OFDM code element.Here, the quantity that is used for the point of IFFT is 2048 (=2
11), 4096 (=2
12) and 8192 (=2
13) among at least one.
Next, in step S140, GI inserts unit 180 and inserts protection (GI) at interval, so as restriction with from the interference between the OFDM code element of the OFDM code element vicinity of 2NIFFT unit 300 outputs.
Then, in step S150, parallel/serial convertor 200 insert from GI unit 180 outputs through 2
NThe paralleled code element that IFFT handles converts the OFDM code element of serial to.
In step S160, the PN sequence is inserted in the OFDM code element of serial that unit 220 is inserted into the PN sequence GI with insertion.
Then, in step S170, pulse shaping filter 320 is used the SRRC filter according to set roll-off factor, and the OFDM code element of the serial of PN sequence with insertion is carried out shaping filter, and the scope of described roll-off factor is from 0.08 to 0.12.Preferably, this roll-off factor is 0.12.
At last, in step S180, RF up converter 260 through pulse shaping filters 320 shaping filters ofdm signal convert the RF signal to.The RF signal that is obtained sends to receiver by antenna 280.
In the situation that GB inserts, method of the present invention also comprises a step S190 after step S120.More particularly, in step S190, from the serial code element M (＜2 of S/P transducer 140
N) entering 2
NCan insert unit 320 by GB earlier before the IFFT unit 300, there, GB inserts unit 320 at the serial code element M (＜2 from S/P transducer 140
N) both sides insert
Next, processing procedure proceeds to step S130, and there, the paralleled code element that has inserted GB is 2
NStand in the IFFT unit 300 to be used to modulate 2
NThe IFFT computing.The data structure that obtains is as shown in Fig. 3 B.For example, GB provides from GB data (being generally zero) feeder (not shown).
According to a preferred embodiment of the invention, can be by 2
NIFFT carries out the OFDM multi-carrier modulation of TS signal, like this, just can reduce the needed calculating of OFDM multi-carrier modulation significantly.In this case, the circuit of system can design simply, and can obtain simple hardware.And with the pulse shaping filter of optimized roll-off factor, pulse shaping filter just can be carried out the shaping filter of sensitivity, and, the fluctuation in the both sides appearance of the signal by pulse shaping filter is minimized.
And the OFDM transmitter according to band GB insertion unit inserts GB by the both sides at serial code element, and data just can be carried on the effective bandwidth of carrier wave.Therefore, the data of transmission will can not lost, and this makes that the transmission of data is more reliable, and, further improved transmission performance.
Although described the preferred embodiments of the present invention, should be understood that the present invention should not be limited in this preferred embodiment, but, within the spirit and scope of the invention that claims limit, those of skill in the art can carry out variations and modifications.
Claims (11)
1. one kind is used to use orthogonal frequency division multiplex ransmitting to send the method for device modulating digital broadcast signal by orthogonal frequency division multiplexing multicarrier, comprises step:
(a) according to the quantity of subcarrier, carry out the quadrature amplitude modulation through the transmission stream signal of forward error correction coding, to produce serial code element, wherein, the quantity of described subcarrier is configured to corresponding with a bandwidth that is assigned with of orthogonal frequency-division multiplex singal;
(b) assemble described serial code element, and convert thereof into paralleled code element;
(c) carry out 2
NThe contrary fast fourier transform of the paralleled code element of individual point, so that obtain the OFDM code element from paralleled code element, wherein, N is a positive integer;
(d) will protect the interval to be inserted into described 2
NIn the code element that contrary fast fourier transform was handled, has the protection parallel OFDM code element at interval of insertion with generation;
(e) the protection described parallel OFDM code element at interval that will have an insertion converts the OFDM code element of serial to;
(f) pseudo noise sequence is inserted in the OFDM code element of described serial;
(g) with square root raised cosine filter the signal that has inserted pseudo noise is carried out shaping pulse filtering; And
(h) will carry out up conversion through the signal of described square root raised cosine filtering and send,
Wherein, N is any one among 11,12 and 13, and
The roll-off factor of described square root raised cosine filter is from 0.08 to 0.12 scope.
2. method as claimed in claim 1, wherein, the bandwidth that is assigned with of orthogonal frequency-division multiplex singal is about 7.14MHz, and with the quantity of the corresponding subcarrier of bandwidth that is distributed be among 2048,4096 and 8192 any one.
3. method as claimed in claim 2 wherein, is inserted protection at interval at interval with 1/4,1/8,1/16 and 1/32 of the shared bandwidth of subcarrier.
4. method as claimed in claim 3, wherein, the roll-off factor of described square root raised cosine filter is 0.12.
5. the method for claim 1; in step (b) afterwards; also comprise a step (b '); in described step (b '); the protection bandwidth is inserted into the both sides of the described paralleled code element of described step (b), and will insert and protect the paralleled code element of bandwidth to be provided to described step (c).
6. an orthogonal frequency division multiplex ransmitting send device, comprising:
The forward error correction coding unit is used for the broadcast singal coding that will be sent out, so that be corrected in the mistake that occurs in the transmission;
The quadrature amplitude modulation modulating unit, be used for quantity, carry out the quadrature amplitude modulation of the signal of forward error correction coding, to produce serial code element according to subcarrier, wherein, the quantity of described subcarrier is configured to corresponding with a bandwidth that is assigned with of orthogonal frequency-division multiplex singal;
The serial transducer is used to assemble described serial code element, and converts thereof into paralleled code element;
2
NContrary fast Fourier transform unit is used for the described paralleled code element from described serial transducer is carried out 2
NThe contrary fast fourier transform of individual point, with the OFDM code element that obtains to walk abreast, wherein, N is an integer;
Protection is inserted the unit at interval, is used for protection is inserted at interval from described 2
NIn the described parallel OFDM code element of contrary fast Fourier transform unit (300) output;
Walk abreast/serial convertor, the parallel OFDM code element that has been used for the insertion of inserting unit (180) from described protection at interval the protection interval converts the OFDM code element of serial to;
Pseudo noise sequence is inserted the unit, is used for pseudo noise sequence is inserted into the OFDM code element of the protection described serial at interval with insertion;
Pulse shaping filter is used for according to set roll-off factor, and the OFDM code element of the serial of pseudo noise sequence with insertion is carried out shaping filter;
The radio frequency up converter, be used for by described pulse shaping filter shaping filter the orthogonal frequency-division multiplex singal up conversion of serial become radiofrequency signal, and give receiver by antenna transmission with it,
Wherein, N is any one among 11,12 and 13, and
The roll-off factor of described pulse shaping filter is from 0.08 to 0.12 scope.
7. transmitter as claimed in claim 6, wherein, the bandwidth that is assigned with of orthogonal frequency-division multiplex singal is about 7.14MHz, and with the quantity of the corresponding subcarrier of bandwidth that is distributed be among 2048,4096 and 8192 any one.
8. transmitter as claimed in claim 7 wherein, inserts protection at interval at interval with 1/4,1/8,1/16 and 1/32 of the shared bandwidth of subcarrier.
9. transmitter as claimed in claim 8, wherein, the roll-off factor of described pulse shaping filter is 0.12.
10. transmitter as claimed in claim 8, wherein, described pulse shaping filter is a square root raised cosine filter.
11. transmitter as claimed in claim 6 also comprises a protection bandwidth insertion unit, this protection bandwidth is inserted unit and is positioned at described serial transducer and described 2
NBetween the contrary fast Fourier transform unit, be used for receiving described paralleled code element, and will protect bandwidth to be inserted into the both sides of described paralleled code element, and will insert and protect the paralleled code element of bandwidth to offer described 2 from described serial transducer
NContrary fast Fourier transform unit.
Applications Claiming Priority (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| KR1020020032070 | 2002-06-07 | ||
| KR1020020032070A KR100698283B1 (en) | 2002-06-07 | 2002-06-07 | A method for OFDM multi-carrier modulating a digital broadcasting signal using the TDS-OFDM transmitter |
| KR1020020032256 | 2002-06-10 | ||
| KR1020020032257 | 2002-06-10 |
Related Parent Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN 03101802 Division CN1212734C (en) | 2002-06-07 | 2003-01-16 | Method for modulating digital broadcast signal by orthogonal frequency division multiplexing multicarrier and transmitter |
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| Publication Number | Publication Date |
|---|---|
| CN1697441A true CN1697441A (en) | 2005-11-16 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CNA2005100750206A Pending CN1697441A (en) | 2002-06-07 | 2003-01-16 | Method for modulating digital broadcast signal by orthogonal frequency division multiplexing multicarrier and transmitter |
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| KR (1) | KR100698283B1 (en) |
| CN (1) | CN1697441A (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101442677B (en) * | 2007-11-23 | 2010-12-22 | 卓胜微电子（上海）有限公司 | Hardware architecture for decoding FEC of DMB-T demodulation chip and decoding method |
| US8743981B2 (en) | 2009-06-16 | 2014-06-03 | Huawei Technologies Co., Ltd. | Modulation method and apparatus |
| CN102629886B (en) * | 2006-11-09 | 2014-12-31 | 日本无线株式会社 | Broadcasting system |
Families Citing this family (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| KR20030094909A (en) * | 2002-06-10 | 2003-12-18 | 삼성전자주식회사 | A method for OFDM multi-carrier modulating a digital broadcasting signal using the TDS-OFDM transmitter |
| KR20030094910A (en) * | 2002-06-10 | 2003-12-18 | 삼성전자주식회사 | A method for OFDM multi-carrier modulating a digital broadcasting signal using the TDS-OFDM transmitter |
| KR20040035288A (en) * | 2002-10-19 | 2004-04-29 | 삼성전자주식회사 | Multi-carrier transmission system capable of improving the performance of receiving and a method proessing signal thereof |
| KR100920722B1 (en) * | 2002-10-19 | 2009-10-07 | 삼성전자주식회사 | Multi-carrier transmission system capable of improving the performance of receiving and a method proessing signal thereof |
| KR20070103917A (en) * | 2006-04-20 | 2007-10-25 | 엘지전자 주식회사 | Method of inserting guard interval and apparatus therefor in communication system |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| KR19980031643A (en) * | 1996-10-31 | 1998-07-25 | 배순훈 | Apparatus and Method for Protecting Interval of Orthogonal Frequency Division Multiplexed Transmission System |
| KR100346205B1 (en) * | 1999-07-12 | 2002-08-01 | 삼성전자 주식회사 | Ofdm/cdma mobile communication system having pilot tone inserting and detecting apparatus |
-
2002
- 2002-06-07 KR KR1020020032070A patent/KR100698283B1/en not_active IP Right Cessation
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- 2003-01-16 CN CNA2005100750206A patent/CN1697441A/en active Pending
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102629886B (en) * | 2006-11-09 | 2014-12-31 | 日本无线株式会社 | Broadcasting system |
| CN101442677B (en) * | 2007-11-23 | 2010-12-22 | 卓胜微电子（上海）有限公司 | Hardware architecture for decoding FEC of DMB-T demodulation chip and decoding method |
| US8743981B2 (en) | 2009-06-16 | 2014-06-03 | Huawei Technologies Co., Ltd. | Modulation method and apparatus |
Also Published As
| Publication number | Publication date |
|---|---|
| KR20030094782A (en) | 2003-12-18 |
| KR100698283B1 (en) | 2007-03-22 |
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