CN100544339C - A kind of digital videocast modulating method and device - Google Patents
A kind of digital videocast modulating method and device Download PDFInfo
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- CN100544339C CN100544339C CNB2005100983742A CN200510098374A CN100544339C CN 100544339 C CN100544339 C CN 100544339C CN B2005100983742 A CNB2005100983742 A CN B2005100983742A CN 200510098374 A CN200510098374 A CN 200510098374A CN 100544339 C CN100544339 C CN 100544339C
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Abstract
The invention discloses a kind of signal modulating method of digital television broadcasting, this method is: the frequency pilot sign that generates and tape symbol is multiplexing on frequency domain synchronously with data-signal, in advance, and multiplex data is carried out OFDM (OFDM) modulation obtain time-domain signal; Described synchronous tape symbol comprises subcarrier that transmits synchronizing symbol and the zero setting subcarrier that does not pass any information, and described zero setting subcarrier distributes in the bilateral symmetry of the subcarrier that transmits synchronizing symbol; Described frequency pilot sign takies a part of subcarrier, and non-conterminous mutually between shared subcarrier; Before time-domain signal, increase protection at interval, and fill out 0 at interval, form an OFDM symbol in protection; Utilize an above OFDM symbol and a pre-pilot signal to generate baseband transmit signals.Simultaneously, the invention also discloses a kind of modulating apparatus of digital television broadcasting.Modulator approach provided by the present invention has the characteristics of low-power consumption, fast synchronous, low peak-to-average ratio.
Description
Technical field
The present invention relates to the digital television broadcasting field, be meant a kind of digital videocast modulating method and device especially.
Background technology
Digital television broadcasting is the research of current broadcast technical field and uses focus, released one after another oneself digital television broadcasting system of many countries.At present, the multiple mode of the modulation technique of digital television broadcasting, wherein, the DVB-T standard is to adopt OFDM (OFDM) modulation aspect transmission, belongs to the multi-carrier transmission technology.
Referring to shown in Figure 1, the modulated structure of the transmitter of DVB-T standard definition comprises OFDM modulating unit 100, inserts protection (CP) unit 104 and one-tenth frame unit 105 at interval.Wherein, OFDM modulating unit 100 comprises serial 101, anti-fast Fourier transform unit 102, parallel/serial converting unit 103.Serial 101 carries out the data-signal that receives to export anti-fast Fourier transform unit 102 to after the serial/parallel conversion, anti-fast Fourier transform unit 102 carries out parallel signal of receiving and the frequency pilot sign that receives to export to parallel/serial converting unit 103 behind the inverse-Fourier transform, after parallel/serial converting unit 103 converts the parallel data signal of receiving the data-signal of serial to again, output to and insert CP unit 104, insert and to send to into frame unit 105 CP unit 104 inserts CP in the data-signal of the serial of receiving after, become frame unit 105 again the physical frame of the data-signal composition of the serial that receives to be sent to radio frequency unit as baseband transmit signals and handle.
From above-mentioned modulating system, through needing to insert CP in the signal after the OFDM modulation, because CP and data have certain correlation properties, receiver relies on CP just can finish regularly synchronously, need consume certain power yet transmit CP.But the special value of fading channel, data-signal etc. all can worsen CP and correlation of data, thereby greatly reduces regularly synchronous speed and precision.
And, for all based on OFDM modulated digital broadcast system, exist a total problem to be: the flat power ratio in peak (PAPR) is generally very high, this will directly cause the service efficiency of the power amplifier of transmitter to descend, particularly when carrier number is very big, during as the 8k pattern of DVB-T, the efficiency power amplifier of transmitter is very low.Regrettably, existing DVB-T system does not consider this problem.
Summary of the invention
In view of this, the purpose of this invention is to provide a kind of digital videocast modulating method and device, make it can improve regularly synchronous speed and precision.
A kind of digital videocast modulating method provided by the invention is achieved in that
A. the frequency pilot sign that generates with data-signal, in advance and tape symbol is multiplexing on frequency domain synchronously, and multiplex data is carried out modulating in OFDM obtain time-domain signal;
Described synchronous tape symbol comprises subcarrier that transmits synchronizing symbol and the zero setting subcarrier that does not pass any information; Described frequency pilot sign takies a part of subcarrier, and non-conterminous mutually between shared subcarrier;
B. before time-domain signal, increase protection at interval, and protect at interval and fill out 0, form an OFDM symbol;
C. utilize an above OFDM symbol and a pre-pilot signal to generate baseband transmit signals.
After step b and between the step c, further comprise: the peak-to-average ratio of the described time-domain signal that obtains among the measuring process a, and whether judge this peak-to-average ratio greater than the threshold value that sets in advance, if greater than, then utilize certain synchronous tape symbol of algorithm adjustment, return step a, otherwise, execution in step c.
Described protection is expanded greater than the maximum delay of physical channel at interval.
Described baseband transmit signals is a physical frame, and pre-pilot is arranged in any position of each physical frame, and perhaps pre-pilot is arranged in before all OFDM symbols of each physical frame.
Described in the step a multiplex data being carried out the step that OFDM modulation obtains time-domain signal comprises:
A1, data-signal is carried out serial/parallel conversion;
A2, with frequency pilot sign and synchronous tape symbol and carry out inverse-Fourier transform through the parallel data-signal after the serial/parallel conversion;
A3, will be that serial signal obtains time-domain signal through the conversion of signals behind the inverse-Fourier transform.
A kind of digital television broadcasting modulating device provided by the invention is achieved in that
A kind of modulating apparatus of digital television broadcasting is used for modulating data, and the baseband transmit signals of modulation is sent to radio frequency unit, and this device comprises:
OFDM modulating unit (300), protection be zero insertion unit (304) and become frame unit (305) at interval, wherein,
OFDM modulating unit (300), the data-signal through frequency domain multiplexing that is used for receiving, frequency pilot sign, synchronous tape symbol carry out the OFDM modulation and obtain time-domain signal, and described synchronous tape symbol comprises subcarrier that transmits synchronizing symbol and the zero setting subcarrier that does not pass any information; Described frequency pilot sign takies a part of subcarrier, and non-conterminous mutually between shared subcarrier;
Protection is zero insertion unit (304) at interval, and being used for increases the protection interval at described time-domain signal, and inserts 0 back formation OFDM symbol in protection at interval;
Become frame unit (305), the physical frame that is used to utilize an above OFDM symbol and pre-pilot to constitute sends to radio frequency unit as baseband transmit signals.
This device further comprises: peak-to-average ratio measuring unit (606) and adjustment algorithm unit (607), wherein,
Peak-to-average ratio measuring unit (606), be used to measure the peak-to-average ratio that receives from the time-domain signal of OFDM modulating unit (300) output, judge that whether peak-to-average ratio is greater than pre-set threshold, if greater than, then this peak-to-average ratio is fed back to adjustment algorithm unit (607), if be not more than, then the time-domain signal that receives is exported to protection zero insertion unit (304) at interval;
Adjustment algorithm unit (607) is used for according to the synchronous tape symbol of peak-to-average ratio adjustment that receives.
OFDM modulating unit (300) comprises serial (301), anti-fast Fourier transform unit (302), parallel/serial converting unit (303), wherein,
Serial (301) is used for sending to anti-fast Fourier transform unit (302) to receiving after data-signal carries out serial/parallel conversion;
Anti-fast Fourier transform unit (302) after the frequency pilot sign that is used for receiving carries out inverse-Fourier transform with synchronous tape symbol and through the parallel data-signal after the serial/parallel conversion, exports parallel/serial converting unit (303) to;
Parallel/serial converting unit (303) is used for exporting to protection zero insertion unit (304) at interval with after being serial signal through the conversion of signals behind the inverse-Fourier transform.
The present invention does not handle not making to insert CP through the data-signal after the OFDM modulation, but will fill 0 in protection at interval, promptly without any signal, has so just saved power overhead.But because zero filling can not improve regularly synchronous speed and precision, the present invention introduces pre-pilot in every frame for this reason.Pre-pilot can obtain by a string sequence (as the PN sequence) that produces is at random carried out inverse-Fourier transform, utilizes the good correlation properties of pre-pilot, just receiver can be rapidly and accurately regularly.Can increase the certain power expense though introduce pre-pilot, but this expense (general＜5%) is much smaller than filling out 0 power of saving (being generally 7%～25%), therefore transmitting power has not only been saved in the modulation after the combination, and helps regularly synchronously rapidly and accurately.
Therefore, the present invention has following advantage and characteristics:
(1) the physical frame structure of employing pre-pilot+OFDM symbol, the quick stationary problem of signal in the solution digital television broadcasting system;
(2) replace existing CP of inserting or PN sequence mode with slotting 0 mode, not only saved power overhead, also avoided resembling inserting and introduced interference the PN mode, thereby made that the complexity of receiver is lower;
(3) insert continuously and/or the scattered pilot symbol at time-frequency domain, guarantee channel estimated accuracy;
(4) the parton carrier wave utilizes synchronous band feature to setover by estimated frequency as synchronous band, can also be used to reducing PAPR simultaneously.
Description of drawings
Fig. 1 is the modulated structure block diagram of prior art;
Fig. 2 is the schematic flow sheet of modulator approach of the present invention;
Fig. 3 is a modulated structure block diagram of the present invention;
Fig. 4 is the structure of the basic frame of physical layer, and wherein N is the integer greater than 1, the OFDM symbolic number that expression is comprised;
Fig. 5 has described the preceding structural representation of various symbols on time-frequency domain of modulation for Fig. 4;
Fig. 6 is for realizing the specific embodiment block diagram of modulated structure of the present invention.
Embodiment
The present invention does not handle not making to insert CP through the data-signal after the OFDM modulation, but will fill 0 in former protection at interval, promptly without any signal, has so just saved power overhead.But because zero filling can not improve regularly synchronous speed and precision, the present invention introduces pre-pilot in every frame for this reason, can design pre-pilot and have good correlation properties, and receiver just can be rapidly and accurately regularly.
Referring to shown in Figure 2, realize that method of the present invention may further comprise the steps:
Step 200: generate and store pre-pilot signal, synchronous tape symbol and frequency pilot sign.Synchronizing symbol and frequency pilot sign can adopt the PN sequence, promptly produce a string value 0, the pseudo random number of 1}, then by BPSK mapping (0-〉1,1-〉-1) become required symbol.
Tape symbol comprises two sub-carriers synchronously, and a kind of is the subcarrier that transmits synchronizing symbol, and a kind of is the zero setting subcarrier that does not pass any information.The zero setting subcarrier distributes in the subcarrier bilateral symmetry that transmits synchronizing symbol.Adopting synchronous signed purpose is to be used for the estimated frequency biasing, can also be used to reducing the PAPR that sends signal, adjusts synchronizing symbol as come self adaptation by the structure of feedback loop.Frequency pilot sign only takies a part of subcarrier, and non-conterminous mutually between the shared subcarrier, the position of subcarrier can change along with the variation of symbol, also can immobilize.
Be with the Frequency Synchronization that is intended to ofdm system synchronously.Symbolic construction such as Fig. 5 a of synchronous band, frequency pilot sign and data.Synchronously band comprises that a plurality of sub carrier group, each sub carrier group comprise a plurality of adjacent subcarriers, except that there being a subcarrier to transmit the synchronizing symbol, claims that this subcarrier is synchronous tape symbol subcarrier, all other subcarriers do not deliver a letter breath, i.e. zero setting in the group.The zero setting subcarrier is symmetrically distributed about synchronous tape symbol subcarrier, as Fig. 5 b.The implication that is symmetrically distributed comprises: if 2n zero setting subcarrier arranged, the zero setting sub-carrier number of synchronizing symbol subcarrier both sides all is n so; If 2n+1 zero setting subcarrier arranged, the zero setting sub-carrier number of synchronizing symbol subcarrier both sides is n and n+1 so, or n+1 and n, and wherein, n is a positive integer.Tape symbol can immobilize along with the variation of time in transport process synchronously, also can be along with the time changes and suitably adjustment.If tape symbol is to adjust to change synchronously, receiving terminal can not known synchronous signed numerical information.
Frequency pilot sign comprises continuous pilot and scattered pilot.Continuous pilot takies some fixing subcarrier, goes up in the time (symbol) and sends known array continuously; And the scattered pilot regular hour (symbol) is gone up the certain subcarrier transmission known array of selection, is characterized in that pilot tone all is discontinuous on time (symbol) and frequency (subcarrier).
Step 201: data, frequency pilot sign and synchronous tape symbol are multiplexing on frequency domain.
Step 202: the data-signal that step 201 is obtained through frequency domain multiplexing carries out the OFDM modulation and obtains time-domain signal.
The data that obtain through frequency domain multiplexing are carried out the step that the OFDM modulation obtains time-domain signal to be comprised: data-signal is carried out serial/parallel conversion; Parallel data-signal after frequency pilot sign and synchronous tape symbol and the serial/parallel conversion of process is carried out inverse-Fourier transform; To be that serial signal obtains time-domain signal through the conversion of signals behind the inverse-Fourier transform.
Step 203: before time-domain signal, increase protection at interval, and in protection at interval, fill out 0, form the OFDM symbol.And protection is expanded greater than the maximum delay of channel at interval.
Step 204: utilize one to generate a physical frame with last OFDM symbol and pre-pilot, with this physical frame as baseband transmit signals.
Referring to shown in Figure 4, the physical frame that generates in the step 204 comprises a pre-pilot and several OFDM symbols, and the pre-pilot in each physical frame takies one or an integer OFDM symbol lengths.And pre-pilot can be placed on any position of physical frame, but generally is placed on before all OFDM symbols.
As shown in Figure 3, based on said method, realize that modulated structure of the present invention comprises: OFDM modulating unit 300, protection be zero insertion unit 304, one-tenth frame unit 305 at interval.Wherein, OFDM modulating unit 300 comprises serial 301, anti-fast Fourier transform unit 302, parallel/serial converting unit 303.Serial 301 links to each other with anti-fast Fourier transform unit 302; anti-fast Fourier transform unit 302 links to each other with parallel/serial converting unit 303; parallel/serial converting unit 303 links to each other zero insertion unit 304 at interval with protection, and protection zero insertion unit 304 at interval links to each other with becoming frame unit 305.
The operation principle of modulated structure of the present invention is: 301 pairs of serial receive after data-signal carries out serial/parallel conversion, send to anti-fast Fourier transform unit 302, anti-fast Fourier transform unit 302 exports parallel/serial converting unit 303 to after the frequency pilot sign that receives is carried out inverse-Fourier transform with synchronous tape symbol and through the parallel data-signal after the serial/parallel conversion; After parallel/serial converting unit 303 will be serial signal through the conversion of signals behind the inverse-Fourier transform again; export to protection zero insertion unit 304 at interval; at interval zero insertion unit 304 is with the data-signal front of the serial that receives or protection that the back increases certain-length at interval in protection; and; in protection at interval, all fill out 0; promptly do not send out in protection at interval signal any, the data-signal that adds after the protection at interval just forms an OFDM symbol.At last, be spaced apart 0 data-signal and input to into frame unit 305 having increased protection, become frame unit 305 with a plurality of OFDM symbols and pre-pilot in time a basic physical frame of multiplexing formation send to radio frequency unit as a baseband transmit signals.And pre-pilot can be placed on any position of basic frame.
Here,, so just reduced the average transmitting power of transmitter, can save the power of power 5%～20% generally speaking owing in protection at interval, all fill out 0.
The present invention can also further increase by one and measure peak-to-average ratio unit and adjustment algorithm unit, reduces transmission signal PAPR by adjusting synchronous tape symbol.Referring to shown in Figure 6, the modulated structure of present embodiment comprises OFDM modulating unit 300, protection zero insertion unit 304, one-tenth frame unit 305, peak-to-average ratio measuring unit 606 and adjustment algorithm unit 607 at interval.Wherein, OFDM modulating unit 300 comprises serial 301, anti-fast Fourier transform unit 302, parallel/serial converting unit 303.Serial 301 links to each other with anti-fast Fourier transform unit 302; anti-fast Fourier transform unit 302 links to each other with parallel/serial converting unit 303; parallel/serial converting unit 303 links to each other zero insertion unit 304 at interval with protection, and protection zero insertion unit 304 at interval links to each other with becoming frame unit 305.
The operation principle of the modulated structure of present embodiment is: 301 pairs of serial receive after data-signal carries out serial/parallel conversion, send to anti-fast Fourier transform unit 302, anti-fast Fourier transform unit 302 exports parallel/serial converting unit 303 to after the frequency pilot sign that receives is carried out inverse-Fourier transform with synchronous tape symbol and through the parallel data-signal after the serial/parallel conversion; After parallel/serial converting unit 303 will be serial signal through the conversion of signals behind the inverse-Fourier transform again, export to peak-to-average ratio measuring unit 606, after peak-to-average ratio measuring unit 606 measures PAPR, judge that whether this PAPR is greater than predefined value, if greater than, then this PAPR is fed back to adjustment algorithm unit 607; Synchronous tape symbol is suitably adjusted according to PAPR information in adjustment algorithm unit 607, such as: with all possible value random alignment of synchronous tape symbol, adjustment algorithm is all chosen next value at every turn by putting in order.Then recirculation is carried out OFDM modulation, PAPR measurement and feedback, is adjusted; when PAPR is not more than pre-set threshold; peak-to-average ratio measuring unit 606 sends to protection zero insertion unit 304 at interval with the data-signal of the serial that receives; at interval zero insertion unit 304 is with the data-signal front of the serial that receives or protection that the back increases certain-length at interval in protection; and; in protection at interval, all fill out 0; promptly do not send out in protection at interval signal any, the data-signal that adds after the protection at interval just forms an OFDM symbol.At last, be spaced apart 0 data-signal and input to into frame unit 305 having increased protection.Become frame unit 305 with a plurality of OFDM symbols and multiplexing in time this physical frame of primordial of pre-pilot, and this physical frame is sent to radio frequency unit as baseband transmit signals.
Can adopt multiple algorithm computation in the above-mentioned adjustment algorithm unit 607, as full-search algorithm and part searching algorithm etc.
Claims (8)
1, a kind of signal modulating method of digital television broadcasting is characterized in that, this method may further comprise the steps:
A. the frequency pilot sign that generates with data-signal, in advance and tape symbol is multiplexing on frequency domain synchronously, and multiplex data is carried out modulating in OFDM obtain time-domain signal,
Described synchronous tape symbol comprises subcarrier that transmits synchronizing symbol and the zero setting subcarrier that does not pass any information; Described frequency pilot sign takies a part of subcarrier, and non-conterminous mutually between shared subcarrier;
B. before time-domain signal, increase protection at interval, and protect at interval and fill out 0, form an OFDM symbol;
C. utilize an above OFDM symbol and a pre-pilot signal to generate baseband transmit signals.
2, method according to claim 1, it is characterized in that, after step b and between the step c, further comprise: the peak-to-average ratio of the described time-domain signal that obtains among the measuring process a, and judge that whether this peak-to-average ratio is greater than the threshold value that sets in advance, if greater than, then utilize certain synchronous tape symbol of algorithm adjustment, return step a, otherwise, execution in step c.
3, method according to claim 1 is characterized in that, described protection is expanded greater than the maximum delay of physical channel at interval.
4, method according to claim 1 is characterized in that, described baseband transmit signals is a physical frame, and pre-pilot is arranged in any position of each physical frame, or pre-pilot is arranged in before all OFDM symbols of each physical frame.
5, method according to claim 1 is characterized in that, described in the step a multiplex data is carried out the step that OFDM modulation obtains time-domain signal and comprises:
A1, data-signal is carried out serial/parallel conversion;
A2, with frequency pilot sign and synchronous tape symbol and carry out inverse-Fourier transform through the parallel data-signal after the serial/parallel conversion;
A3, will be that serial signal obtains time-domain signal through the conversion of signals behind the inverse-Fourier transform.
6, a kind of modulating apparatus of digital television broadcasting is used for modulating data, and the baseband transmit signals of modulation is sent to radio frequency unit, it is characterized in that this device comprises:
OFDM modulating unit (300), protection be zero insertion unit (304) and become frame unit (305) at interval, wherein,
OFDM modulating unit (300), the data-signal through frequency domain multiplexing that is used for receiving, frequency pilot sign, synchronous tape symbol carry out the OFDM modulation and obtain time-domain signal, and described synchronous tape symbol comprises subcarrier that transmits synchronizing symbol and the zero setting subcarrier that does not pass any information; Described frequency pilot sign takies a part of subcarrier, and non-conterminous mutually between shared subcarrier;
Protection is zero insertion unit (304) at interval, and being used for increases the protection interval at described time-domain signal, and inserts 0 back formation OFDM symbol in protection at interval;
Become frame unit (305), the physical frame that is used to utilize an above OFDM symbol and pre-pilot to constitute sends to radio frequency unit as baseband transmit signals.
7, device according to claim 6 is characterized in that, this device further comprises: peak-to-average ratio measuring unit (606) and adjustment algorithm unit (607), wherein,
Peak-to-average ratio measuring unit (606), be used to measure the peak-to-average ratio that receives from the time-domain signal of OFDM modulating unit (300) output, judge that whether peak-to-average ratio is greater than pre-set threshold, if greater than, then this peak-to-average ratio is fed back to adjustment algorithm unit (607), if be not more than, then the time-domain signal that receives is exported to protection zero insertion unit (304) at interval;
Adjustment algorithm unit (607) is used for according to the synchronous tape symbol of peak-to-average ratio adjustment that receives.
8, device according to claim 6 is characterized in that, OFDM modulating unit (300) comprises serial (301), anti-fast Fourier transform unit (302), parallel/serial converting unit (303), wherein,
Serial (301) is used for sending to anti-fast Fourier transform unit (302) to receiving after data-signal carries out serial/parallel conversion;
Anti-fast Fourier transform unit (302) after the frequency pilot sign that is used for receiving carries out inverse-Fourier transform with synchronous tape symbol and through the parallel data-signal after the serial/parallel conversion, exports parallel/serial converting unit (303) to;
Parallel/serial converting unit (303) is used for exporting to protection zero insertion unit (304) at interval with after being serial signal through the conversion of signals behind the inverse-Fourier transform.
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| CNB2005100983742A CN100544339C (en) | 2005-09-08 | 2005-09-08 | A kind of digital videocast modulating method and device |
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| CN101409699B (en) * | 2008-11-28 | 2011-03-30 | 清华大学 | Signal transmission method for wideband wireless mobile commutation system |
| CN106878221B (en) * | 2015-12-14 | 2021-08-06 | 中兴通讯股份有限公司 | Method and device for generating multi-carrier signal |
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