CN100578978C - Method for decreasing power inequality in-band of transmitter - Google Patents
Method for decreasing power inequality in-band of transmitter Download PDFInfo
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- CN100578978C CN100578978C CN200810102092A CN200810102092A CN100578978C CN 100578978 C CN100578978 C CN 100578978C CN 200810102092 A CN200810102092 A CN 200810102092A CN 200810102092 A CN200810102092 A CN 200810102092A CN 100578978 C CN100578978 C CN 100578978C
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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- Y02D—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN INFORMATION AND COMMUNICATION TECHNOLOGIES [ICT], I.E. INFORMATION AND COMMUNICATION TECHNOLOGIES AIMING AT THE REDUCTION OF THEIR OWN ENERGY USE
- Y02D30/00—Reducing energy consumption in communication networks
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Abstract
The invention discloses a method for reducing the unevenness of power in a belt of a transmitter, in particular to a method for reducing the unevenness of power in the belt of a China mobile multimedia broadcast transmitter. The signal source data symbol of the transmitter is mapped to the data subcarrier of each orthogonal frequency division multiplexing symbol to carry out sending after being mapped by a constellation; the method comprises: the data symbol loaded by the data subcarrier which is not used for loading the data symbol after constellation mapping is set as a value not to be zero and then sent together with the data symbols loaded by other data subcarriers. The invention improves the unevenness of power in the belt of the transmitter under the premise of not affecting the performances of a receiver and the technical schemes, can eliminate the defects of the prior art by setting different methods according to different bandwidths of physical layers and has the characteristic of simple implement method.
Description
Technical field
The invention belongs to the mobile multimedia technical field, relate in particular to a kind of China Mobile multimedia broadcasting (China Mobile Multimedia Broadcasting, CMMB) method of power inequality in-band of transmitter of reducing.
Background technology
It is different that broadcast system transmitter and transmitter of mobile communications system have greatly, and this transmitting power with them is directly related.The transmitting power of broadcast system transmitter is all very high usually, and as transmitter of CMMB system etc., its transmitting power reaches as high as four or five kilowatts.And the transmitter of mobile communication system, as transmitter of 3G communication system etc., its transmitting power is all lower usually, the highlyest is no more than 40 watts.Transmitting power caused the performance requirement of transmitter is existed a great difference than big-difference, wherein fairly obvious and important different performance requirement is exactly the power inequality in the passband.The transmitter of mobile communication system does not apply any requirement to this performance basically, and the transmitter of broadcast system is very strict to this performance demands, generally requires the power inequality in the passband to be limited in the 1dB (decibel).So-called band internal power unevenness is:
10*lg (maximum/minimum of subcarrier data carried by data power in the passband).
Because the power inequality in the passband directly affects the fluctuation situation of the signal power of transmitter actual transmission, especially for powerful broadcast system transmitter, that is with interior unevenness just might cause the bigger variation of actual emission power than minor swing, thereby directly affects the coverage condition of signal and user's reception condition.This is a very great problem concerning broadcast system.Therefore, the band internal power unevenness that reduces transmitter as possible is a thing that can not be ignored.
The CMMB system is the leading a kind of emerging broadcast system towards Mobile Multimedia Broadcasting of China national General Bureau of Radio, Film and TV.In October, 2006, General Bureau of Radio, Film and Television is defined as the radio, film and television industry standard with CMMB.Advance the industrialization work of CMMB system subsequently with all strength.In the industrialization process of CMMB system, the CMMB transmitter is the most basic, most important a kind of product.
The formulation of a broadcast standard considers mainly to guarantee how expeditiously that receiver obtains high-performance and low complex degree, certainly the performance to transmitter also can propose clear and definite requirement, but difficult all measures that provide definite guaranteed performance are for example about some measures of the band internal power unevenness that reduces transmitter.
Below the flow chart of data processing of the physical layer signal of CMMB system is done simple declaration.
With reference to shown in Figure 1, be the timeslot-based frame structure schematic diagram of CMMB system, provided the frame structure of CMMB system.CMMB system physical layer signal was a frame in per 1 second, was divided into 40 time slots (promptly the time slot among the figure 0 is to time slot 39).Each time slot comprises a beacon and 53 OFDM (Orthogonal Frequency Division Multiplexing, OFDM) symbol (i.e. 0 to the OFDM symbol 52 of OFDM symbol among the figure).Beacon does not carry the information source data, and the information source data are by 53 OFDM symbols carry.
The information source data of whole time slot through step process such as byte-interleaved, chnnel coding, Bit Interleave and constellation mapping after and scattered pilot, continuous pilot be mapped to together on the subcarrier in frequency domain shown in Fig. 2 signal distribution plots.TS represents Time Slot (time slot), N among Fig. 2
VRepresent the effective number of sub carrier wave in the OFDM symbol.
With reference to shown in Figure 3, be QPSK (Quadrature Phase Shift Keying) the constellation mapping figure in the GY/T 220.1-2006 standard.As can be seen from the figure, all 4 constellation point all are positioned on the unit circle.And owing to comprised the power normalization factor in the planisphere, the average amplitude of the data symbol after the process constellation mapping equals 1.Simultaneously, be mapped to the amplitude of the continuous pilot symbol on the subcarrier in frequency domain and the amplitude of scattered pilot symbol and also all equal 1.Therefore, the band internal power unevenness of this time-frequency spectrum equals 0dB.
Next, the subcarrier in frequency domain data carried by data symbol and the frequency pilot sign of whole time slot carried out scrambling, the power of each the scrambler sample in the scrambler sequence is 1, again the data symbol is carried out IFFT (inverse fast Fourier transform) operation after carrying out scrambling and handling.
But, when physical layer bandwidth B f=8MHz, can be used for carrying data symbol owing to exist 138330 subcarriers in each time slot, and the data symbol after constellation mapping that needs to carry in each time slots has only 138240, therefore in the industry standard GY/T220.1-2006 of General Bureau of Radio, Film and Television's promulgation the value of last 90 the data subcarrier data carried by data symbols in each time slot is changed to 0, the amplitude that is about to last 90 data symbols is set to 0.Same, when physical layer bandwidth B f=2MHz, exist 27666 subcarriers in each time slot and can be used for carrying data symbol, wherein preceding 27648 subcarriers are used to carry the data symbol after the constellation mapping, and the value of last 18 the data subcarrier data carried by data symbols in each time slot is set to 0.
The minimum value of the interior subcarrier data carried by data power of passband this moment is 0, according to the computational methods of being with the internal power unevenness as can be known, this way has caused the interior power inequality of spectral passband this moment no longer to equal 0 inevitably, again through subsequently treatment step, if treatment step subsequently (such as the IFFT operation) shows imperfection, unevenness will be probably more abominable in the band so.
The band internal power unevenness of CMMB transmitter is a comparatively harsh performance requirement at present, requires in 0.5dB.Because the CMMB system has adopted the OFDM modulation technique, the particular hardware implementation of IFFT also can influence the power inequality performance in the transmitter strap.Except the particular hardware implementation that improves IFFT, the method that reduces the band internal power unevenness of transmitter also comprises the optimal design filter, conscientiously selects analogue device etc.But, point out as above-mentioned, because the way of the industry standard GY/T 220.1-2006 of General Bureau of Radio, Film and Television's promulgation has caused data symbol before carrying out the IFFT processing, power inequality in the spectral passband no longer equals 0, after like this data symbol being carried out the IFFT processing, if IFFT shows imperfection, will cause the band internal power unevenness of IFFT hardware configuration output to worsen more, can not satisfy the system stability requirements of one's work even.Thereby, how to overcome the defective of prior art, reduce power inequality in-band of transmitter better, be that the technical staff still needs the problem explored.
Summary of the invention
Technical problem to be solved by this invention provides a kind of method of the CMMB of reducing power inequality in-band of transmitter, to reduce the band internal power unevenness of CMMB transmitter.
In order to solve the problems of the technologies described above, the invention provides a kind of method that reduces power inequality in-band of transmitter, the information source data symbol of described transmitter is after constellation mapping, be mapped on the data subcarrier of each OFDM symbol and send, described method comprises: transmitter is for variable assignments the time, for the data subcarrier that is not used in the data symbol of carrying after the constellation mapping, its data carried by data symbol is set to non-0 value, sends with other data subcarrier data carried by data symbols then.
Further, when physical layer bandwidth B f=8MHz, last 90 the data subcarrier data carried by data symbols that are not used in the data symbol of carrying after the constellation mapping in each time slot are set to non-0 value.
Further, when physical layer bandwidth B f=2MHz, last 18 the data subcarrier data carried by data symbols that are not used in the data symbol of carrying after the constellation mapping in each time slot are set to non-0 value.
Further, described data symbol is set to non-0 value and comprises: the range value that guarantees described data symbol is 1.
Further, the described data symbol value that is not used in the data subcarrier of the data symbol of carrying after the constellation mapping all is set to+and 1, perhaps all be set to-1.
Further, the described data symbol value that is not used in the data subcarrier of the data symbol of carrying after the constellation mapping be set at random+1 or-1.
Further, the described data symbol value that is not used in the data subcarrier of the data symbol of carrying after the constellation mapping is, a constellation point in the picked at random GY/T 220.1-2006 standard in the Quadrature Phase Shift Keying planisphere, with the coordinate figure of this constellation point as the value of any one data symbol wherein.
Further, described transmitter is that variable assignments is finished by modulator.
The band internal power unevenness that reduces the CMMB transmitter need be united the multiple measure of adopting, and the scheme that the present invention proposes is the band internal power unevenness performance of auxiliary improvement CMMB transmitter very effectively.The present invention is for the data subcarrier that is not used in the data symbol of carrying after the constellation mapping of each time slot in the every frame of physical layer signal, its data carried by data value of symbol is set to non-0 value, can improve the data symbol amplitude difference of input IFFT like this, thereby will the band internal power unevenness that the data symbol carries out the frequency spectrum before IFFT handles be reduced.The data symbol range value that the present invention also provides assurance to import IFFT is 1 method, thereby will be reduced to 0dB to the band internal power unevenness that the data symbol carries out the frequency spectrum before IFFT handles, and then after data symbol being carried out the IFFT processing, the band internal power unevenness of IFFT hardware configuration output improves.New departure that improves the CMMB power inequality in-band of transmitter that the present invention proposes, can be under the precondition that does not influence receiver performance and implementation, improve the band internal power unevenness of CMMB transmitter, and diverse ways is set according to different physical layer bandwidth, can eliminate the defective of prior art, and have the implementation method characteristic of simple.
Description of drawings
Fig. 1 is the timeslot-based frame structure schematic diagram of CMMB system.
Fig. 2 is the signal distribution plots of CMMB system.
Fig. 3 is the QPSK constellation mapping figure in the GY/T 220.1-2006 standard.
Fig. 4 is the method flow diagram of one embodiment of the invention.
Embodiment
Main thought of the present invention is the data subcarrier that is not used in the data symbol of carrying after the constellation mapping for each time slot in the every frame of physical layer signal, its data carried by data value of symbol is set to non-0 value, the data symbol range value that can guarantee input IFFT like this is 1, and then can better eliminate band internal power unevenness, improve the CMMB transmitter performance.
Below in conjunction with accompanying drawing to a preferred embodiment of the present invention will be described in detail.
With reference to shown in Figure 4, be the method flow diagram of one embodiment of the invention.Said method comprising the steps of:
Step 301: judge the physical layer bandwidth, if the physical layer bandwidth is Bf=8MHz, execution in step 302, if the physical layer bandwidth is Bf=2MHz, execution in step 303;
Step 302: transmitter is when being variable assignments, and last 90 the data subcarrier data carried by data symbols in each time slot are set to non-0 value, execution in step 304;
Step 303: transmitter is when being variable assignments, and last 18 the data subcarrier data carried by data symbols in each time slot are set to non-0 value, execution in step 304;
Step 304: the data symbol of described non-0 value is sent with other data subcarrier data carried by data symbols.
By the processing of step 302, step 303 and step 304, the band internal power unevenness of the frequency spectrum before IFFT can being handled is reduced to 0dB.
Described transmitter is that variable assignments is finished by modulator.
Furthermore, can be set to 1 by the corresponding data value of symbol.
Specifically, the value of the range value of corresponding data symbol can have a variety of options in step 302 and the step 303, as long as guarantee that range value all is a non-zero, for a plurality of data subcarriers that are not used in the data symbol of carrying after the constellation mapping, the value of its data symbol can be the same, also can be different.Exemplarily provide 3 kinds of methods to set up below, certainly, the present invention is not exceeded with following three kinds of methods to set up:
1, the data symbol value of a plurality of data subcarriers all be set to+1, perhaps all be set to-1.
2, each the symbol value in the data symbol of a plurality of data subcarriers all is set at random+1 or-1.
3, in the picked at random GY/T 220.1-2006 standard coordinate figure of a constellation point in the QPSK planisphere as the value of a data symbol in the data symbol of a plurality of data subcarriers.For this planisphere, because each constellation point in the planisphere is all on a circumference, so the coordinate figure of getting any one constellation point wherein during as the value of data symbol, the range value that can guarantee data symbol is 1.
The method of the data symbol value of above different data subcarrier, because the range value of data symbol is 1, therefore, the band internal power unevenness of the frequency spectrum before all IFFT can being handled be reduced to 0dB.
Because the radio and TV operator is comparatively harsh to the performance requirement of the band internal power unevenness of CMMB transmitter, adopts traditional single alternative possibly can't satisfy this requirement.The present invention proposes a kind of new method that reduces the CMMB power inequality in-band of transmitter, it can eliminate the defective of prior art, better eliminates band internal power unevenness, satisfies system's requirement of actual application, and has the implementation method characteristic of simple.
It should be noted last that above embodiment is only unrestricted in order to technical scheme of the present invention to be described, the modification that those of ordinary skill in the art carries out technical scheme of the present invention or be equal to replacement all is encompassed in the middle of the claim scope of the present invention.
Claims (7)
1, a kind of method that reduces power inequality in-band of transmitter, be applied to the China Mobile multimedia broadcasting transmitter, the information source data symbol of described transmitter is after constellation mapping, be mapped on the data subcarrier of each OFDM symbol and send, it is characterized in that, described method comprises: transmitter is for variable assignments the time, be not used in the data subcarrier of the data symbol of carrying after the constellation mapping in each time slot for the every frame of physical layer signal, its data carried by data symbol is set to non-0 value and guarantees that range value is 1, sends with other data subcarrier data carried by data symbols then.
2, the method for claim 1 is characterized in that, when physical layer bandwidth B f=8MHz, last 90 the data subcarrier data carried by data symbols that are not used in the data symbol of carrying after the constellation mapping in each time slot are set to non-0 value.
3, the method for claim 1 is characterized in that, when physical layer bandwidth B f=2MHz, last 18 the data subcarrier data carried by data symbols that are not used in the data symbol of carrying after the constellation mapping in each time slot are set to non-0 value.
4, as any described method of claim 1 to 3, it is characterized in that, the described data symbol value that is not used in the data subcarrier of the data symbol of carrying after the constellation mapping all is set to+and 1, perhaps all be set to-1.
5, as any described method of claim 1 to 3, it is characterized in that, the described data symbol value that is not used in the data subcarrier of the data symbol of carrying after the constellation mapping is set at random+and 1 or-1.
6, as any described method of claim 1 to 3, it is characterized in that, the described data symbol value that is not used in the data subcarrier of the data symbol of carrying after the constellation mapping is, a constellation point in the picked at random GY/T 220.1-2006 standard in the Quadrature Phase Shift Keying planisphere, with the coordinate figure of this constellation point as the value of any one data symbol wherein.
As any described method of claim 1 to 3, it is characterized in that 7, described transmitter is that variable assignments is finished by modulator.
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| Application Number | Priority Date | Filing Date | Title |
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| CN200810102092A CN100578978C (en) | 2008-03-17 | 2008-03-17 | Method for decreasing power inequality in-band of transmitter |
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| CN200810102092A CN100578978C (en) | 2008-03-17 | 2008-03-17 | Method for decreasing power inequality in-band of transmitter |
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| CN100578978C true CN100578978C (en) | 2010-01-06 |
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Non-Patent Citations (2)
| Title |
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| CMMB中国移动多媒体广播. 殷新等.中国传媒科技，第1卷第1期. 2008 |
| CMMB中国移动多媒体广播. 殷新等.中国传媒科技，第1卷第1期. 2008 * |
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