CN1913511A - Method for reducing peak balance ratio in multi-carrier modulation system - Google Patents
Method for reducing peak balance ratio in multi-carrier modulation system Download PDFInfo
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- CN1913511A CN1913511A CN 200510090085 CN200510090085A CN1913511A CN 1913511 A CN1913511 A CN 1913511A CN 200510090085 CN200510090085 CN 200510090085 CN 200510090085 A CN200510090085 A CN 200510090085A CN 1913511 A CN1913511 A CN 1913511A
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Abstract
This invention relates to a method for reducing peak-to-average ratio in a multi-carrier modulation system including: transmitting multiple assistant information on a vacancy sub-carrier, each piece of assistant information is combined with effective data in linearity, computing the peak-to-average ratio of each after the IFFT output to select the optimum ratio by multiple comparison and weighting the data of the vacancy sub-carrier data, which increases the stability of the system not necessary to increase extra redundant transmission phase factor information.
Description
Technical field
The present invention relates in a kind of wireless communication system, especially in OFDM (OFDM) system, reduce the method for peak-to-average power, reduce the method for peak-to-average force ratio in particular a kind of multicarrier modulation system than (PAPR).
Background technology
The OFDM of prior art (OFDM) system is a kind of multicarrier modulation system, and certain if a plurality of carrier waves superpose with same direction, big peak value then can occur, so require power amplifier to have the very big range of linearity constantly.If the range of linearity less than the signal peak-peak, then can produce signal distortion when peak value enters the power amplifier nonlinear area, thereby produce Intermodulation Interference and out-of-band radiation between subcarrier, destroy the orthogonality between subcarrier, reduce systematic function.If power amplifier is operated under the high-power compensating coefficient, can causes low-down amplification efficient, and make the transmitter cost very expensive.The peak-to-average force ratio problem has become a bottleneck of OFDM technology extensive use, therefore, must adopt certain technology to reduce peak-to-average force ratio, makes transmitter intermediate power amplifier efficient operation, improves the overall performance of system simultaneously.
The technology that solves the peak-to-average force ratio problem at present mainly is divided into 3 big classes: amplitude limit class technology, coding class technology and probability class technology.
In the amplitude limit class technology, when signal amplitude surpassed the threshold value of predesignating, the amplitude that surpasses the thresholding part was promptly cut down, and causes signal distortion.So nonlinear operation can cause that interband disturbs in the amplitude limit class technology, increases the intersymbol interference (ISI) and the error rate (BER), in addition, out-of-band noise also may cause interchannel interference, reduces the availability of frequency spectrum.
The patent of " in the OFDM communication system, reducing the apparatus and method (Apparatus and method for reducing PAPR in OFDM communicationsystem) of PAPR " by name that Korea S Samsung is proposed, european patent number EP1515504, promptly belong to amplitude limit class technology, its main thought is: to carrying out N the subcarrier of IFFT, wherein N-L subcarrier transmits data, L subcarrier transmits auxiliary data, produce a pulse, change the phase place of pulse, make it identical with the phase place of peak-peak behind N-L the subcarrier IFFT, decide the scaling of the pulse signal of generation with the difference of peak-peak and threshold power value, then the linear addition output of the output signal of pulse signal and IFFT.But this patent is not considered the interference between the adjacent OFDM symbol on the frequency spectrum, owing to utilize L subcarrier to transmit auxiliary data, will inevitably cause the expansion of frequency spectrum, influences adjacent OFDM symbol.In addition, if directly utilize L the data on the subcarrier directly to carry out peak value offset, not only can not reach the optimization effect, can worsen peak-to-average force ratio on the contrary, shown in Figure 2 as in the simulating, verifying, as can be seen, reach the effect of optimizing peak-to-average force ratio, must be weighted L subcarrier data when peak value offset, weight coefficient is less than 1, and the coefficient of weighting can rule of thumb be determined.
In addition, improve peak-to-average force ratio with L subcarrier auxiliary data among the patent EP1515504, it improves performance and largely depends on the L size, and L is big more, and performance is good more, but N-L can reduce simultaneously, and promptly useful information reduces, and has reduced the efficient of system.When simulating, verifying patent EP1515504, find this method when carrying out peak value offset, if not to L data weighting, can cause peak-to-average force ratio to worsen, as shown in Figure 2, according to the different weights value, peak-to-average force ratio alters a great deal, and when weighted value was 0.2, peak-to-average force ratio improved; And when weighted value was 0.5, peak-to-average force ratio worsened on the contrary.So for patent EP1515504, weighted value is a very important parameters,, need to rely on engineering experience to determine for its selection.
The main thought of coding class technology is: the signal codeword set that restriction can be used for transmitting, the code word of having only amplitude peak to be lower than the power amplifier maximum magnitude just can be used for transmission, thereby avoid signal peak fully, and what prove better performances at present is the Golay coding techniques.But this coding techniques is counted more for a long time at subcarrier, encoding rate is too low, as IFFT points N=256 o'clock, corresponding encoding rate only is about 0.05, these redundant informations can reduce the availability of frequency spectrum of effective information significantly, in addition, the coding of Golay sign indicating number and decoding technique are very complicated, and be obviously inadvisable in Project Realization.
The starting point of probability class technology is to reduce the peak value probability of occurrence, rather than reduces the signal amplitude maximum, finishes by linear change, but under normal conditions, needs the extra supplementary of transmission, increases redundant.What belong to such technology has: select reflection method (SLM Selected Mapping), partial transmission sequence method (PTS Partial Transmit Sequence), impulse shaping (PS Pulse Shaping) etc.
SLM (sees also Stefan H Muller, Johannes B Huber.A comparison of peakpower reduction schemes for OFDM.Global Telecommunications Conference.1997.GLOBECOM ' 97, IEEE, 1997,1:3～8) in the method, identical block is multiplied by a different M phase sequence, and M phase sequence length is N (N is and will carries out counting of IFFT), and they add up independent each other.Carry out the IFFT operation after a data block and M phase sequence multiplies each other respectively, the peak-to-average force ratio on M road is calculated in the output back, compares, and selects the transmission of data blocks with minimum peak-to-average force ratio.The advantage of SLM method is to carry out linear transformation, can not cause signal distortion.But shortcoming is to need M IFFT to handle, and takies than large resource, need utilize redundant information transmission phase sequence information.
PTS (sees also Stefan H Muller, Johannes B Huber.A comparison of peakpower reduction schemes for OFDM.Global Telecommunications Conference.1997.GLOBECOM ' 97, IEEE, 1997,1:3～8) method is based on the principle identical with SLM, but its converting vector has different structures, the PTS method at first is divided into M sub-piece with the data of input, each sub-piece carries out the IFFT operation that N is ordered respectively, each data block is taken advantage of a phase factor behind the IFFT, last M circuit-switched data addition, obtain whole data I FFT result,, calculate the peak-to-average force ratio of its corresponding data respectively for many groups phase factor, find out smallest peaks wherein all than the phase factor (M) of correspondence, output IFFT result and phase factor information.PTS method advantage is the no signal distortion, but its shortcoming is will carry out M IFFT to handle, and needs to increase redundancy and transmits phase factor information.
No matter PTS method, or SLM method all needs the high accuracy of the phase information of strict guarantee additional transmissions, in case otherwise this phase information makes a mistake the complete mistake of receiving terminal then.So for guaranteeing the accuracy of phase information, must introduce coding techniques transmits this phase information, thereby can bring the partial information redundancy.
Therefore, there is defective in prior art, and awaits improving and development.
Summary of the invention
The object of the present invention is to provide the method that reduces peak-to-average force ratio in a kind of multicarrier modulation system, propose a kind of method of improving peak-to-average force ratio of novelty, be used for reducing the ofdm system peak-to-average force ratio, produce less extra adjacent band simultaneously and disturb.
Technical scheme of the present invention comprises:
Reduce the method for peak-to-average force ratio in a kind of multicarrier modulation system, wherein, may further comprise the steps:
A, on vacant subcarrier transmission multichannel auxiliary data, every road auxiliary data and valid data linear combination;
B, calculate the peak-to-average force ratio after IFFT output is carried out on each road, by multichannel relatively, select minimum peak-to-average force ratio;
C, auxiliary data on the vacant subcarrier is weighted.
Described method also comprises step:
N indicates to carry out the length of IFFT; L represents the length of auxiliary data; N-L represents the length of valid data; M is illustrated in the M group data and chooses minimum peak-to-average force ratio;
A1, generation length are the M group MPSK modulation symbol b of L
1, b
2..., b
L1, b
L1+1..., b
L, every group code is divided into two parts, and length is respectively L1, L2, and L1+L2=L;
B1, for two parts modulation symbol that produces, be multiplied by weight coefficient w respectively
1, w
2..., w
L1And w
L1+1, w
L1+2..., w
L
C1, with the M after weighting group modulation symbol respectively with the valid data combination, valid data are expressed as: x
1, x
2..., x
N-L-1, x
N-LThen combination back M circuit-switched data wherein one the tunnel is expressed as:
w
1b
1，w
2b
2，...，w
L1b
L1，x
1，x
2，...，x
N-L-1，x
N-L，w
L1+1b
L1+1，...，w
Lb
L；
D1, the M circuit-switched data after the combination is carried out N point IFFT respectively export;
The peak-to-average force ratio of M circuit-switched data behind E1, the calculating process IFFT, and compare, select minimum peak-to-average force ratio output.
Reduce the method for peak-to-average force ratio in a kind of multicarrier modulation system provided by the present invention, compare with existing probability class algorithm SLM, handle though all will carry out a plurality of IFFT, the inventive method need not to increase extra redundant transmission phase factor information, has increased the reliability of system; Though after the weighting systematic function is had certain influence, with reducing peak-to-average force ratio systematic function contribution is compared, within allowed band.
Description of drawings
Fig. 1 is for reducing the flow chart of the method for peak-to-average force ratio in the multicarrier modulation system of the present invention;
Fig. 2 is the schematic diagram of prior art patent EP1515504 peak-to-average force ratio when the different weights value;
Fig. 3 is the CCDF under the different choice way M (N=256, QPSK, M=3,5, a 7) schematic diagram in the inventive method;
Fig. 4 is that PAPR of the present invention improves performance and prior art patent EP1515504, SLM methods and results contrast schematic diagram;
Fig. 5 is the empty subcarrier interpolation not of the inventive method, when promptly data are zero, and the power spectrum chart of data after through 256 IFFT;
When Fig. 6 is a value after the empty subcarrier of the inventive method inserts weighting, and weight coefficient is linear envelope, the power spectrum chart of data after through 256 IFFT.
Embodiment
Below in conjunction with accompanying drawing, will carry out comparatively detailed explanation to each preferred embodiment of the present invention.
Reduce the method for peak-to-average force ratio in the multicarrier modulation system of the present invention, its core concept is to utilize that vacant subcarrier improves peak-to-average force ratio in the ofdm system.Transmission multichannel supplementary on vacant subcarrier, every road supplementary and valid data carry out linear combination, calculate the peak-to-average force ratio after IFFT output is carried out on each road then, by multichannel relatively, select optimum peak-to-average force ratio.Because vacant subcarrier data is in both sides in the OFDM symbol, can be subjected to the interference of adjacent OFDM symbol, therefore pass into disuse the ordinary circumstance zero padding usually at receiving terminal.In the methods of the invention,, insert some special data, in multiple signals, choose a road best signal of peak-to-average force ratio for vacant subcarrier.The benefit of the inventive method is to have utilized vacant subcarrier, contributes to reducing peak-to-average force ratio, and the interference of the frequency spectrum adjacent-symbol of introducing in order to prevent the inventive method from utilizing vacant subcarrier need be weighted vacant subcarrier data.In addition, described vacant subcarrier data can be shared a part of power, and the power of useful information is decreased.
The flow process of the inventive method as shown in Figure 1, concrete steps can comprise as follows:
Wherein N indicates to carry out the length of IFFT; L represents the length of auxiliary data; N-L represents the length of valid data; M is illustrated in the M group data and chooses optimum peak-to-average force ratio.
The first step, producing length is the M group MPSK modulation symbol of L, and every group code is divided into two parts, and length is respectively L1, L2, and L1+L2=L is then arranged.Modulation symbol b
1, b
2..., b
L1, b
L1+1..., b
LExpression.
In second step, two groups of modulation symbols for producing are multiplied by weight coefficient w respectively
1, w
2..., w
L1And w
L1+1, w
L1+2..., w
L, it is to insert the influence of data to spread spectrum in order to reduce that symbol is weighted, and reduces the interference between nearby frequency bands.
In the 3rd step, the group of the M after weighting modulation symbol is made up with valid data respectively, if valid data are expressed as: x
1, x
2..., x
N-L-1, x
N-L
Then combination back M circuit-switched data wherein one the tunnel can be expressed as:
w
1b
1，w
2b
2，...，w
L1b
L1，x
1，x
2，...，x
N-L-1，x
N-L，w
L1+1b
L1+1，...，w
Lb
L；
In the 4th step, the M circuit-switched data after the combination is carried out N point IFFT respectively;
The 5th step, calculate peak-to-average force ratio, and compare through M circuit-switched data behind the IFFT, select minimum peak-to-average force ratio.
In the 6th step, smallest peaks is all exported than the data of correspondence.
For the performance of checking the inventive method,, can carry out simulating, verifying according to physical layer specifies in 802.16 agreements.
At ofdm system baseband transmission end, 192 of data subcarriers, add 8 pilot sub-carriers, 200 effective subcarrier datas altogether, utilizing sequence number is 28 to 127,129 to 228 subcarrier transmission, to the subcarrier of sequence number 1 to 27,128 and 229 to 256, be called empty subcarrier, empty subcarrier is in both sides in the OFDM symbol, can be subjected to the interference of adjacent OFDM symbol, the ordinary circumstance zero padding.The inventive method is promptly utilized empty subcarrier transmission auxiliary data, and auxiliary data is the data after the MPSK modulation symbol process weighting that produces at random, and the concrete step of implementing is as follows:
1. 200 valid data are put into sequence number and are on 28 to 127,129 to 228 the subcarrier, all the other position subcarrier datas are zero;
2. data are carried out N (N=256) some IFFT conversion, obtain x
N-L(n);
3. produce M road random Q PSK modulation symbol, the individual modulation symbol of every road L (L=55), separated into two parts: 27 QPSK modulation symbols of a part, weight coefficient is w1, w2 ..., w27, being put into sequence number is on 1 to 27 subcarrier, 28 QPSK modulation symbols of another part, and weight coefficient is w28, w29, ..., w55 is put into sequence number and is on 229 to 256 the subcarrier.All the other subcarriers (sequence number 28 to 228) data all are zero.W1 in the emulation, w2 ..., the w27 value is [1/28:1/28:1-1/28], w28, and w29 ..., the w55 value is [1:-1/28:1/28];
4. this M road signal is carried out the IFFT operation that N is ordered respectively, output M road signal x
L 1(n), x
L 2(n) ..., x
L M(n);
5. the x that the M road signal of IFFT output is produced with step 2 respectively
N-L(n) addition obtains x
1(n), x
2(n) ..., x
M(n);
6. with x
1(n), x
2(n) ..., x
M(n) peak-to-average force ratio is calculated in the output of M group respectively altogether, and compares, and exports the data of minimum PAPR correspondence.
M value in the simulating, verifying can change, the selection of M is the main points that influence performance and resource, and M is big more, selects the path just many more, the effect of improving peak-to-average force ratio is good more, but simultaneously,, carry out 256 IFFT computings and increase along with the increase of M, taking resource also increases, need between effect and resource, look for a balance,, can find best M value by emulation according to the needs of different system.Shown the situation of improving peak-to-average force ratio when the different M value as Fig. 3.
Then shown the auxiliary data frequency spectrum diagram after the weighted sum weighting not as Fig. 5 and Fig. 6.
In order to compare with additive method, SLM algorithm and patent EP1515504 are also carried out emulation, comparative result as shown in Figure 4, the inventive method is compared with existing probability class algorithm SLM, though all will carry out a plurality of IFFT handles, but the inventive method need not to increase extra redundant transmission phase factor information, has increased the reliability of system.EP1515504 compares with patent, all utilize and insert data reduction peak-to-average force ratio, but during actual the use, patent EP1515504 does not solve the spread spectrum problem that causes because of the increase data, and the inventive method is utilized to both sides auxiliary data in the OFDM symbol and is weighted to reduce spectral interference, can be reached a conclusion by simulation result: though after the weighting systematic function is had certain influence, with reduce peak-to-average force ratio to systematic function contribution compare, within allowed band, obtained extraordinary effect.
Should be pointed out that above-mentioned description at specific embodiment is comparatively concrete, can not therefore be interpreted as the restriction to scope of patent protection of the present invention, scope of patent protection of the present invention should be as the criterion with claims.
Claims (2)
1, reduce the method for peak-to-average force ratio in a kind of multicarrier modulation system, it is characterized in that, may further comprise the steps:
A, on vacant subcarrier transmission multichannel auxiliary data, every road auxiliary data and valid data linear combination;
B, calculate the peak-to-average force ratio after IFFT output is carried out on each road, by multichannel relatively, select minimum peak-to-average force ratio;
C, auxiliary data on the vacant subcarrier is weighted.
2, method according to claim 1 is characterized in that, also comprises step:
N indicates to carry out the length of IFFT; L represents the length of auxiliary data; N-L represents the length of valid data; M is illustrated in the M group data and chooses minimum peak-to-average force ratio;
A1, generation length are the M group MPSK modulation symbol b of L
1, b
2..., b
L1, b
L1+1..., b
L, every group code is divided into two parts, and length is respectively L1, L2, and L1+L2=L;
B1, for two parts modulation symbol that produces, be multiplied by weight coefficient w respectively
1, w
2..., w
L1And w
L1+1, w
L1+2..., w
L
C1, with the M after weighting group modulation symbol respectively with the valid data combination, valid data are expressed as: x
1, x
2..., x
N-L-1, x
N-LThen combination back M circuit-switched data wherein one the tunnel is expressed as:
w
1b
1，w
2b
2，...，w
L1b
L1，x
1，x
2，...，x
N-L-1，x
N-L，w
L1+1b
L1+1，...，w
Lb
L；
D1, the M circuit-switched data after the combination is carried out N point IFFT respectively export;
The peak-to-average force ratio of M circuit-switched data behind E1, the calculating process IFFT, and compare, select minimum peak-to-average force ratio output.
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| CNB2005100900858A CN100568867C (en) | 2005-08-12 | 2005-08-12 | Reduce the method for peak-to-average force ratio in a kind of multicarrier modulation system |
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| CN100568867C CN100568867C (en) | 2009-12-09 |
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Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2011009239A1 (en) * | 2009-07-23 | 2011-01-27 | Huawei Technologies Co., Ltd. | Spectral shaping of multicarrier signals |
| CN101374125B (en) * | 2007-08-24 | 2011-03-09 | 大唐移动通信设备有限公司 | Method and apparatus for reducing PAR |
| CN101136888B (en) * | 2007-05-18 | 2011-09-21 | 中兴通讯股份有限公司 | Modulation method to reduce signal peak-to-average power ratio |
| CN102571678A (en) * | 2012-02-28 | 2012-07-11 | 中兴通讯股份有限公司 | Selection method and device for time-domain alternative signals |
| CN103297377A (en) * | 2013-03-18 | 2013-09-11 | 苏州五希通信科技有限公司 | Digital power carrier communication based modulation method |
-
2005
- 2005-08-12 CN CNB2005100900858A patent/CN100568867C/en not_active Expired - Fee Related
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101136888B (en) * | 2007-05-18 | 2011-09-21 | 中兴通讯股份有限公司 | Modulation method to reduce signal peak-to-average power ratio |
| CN101374125B (en) * | 2007-08-24 | 2011-03-09 | 大唐移动通信设备有限公司 | Method and apparatus for reducing PAR |
| WO2011009239A1 (en) * | 2009-07-23 | 2011-01-27 | Huawei Technologies Co., Ltd. | Spectral shaping of multicarrier signals |
| CN102571678A (en) * | 2012-02-28 | 2012-07-11 | 中兴通讯股份有限公司 | Selection method and device for time-domain alternative signals |
| CN103297377A (en) * | 2013-03-18 | 2013-09-11 | 苏州五希通信科技有限公司 | Digital power carrier communication based modulation method |
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| CN100568867C (en) | 2009-12-09 |
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