Summary of the invention
Technical problem to be solved by this invention is to solve in the multicarrier system (especially personal network MC-SS system) of spectrum criterion in 4 times of bandwidth ranges, the too high out of band spectrum that causes of peak-to-average force ratio leaks, coverage reduces, problems such as power efficiency descends, distorted signals, and keeps very low complexity.
In order to solve the problems of the technologies described above, the technical solution adopted in the present invention is:
A kind of method for suppressing peak to average ratio that is applied to multicarrier system in 4 times of bandwidth ranges is provided, it is characterized in that, comprise the steps:
Step 1 at first sends signal to frequency domain and carries out the frequency domain zero padding, does the IFFT conversion then and converts the signal into time domain, obtains the time-domain signal of 2 times of over-samplings;
Step 2, the time-domain signal of described 2 times of over-samplings is carried out peak clipping handle;
Step 3, the signal after described peak clipping handled carry out 2 times of up-samplings, thereby make signals sampling speed bring up to 4 sampling speed;
Step 4, the signal of described 4 sampling speed is carried out filtering.
Further, after described step 1, also comprise step: the time-domain signal of above-mentioned 2 times of over-samplings is implemented power control.
Further, the finite impulse response filtering that is filtered into no intersymbol interference in the described step 5, that is, except middle tap coefficient is 1, outside primary signal, the tap coefficient of its even number position is zero.
In addition, the present invention also provides a kind of method for suppressing peak to average ratio that is applied to multicarrier system in 4 times of bandwidth ranges, comprises the steps:
Step 1 at first sends signal to frequency domain and carries out the frequency domain zero padding, does the IFFT conversion then and converts the signal into time domain, obtains the time-domain signal of 2 times of over-samplings;
Step 2, the time-domain signal of described 2 times of over-samplings is carried out 2 times of up-samplings, thereby make signals sampling speed bring up to 4 sampling speed;
Step 3, the transmission signal of described 4 sampling speed is carried out peak clipping handle;
Step 4, the signal after the described peak clipping is carried out filtering.
Further, after described step 1, also comprise step: the time-domain signal of above-mentioned 2 times of over-samplings is implemented power control.
The present invention does not need 4 times of over-samplings (4 times of DFT sizes) of adopting complexity high, only need by adopting 2 times of over-samplings (2 times of DFT sizes) and 2 times of up-samplings (complexity is low) to combine, and after connect the filter of the no intersymbol interference that is complementary with it and designs, satisfy at the same time under the prerequisite that personal network's spectrum criterion requires, by very low computation complexity, reach requirements such as reducing peak-to-average power ratio, symbol out of band spectrum standard, and under the prerequisite of receiving terminal normal synchronized, do not influence error rate of system/frame error rate performance basically.And the receiving terminal in the MC-SS system does not need to carry out extra processing.
Embodiment
MC-SS fundamental system with the 40MHz sample frequency is an example below, specifies the application process of the present invention in the personal network.
To the MC-SS system of 40MHz sample frequency, its basic system parameter is as shown in table 1.
The basic parameter of table one 40MHz sample frequency MC-SS system
The MC-SS system parameters |
Value |
Sample frequency (MHz) |
40 |
FFT length |
256 |
The data subcarrier number |
192 |
The pilot sub-carrier number |
18 |
The subcarrier number of protection sideband |
45 |
Subcarrier spacing (kHz) |
195.3 |
The CP sampling number |
16 |
Total sampling number of MC-SS symbol |
272 |
The time span (μ s) of data division in the MC-SS symbol |
6.4 |
The time span (μ s) of CP part in the MC-SS symbol |
0.4 |
The total time length of MC-SS symbol (μ s) |
6.8 |
The spreading factor of MC-SS system |
8 |
Defining its subcarrier sequence number is-127 ,-126 ..., 127,128, wherein the pairing subcarrier sequence number of DC is 0, effectively the pairing sequence number of subcarrier (comprising data subcarrier and pilot sub-carrier) is-105 ,-104 ... ,-2 ,-1 and 1,2 ..., 104,105.It is S (n) that frequency domain is sent signal indication, and wherein n is the subcarrier sequence number.
The method for restraining peak average power ratio step of implementing at transmitting terminal is as follows:
Step 1, to the frequency domain of this MC-SS system S (k) that transmits; except mending a zero-sum at n=-128 at the dc position of n=0;-126; ,-106 and n=106,107; 127 edge protection belt carrier position is mended outside 45 zero, simultaneously at n=-256, and-254;-129 and n=128,130 ... 255 high band sub-carrier positions is mended 256 zero; the IFFT that does then at 512 converts the signal into time domain, inserts 20 Cyclic Prefix, obtains the MC-SS time-domain signal of 2 times of over-samplings.
For 512 IFFT module, the pairing input position of frequency-region signal S (n) of this MC-SS system as shown in Figure 2.
These 512 IFFT modules are output as time-domain signal s ' (m), m=0, and 1 ..., 511.After inserting 20 Cyclic Prefix, the time domain output sequence s (k) of these 2 times of oversampled signals in a MC-SS symbol is s ' (492), s ' (493) ..., s ' (511), s ' (0), s ' (1) ..., s ' (511), length is 532.
Step 2, to the time domain discrete signal s (k) of above 2 times of over-samplings, implement power control, according to the requirement of power control instruction, regulate the average transmit power of time-domain signal.
s
PC(k)=α·s(k)
Wherein α is the real scalar multiplication factor of power control usefulness.
Step 3, to 2 times of oversampled signals s after the control of above power
PC(k), power is surpassed threshold value P
CLBaseband signal, keep its phase invariant, and its amplitude be restricted to
Obtain the later signal s of amplitude limit
CL(k).
If the saturation power of power amplifier is P
Sat, the average transmit power of power control instruction defined is P
Ave, A then
CLBy both difference backoff=P
Sat-P
AveDecision.From the backoff value to A
CLThe mapping relations of value, should be according to the parameters such as saturation power of power control step-size and selected power amplifier hardware, by the off-line performance optimization, set up a mapping table, method by tabling look-up when working online, according to current backoff value, take all factors into consideration factors such as frequency spectrum, performance, power consumption, determine the A of current optimum
CLValue.8, according to claim 1 or the 7 described method for suppressing peak to average ratio that are applied to multicarrier system in 4 times of bandwidth ranges, it is characterized in that, peak clipping processing method in the described step 3, the selection step that also comprises optimal threshold: the parameters such as full each power of putting into big device hardware according to power control step-size and selected power, by the off-line performance optimization, set up a mapping table, method by tabling look-up when working online, according to the difference value between current average transmit power and the saturation emission power, take all factors into consideration frequency spectrum, performance, factors such as power consumption are determined optimum threshold value.In this specific embodiment, an example of the mapping table method for building up of employing is: at first according to power control step-size, 1.5dB for example determines the value set of power amplifier rollback parameter, 1dB for example, and 2.5dB, 4dB, 5.5dB, Then under every kind of power amplifier rollback parameter value, off-line carries out with various peak clipping threshold values, is step-length with 1dB for example, and 1dB can be arranged, 2dB, 3dB ..., removal wherein makes the system spectrum performance can not satisfy the peak clipping threshold value of spectrum criterion requirement, when for example power amplifier rollback parameter value is 5.5dB, the peak clipping threshold value is if surpass 4dB, and spectrum criterion just can not satisfy well, therefore must be taken as below the 4dB; After this can choose the pairing optimum peak clipping threshold value of each power amplifier rollback parameter value according to other performance requirements such as system's frame error rate.
Step 4, to the signal s after the above peak clipping
CL(k), carry out 2 times of up-samplings, promptly between per two neighbouring sample points, insert one zero, obtain the signal s of 4 sampling speed
US(k).
s
US(2k)=s
CL(k),s
US(2k+1)=0,k=0,1,…,531
Step 5, to above signal s through up-sampling
US(k), do not have the finite impulse response filtering of intersymbol interference, reach the spectrum criterion requirement with the control out of band spectrum.
s
FIR(k)=g(k)*s
US(k)
Wherein g (k) is a FIR filter coefficient sequence, and symbol * represents convolution algorithm.
For not disturbing between created symbol, can utilize the characteristic of 2 times of up-sampling signals, design g (k) sequence makes it except that the tap position corresponding to original signal, and the tap coefficient of other all even number positions is equal to zero.Here the coefficient of filter that provides one 23 tap is as example:
C
filter=[-0.0055,0.0000,0.0152,-0.0000,-0.0383,0.0000,0.0839,-0.0000,-0.1836,0.0000,0.6266,1.0000,0.6266,0.0000,-0.1836,-0.0000,0.0839,0.0000,-0.0383,-0.0000,0.0152,0.0000,-0.0055]
The length of this finite impulse response filter is at 6 samplings of original signal s (k) in cycle time.Except middle tap coefficient is a nonzero value, corresponding to primary signal outer (in this specific embodiment, this value is 1), the tap coefficient of its even number position is equal to zero, therefore for the signal among the present invention, can eliminate intersymbol interference well through 2 times of up-samplings.
Described step 3 and step 4 can exchange, and do not influence performance, but complexity can more slightly increase.
The spectral characteristic of this filter as shown in Figure 3.
Under the condition of carrying out the 4dB amplitude limit, the signal s before the filtering
CL(k) spectral characteristic as shown in Figure 4.Owing to adopted 2 times of up-samplings, so formed image spectra in both sides.Under the condition of carrying out the 4dB amplitude limit, through the filtered signal s of above-mentioned finite impulse response filter
FIR(k) spectral characteristic as shown in Figure 5.In Fig. 4 and Fig. 5, red broken line is the spectrum criterion requirement of MC-SS system.
The statistical distribution characteristic of filtered peak-to-average power ratio as shown in Figure 6.As seen from the figure, owing to adopted 2 times of over-samplings, thus also little by the peak value regeneration that produces after the finite impulse response filtering, can control the Distribution Statistics of filtered peak-to-average power ratio by control limiting threshold parameter.
Fig. 7, Fig. 8 and Fig. 9 have provided respectively when the power amplifier rollback and have equaled 8.5dB, when 7dB and 5.5dB, and after suppressing to handle through above peak-to-average power ratio, the frame error rate performance of MC-SS system.Adopt the QPSK modulation, 1/2 convolutional encoding, MATRICE power amplifier model, HIPERLAN2 multidiameter fading channel.
In the analogous diagram of above three frame error rate, the span of limiting threshold has guaranteed that all out of band spectrum can satisfy the MC-SS system requirements.Abscissa is total Eb/NO, has promptly considered power amplifier rollback bit signal noise ratio level afterwards simultaneously.
By carrying out above some emulation like this, promptly can determine when each back-off value (promptly corresponding to transmission power level), under the prerequisite that satisfies the out of band spectrum requirement, the limiting threshold parameter of frame error rate best performance.
When Figure 10 is the different capacity rollback value that draws according to above result, adopt the MC-SS system frame error rate performance of optimum limiting threshold.For justice compares, abscissa adopts the reference Eb/NO level when power amplifier adopts saturation power.With reference to the Eb/NO level be: the reference Eb/NO-power amplifier rollback when total Eb/NO=adopts saturation emission power with the conversion relation of the used total Eb/NO in front.For example: when the power amplifier rollback equaled 7dB, the reference Eb/NO of 12dB was corresponding to total Eb/NO of 5dB.
As seen from Figure 10, generally, along with the increase of power amplifier rollback, the bit error rate performance variation, this is because transmitting power reduces MC-SS system frame error rate Effect on Performance, has surpassed optimum peak clipping threshold value and has increased and make signal non-linear distortion reduce improvement to the MC-SS systematic function.
When the channel signal to noise ratio was better, bigger with reference to Eb/NO, the frame error rate performance under some kinds of parameters dispose all satisfied the quality of service requirement of system, and can adopt the configuration of power amplifier rollback maximum this moment, to reduce the transmitter power consumption.This moment, optimum peak clipping threshold value was very high, and system works in linear zone basically.When the channel signal to noise ratio is big, less with reference to Eb/NO, to have only when power amplifier rollback during less than certain value, frame error rate can satisfy the quality of service requirement of system, and this moment, transmitter power must be brought up to enough levels.When the non-constant of channel conditions, very low with reference to Eb/NO, improve transmitter power this moment in any case, all can not reach the frame error rate performance requirement of system when satisfying the out of band spectrum standard.Therefore, by above processes, just can obtain under the different channels condition, peak-to-average power ratio suppresses the optimized parameter of module.