CN1169319C - Amplitude compressino and expansion control method for peak-to-average ratio of orthogonal frequency division multi-plexing communication system - Google Patents
Amplitude compressino and expansion control method for peak-to-average ratio of orthogonal frequency division multi-plexing communication system Download PDFInfo
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- CN1169319C CN1169319C CNB021363390A CN02136339A CN1169319C CN 1169319 C CN1169319 C CN 1169319C CN B021363390 A CNB021363390 A CN B021363390A CN 02136339 A CN02136339 A CN 02136339A CN 1169319 C CN1169319 C CN 1169319C
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Abstract
The present invention relates to an amplitude value companding and inhibiting method for peak-to-average ratios of an orthogonal frequency division multiplexing communication system, which comprises: when power regulation and delay compensation are carried out on baseband signals modulated by OFDM of two paths of I and Q at a transmitting terminal, amplitude values are solved and are compressed; the compressed signal amplitude values are divided by the amplitude values before compression to obtain a compression ratios; the compression ratios are respectively multiplied by the baseband signals which are treated by power regulation and delay compensation of two paths of I and Q so as to complete compression operation; when the operation of power regulation and delay compensation is carried out on the received baseband signals of the two paths of I and Q at the receiving end, amplitude values are solved for expanding, and then, the amplitude values are divided by the amplitude value before expanding to obtain expanding ratios; then, the expanding ratios are multiplied by the baseband signals of the two paths of I and Q after time delay compensation so as to complete expanding operation. The present invention enables the ratio of signal peak power to mean power to be reduced so as to inhibit the peak-to-average ratios of the system, and scarcely has no damage to the signals. The present invention has the advantage of easy realization, and can be used for various communication systems using the OFDM modulation method.
Description
Technical field:
The present invention relates to a kind of amplitude companding inhibition method of orthogonal FDM communication system peak-to-average ratio, be a kind of method of utilizing the amplitude companding technology in orthogonal FDM communication system, to suppress signal peak power, reduction peak-to-average ratio, belong to digital communication technology field.
Background technology:
(Orthogonal Frequency Division Multiplexing is the very high modulation system of a kind of channel utilization OFDM), has good anti-fading ability, and can realize the parallel convey of data in the OFDM modulation.Along with the extensive use of digital signal processing technology rapid development and large scale integrated circuit, OFDM is subjected to paying close attention to widely day by day, especially in the high-speed digital communication field.
In ofdm communication system, use has synchronized relation on frequency a plurality of carrier waves come modulation signal, because the envelope value of each carrier wave statistics is independent, increase along with carrier number, the peak power of stack back signal and the ratio of average power, be that (peak-to-average power ratio, numerical value PAPR) is bigger for peak-to-average ratio.Therefore, the dynamic range of modulation signal is quite big, this has higher linear amplification scope with regard to requiring the power amplifier in the system, with frequency spectrum diffusion and the nonlinear distortion of avoiding transmission signals, simultaneously also require follow-up D/A converter to have bigger transition width, so just increased system cost and realized difficulty.
At present, reduce the ofdm communication system signal peak-to-average than following several method is generally arranged: direct slicing, windowing, partial transmission sequence etc.Directly slicing is promptly directly pruned the peak power that is higher than thresholding, and it is the most simple and practical method, but it has introduced new noise to system, and bigger to the influence of spectral characteristic, makes the band outdiffusion serious, influences the signal of adjacent channel.The method of windowing limits signal peak power with a window function, for in order to be effective, need under the later higher rate of up-sampling, handle signal, therefore implement the comparison difficulty, and it also can influence the spectral characteristic of signal, and this method is proposed in civilian Reducing the Peak-to-Average Power Ratio of OFDM (IEEE VTC ' 98) by Richard van and Arnout de Wild.The method of partial transmission sequence is, if one group of time-domain signal amplitude that sends symbol is higher than desired threshold value, then this group code is carried out conversion by the known conversion of a kind of receiving end, till its time domain signal amplitude meets the demands, simultaneously the parameter of conversion is sent to the other side with very little cost, though it is relatively good that this method reduces the effect of peak-to-average ratio, but it is difficult in realization, and all need add-on module at the modulation end, this method by Leonard J.Cimini and Nelson R.Sollenberger at civilian Peak-to-Average Power RatioReduction of an OFDM Signal Using Partial Transmit Sequences (IEEECOMMUNICATIONS LETTERS, VOL.4 NO.3, MARCH 2000) the middle proposition.
Summary of the invention:
The objective of the invention is to above-mentioned deficiency at prior art, a kind of new amplitude companding inhibition method that is applicable to the orthogonal FDM communication system peak-to-average ratio is provided, utilize the amplitude companding technology, at transmitting terminal signal is compressed processing, make signal peak-to-average than reducing, receiving terminal carries out the operation opposite with transmitting terminal, recovers original signal, thereby accomplish under the prerequisite of damage signal hardly, to reduce the peak-to-average ratio of system.
For realizing such purpose, in the technical scheme of the present invention, at transmitting terminal, subcarrier baseband signal after the OFDM modulation is sent into compression unit carry out amplitude compression, reduce the signal peak-to-average ratio, carry out the power adjustment simultaneously and change, carry out opposite operation at receiving terminal with the power that compensation causes in the amplitude compression, thus carry out to the received signal the amplitude expansion recover with the transmitting terminal compression before the same signal.Concrete operations of the present invention are carried out as follows:
1, transmitting terminal through the I of OFDM modulation, Q two-way baseband signal sends into power adjustment unit and the delay compensation unit carries out power adjustment and delay compensation, specific practice is, at first the ratio that average power signal is changed according to squeeze operation is adjusted the influence that signal power is caused with the compensation squeeze operation to the signal power value, in the delay compensation unit, adjust the time delay of signal path then, make the signal transmission reach synchronous.
2, send into the amplitude compression device after obtaining the baseband signal amplitude, therein the amplitude of signal is carried out squeeze operation, concrete operations are: amplitude be multiply by
Wherein m determines in advance good parameter, and V is the maximum of baseband signal amplitude, obtains by actual measurement in system, then the result of previous step is added 1 and takes from right logarithm, the logarithm value that obtains with
Multiply each other, promptly obtained the amplitude after the compression.
3, the signal amplitude after overcompression obtains compression ratio divided by the amplitude before compressing, this ratio be multiply by I, Q two-way baseband signal through overpower adjustment and delay compensation respectively, thereby finish the squeeze operation of transmitting terminal, the peak-to-average ratio of the signal of process squeeze operation has obtained bigger inhibition.
4, at receiving terminal the I, the Q two-way baseband signal that receive are sent into power adjustment unit and delay compensation unit, the adjustment parameter of power adjustment unit is the inverse that transmitting terminal power is adjusted parameter.
5, the I that receives, Q two-way baseband signal are sent into the amplitude expander after obtaining amplitude, therein the amplitude of signal are carried out dilation procedure, and concrete operations are: at first amplitude be multiply by
It is to subtract 1 after the Index for Calculation at the end that the result is carried out with e, the logarithm value that obtains at last with
Multiply each other, multiplied result is the amplitude after the expansion.
6, obtain expanding ratio through the amplitude of the signal amplitude behind the dilation procedure before, this ratio be multiply by respectively through compensation of delay and the adjusted I of power, Q two-way baseband signal, thereby finish dilation procedure divided by expansion.
Employed m is the companding parameter in the aforesaid operations step, the m value is big more, it is many more to reduce peak-to-average ratio, but this ginseng was worth conference reduces discrimination between signal but to suppress the performance boost of peak-to-average ratio not high, therefore generally getting m and be 3 to 6 can be suppressed the peak-to-average ratio effect preferably and guaranteed the signaling zone calibration simultaneously, if system is very high to suppressing the peak-to-average ratio requirement, can suitably increase the value of m again.
The present invention makes the bigger peak signal of amplitude constant substantially at the transmitting terminal of ofdm communication system by compression, but improved the amplitude of amplitude than small-signal, the ratio of signal peak power and average power is reduced, thereby the peak-to-average ratio that has suppressed system, in addition, because the operating process of companding is reversible, therefore after receiving terminal carries out the dilation procedure opposite with transmitting terminal, can recover the original signal of transmitting terminal, so just can accomplish almost not damage of signal.As reduction peak-to-average ratio methods such as partial transmission sequence, in the signal that sends, do not add extra information in the present invention, so the complexity that realizes also is lower.
Verify that through in the ofdm communication system link simulation, adding amplitude companding unit the result who obtains shows that method of the present invention is significantly to the effect that reduces system's peak-to-average ratio, and very little to the damage of signal.Compare with the method for windowing with direct slicing, method of the present invention is much smaller to the damage of signal, but equally can reach good reduction peak-to-average ratio effect; Compare with the method for partial transmission sequence, the present invention needn't add the relevant extraneous information that suppresses peak-to-average ratio and still can accomplish equally almost not damage of signal in the signal that sends, therefore, it is effective that the method for amplitude companding of the present invention has the peak-to-average ratio of reduction, and realize the low characteristics of difficulty, be a more satisfactory method that reduces the ofdm communication system peak-to-average ratio.
The present invention can be used for single carrier ofdm communication system, multi-carrier OFDM communication system, also can be applied to WLAN (wireless local area network) and adopt in the communication system of OFDM modulation system as 802.11 serial protocols and HD digital television broadcasting such as DVB agreement etc.
Description of drawings:
Fig. 1 is for suppressing the functional block diagram of ofdm communication system peak-to-average ratio by the amplitude companding technology
As shown in the figure, after the position of transmitting terminal adding amplitude compression unit is OFDM modulation and IFFT, before up-sampling and the molding filtration; After the position of receiving terminal adding amplitude expansion elements is down-sampling and molding filtration, before FFT and the OFDM demodulation.
Fig. 2 is the amplitude compression cellular construction of transmitting terminal.
As shown in the figure, when sending into power adjustment unit and delay compensation unit and carry out power adjustment and delay compensation through I, the Q two-way baseband signal of OFDM modulation, obtain amplitude and send into compressor reducer, the amplitude to signal in compressor reducer is carried out squeeze operation, at first amplitude be multiply by
Take from right logarithm after the gained result adds 1, the logarithm value that obtains with
Multiply each other, promptly obtained the amplitude after the compression.The amplitude of signal amplitude after overcompression before divided by compression obtains compression ratio, this ratio be multiply by I, Q two-way baseband signal through overpower adjustment and delay compensation respectively, thereby finish the squeeze operation of transmitting terminal.
Fig. 3 is the amplitude expansion elements structure of receiving terminal.
As shown in the figure, the I that receives, when Q two-way baseband signal is sent into power adjustment unit and delay compensation unit, obtain amplitude and send into expander, the amplitude to signal in expander is carried out dilation procedure, at first amplitude be multiply by
It is to subtract 1 after the Index for Calculation at the end that the result is carried out with e, then with
Multiply each other, promptly obtained the amplitude after the expansion.Obtain expanding ratio through the amplitude of the signal amplitude behind the dilation procedure before, this ratio be multiply by respectively through compensation of delay and the adjusted I of power, Q two-way baseband signal, thereby finish the dilation procedure of receiving terminal divided by expansion.
Embodiment:
Below by specific embodiment technical scheme of the present invention is further described.Embodiment is for having used WLAN (wireless local area network) 802.11a protocol system of the present invention.This system has adopted the modulation system of QPSK.The m value is taken as 3, through the statistics of the measurement in system link, signal maximum amplitude V=0.2, constant in order to guarantee companding front and back average power signal, in the adjustment parameter that sends with the power adjustment unit of receiving terminal is 0.65, in order to estimate the degree of injury of prediction slicing to signal, vector error mean value commonly used on the engineering, promptly EVM (Error Vector Mean) is as evaluation standard.The concrete steps that the present invention is applied to the 802.11a protocol system are:
1, transmitting terminal through the I of OFDM modulation, Q two-way baseband signal sends into power adjustment unit and the delay compensation unit carries out power adjustment and delay compensation, specific practice is, in power adjustment unit, make signal power be reduced to original 65%, in the delay compensation unit, adjust the time delay of signal path then, make the signal transmission reach synchronous.
2, obtain and send into the amplitude compression device after the baseband signal amplitude and therein the amplitude of signal is carried out squeeze operation, be divided into following three steps: at first amplitude be multiply by
M=3 wherein, V=.02.Result with previous step adds 1 then, takes from right logarithm.At last the logarithm value that obtains with
Multiply each other, promptly obtained the amplitude after the compression.
3, the amplitude of the signal amplitude after overcompression before divided by compression obtains compression ratio, this ratio be multiply by I, Q two-way baseband signal through overpower adjustment and delay compensation respectively, thereby finish the squeeze operation of transmitting terminal.
4, the I that receives, Q two-way baseband signal are sent into power adjustment unit and delay compensation unit, and making the power increase of signal in power adjustment unit is original 1.538 times.
5, the I that receives, Q two-way baseband signal are sent into the amplitude expander after obtaining amplitude, therein the amplitude of signal are carried out dilation procedure, are divided into following three steps: at first amplitude be multiply by
Then the result of previous step is carried out with e is to subtract 1 after the Index for Calculation at the end.Last with
Multiply each other, promptly obtained the amplitude after the expansion.
6, obtain expanding ratio through the amplitude of the signal amplitude behind the dilation procedure before, this ratio be multiply by respectively through compensation of delay and the adjusted I of power, Q two-way baseband signal, thereby finish dilation procedure divided by expansion.
When not carrying out the operation of amplitude companding, 802.11a the peak-to-average ratio of wireless local area network (WLAN) system is about 10dB, after above-mentioned companding operation, system's peak-to-average ratio is reduced to 7.2dB, the EVM value of simultaneity factor is-18, the highest EVM value is-13 under the QPSK modulation system 802.11a be defined in the agreement, consider that reserving surplus for modules such as back digital-to-analogue conversion and radio frequencies is 3, be that the EVM value will be lower than-16, and-18 performance satisfy this requirement, therefore, after having used the present invention, under the prerequisite that guarantees systematic function, reduce peak-to-average ratio and reach 2.8dB, obtained good effect.
Claims (3)
1, a kind of amplitude companding inhibition method of orthogonal FDM communication system peak-to-average ratio, it is characterized in that at the I of transmitting terminal through the OFDM modulation, when Q two-way baseband signal is sent into power adjustment unit and delay compensation unit and is carried out power adjustment and delay compensation, obtain amplitude and send into compressor reducer, therein the amplitude of signal is carried out squeeze operation, signal amplitude after overcompression obtains compression ratio divided by the amplitude before compressing, this ratio be multiply by I through overpower adjustment and delay compensation respectively, Q two-way baseband signal, thus squeeze operation finished; When receiving terminal is sent the I, the Q two-way baseband signal that receive into power adjustment unit and delay compensation unit, obtain amplitude and send into expander, therein the amplitude of signal is carried out dilation procedure, obtain expanding ratio through the signal amplitude after the expansion divided by the preceding amplitude of expansion, this ratio be multiply by respectively through compensation of delay and the adjusted I of power, Q two-way baseband signal, thereby finish dilation procedure.
2,, when it is characterized in that the amplitude of signal carried out squeeze operation, amplitude be multiply by as the amplitude companding inhibition method of the said orthogonal FDM communication system peak-to-average ratio of claim 1
Then the result is added 1 and takes from right logarithm, the logarithm value that obtains with
Multiply each other, the signal amplitude after obtaining compressing when the amplitude of signal is carried out dilation procedure, multiply by amplitude
It is to subtract 1 after the Index for Calculation at the end that the result is carried out with e, the logarithm value that obtains at last with
Multiply each other, the signal amplitude after obtaining expanding, wherein, companding parameter m value is 3 to 6, V is the maximum of baseband signal amplitude.
3,, it is characterized in that being applied in the ofdm communication systems such as single carrier, multicarrier and WLAN (wireless local area network) 802.11 serial protocols and HD digital television broadcasting DVB agreement as the peak-to-average ratio amplitude companding inhibition method of the said orthogonal FDM communication system of claim 1.
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| CN101005474B (en) * | 2006-01-17 | 2010-10-13 | 中山大学 | New compression extension method for reducing OFDM signal peak to average ratio |
| CN101582872B (en) * | 2008-05-15 | 2013-03-06 | 北京六合万通微电子技术股份有限公司 | Method for correcting amplitude and phase deviation of OFDM receiver |
| CN103259758B (en) * | 2013-05-27 | 2016-04-06 | 重庆邮电大学 | A kind of ofdm communication system based on companding and method |
| CN105450571A (en) * | 2014-08-26 | 2016-03-30 | 国基电子（上海）有限公司 | Method and device for reducing peak to average power ratio |
| CN104901917B (en) * | 2015-05-20 | 2018-03-30 | 北京大学 | The loop method of adjustment and its realization device of IQ delay inequalities in ofdm communication system |
| CN106230764A (en) * | 2016-07-28 | 2016-12-14 | 长安大学 | Ofdm signal method for inhibiting peak-to-average ratio based on truncation companding |
| CN113853772A (en) * | 2019-05-10 | 2021-12-28 | 株式会社Ntt都科摩 | Terminal and transmission method |
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