CN1984110B - Method for decreasing peak equilibrium ratio and orthogonal frequency division multiplexing system - Google Patents

Abstract

The present invention relates to a method for reducing the peak-to-average ratio and an OFDM system with a low peak-to-average ratio. The phase is completely removed or part of the process is reserved, and the transfer function is added; the receiver removes the transfer function in the frequency domain sequence obtained after the fast Fourier transform (FFT), and performs initial phase processing on the frequency domain sequence from which the transfer function has been removed, and then restores out of the send sequence. The present invention only needs to perform N times of complex multiplication operations when adding the transfer function, so it can reduce the implementation complexity of the transmitter and the receiver under the premise of effectively reducing the peak-to-average ratio. In addition, by using the method of multiplying the initial phase of the transmission sequence by the phase factor to retain part of the initial phase of the transmission sequence, the sending end does not need to send any redundant information such as sideband information, thus further reducing the complexity of the transmitter and receiver implementation Spend.

Description

Method for reducing peak-to-average ratio and OFDM system with low peak-to-average ratio

technical field

The invention relates to the field of wireless communication, in particular to a technology for reducing peak-to-average ratio based on Orthogonal Frequency Division Multiplexing (OFDM) technology. the

Background technique

With the development of mobile communication services, various multimedia services continue to emerge. OFDM technology has been used in digital audio broadcasting (DAB), digital video broadcasting (DVB), asymmetric digital subscriber line (ADSL), and networks based on IEEE802.11 and 802.16 standards. It has been applied in wireless local area network (WLAN) and has become the main candidate technology of 4G. the

OFDM technology is a multi-carrier broadband digital modulation technology. It divides the data stream into several sub-bit streams, so that each sub-data stream has a lower transmission bit rate, and uses these data streams to modulate several orthogonal carrier waves. The data transmission rate of each modulated subcarrier is relatively low, and the symbol period is long. As long as the delay spread is less than a certain ratio compared with the symbol period, intersymbol interference will not occur. In addition, OFDM technology allows 1/2 overlap of each sub-channel spectrum due to the use of the time-frequency orthogonality of the signal, so that the spectrum utilization rate is nearly doubled compared with the single-carrier transmission system. When a certain frequency band in the transmission channel fades, those modulated carrier signals that fall into this frequency band are affected, while the modulated carrier signals of other frequency bands are not affected. Compared with the traditional single-carrier transmission system (such as time division multiple access TDMA), the OFDM system using OFDM technology has obvious anti-multipath interference ability, and can also form a single frequency network, so it is especially suitable for the requirements of terrestrial broadcasting channels, and can also be used A digital signal processor (DSP) chip achieves the purpose of reducing costs. the

A block diagram of an OFDM system is shown in FIG. 1 , which includes a transmitter 100 and a receiver 150 . The transmitter 100 includes a channel encoder 102, a symbol mapping unit 104, a serial-to-parallel converter 106, a pilot symbol inserter 108, an inverse fast Fourier transform (IFFT) unit 110, a parallel-to-serial converter 112, a guard interval insertion unit 114, D /A converter 116, radio frequency unit 118. the

The channel encoder 102 receives input data, performs channel encoding on the input data, and sends the input data to the symbol mapping unit 104 . The channel coding can be in the form of RS code, convolutional code, TURBO code or LDPC code or multiple codes concatenated. the

The symbol mapping unit 104 maps the code stream from the channel encoder 102 according to a predetermined constellation mapping method to form modulated symbols, and sends them to the serial-to-parallel converter 106 . Constellation mapping methods include but are not limited to the following: BPSK, QPSK, 16QAM, 64QAM. the

Each subcarrier of the OFDM system can use different modulations according to channel conditions, and the best balance between spectrum utilization and bit error rate is the criterion. The maximum spectral efficiency can be obtained by selecting the best modulation method that satisfies a certain bit error rate. The frequency selective attenuation of the multipath channel will lead to a significant drop in the power of the received signal, and the use of a modulation method that matches the signal-to-noise ratio can improve spectrum utilization. As we all know, reliability is an important assessment index for whether the communication system is running well, so the system usually chooses BPSK or QPSK modulation, which can ensure that the system can obtain good performance even under the worst channel conditions. But the spectral efficiency of these two modulations is too low. If adaptive modulation is used, the terminal can use higher modulation when the channel is good, and the spectrum utilization rate of the whole system is greatly improved, and the self-adaptation can significantly increase the system capacity. the

Serial-to-parallel converter 106 converts the serial modulation symbols to parallel modulation symbols. The parallel data is output into the pilot symbol inserter 108 . the

Pilot inserter 108 inserts pilot symbols into parallel modulation symbols, and then outputs to IFFT unit 110 . the

The IFFT unit 110 performs an N-point IFFT operation, completes multi-carrier quadrature modulation, and outputs data to the parallel-to-serial converter 112 . the

Parallel-to-serial converter 112 converts the IFFT-transformed parallel data into serial data and sends it to insertion guard interval unit 114. the

The inserting guard interval unit 114 inserts a corresponding guard interval for each symbol, and outputs data to the D/A converter 116 . As long as the guard interval is greater than the maximum delay spread of the channel, the intersymbol interference (ISI) caused by multipath can be avoided. A specific manner of inserting a guard interval may be a manner of inserting all 0s, but this manner will cause inter-channel interference (ICI). Another way is to use a cyclic prefix or a cyclic suffix. The method of inserting a cyclic prefix (Cyclic Prefix) is to add a certain length of repetition value after the symbol before each symbol. the

The D/A converter 116 converts the digital signal into an analog signal and sends it to the radio frequency unit 118 . the

The radio frequency unit 118 includes a shaping filter and a front-end unit, processes the analog signal, and then transmits the signal through the antenna. the

The receiver includes a radio frequency unit 152, an A/D converter 154, a synchronization unit 156, a frequency offset correction unit 158, a deguard interval unit 160, a serial-to-parallel converter 162, an FFT unit 164, a pilot symbol extractor 166, and a channel estimation unit 168 , a parallel-to-serial converter 170 , a symbol demapping unit 172 , and a channel decoder 174 . The processing procedure of the receiver is basically opposite to that of the transmitter, and will not be described in detail here. the

One of the main disadvantages of the OFDM system is the problem that the peak power to average power ratio (Peak to Average Power Ratio, PAPR) is too high, that is, the instantaneous value of the output signal of the OFDM transmitter will fluctuate greatly. This is because OFDM is the superposition of multiple sine waves. When the number of subcarriers reaches a certain level, the OFDM symbol waveform is a Gaussian random process according to the central limit theorem. Thus its envelope is not constant. This requires components such as power amplifiers, A/D, and D/A converters to have a large linear range. In turn, the non-linearity of these components will produce non-linear distortion of the signal, resulting in an increase in the bit error rate and an increase in out-of-band leakage. This leads to a decrease in the performance of the entire system. Therefore, to improve system performance, it is necessary to try to reduce PAPR. the

In an OFDM system, typical methods for reducing PAPR include clipping, selective mapping (SLM), partial transmit sequence (PTS) coding methods, and so on. the

The prior art one relevant to the present invention proposes a kind of simplest method of reducing PAPR, and its core is: reduce PAPR by limiting the peak amplitude of OFDM signal. The basic principle is: before the signal passes through the amplifier, a non-linear operation is used directly at or near the peak amplitude of the OFDM signal to reduce the PAPR value so that it will not exceed the dynamic range of the amplifier, thereby avoiding the occurrence of a large PAPR. Simply put, it can be considered that the original OFDM signal passes through a rectangular window function, and the amplitude of this window is the maximum amplitude of the signal. the

In an OFDM system, since the probability of large peaks appearing is very small, the method of prior art 1 can reduce PAPR very directly and effectively. However, clipping is a nonlinear process. From the perspective of signal processing, the rectangular window The introduction will inevitably affect the frequency spectrum of the original signal, which will easily cause signal distortion, which will lead to serious in-band interference and out-of-band interference, and then cause the reduction of the bit error rate performance of the entire system and out-of-band leakage. the

The prior art 2 related to the present invention proposes another technique for reducing the PAPR, the core of which is: reduce the PAPR by the method of selective mapping (SLM), the principle of this method is to generate M statistically independent The random sequences r1, r2, ..., rM are XORed with the original sequence respectively to output M different sequences, and finally the one with the smallest PAPR is selected from the modulated signals for transmission. the

As can be seen from prior art two, it has the following defects:

1. Need sideband information

The second prior art requires the transmitter to transmit sideband information to restore the original data, which requires additional bandwidth. At the same time, it is necessary to additionally consider the reliability problem in the sideband information transmission, and generally increase the power to solve it or increase the error correction code, which brings additional overhead. At the receiving end, an additional receiver processing module is required to receive the sideband information for recovering the correct data from the received data stream. the

2. High complexity

When the prior art 2 is adopted, additional M-1 groups of I FFT operations need to be calculated. As M increases, the number of searches performed by the system also increases correspondingly, so that the calculation amount of the system increases linearly with M, so the algorithm complexity of the prior art 2 is high.

Contents of the invention

The purpose of the present invention is to provide a method for reducing the peak-to-average ratio and an OFDM system with a low peak-to-average ratio. Through the present invention, under the premise of effectively reducing the peak-to-average ratio of the transmitted data sequence, it can effectively Reduce the implementation complexity of the transmitter and receiver. the

The purpose of the present invention is achieved by the following technical solutions:

The invention provides a method for reducing the peak-to-average ratio, which includes:

A. Before the fast inverse Fourier transform IFFT transformation, the transmitter removes the initial phase of the modulated transmission sequence and adds a transfer function;

B. The receiver removes the transfer function in the frequency domain sequence obtained after the fast Fourier transform (FFT), and performs initial phase processing on the frequency domain sequence from which the transfer function has been removed, and restores the transmission sequence sent by the transmitter;

Wherein, when the transmitter completely removes the initial phase of the transmission sequence, the transmitter transmits the initial phase information including each subcarrier while sending the processed transmission sequence; , adding an initial phase to the frequency domain sequence after removing the transfer function;

Or, when the transmitter removes the initial phase part of the transmission sequence, the transmitter multiplies all the initial phases in the modulated transmission sequence by the phase factor to obtain the correction sequence; the receiver removes the transfer function The frequency domain sequence removes the phase factor. the

Wherein, before said step A includes:

Generate a transmit sequence with an initial phase. the

The present invention provides a low peak-to-average ratio OFDM system, including a transmitter and a receiver, wherein the transmitter includes an IFFT unit, and the receiver includes an FFT unit,

The transmitter also includes a first bandpass filter, which is used to remove the initial phase in the transmission sequence before entering the IFFT unit, and add a transfer function, and then transmit it to the IFFT unit;

The receiver also includes a second bandpass filter, which is used to remove the transfer function in the frequency domain sequence obtained after being transformed by the FFT unit, and perform initial phase processing on the frequency domain sequence from which the transfer function has been removed, and recover the The transmit sequence sent by the transmitter. the

Wherein, when the first bandpass filter includes:

When the first initial phase processing module is used to completely remove the initial phase in the transmission sequence before entering the IFFT unit, the second bandpass filter includes:

The second initial phase processing module is used to add the initial phase received from the transmitter to the sequence obtained after removing the transfer function;

or, when the first bandpass filter comprises:

The first initial phase processing module is used to multiply all initial phases in the transmission sequence before entering the IFFT unit by the phase factor, and the second bandpass filter includes:

The second initial phase processing module is used to remove the phase factor in the sequence obtained after removing the transfer function. the

As can be seen from the technical solution provided by the present invention above, in the present invention, before performing the fast inverse Fourier transform IFFT, the transmitter removes the initial phase of the transmission sequence and adds a transfer function; the receiver will undergo the fast Fourier transform FFT The transfer function in the obtained frequency domain sequence is removed, and the initial phase processing is performed on the frequency domain sequence from which the transfer function is removed, and then the transmission sequence is recovered. Since the sending end only needs to perform N complex multiplication operations when adding the transfer function, the present invention can reduce the implementation complexity of the transmitter and the receiver under the premise of effectively reducing the peak-to-average ratio of the transmitted data sequence. the

In addition, the present invention retains part of the initial phase of the transmission sequence by multiplying the initial phase of the transmission sequence by the phase factor, so that the sending end does not need to send any redundant information such as sideband information, and the receiving end can recover from the transmission sequence. out of the original sequence, thus further reducing the complexity of the transmitter and receiver implementation. the

Description of drawings

Fig. 1 is the frame diagram of OFDM system in the background technology;

Fig. 2 is the frame diagram of the first embodiment provided by the present invention;

Fig. 3 is the flow chart of the second embodiment that the present invention provides;

Fig. 4 is the flow chart of the third embodiment that the present invention passes;

Fig. 5 is a simulation effect diagram after implementing the present invention. the

Detailed ways

According to the definition of peak-to-average ratio, the larger peak-to-average ratio is caused by the consistency of subcarrier phases. If the appropriate phase relationship can be maintained between each subcarrier, the peak-to-average ratio can be effectively reduced. In the literature proposed by Newman (Newman D J.A n L 1 extremal problem for polynominals.Proc.Amer.Math.Soc., 1965, 16:1287～1290.) and the literature proposed by Boyd (Boyd S.Multitone Signals with Low Crest Factor[ J].IEEETrans.Circuits Syst.1986, CAS-33:1018～1022.) pointed out that when the subcarrier phase distribution in multi-carrier conforms to the Newman distribution, the OFDM time domain signal after IFFT transformation has the lowest peak-to-average ratio . Therefore, in the information scrambling method for reducing the multi-carrier peak-to-average ratio provided by the present invention, the transmitting end uses the polynomial of the Newman phase sequence to change the phase distribution of the transmitted frequency domain sequence, thereby being able to change the power probability density distribution. In the IFFT transform After that, the PAPR can be greatly reduced. the

The first embodiment provided by the present invention is an OFDM system with a low peak-to-average ratio, in which a band-pass filter is added to the transmitter and receiver of the prior art, and its implementation framework is shown in Figure 2 , including a transmitter 100 and a receiver 150. The transmitter 100 includes a channel encoder 102, a symbol mapping unit 104, a serial-to-parallel converter 106, a pilot symbol inserter 108, a first bandpass filter 109, and a fast inverse Fourier transform (IFFT) unit 110 , a parallel-to-serial converter 112 , an insertion guard interval unit 114 , a D/A converter 116 , and a radio frequency unit 118 . Wherein the first bandpass filter 109 includes a first initial phase processing module, which is used to completely remove the initial phase in the transmission sequence before entering the IFFT unit; or, is used to completely remove the transmission sequence before entering the IFFT unit All initial phases in are multiplied by the phase factor. the

The channel encoder 102 receives input data, performs channel encoding on the input data, and sends the input data to the symbol mapping unit 104 . The symbol mapping unit 104 maps the code stream from the channel encoder 102 according to a predetermined constellation mapping method to form modulated symbols, and sends them to the serial-to-parallel converter 106 . Constellation mapping methods include but are not limited to the following: BPSK, QPSK, 16QAM, 64QAM. Serial-to-parallel converter 106 converts the serial modulation symbols to parallel modulation symbols. The parallel data sequence is output into the pilot symbol inserter 108 . The pilot inserter 108 inserts pilot symbols into the parallel modulation symbols to generate a transmission sequence, which is then sent to the first bandpass filter 109 . the

The transfer function of the first bandpass filter 109 is shown in formula 1 and formula 2:

$h_{\left(\mathrm{\ω}\right)}=e^{-j\&Center\; Dot;\frac{{\mathrm{\ω}}^2}{4\mathrm{\α}}}$ Formula 1

$\mathrm{\&alpha;}=\frac{N\&Center\; Dot;\mathrm{\&pi;}}{{\mathrm{<figure-callout\; id="2"\; label="T"\; filenames="H06176003920060429E000031.png,H06176003920060429E000041.png"\; state="\{\{state\}\}">T</figure-callout>}}^2}$ Formula 2

Wherein, N refers to the maximum number of subcarriers, and T refers to the OFDM symbol length. the

For larger N, no matter what the value of T is, for any OFDM symbol, this phase relationship always leads to the same lower peak-to-average ratio. the

Put formula 2 into formula 1, get:

$h_{\left(f\right)}=e^{-j\&Center\; Dot;\frac{\mathrm{\&pi;}\&Center\; Dot;{\mathrm{<figure-callout\; id="2"\; label="T"\; filenames="H06176003920060429E000031.png,H06176003920060429E000041.png"\; state="\{\{state\}\}">T</figure-callout>}}^2\&CenterDot;f^2}{\mathrm{<figure-callout\; id="3"\; label="N\; Formula"\; filenames="H06176003920060429E000031.png"\; state="\{\{state\}\}">N</figure-callout>}}}$ Formula 3

In the baseband signal, the f is:

$f=(\mathrm{no}-1)\&CenterDot;\frac{1}{\mathrm{<figure-callout\; id="4"\; label="T\; Formula"\; filenames="H06176003920060429E000031.png"\; state="\{\{state\}\}">T</figure-callout>}}$ Formula 4

Put formula 4 into formula 3 to get:

$h_{\left(\mathrm{no}\right)}=e^{-j\&CenterDot;\frac{\mathrm{\&pi;}\&Center\; Dot;{(\mathrm{no}-1)}^2}{\mathrm{<figure-callout\; id="5"\; label="N\; Formula"\; filenames="H06176003920060429E000031.png,H06176003920060429E000041.png"\; state="\{\{state\}\}">N</figure-callout>}}}$ Formula 5

Formula 6

The above formula 5 is the transfer function of the first bandpass filter, and the formula 6 shows the newman phase sequence, where n=1, 2, 3, . . . , N is the subcarrier number. the

After the first bandpass filter 109 receives the transmission sequence sent by the pilot inserter 108, it processes the phase factor therein, and then uses the transfer function therein to perform N complex multiplication operations on the transmission sequence , to obtain the frequency domain sequence to be sent, and then output to the IFFT unit 110 . the

Here, the first bandpass filter 109 uses two algorithms to process the transmission sequence sent by the pilot inserter 108 . the

The first one is: first remove the initial phase of each sub-carrier in the modulated transmission sequence through the first initial phase processing module, and store it separately, and then perform a process on the transmission sequence with the initial phase removed and its internal transfer function N times of complex multiplication operations to obtain the frequency domain sequence to be sent, and transmit the time domain sequence and the initial phase information of each subcarrier to the IFFT unit 110 . the

The second is: multiply all initial phases of each subcarrier in the modulated transmission sequence by a phase factor through the first initial phase processing module, and then perform N times with the transfer function of the first bandpass filter The complex multiplication operation obtains the frequency domain sequence to be sent, and transmits the time domain sequence and the initial phase information of each subcarrier to the IFFT unit 110 . the

The IFFT unit 110 performs N-point IFFT operations, completes multi-carrier quadrature modulation, and outputs data to the parallel-to-serial converter 112. The parallel-to-serial converter 112 converts the IFFT-transformed parallel data into serial data and sends it to the insertion guard interval unit 114 . The inserting guard interval unit 114 inserts a corresponding guard interval for each symbol, and outputs data to the D/A converter 116 . The D/A converter 116 converts the digital signal into an analog signal and sends it to the radio frequency unit 118 . The radio frequency unit 118 includes a shaping filter and a front-end unit, processes the analog signal, and then transmits the signal through the antenna. the

The receiver includes a radio frequency unit 152, an A/D converter 154, a synchronization unit 156, a frequency offset correction unit 158, a deguard interval unit 160, a serial-to-parallel converter 162, an FFT unit 164, a second bandpass filter 165, a pilot Symbol extractor 166 , channel estimation unit 168 , parallel-to-serial converter 170 , symbol demapping unit 172 , and channel decoder 174 . The second bandpass filter 165 described therein includes a second initial phase processing module, which is used to add the received initial phase to the sequence obtained after the transfer function removal process; or, to remove the received initial phase after the transfer function removal process. The phase factor in the sequence. the

The processing process of the receiver is basically the opposite of that of the transmitter. When the radio frequency unit 152, A/D converter 154, synchronization unit 156, frequency offset correction unit 158, deguard interval unit 160, serial-to-parallel converter 162 and FFT unit 164 are sequentially processed After that, the frequency domain sequence is recovered, and then the frequency domain sequence is transmitted to the second bandpass filter 165 . the

The second bandpass filter 165 is corresponding to the processing procedure of the first bandpass filter 109 in the transmitter, and two processing algorithms can also be adopted:

The first one is for the algorithm of removing the initial phase of each subcarrier in the transmitter, and its working principle is:

The transfer function H _(n) is removed, and the received phase information of the corresponding subcarrier is added through the second initial phase processing module, and then sent to the pilot symbol extractor 166 .

The second is for the algorithm of multiplying the initial phase of each subcarrier by the phase factor in the transmitter, and its working principle is:

The transfer function of the bandpass filter is removed, and the phase factor α is removed by the second initial phase processing module, and then sent to the pilot symbol extractor 166 . the

After sequential processing by the pilot symbol extractor 166, the channel estimation unit 168, the parallel to serial converter 170, the symbol demapping unit 172 and the channel decoder 174, the original sequence sent by the transmitter is recovered. the

The second embodiment provided by the present invention is an information scrambling method for reducing the peak-to-average ratio, as shown in Figure 3, comprising the following steps:

Step 1, generate a transmission sequence with an initial phase, as shown in formula 7:

$S_{\left(k\right)}=A_k\&Center\; Dot;e^{-j\&Center\; Dot;{\mathrm{\&theta;}}_{\mathrm{<figure-callout\; id="7"\; label="k\; Formula"\; filenames="H06176003920060429E000041.png"\; state="\{\{state\}\}">k</figure-callout>}}}$ Formula 7

Where θ _k is the initial phase of subcarrier k, and A _k is the amplitude of subcarrier k.

Step 2, after the transmission sequence is modulated, the original phase information is removed before the IFFT transformation, and then the transfer function is added through the bandpass filter: $h_{\left(\mathrm{no}\right)}=e^{-j\&Center\; Dot;\frac{\mathrm{\&pi;}\&CenterDot;{(\mathrm{no}-1)}^2}{N}},$ The obtained frequency domain sequence before IFFT transformation is shown in Formula 8:

$S_{\left(k\right)}=A_k\&CenterDot;e^{-j\&CenterDot;\frac{{(\mathrm{no}-1)}^2\&Center\; Dot;\mathrm{\&pi;}}{N}}$ Formula 8

Step 3: Perform IFFT transformation on the S _(k) sequence shown in Formula 8 to obtain the time domain sequence to be transmitted.

Step 4: Send the time domain sequence to be sent and the phase information of each subcarrier. the

After the receiver receives the time-domain sequence sent by the transmitter, perform the following steps:

Step 5, perform FFT transformation on the received time-domain sequence, and restore the corresponding S _(k) frequency-domain sequence as shown in formula 8.

In step 6, the transfer function H _(n) is removed by a band-pass filter, and the received phase information of the corresponding subcarrier is added to restore the transmission sequence with the initial phase as shown in formula 7.

In the second embodiment provided by the present invention, because the phase information of the original sequence is no longer included in the transmission sequence, the transmitter at the sending end must send auxiliary information containing the phase information of each subcarrier to the receiver at the receiving end, and the receiver receives The obtained phase information corresponding to the subcarrier restores the transmission sequence sent by the transmitting end, that is, the transmission sequence with the initial phase as shown in formula 7. the

The third embodiment provided by the present invention does not require the transmitter to transmit auxiliary information including phase information of each subcarrier. The main idea is: properly retain a part of the original phase information in the sending sequence, so that the phase of the sending sequence approximates the Newman distribution, so that the transmitter at the sending end does not need to send any redundant information, and the receiver can completely recover the phase information of the original sequence , so as to obtain the original sequence sent by the transmitter. The concrete implementation process of this embodiment is shown in Figure 4, comprises the following steps:

On the transmitter side:

Step 1, generate the transmission sequence with the initial phase, still as shown in formula 7:

$S_{\left(k\right)}=A_k\&CenterDot;e^{-j\&Center\; Dot;{\mathrm{\&theta;}}_{\mathrm{<figure-callout\; id="7"\; label="k\; Formula"\; filenames="H06176003920060429E000041.png"\; state="\{\{state\}\}">k</figure-callout>}}}$ Formula 7

Where θ _k is the initial phase of subcarrier k, and A _k is the amplitude of subcarrier k.

Step 2, multiply the phase θ _k of all subcarriers in the modulated transmission sequence by a phase factor α to obtain the modified sequence S′ _(k) , as shown in formula 9:

${S^{\&prime;}}_{\left(k\right)}=A_k\&CenterDot;e^{-j\&CenterDot;\mathrm{\&alpha;}\&CenterDot;{\mathrm{\&theta;}}_k}$ Formula 9

Step 3, add the transfer function through the bandpass filter to obtain the frequency domain sequence S″ _(k) to be sent, as shown in formula 10:

${S^{\&prime;\&prime;}}_{\left(k\right)}=A_k\&Center\; Dot;e^{-j\&Center\; Dot;(\frac{{(\mathrm{no}-1)}^2\&CenterDot;\mathrm{\&pi;}}{N}+\mathrm{\&alpha;}\&CenterDot;{\mathrm{\&theta;}}_k)}$ Formula 10

Since the transfer function of the bandpass filter is: $h_{\left(\mathrm{no}\right)}=e^{-j\&CenterDot;\frac{\mathrm{\&pi;}\&CenterDot;{(\mathrm{no}-1)}^2}{N}},$ The modified sequence S′ _(k) is multiplied N times by the transfer function of the bandpass filter to obtain the frequency domain sequence S″ _(k) to be sent as shown in the above formula 10.

Step 4, performing IFFT transformation on the frequency domain sequence S″ _(k) to be transmitted to obtain the time domain sequence s _(k) to be transmitted, as shown in formula 11:

$S_{\left(k\right)}=\underset{i=0}{\overset{N-1}{\mathrm{\&Sigma;}}}{S}_{\left(i\right)}\&CenterDot;e^{j\&Center\; Dot;2\&Center\; Dot;\mathrm{\&pi;}\&Center\; Dot;i\&Center\; Dot;k/N}$ Formula 11

Step 5, transmitting the time domain sequence. the

at the receiver end

Step 6: After receiving the time-domain sequence, the receiver performs FFT transformation on the time-domain sequence to obtain the corresponding frequency-domain sequence S″ _(k) to be transmitted as shown in the above formula 10.

Step 7, remove the transfer function of the bandpass filter to obtain the corresponding modified sequence S′ _(k) as shown in formula 9.

Step 8, remove the phase factor α, and restore the transmission sequence S _(k) with the initial phase.

The original sequence S _(k) obtained by the method described in the third embodiment provided by the present invention has a lower peak-to-average ratio, and when this method is adopted, the sending end does not need to deliberately transmit redundant information containing phase information of each subcarrier remaining information.

The technology provided by the present invention can be applied to any multi-carrier communication system, including but not limited to: DVB, DMB, DAB, ADSL, WLAN, next generation mobile communication system and so on. the

As can be seen from the specific implementation of the foregoing embodiments, the present invention has the following advantages compared with the SLM method and the clipping method adopted in the prior art:

1. Reduced complexity

The added complexity of the sending end is relatively low, and only N times of complex multiplication operations are required, which is much lower than the complexity of the SLM and PTS methods; the algorithm is also relatively simple to implement. the

2. Good performance

The simulation effect shown in FIG. 5 shows the peak-to-average ratio performance curve of the Newman distribution reduction. It can be seen that the peak-to-average ratio of the time domain sequence obtained after IFFT transformation is significantly reduced through the present invention. the

3. No need for sideband information

When the third embodiment is adopted, since part of the initial phase of each subcarrier is reserved, the sending end does not need to send any redundant information, and the receiving end can recover the original sequence from the sending sequence, thereby improving the processing speed of the transmitted information. the

The above is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art can easily conceive of changes or modifications within the technical scope disclosed in the present invention. Replacement should be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention should be determined by the protection scope of the claims. the

Claims (3)

1. a method that reduces peak-to-average force ratio is characterized in that, comprising:

A, before carrying out quick inverse-Fourier transform IFFT conversion, transmitter is removed processing to the initial phase of the transmission sequence after ovennodulation, and adds transfer function;

Described transfer function is Wherein

Be the newman phase sequence, and N is the maximum number of subcarrier;

B, receiver will be removed through the transfer function in the frequency domain sequence that obtains behind the fast fourier transform FFT, and the described frequency domain sequence of removing transfer function is carried out initial phase processing, recover the transmission sequence that described transmitter sends;

Wherein, when transmitter was removed fully to the initial phase that sends sequence, described transmitter sent the initial phase information that comprises each subcarrier when sending treated transmission sequence; Described receiver adds initial phase according to received phase information to the described frequency domain sequence after the removal transfer function;

Or when transmitter was partly removed the initial phase that sends sequence, all initial phases in the transmission sequence after described transmitter will be modulated were multiplied by phase factor respectively, obtain Orders Corrected; Described receiver is removed phase factor to the described frequency domain sequence of removing after the transfer function.

2. method according to claim 1 is characterized in that, comprises before described steps A:

Generation has the transmission sequence of initial phase.

3. the ofdm system with low peak average ratio comprises transmitter and receiver, and wherein said transmitter comprises the IFFT unit, and described receiver comprises the FFT unit, it is characterized in that:

Described transmitter also comprises first band pass filter, is used for the initial phase that enters IFFT unit transmission sequence is before removed processing, and adds transfer function, sends the IFFT unit then to,

Described transfer function is Wherein Be the newman phase sequence, and N is the maximum number of subcarrier;

Described receiver also comprises second band pass filter, be used for transfer function removal to the frequency domain sequence that obtains after the process FFT unit conversion, and the described frequency domain sequence of removing transfer function carried out initial phase processing, recover the transmission sequence that described transmitter sends;

Wherein, comprise when described first band pass filter:

The first initial phase processing module, when being used for the initial phase that enters the transmission sequence before the IFFT unit got rid of fully, described second band pass filter comprises:

The second initial phase processing module is used for adding the initial phase that receives from described transmitter through removing the sequence that obtains after transfer function is handled;

Or, when described first band pass filter comprises:

The first initial phase processing module, be used for will enter all initial phases of transmission sequence before the IFFT unit when multiply by phase factor, described second band pass filter comprises:

The second initial phase processing module is used for removing through removing the described phase factor of the sequence that obtains after transfer function is handled.

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