CN101174867B - Method for reducing height power ratio in multi-carrier system - Google Patents

Abstract

The invention proposes a method for reducing the peak-to-average power ratio of a multi-carrier system based on an orthogonal matrix transformation of a constant envelope zero autocorrelation sequence (CAZAC). By destroying the correlation characteristics of frequency domain signals, the peak-to-average power ratio of multi-carrier systems is reduced, especially suitable for Orthogonal Frequency Division Multiplexing (OFDM) systems, and can be flexibly applied to single-antenna (SISO) and multiple-antenna (MIMO) multi-carrier system. The method includes the steps of: given the CAZAC sequence, constructing an N*N order orthogonal transformation matrix. Before multi-carrier modulation at the transmitting end, each OFDM symbol (frequency domain signal) on each transmitting antenna is multiplied by an orthogonal transformation matrix, thereby reducing the peak-to-average power ratio of the system. This method does not require any side information (SI), and can effectively improve frequency band utilization. Due to the use of orthogonal transformation, fast algorithms can be used to reduce the complexity of system implementation.

Description

A Method for Reducing Peak-to-Average Power Ratio in Multi-Carrier Systems

technical field

The invention proposes a method for reducing the signal peak-to-average power ratio in a multi-carrier system, which is suitable for single-antenna and multi-antenna systems.

Background technique

Multi-carrier modulation (for example, Orthogonal Frequency Division Multiplexing (OFDM) technology) has attracted more and more attention due to its high spectrum efficiency and strong anti-interference ability. At present, multi-carrier modulation technology has become a part of the wireless local area network standard, and has become one of the most promising technologies in systems such as super three-generation mobile communication.

Since the output of a multi-carrier system is the superposition of multiple sub-channel signals, if the phases of multiple signals are consistent, the instantaneous power of the superimposed signal obtained will be far greater than the average power of the signal, resulting in a higher peak-to-average power ratio. The high peak-to-average power ratio causes signal distortion, which introduces inter-subcarrier interference and out-of-band radiation, degrades system performance, and reduces power amplifier efficiency.

At present, many methods have been proposed to reduce the peak-to-average power ratio of the multi-carrier system, such as clipping filter, block coding, selective mapping (SLM), partial transmission sequence (PTS) and so on. However, these methods have their own limitations, or the system implementation complexity is too high, or the data transmission rate is reduced, or the signal is distorted too much, resulting in a decrease in system bit error performance. Therefore, there is an urgent need for a method that is simple and feasible and has a good peak-to-average power ratio reduction effect.

Contents of the invention

Aiming at the problem of higher peak-to-average power ratio existing in the multi-carrier system, the present invention proposes a method for reducing the higher peak-to-average power ratio based on the change of the orthogonal matrix of the constant envelope zero autocorrelation sequence CAZAC sequence, including steps:

For a multi-carrier system with N effective subcarriers, the transmitting end constructs a CAZAC sequence, and rearranges the CAZAC sequence by column to obtain an N×N order orthogonal transformation matrix;

multiplying the frequency domain signal by the orthogonal transformation matrix, and sending out after multi-carrier modulation;

The receiving end inversely transforms the received frequency domain signal to restore the signal corresponding to the original frequency domain signal of the transmitting end.

Preferably, for the single-input-single-out SISO system, the sending end constructs a sequence with a length of ^N2 , and rearranges the sequence by column to obtain an N×N order orthogonal transformation matrix.

Preferably, in the SISO system, the column vector formed by the orthogonal transformation matrix and the original frequency domain signal is multiplied to form the frequency domain signal of the final transmitted signal, thereby reducing the peak-to-average power ratio of the system.

The multiplication of the orthogonal transformation matrix and the column vector formed by the original frequency domain signal can be replaced by a corresponding fast orthogonal algorithm in signal processing.

Preferably, for a multiple-input multiple-output MIMO system, the transmitting end constructs multiple sequences with a length of ^N2 , and rearranges the sequences by columns to obtain multiple N×N order orthogonal transformation matrices.

Preferably, in the MIMO system, one or more orthogonal transformation matrices are multiplied by the column vector formed by the original frequency domain signal on each transmitting antenna, so as to reduce the peak-to-average power ratio of the system.

The multiplication of the orthogonal transformation matrix and the column vector formed by the original frequency domain signal can be replaced by a corresponding fast orthogonal algorithm in signal processing.

Specifically, the method of the present invention comprises the following specific steps:

first step:

(k＝0，1，...，M-1)可根据式(1)获得：For a multi-carrier system with T _x transmitting antennas, given T _x prime numbers p _i , (i=1, 2, . . . , T _x ), these prime numbers can be equal or unequal. Corresponding to different prime numbers P _i get the corresponding CAZAC sequence $Z^{P_i}=\{Z_0^{P_i},Z_1^{P_i},...,Z_{m-1}^{P_i}\},$ The sequence length M satisfies the relationship with the number of effective subcarriers N of the multi-carrier system: M=N ² . CAZAC sequence

(k=0, 1, ..., M-1) can be obtained according to formula (1):

Rearrange the CAZAC sequence into an orthogonal transformation matrix of order N×N

Step two:

相乘，得到新的频域信号Yⁱ(其中Xⁱ[k]表示第k个子载波上的信号)。Yⁱ为原始频域信号Xⁱ的线性变换。对新频域信号Yⁱ进行多载波调制(如IFFT变换)后经发送天线发送出去。此处原始频域信号Xⁱ变换为新的频域信号Yⁱ可采用信号处理中相应的正交快速算法代替矩阵相乘。The frequency domain signal X ⁱ =[X ⁱ [0], ^Xi [1], ..., ^Xi [N-1]] ^T on the i-th transmitting antenna and the corresponding orthogonal transformation matrix

multiplied to obtain a new frequency-domain signal Y ⁱ (where ^Xi [k] represents the signal on the kth subcarrier). Y ⁱ is the linear transformation of the original frequency domain signal ^Xi . Multi-carrier modulation (such as IFFT transformation) is performed on the new frequency domain signal Y ⁱ and then sent out through the transmitting antenna. Here, the original frequency domain signal X ⁱ is transformed into a new frequency domain signal Y ⁱ , and the corresponding fast orthogonal algorithm in signal processing can be used instead of matrix multiplication.

According to the method of the present invention, a method for reducing the peak-to-average power ratio of the multi-carrier system based on the orthogonal matrix transformation of the constant envelope zero autocorrelation sequence CAZAC sequence is proposed. By destroying the correlation characteristics of the frequency domain signal, the peak-to-average power ratio of the multi-carrier system is reduced, especially suitable for the orthogonal frequency division multiplexing system, and can be flexibly applied to the single-antenna and multi-antenna multi-carrier systems. The method includes the steps of: given the CAZAC sequence, constructing an N*N order orthogonal transformation matrix. Each OFDM symbol (frequency domain signal) on each transmitting antenna is multiplied by an orthogonal transformation matrix before multi-carrier modulation at the transmitting end, thereby reducing the peak-to-average power ratio of the system. This method does not require any side information (SI), and can effectively improve frequency band utilization. Due to the use of orthogonal transformation, fast algorithms can be used to reduce the complexity of system implementation.

Description of drawings

Fig. 1 is a functional block diagram of the CAZAC sequence-based orthogonal matrix transformation of the present invention in a single-antenna OFDM system.

Fig. 2 is a functional block diagram of the CAZAC sequence-based orthogonal matrix transformation of the present invention in a multi-antenna OFDM system.

Detailed ways

The present invention is illustrated below with reference to the accompanying drawings.

Fig. 1 is a functional block diagram of the CAZAC sequence-based orthogonal matrix transformation of the present invention in a single-antenna OFDM system. The source signal at the sending end is encoded and modulated to obtain a frequency-domain OFDM signal X=[X[0], X[1],...,X[N-1]] ^T , and the signal is compared with the system set After multiplying the orthogonal transformation matrix A _P constructed by a certain CAZAC sequence, a new frequency domain signal Y is obtained:

Y＝A _P X (3)

The frequency domain signal Y is transformed by IFFT, and a cyclic prefix is added to form a complete time domain OFDM symbol, which is sent out through the transmitting antenna. Here, the original frequency domain signal X is transformed into the frequency domain signal Y, and the corresponding fast orthogonal algorithm in signal processing can be used instead of matrix multiplication.

Fig. 2 is a functional block diagram of the CAZAC sequence-based orthogonal matrix transformation of the present invention in a multi-antenna OFDM system. This figure takes a MIMO system with 2 transmit antennas as an example. The source signals at the transmitting end are coded, modulated and space-time processed to obtain frequency-domain OFDM signals X ¹ and X ² on each transmitting antenna. Multiply the signals on the two transmitting antennas with the system-given orthogonal transformation matrices A _P1 and A _P2 (A _P1 and A _P2 can be the same or different) constructed by the CAZAC sequence to obtain a new frequency domain signal Y ¹ , Y ² :

${\mathrm{<span\; class="notranslate">\; Y</span>}}^{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; A</span>}}_{{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}}{\mathrm{<span\; class="notranslate">\; x</span>}}^{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; ,</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1,2</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 4</span>}<span\; class="notranslate">\; )</span>$

Here, the original frequency domain signal X ⁱ is transformed into a new frequency domain signal Y ⁱ , and the corresponding fast orthogonal algorithm in signal processing can be used instead of matrix multiplication. The frequency domain signals Y ⁱ (i=1, 2) are respectively subjected to IFFT transformation, and a cyclic prefix is added to form a complete OFDM symbol, which is sent out through respective transmitting antennas.

The invention has been described with reference to specific examples. However, the descriptions herein are illustrative only and should not be considered limiting in any way. The patent protection scope of the present invention is given by the appended claims, rather than the foregoing description. Therefore, all the various modifications and equivalent forms falling within the scope of the claims shall fall within the scope of patent protection of the present invention.

Claims (5)

1. method that reduces high peak-to-average power ratio in the multicarrier system, said method comprises:

For having N the effectively multicarrier system of subcarrier, transmitting terminal is constructed permanent envelope zero autocorrelation sequence CAZAC sequence, and wherein, said structure CAZAC sequence comprises:

Said multicarrier system has T _xThe root transmitting antenna, given T _xIndividual prime number P _i, (i=1,2 ..., T _x), said P _iCan be identical also can be inequality; Corresponding said prime number P _iObtain corresponding CAZAC sequence

The effective sub-carrier number N of said CAZAC sequence length M and said multicarrier system satisfies M=N ²In the said CAZAC sequence

(k=0,1 ..., M-1) be specially:

Said CAZAC sequence is obtained the orthogonal transform matrix on a N * N rank by rearrangement;

Frequency-region signal and said orthogonal transform matrix are multiplied each other, and after multi-carrier modulation, send;

Receiving terminal carries out inverse transformation to the frequency-region signal that receives, and recovers and the corresponding signal of the original frequency-region signal of transmitting terminal.

2. according to the method for claim 1, it is characterized in that for singly going into singly to go out the SISO system, length of transmitting terminal structure is N ²The CAZAC sequence, and said sequence obtained the orthogonal transform matrix on a N * N rank by rearrangement.

3. according to the method for claim 2, in said SISO system, the column vector that said orthogonal transform matrix and original frequency-region signal are constituted multiplies each other and forms the frequency-region signal of final transmission signal, thereby reduces the peak-to-average power ratio of system,

The column vector that said orthogonal transform matrix and original frequency-region signal constitute multiplies each other and can adopt corresponding quadrature fast algorithm replacement matrix multiple in the signal processing.

4. according to the method for claim 1, it is characterized in that for the multiple-input, multiple-output mimo system, it is N that transmitting terminal is constructed a plurality of length ²The CAZAC sequence, and said sequence obtained the orthogonal transform matrix on a plurality of N * N rank by rearrangement.

5. according to the method for claim 4, it is characterized in that in mimo system, the column vector that the original frequency-region signal on one or more orthogonal transform matrixs and the every antenna constitutes multiplies each other, thereby reduce the peak-to-average power ratio of system,

The column vector that said orthogonal transform matrix and original frequency-region signal constitute multiplies each other and can adopt corresponding quadrature fast algorithm replacement matrix multiple in the signal processing.

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