CN104780135A

CN104780135A - DFT-GCS-based visible light DCO-OFDM system peak-to-average ratio restraining method

Info

Publication number: CN104780135A
Application number: CN201510222977.2A
Authority: CN
Inventors: 王九如
Original assignee: Linyi University
Current assignee: Linyi University
Priority date: 2015-05-05
Filing date: 2015-05-05
Publication date: 2015-07-15

Abstract

The invention discloses a DFT-GCS-based visible light DCO-OFDM system peak-to-average ratio restraining method. The method comprises the steps of firstly, coding input signals through DFT in advance, then conducting sub-block segmentation on obtained sequences, and finally conducting different times of cyclic shifting on all sub-blocks. According to shifting of different combinations, the signal with the lowest peak-to-average ratio is selected as the final signal to be transmitted.

Description

A kind of visible ray DCO-OFDM system peak-to-average based on DFT-GCS compares suppressing method

Technical field

The invention belongs to communication technical field, particularly a kind of for the method for suppressing peak to average ratio based on DFT-GCS in visible ray DCO-OFDM system.

Background technology

Optical communication direct current biasing OFDM (Direct Current-biased Optical-Orthogonal Frequency Division Multiplexing, DCO-OFDM) system to be spread out the multi-carrier modulation stretched by OFDM, therefore there is the too high shortcoming of signal transmission peak-to-average force ratio equally.Too high peak-to-average force ratio can cause time-domain transmission channel producing nonlinear distortion through amplifier, causes system reliability penalty.By carrying out discrete Fourier transform (Discrete Fourier Transform, DFT) precoding conversion to input digital modulation symbol, then carrying out sub-block segmentation, and cyclic shift is carried out to each sub-block, thus reaching the function of peak-to-average force ratio reduction.Traditional DCO-OFDM adopts and suppresses based on discrete cosine transform-grouping cyclic shift (Discrete Cosine Transform-Grouping Cyclic Shift, the DCT-GCS) peak-to-average force ratio of algorithm to signal transmission.Because GCS algorithm requires that each sub-block has identical cyclic shift, and strict restriction is existed to input data symbol number, namely input the integral multiple that data symbol number is necessary for block number, be unfavorable for the flexibility expansion of system.Specifically can see document: Zhang Jun, Zhang Jian, kingly way Min, " reducing the DCT-GCS method [J] of visible ray DCO-OFDM system peak-to-average ratio ", signal transacting, 2015,31(1): 39-44.The system peak-to-average that this algorithm obtains is more too high than still, and application scenarios is limited, is therefore unfavorable for the extensive use of algorithm.

Summary of the invention

The object of the invention is to solve the problem that in visible light communication, DCO-OFDM system transfers signal peak-to-average ratio is too high, propose a kind of for the method for suppressing peak to average ratio of visible ray DCO-OFDM system based on DFT-GCS.

To achieve these goals, technical scheme of the present invention is: a kind of for the method for suppressing peak to average ratio based on DFT-GCS in visible ray DCO-OFDM system, specifically comprises the steps:

Step 1: system parameters initialization step.Initialization total number of sub-carriers order , input length is digital modulation symbolic vector , sub-block segmentation number , the maximum permission number of times of cyclic shift is , point DFT transformation matrix is , wherein for downward floor operation;

Step 2:DFT pre-encode operation.To the modulation symbol vector in step 1 carry out DFT conversion and obtain symbolic vector , namely ;

Step 3: sub-block cutting operation.By the data symbol vector after DFT precoding be divided into non-overlapping copies individual sub-block , Qi Zhong the data length of individual sub-block is

；

As sub-block data be , the data symbol vector so after a cyclic shift becomes ;

Step 4: note the the cyclic shift number of times of individual sub-block is , order , , ;

Step 5: order , and to individual sub-block is carried out secondary cyclic shift , then conjugation carried out to all frequency domain datas symmetrical and add data 0 operation and obtain length and be complete DCO-OFDM frequency domain data symbolic vector ;

Step 6: to the complete frequency domain data symbolic vector in step 5 carry out point IFFT operation obtains time-domain transmission channel , calculate peak power now ;

Step 7: order , repeat step 5 until ;

Step 8: compare the peak power that secondary different cyclic shift obtains, therefrom selects cyclic shift number of times corresponding to minimum peak power as the final cyclic shift number of times of individual sub-block, namely ;

Step 9: order , repeat step 5 until ;

Step 10: compared by above-mentioned loop iteration, can obtain each sub-block suboptimum cyclic shift number of times , and by the time-domain signal under this parameter configuration as final signal transmission.

Further, also comprise the step of the sequence in step 3 being carried out to sub-block segmentation, common dividing method mainly contains Interleaved partitioning scheme, adjacent segmentation and random division.In addition in step 8 when peak-to-average force ratio compares, because the cyclic shift between sub-block does not affect the average power of time-domain signal, the mode therefore by comparing peak power is carried out peak-to-average force ratio and is compared, thus reduces System Implementation complexity.

Beneficial effect of the present invention: first method for suppressing peak to average ratio of the present invention reduces the correlation between incoming symbol by DFT precoding, then sub-block segmentation is carried out, again different cyclic shifts is carried out to sub-block, therefrom select the suboptimum cyclic shift number of times combination that a peak-to-average force ratio is minimum, thus reach the object reducing time-domain signal peak-to-average force ratio.Method of the present invention can directly apply to visible light communication DCO-OFDM system, compares peak-to-average force ratio by the mode comparing peak power, therefore, it is possible to effectively reduce the enforcement complexity of DCO-OFDM system.

Accompanying drawing explanation

Fig. 1 is the transmitting terminal schematic diagram of method for suppressing peak to average ratio of the present invention.

Embodiment

Below in conjunction with accompanying drawing, provide specific embodiments of the invention.It should be noted that: the parameter in embodiment does not affect generality of the present invention.

Elaboration embodiment before, first introduce sub-block segmentation principle: set length as data vector be divided into individual sub-block , then the length of individual sub-block is

，

Wherein for downward floor operation.Common partitioning scheme mainly contains adjacent segmentation, Interleaved partitioning scheme and random division three kinds.

When so adopting adjacent completing a business transaction

，

Wherein be respectively vector ? individual element.

When adopting Interleaved partitioning scheme, for the then have

，

Remaining data are then assigned to the individual sub-block.

When adopting random division, be randomized to either in, and one of them sub-block can only be belonged to.

No matter adopt which kind of partitioning scheme, in the equal non-overlapping copies of element, and meet .

Be described the detailed process that the present invention is used for based on the method for suppressing peak to average ratio of DFT-GCS in visible light communication DCO-OFDM system below, operation principle as shown in Figure 1, specifically comprises the steps:

；

As sub-block data be , the data symbol vector so after a cyclic shift becomes ;

Step 7: order , repeat step 5 until ;

Step 9: order , repeat step 5 until ;

First method for suppressing peak to average ratio of the present invention converts by carrying out DFT precoding to input data symbol the probability reducing the correlation between data symbol and occur to reduce high peak power, then sub-block segmentation is carried out to data, and by carrying out different cyclic shifts to each sub-block, therefrom select the cyclic shift number of times combination that peak power is minimum, thus reach the object suppressing peak-to-average force ratio.The number of method of the present invention to input data symbol does not do strict restriction, and the comparison of peak-to-average force ratio is carried out by the mode comparing peak power, therefore not only can expand the application flexibility of the method, can also ensure effectively to reduce System Implementation complexity while suppression peak-to-average force ratio performance.

Those of ordinary skill in the art will appreciate that, embodiment described here is to help reader understanding's principle of the present invention, should be understood to that protection scope of the present invention is not limited to so special statement and embodiment.Those of ordinary skill in the art can make various other various concrete distortion and combination of not departing from essence of the present invention according to these technology enlightenment disclosed by the invention, and these distortion and combination are still in protection scope of the present invention.

Claims

1., based on a method for suppressing peak to average ratio in the visible ray DCO-OFDM system of DFT-GCS, specifically comprise the steps:

Step 1: system parameters initialization step; Initialization total number of sub-carriers order , input length is digital modulation symbolic vector , sub-block segmentation number , the maximum permission number of times of cyclic shift is , point DFT transformation matrix is , wherein for downward floor operation;

Step 2:DFT pre-encode operation; To the modulation symbol vector in step 1 carry out DFT conversion and obtain symbolic vector , namely ;

Step 3: sub-block cutting operation; By the data symbol vector after DFT precoding be divided into non-overlapping copies individual sub-block , Qi Zhong the data length of individual sub-block is

；

As sub-block data be , the data symbol vector so after a cyclic shift becomes ;

Step 7: order , repeat step 5 until ;

Step 9: order , repeat step 5 until ;

2. according to claim 1ly it is characterized in that based on DFT-GCS method for suppressing peak to average ratio, also comprise and carry out sub-block segmentation to the sequence in step 3, common partitioning scheme mainly contains Interleaved partitioning scheme, adjacent segmentation and random division.

3. according to claim 1 based on DFT-GCS method for suppressing peak to average ratio, it is characterized in that, also comprise and the peak-to-average force ratio in step 8 is compared, because the cyclic shift between sub-block does not affect the average power of time-domain signal, therefore the mode by comparing peak power is carried out peak-to-average force ratio and is compared, thus reduces System Implementation complexity.