CN1812390A - Sideband information transmitting and frame synchronizing method and apparatus in OFDM communication system - Google Patents

Abstract

This invention discloses a kind of method for sideband information transmission and frame synchronism in OFDM communication system. It also discloses the corresponding apparatus. This invention is used for resolving peak value regeneration and frame synchronism questions in OFDM system. The steps are: the length of sideband information SI symbol is determined; all the OFDM symbols in each frame are carries out PTS processing for lowing peak value; the PTS phase optimized phase rotation information is used as SI information. All the SI information of one OFDM symbol frame are aggregated so as to using as a SI symbol dependent from other OFDM; the integrated SI symbol is copied for many times. Then, the copied symbols are inserted before OFDM symbol of the frame and transmitted; the position of OFDM frame initial sampling point is calculated by maximum-likelihood algorithm; by use of the SI information containing in SI symbols, the other frame synchronized OFDM symbols are recovered to the OFDM symbols that have not been PTS processed. The apparatus for the said method concludes: transmitting end that is consisted of PTS unit, SI information extraction unit and combiner; receiving end that is consisted of frame synchronism unit, SI symbol and OFDM symbol separation unit and information restorer.

Description

Ofdm communication system Intermediate Side Band message transmission and frame synchornization method and device

Technical field

The invention belongs to radio communication or cable communicating technology field, it is particularly related to orthogonal frequency division multiplex OFDM system and reduces the method for peak-to-average power than PAPR, and maximum likelihood method realizes the method for timing synchronization.Specifically be OFDM Intermediate Side Band message transmission and frame synchornization method and device.

Background technology

The basic principle of OFDM be exactly whole channel is divided into a plurality of overlapped and keep the subchannel of quadrature, the subcarrier-modulated information symbol of each subchannel by separately.Owing to have orthogonality between each subcarrier of ofdm system, allow the frequency spectrum of subchannel overlapped, can almost save 50% frequency spectrum resource.Just because of these advantages, the OFDM technology was widely used in recent years.But the OFDM technology also has its specific defective.

Because the OFDM symbol is independently to be formed through the sub-carrier signal addition of ovennodulation by a plurality of, the synthetic signal of these stochastic variables such as frequency domain qam symbol will bigger peak power promptly occur at the curve that time domain has produced similar Gaussian Profile, can bring bigger peak-to-average power ratio thus, be called for short peak-to-average power ratio.Peak-to-average power ratio can be defined as:

$\mathrm{PAPR}=10{\log }_{10}\left(\frac{\underset{n}{\max }\left({\left|x_n\right|}^2\right)}{E\left({\left|x_n\right|}^2\right)}\right)$

X wherein _nExpression is through resulting output signal after the fast fourier inverse transformation IFFT computing.At how reducing peak-to-average power ratio, carried out a large amount of research both at home and abroad, certain methods has also been proposed, for example: part transfer sequence (PTS:Partial Transmit Sequences), selectivity mapping (SLM:Selected Mapping) etc.In the reduction PAPR method that has proposed, there is a class need transmit side information (SI, Side Information is hereinafter to be referred as SI information), it can make the OFDM symbol can be resumed into PAPR reduction OFDM symbol before.As PTS method, SLM method etc., all need to transmit SI information.Wherein, the SLM method is a kind of special circumstances of PTS method.

The basic principle of PTS method is: utilize vector to come definition of data symbol X=[X ₁, X ₂..., X _N]; Then vectorial X is divided into the V group, each group is exactly the sub-piece of PTS, respectively by { X _v, v=1,2 ..., V} represents.Its dividing method can have multiple, as adjacent split plot design, the split plot design that interweaves, random division method etc., supposes that included number of subcarriers is identical in each grouping, then this V grouping is combined as follows: $X^{\′}=\underset{v=1}{\overset{V}{\mathrm{\Σ}}}{b}_v{X}_v.$ { b wherein _v, v=1,2 ..., V} is a twiddle factor, and satisfies b _v=exp (j _v) and _v∈ [0.2 π], b _vSide information is otherwise known as: then X ' is carried out inverse fast fourier transform IFFT, obtain x '=IFFT{X ' }.According to the linearity of IFFT, can utilize V independent invert fast fourier transformation IFFT, each grouping is calculated: $x^{\′}=\underset{v=1}{\overset{V}{\mathrm{\Σ}}}{b}_v\·\mathrm{IFFT}\left\{X_v\right\}=\underset{v=1}{\overset{V}{\mathrm{\Σ}}}{b}_v\·X_v,$ Wherein introduced V part transmission sequence PTS, X _v=IFFT{X _v.Select auxiliary weight coefficient b by using optimized Algorithm _v, make peak signal reach optimization.The theory diagram of PTS as shown in Figure 1.Receiver must be known the employed concrete twiddle factor of transmitter definitely obviously, and this twiddle factor is notified receiver by the form of SI information usually.As seen SI information must be by careful protection, careful transmission, to guarantee the operate as normal of PTS-OFDM system.

Traditional PTS side information transmission plan mainly contains two kinds:

1, utilizes preserved sub-carrier

This scheme is meant the subcarrier of all reserving right quantity in each sub-piece, transmits in carrying out after PTS optimizes the SI information of this piece being inserted the subcarrier of these reservations.

2, utilize the sub-piece of reservation

This scheme then is meant reserves a sub-piece in the OFDM symbol when carrying out PTS optimizes, the SI information of other the sub-piece in this symbol is concentrated to be put in to reserve in the sub-piece transmit.

More than two kinds of schemes no matter which kind of all is after PAPR optimizes, the OFDM symbol that SI information is inserted after optimizing transmits, and therefore brings following shortcoming to I haven't seen you for ages:

1, except the data of OFDM symbol itself, also inserts SI information, can change the structure of original OFDM symbol;

2, owing to after the PAPR optimization, also must return frequency domain SI information is inserted, carry out the IFFT conversion then again, therefore can bring additional hsrdware requirements and time-delay;

3, all inevitably cause peak value regeneration.Because that general PTS method optimization is the PAPR that does not contain the data symbol of SI information, no longer continue to optimize after inserting SI information, also promptly being applied to add new symbol after the SI information with the optimization coefficient of original symbol, so may cause peak value regeneration, also is the deterioration of PAPR.

The content of invention

The object of the invention is to avoid the deficiency of above-mentioned prior art, by analyzing the essential problem in the ofdm system, a kind of ofdm system Intermediate Side Band message transmission and frame synchornization method and device have been proposed, adopt side information transmission and frame synchronization federal solution, reduce system peak regeneration as much as possible.

The side information transmission of realization the object of the invention and the foundation of frame synchornization method as an OFDM symbolic frame, reduce the PTS processing of PAPR with a plurality of OFDM symbols respectively by the correlation of signal to each the OFDM symbol in the frame; Extract the contrary required information of PTS process then, i.e. the twiddle factor of each height piece of PTS, these information are also referred to as SI information; At last with the SI information of a frame OFDM symbol as a SI symbol, repeatedly duplicate as frame head, with other OFDM symbol combination and send.Utilize the correlation of asking of identical continuous a plurality of SI symbols, use maximum likelihood method realization timing synchronization technology to carry out synchronously.The present invention adopts following process to carry out side information transmission and frame synchronization in system, to solve peak value regeneration and frame synchronization problem in the ofdm system:

Transmitting terminal

(1), determines the length of side information SI symbol according to the parameter of ofdm communication system;

(2) OFDM symbols all in the frame is carried out part transfer sequence PTS and handle, to reduce PAPR;

(3) the phase place rotation information that the phase optimization of PTS unit is obtained gets up all SI ensembles of communication of an OFDM symbolic frame as SI information, is independent of other OFDM symbol as one, and promptly the SI symbol transmits, to reduce peak value regeneration;

(4) complete SI symbol is duplicated repeatedly and inserts before this frame OFDM symbol, directly launch then;

Receiving terminal

(1) according to the maximum likelihood algorithm formula ${\hat{d}}_{\mathrm{ML}}=\arg \max \left\{\right|\mathrm{\γ}\left(d\right)|-\mathrm{\ρ\Φ}\left(d\right)\}$ , calculating the position of the initial sampled point of OFDM symbolic frame, achieve frame is synchronous;

(2) other OFDM symbol after utilizing SI information that the SI symbol carries with frame synchronization recovers OFDM symbol before PTS handles according to the inverse process of PTS.

Transmitting terminal based on the device of the inventive method mainly comprises: PTS unit, SI signal extraction unit, integrator; Wherein:

The PTS unit is used for handling through after QAM or the PSK modulation, and the data before the lFFT conversion reduce the PAPR of these data; And generation needs the SI information of transmission;

The SI signal extraction unit is used to extract the SI information that the single binary of PTS produces;

Combiner is used for complete OFDM symbol of the information integrated one-tenth of SI that a frame OFDM symbol will be transmitted, to call in the following text: the SI symbol; And duplicate repeatedly and insert before this frame OFDM symbol, directly launch then.

The receiving terminal of realizing the device of the inventive method mainly comprises: frame synchronization unit, SI symbol and OFDM symbol separative element, signal restorer.Wherein:

The frame synchronization unit is used to realize that the OFDM symbolic frame is synchronous.

SI symbol and OFDM symbol separative element, the signal that is used for receiving transmits by two-way, and promptly one the tunnel transmits the SI symbol, the original OFDM symbol of another road transmission.

The signal restorer is used to receive the two paths of signals of SI symbol and original OFDM symbol separative element, recovers original OFDM symbol by the information on the SI symbol.

Technical scheme of the present invention not only can focus on SI information in the specific SI symbol to be transmitted, and its P OFDM symbol can't be as conventional method after carrying out PAPR optimization, because by preserved sub-carrier or reserve sub-piece transmission SI information, inserting SI information through the OFDM symbol that falls after PAPR handles, changing the structure of falling the OFDM symbol after PAPR handles and cause peak value regeneration.Be received and demodulation at receiving terminal SI symbol, the information that this SI symbol carries is exactly the SI information of P OFDM data symbol of this OFDM symbolic frame, and other a m data just can be resumed into PTS and handle OFDM symbol before like this.

The present invention compares with utilizing the preserved sub-carrier transmission plan, has the following advantages:

1, avoids peak value regeneration.In traditional SI information transmission scheme, can optimize the back at PAPR and in subcarrier of reserving or sub-piece, insert SI information, so can cause peak value regeneration.But in improved plan, because SI information is focused on unified transmission in the specific SI symbol, the SI transmission of Information can't influence the data symbol after these PAPR optimize so, so can not cause peak value regeneration.

2, do not influence symbolic construction.In traditional SI information transmission scheme, for receiver, each the OFDM symbol that receives all is the mixture of data and SI information, certainly will influence original symbolic construction like this, and has increased the complexity of receiver.And SI information of new departure and data symbol transmit respectively, so can not influence symbolic construction.

3, be convenient to the centralized management of SI information.Because it is most important that the SI information butt joint is received the correct demodulating ofdm symbol of machine, so often need special coding protection.The mixed transport of data and SI information in traditional like this SI information transmission scheme must increase the encoder complexity of transmitter, also promptly needs data and SI message part are handled respectively.And SI information concentrates on the unified transmission of SI symbol in the improved method, so also is convenient to unified coding and management.

4, realized the frame synchronization of ofdm system.The integration scenario of frame synchronization that the present invention proposes and reduction PAPR not only reduces peak value regeneration, and can realize the frame synchronization of ofdm system.But improve the performance of communication system thus, reduce system cost.

Description of drawings

Fig. 1 is existing PTS method schematic diagram

Fig. 2 is the side information transmission that proposes of the present invention and the pie graph of the SI symbol of frame synchornization method

Fig. 3 is the side information transmission that proposes of the present invention and the frame structure schematic diagram of frame synchornization method

Fig. 4 is the side information transmission and frame synchornization method realization flow figure that the present invention proposes

Fig. 5 is the side information transmission and frame-synchronizing device structured flowchart that the present invention proposes

Fig. 6 is the side information transmission that proposes of the present invention and the CCDF-PAPR comparison diagram of frame synchornization method and traditional side information transmission method

Fig. 7 is the side information transmission that proposes of the present invention and the frame synchronizing effect figure of frame synchornization method

Embodiment

Followingly the present invention is described in further detail with reference to accompanying drawing.

With reference to Fig. 4, be used for side information transmission of the present invention and frame synchornization method at ofdm system, carry out according to the following procedure:

The first step according to the parameter of ofdm communication system, is determined the length of SI symbol.The parameter relevant with SI length is that PTS piece is counted V, total number Q of twiddle factor, and modulation system constellation point number M is set the OFDM symbol numbers P that an OFDM symbolic frame comprises.Suppose S _iBe any shared sign bit of OFDM symbol SI information, the length of SI symbol (corresponding to the number of the point on the planisphere) is S, and then the relation between them is as follows:

$S=\underset{i=1}{\overset{P}{\mathrm{\Σ}}}{S}_i$

Wherein,

Round in the expression.Suppose V parameter=8, Q=2, P=16, M=4.Then needing the length of the SI symbol that transmits is 64 sign bits (sign bit is point on the planisphere) or 128 bits.No matter whether the SI symbol lengths is identical with the OFDM symbol lengths, and the present invention will regard it as an independent signal and handle.This is because of V parameter, and Q, M, P are by whole PTS-OFDM communication system decision, and can not change after the PTS-OFDM communication system is finished, and the length of SI symbol can not change yet, and promptly the length of SI symbol does not influence the design of frame synchronization.If but the length that it should be noted that the SI symbol surpasses the OFDM symbol lengths, will bring difficulty for the transmission of SI symbol.Can insert random sequence during less than the length of OFDM symbol when the length of SI symbol behind the SI symbol replenishes or uses other means to make the SI symbol lengths identical with the OFDM symbol lengths.

In side information transmission of the present invention and frame synchronization, if the twiddle factor of OFDM symbol is many more, the sub-piece number that PTS is cut apart is many more, and the possible twiddle factor of OFDM symbol makes up just many more, represent that the required sign bit of SI information is also just many more, promptly the contained sign bit of SI symbol is just many more.Because the sign bit that the SI symbol comprises is many, utilize maximum likelihood method to carry out frame synchronization owing to the probability that accidentalia obtains high coefficient correlation just significantly reduces, frame synchronizing effect can be better.Because need the sideband signals of processing too many, the time delay of system has just raise naturally yet on the other hand.

In second step, in transmitting terminal, the OFDM symbol of all inputs is carried out the PTS identical with conventional P TS-OFDM communication system handle, to reduce the PAPR of system.Here suppose that any one OFDM symbol is carrying out all being divided into the v piece when PTS handles, then any one OFDM symbol all can be expressed as in the frame: X _n=[X _{N, 1}, x _{N, 2}..., x _{N, V}].

In the 3rd step, with reference to Fig. 1, utilize the SI signal extraction unit to extract the phase place rotation information that all OFDM symbols in the frame is carried out the phase place rotation from the phase optimization device: the SI information of an OFDM symbol can be expressed as to the V piece from the 1st: b ₁, b ₂..., b _VAnd comprise a plurality of OFDM symbols in the frame, for convenience of description,, be expressed as respectively to the V piece from the 1st: b the SI information of n OFDM symbol _{N, 1}, b _{N, 2}..., b _{N, V}

The 4th step with reference to Fig. 2, focused on a specific OFDM symbol with the SI information of OFDM symbols all in the frame signal, i.e. the unified transmission of SI symbol.Specifically, exactly an OFDM symbol is respectively: X ₁, X ₂..., X _mEach OFDM symbol all is divided into the v piece when carrying out PTS, then any one OFDM symbol all can be expressed as in the frame: X _n=[x _{N, 1}, x _{N, 2}..., x _{N, V}]; And the SI information of n OFDM symbol is respectively to the V piece from first: b _{N, 1}, b _{N, 2}..., b _{N, V}All SI information of OFDM symbolic frame focus on the SI symbol transmission.This frame SI symbol SI=[B ₁, B ₂..., B _m], B wherein _n=[b _{N, 1}, b _{N, 2}..., b _{N, V}].

Because technical scheme of the present invention focuses on SI information in the specific SI symbol and transmits, its P OFDM symbol carry out PAPR can be as conventional method after optimizing: through falling in the OFDM symbol after PAPR handles by preserved sub-carrier or reserving sub-piece and insert SI information, changed the structure of falling the OFDM symbol after PAPR handles and caused that peak value regenerates.

The 5th step, with reference to Fig. 3, handle a frame OFDM symbol after, complete SI symbol is duplicated repeatedly and inserts before this frame OFDM symbol, directly launch then.Duplicating 1 time with the SI symbol is example, the OFDM symbolic frame Z=[SI that launches, SI, X ₁, X ₂..., X _m].

In the 6th step, receiving terminal utilizes the correlation between identical continuous a plurality of SI symbols, uses maximum likelihood method to realize timing synchronization.Just undertaken synchronously by following formula:

${\hat{d}}_{\mathrm{ML}}=\arg \max \left\{\right|\mathrm{\γ}\left(d\right)|-\mathrm{\ρ\Φ}\left(d\right)\}$

Result of calculation

Make the sampled point of coefficient correlation maximum exactly, i.e. the initial sampling point position of OFDM symbolic frame.

Wherein $\mathrm{\ρ}=\left|\frac{E\left\{x\left(k\right)x^{*}(k+S)\right\}}{\sqrt{E\left\{{\left|x\left(k\right)\right|}^2\right\}E\left\{{\left|x(k+S)\right|}^2\right\}}}\right|=\left|\frac{{\mathrm{\σ}}_s^2}{{\mathrm{\σ}}_s^2+{\mathrm{\σ}}_n^2}\right|=\frac{\mathrm{SNR}}{\mathrm{SNR}+1},$ The amplitude of coefficient correlation between expression x (k) and the x (k+L).

And

$\mathrm{\γ}\left(m\right)=\underset{k=m}{\overset{m+S-1}{\mathrm{\Σ}}}x\left(k\right)x^{*}(k+S);\mathrm{\Φ}\left(m\right)=\frac{1}{2}\underset{k=m}{\overset{m+S-1}{\mathrm{\Σ}}}{\left|x\left(k\right)\right|}^2+{\left|x(k+S)\right|}^2.$

Wherein, m represents any sampled point; S represents the length (weighing with the sampled point number) of SI symbol.

The SI symbol that above-mentioned frame synchronization step will be carried SI information duplicates repeatedly and transmits as frame head, thereby can guarantee the accurate transmission of this important sign, can utilize simultaneously the correlation between the OFMD symbol that repeats to transmit, by maximum likelihood algorithm, arrive the purpose of the frame synchronization of obtaining ofdm system.

In the 7th step, carry out extracting afterwards synchronously a complete SI information.SI information and remaining signal will be delivered to the signal restorer, recover through the sign format before the PTS.

The device of realizing the inventive method comprises transmitting terminal and receiving terminal.Wherein sending part mainly comprises: PTS unit, SI signal extraction unit, combiner; Receiving unit comprises: lock unit, SI symbol and OFDM symbol separative element, signal restorer.The course of work of whole ofdm communication system is as follows:

One, the transmitting terminal of ofdm communication system

During transmission, the data symbol stream 2 of the information of carrying that information source 1 produces is delivered to modulator 3, carries out m-QAM or BPSK or QPSK modulation.Binary data stream just is mapped as binary data on each parallel channel the point on the signal constellation which after ovennodulation, promptly form the data sequence of plural form.These data become the data 5 of multichannel to deliver to the transmitting terminal of OFDM through serial to parallel conversion 4 backs.Should carry out the modulation second time by parallel sequence of complex numbers by 6 pairs of PTS processors, and be about to the parallel sequence of complex numbers grouping of each group, the different phase place of each group rotation is broken the parallel consistency of sequence of complex numbers on phase place of this group, thereby reduces the PAPR of transmitting terminal.For the signal that recovers to handle through PTS, SI signal extraction unit 7 extracts PTS to the phase place rotation information 8 of every block signal, a complete OFDM symbol of the information integrated one-tenth of SI that a frame OFDM symbol will be transmitted by combiner 10 is to call in the following text: the SI symbol.In order not change the structure of the symbol of handling through PTS, the present invention puts together all SI information, is integrated into an independently SI symbol.In order to keep frame synchronization, this independently the SI symbol duplicate repeatedly, as this frame frame head transmission, perhaps transmit as the next frame frame head.Fig. 3 is replicated the frame structure schematic diagram as frame head 1 time with the SI symbol.After adding OFDM symbol input combiner 10 combinations of process PTS behind a plurality of identical SI symbols, this complex data is merged into serial data stream 12 by parallel serial conversion 11 with the data flow of each passage, it is the OFDM symbol, through digital-to-analogue conversion 13, after low pass filter 15 filtering, be launched in the channel 17.

Two, the receiving terminal of ofdm communication system

During reception, the signal 18 by channel 17 needs obtain analog signal through low pass filters 19, and this filter is also referred to as matched filter.This analog signal becomes digital signal 21 after by analog to digital converter 20.This digital signal is carried out frame synchronization by frame synchronizer 22, and signal 23 enters SI symbol and OFDM symbol separative element 24 after the frame synchronization, is divided into two ways of digital signals output, is respectively SI symbol 25 and OFDM symbol 26.Two paths of signals is sent into signal restorer 27 simultaneously and is done the PTS inverse transformation, and the information of utilizing the SI symbol to carry is recovered original OFDM symbol.The original OFDM symbol that recovers directly enters serial-parallel converter 29 by transmission line 28; Undertaken obtaining signal 31 after the demodulation by 30 pairs of these data flow of fast fourier transform FFT digital signal processor then, this signal is again through recovering and raw information 2 essentially identical reception information 34 behind parallel serial conversion 32 and the demodulator 33, to satisfy the requirement of the stay of two nights 35.

Effect of the present invention can further specify by Fig. 6, Fig. 7.

In order to illustrate that the present invention can avoid peak value this advantage of regenerating as far as possible, also in order to study the systematic function that adopts after side information transmission and the frame synchornization method.For this reason we under the 4-QAM modulation condition emulation side information transmission that proposes of the present invention and the CCDF-PAPR of frame synchornization method and traditional side information transmission method; And the output of maximum likelihood function.

One. with side information Propagation Simulation of the present invention

Transmission of table 1 side information and frame synchornization method PAPR performance simulation condition

Sub-carrier number	128
		Modulation system	4-QAM
The phase place revolution space	{-1，1}
		Sub-piece number	8
Every frame OFDM symbolic number	32
		The OFDM symbolic frame sum of emulation	150

In table 1, transmit as a frame by per 32 OFDM symbols, and these 32 OFDM symbols are put together the symbol transmission as SI through the SI information that PTS handles generation.Each OFDM symbol is divided into 8 sub-pieces, and the phase place revolution space is that { 1,1} represents that so the phase place rotation needs 2bit, and 16 OFDM symbols need 128 sign bits or 256bits to represent the SI information of these 32 data symbols altogether.

Fig. 6 has provided the CCDF curve chart of the PAPR under the listed simulated conditions of table 1.Fig. 6 is the PAPR distribution of weighing ofdm system with the CCDF CCDF of PAPR.Promptly calculate PAPR and surpass a certain threshold value PAPR ₀Probability, the CCDF CCDF that obtains.Can be expressed as with the mathematics formula: Prob{PAPR＞PAPR ₀.As can see from Figure 6: utilize traditional side information transmission plan to carry out side information transmission back PAPR and PTS in theory and handle the PAPR that draws and compare PAPR and very big deviation is arranged, so-called peak value regeneration that Here it is.This be since traditional PTS method optimization be the PAPR that does not contain the OFDM symbol of SI information, no longer continue to optimize after inserting SI information.Yet, insert the symbolic construction of the PAPR optimum that has destroyed the OFDM symbol after PTS handles after the SI information, must cause peak value regeneration.Can be clear that from Fig. 6: utilize side information transmission that the present invention proposes to carry out side information transfer ratio utilization tradition side information transmission plan with frame synchornization method and carry out the regeneration of side information transmission can still less causing peak value, the CCDF-PAPR curve that its emulation draws overlaps substantially with the CCDF-PAPR curve that PTS processing in theory draws.From Fig. 6, can further be clear that: when CCDF is 10 ^-3The time, the PAPR behind transmission of employing side information and the frame synchornization method is 8.25dB, the PAPR after traditional side information transmission is that the former PAPR of 9.82dB is than the low 1.57dB of the latter.

Two. frame synchronization emulation

Table 2 frame synchronizing effect simulated conditions

Sub-carrier number	128
		Modulation system	4-QAM
The phase place revolution space	{-1，1}
		Sub-piece number	8
Vertical shift	150 samplings
		SI symbol number of repetition	1
Every frame OFDM symbolic number	32
		Signal to noise ratio (snr)	10

Fig. 7 has provided the output of the maximum likelihood function of an OFDM frame under the listed simulated conditions of table 2.Fig. 7 is a validity of weighing frame synchronization with the output of maximum likelihood function.From Fig. 7, can clearly see: in the sample range of whole simulation, continuous 128 sampled points that utilize maximum likelihood method to calculate are separated by in the correlogram of 128 sampled points, only calculate maximum correlation coefficient on the position of a sampled point.Can also further be clear that from Fig. 7: this sampled point is exactly the 151st sampled point.The position of first sampled point that OFDM symbolic frame begins in the l-G simulation test just.

Because the present invention can implement under the situation that does not break away from its essence spirit and substantive characteristics in a variety of forms, therefore should be understood that, aforesaid embodiment is not limited by previously described any details, unless be specifically noted in addition, within the invention spirit and scope of appending claims definition, should broadly explain, therefore all changes and revision all should drop on these claims in the fixed scope, perhaps be equal to claims that the description of this scope also should be added in the present invention and cover.

Claims (4)

1. ofdm communication system Intermediate Side Band message transmission and frame synchornization method adopt following process to carry out side information transmission and frame synchronization, to solve peak value regeneration and frame synchronization problem in the ofdm system:

Transmitting terminal

(1), determines the length of side information SI symbol according to the parameter of ofdm communication system;

(2) OFDM symbols all in the frame is carried out part transfer sequence PTS and handle, compare PAPR to reduce peak-to-average power;

(3) the phase place rotation information that the phase optimization of PTS unit is obtained gets up all SI ensembles of communication of an OFDM symbolic frame as SI information, is independent of other OFDM symbol as one, and promptly the SI symbol transmits;

(4) complete SI symbol is duplicated repeatedly and inserts before this frame OFDM symbol, directly launch then;

Receiving terminal

(1) according to formula ${\hat{d}}_{\mathrm{ML}}=\arg \max \left\{\right|\mathrm{\γ}\left(d\right)|-\mathrm{\ρ\Φ}\left(d\right)\},$ Calculate the position of the initial sampled point of OFDM symbolic frame, achieve frame is synchronous;

(2) other OFDM symbol after utilizing SI information that the SI symbol carries with frame synchronization recovers OFDM symbol before PTS handles according to the inverse process of PTS.

2. realize the described square law device of claim 1, comprise transmitting terminal and receiving terminal, it is characterized in that: this transmitting terminal mainly comprises PTS unit, SI signal extraction unit, combiner; This receiving terminal mainly comprises frame synchronization unit, SI symbol and OFDM symbol separative element, signal restorer, wherein:

The PTS unit is used for handling before carrying out contrary fourier transform IFFT, through the data after QAM or the PSK modulation, reduces the PAPR of these data; And generation needs the SI information of transmission;

The SI signal extraction unit is used to extract the SI information that the PTS unit produces;

Combiner is used for the information integrated one-tenth of SI complete OFDM symbol, i.e. a SI symbol that a frame OFDM symbol will be transmitted; This SI symbol is duplicated repeatedly and inserts before this frame OFDM symbol, directly launch then;

The frame synchronization unit, it is synchronous to be used for the OFDM symbolic frame;

SI symbol and OFDM symbol separative element are used for transmitting by two-way receiving signal, and promptly one the tunnel transmits the SI symbol, the original OFDM symbol of another road transmission;

The signal restorer is used to receive the two paths of signals of SI symbol and original OFDM symbol separative element, recovers original OFDM symbol by the information on the SI symbol.

3. ofdm communication system Intermediate Side Band message transmission according to claim 1 and frame synchornization method, it is characterized in that: the length of described SI symbol is determined by following parameter: PTS piece is counted V, total number Q of twiddle factor, modulation system constellation point number M and the OFDM symbol numbers P that the OFDM symbolic frame is comprised, S _iBe any shared sign bit of OFDM symbol SI information, the length of SI symbol is S, and then the relation between them is as follows:

$S=\underset{i=1}{\overset{P}{\mathrm{\Σ}}}{S}_i$

Wherein,

4. ofdm communication system Intermediate Side Band message transmission according to claim 1 and frame synchornization method, it is characterized in that: the realization of described frame synchronization is to duplicate repeatedly and transmit as frame head by the SI symbol that will carry SI information, thereby guarantee the accurate transmission of SI symbol, utilize the correlation between the SI symbol that repeats to transmit simultaneously, by maximum likelihood algorithm, obtain the frame synchronization of ofdm system.

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