CN104410597A - Method of synchronizing OFDM (Orthogonal Frequency Division Multiplexing) signal time domain based on two-stage synchronous head sequence - Google Patents
Method of synchronizing OFDM (Orthogonal Frequency Division Multiplexing) signal time domain based on two-stage synchronous head sequence Download PDFInfo
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L27/00—Modulated-carrier systems
- H04L27/26—Systems using multi-frequency codes
- H04L27/2601—Multicarrier modulation systems
- H04L27/2647—Arrangements specific to the receiver only
- H04L27/2655—Synchronisation arrangements
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Abstract
The invention relates to the field of optical communication, in particular to a method of synchronizing an optical OFDM (Orthogonal Frequency Division Multiplexing) signal time domain based on a symmetrical and asymmetrical mixed sequence. The original conventional method of synchronizing the OFDM signal time domain is divided into two stages: the first stage is rough synchronization, namely, correlation between the first half of data and the second half of data in a synchronous head TN is utilized, and the possible range of an optimum starting point of an OFDM signal is quickly found by utilizing a recursive algorithm; the second stage is fine synchronization, namely, a precise position of the optimum starting point of the OFDM signal is computed by utilizing the characteristics of a fore-and-aft symmetrical data structure in the synchronous head TN. The method has the characteristics of small hardware expenditure, fast arithmetic speed, precise location of the starting point and the like.
Description
Technical field
The present invention relates to optical communication field, specifically relate to a kind of light ofdm signal time-domain synchronizing method based on symmetric and unsymmetric mixed sequence.
Background technology
Along with the fast development of multimedia technology, the demand of people to information constantly increases.For meeting growing capacity requirement, super 100bit/s even research just like a raging fire the carrying out in the whole world of 1Tb/s follow-on optical transfer network key technology.In order to promote the capacity of existing wavelength-division multiplex system, high spectrum efficiency modulation format and single channel two-forty are considered to effective solution, but due to electronic component bandwidth restriction, the bandwidth sum sample rate restriction of such as digital to analog converter, merely by promoting monochromatic light carrier wave baud rate in conjunction with higher order modulation formats, its channel speed promotes limited.In order to break through the restriction of electronic component bandwidth, realize the single channel transmission speed of higher rate, utilize the mode that many light carriers are multiplexing, the light carrier of low-rate modulation is parallel multiple on frequency domain, be used for promoting the method for channel optical transmission speed, be considered to T bit-level transmission preferred option.
Light OFDM(Orthogonal Frequency Division Multiplexing, OFDM) have significantly different from single carrier optical transmission.Generally there is not frame structure in physical layer in single carrier optical transmission signal, can be with random time in principle to observe starting point, do not need to carry out demodulation at specific watch window to signal.And ofdm signal exists the concept of frame, each OFDM frame structure is made up of N number of OFDM symbol and corresponding protection interval.Therefore, determine the original position of OFDM frame structure watch window extremely important.Inappropriate original position can cause larger intersymbol interference (ISI) and intercarrier crosstalk (ICI).
OFDM window synchronization method the most popular is the symmetrical synchronous head method that Schmidl and Cox proposes at present.Suppose A
nfor the bipolarity pseudo random sequence that length is N, in this approach, need to send continuously two identical random sequences as synchronous head, i.e. P={A
n, A
n.1/2(and N with this synchronous head length) be benchmark, the data received are carried out degree of correlation verification before and after degree of correlation verification, the point finally obtaining maximum related value place is best timing point.The advantage of this synchronous head structure to be reduced the complexity of real-time DSP, and the expense of hardware is less, and synchronizing speed is very fast.But its shortcoming in degree of correlation change curve is a smooth change curve at the areas adjacent at the place of optimized start point, cannot accurately find optimized start point particular location.
In order to reduce to find the uncertainty of optimized start point and reduce the error of time synchronized, Minn proposes a kind of follow-on synchronous head structure.Suppose A
nfor the bipolarity pseudo random sequence that length is N, at two continuous and identical pseudo random sequence A
lafterwards, continuous two and A is in turn gived
nthe opposite polarity pseudo random sequence of sequence-A
n, overall structure is P={A
n, A
n,-A
n,-A
n.1/4(and N with this synchronous head length) be benchmark, the data received are carried out degree of correlation verification before and after degree of correlation verification, the point finally obtaining maximum related value place is best timing point.This synchronous head structure obtain timing accuracy more better than Schmidl method, but still cannot obtain timing point accurately, near real starting point in a less scope, the rate of change of Correlation Calibration value is still less, also can there is another associated check value larger " secondary peak " point simultaneously.
In order to improve the timing accuracy of synchronous head further, the people such as Park proposed a kind of timing method based on symmetric form synchronous head sequence in 2010.Suppose B
2N-1for the symmetrical pseudo random sequence of bipolarity that length is 2N-1.Its arrangement mode is B
2N-1={ S
1, S
2, S
3.... S
n-2, S
n-1, S
n, S
n-1, S
n-2..., S
3, S
2, S
1.The method that Park proposes is exactly with B
2N-1for synchronous head, carry out axisymmetric Correlation Calibration calculating using the time starting point estimated as symmetry axis.This method, can obtain larger timing accuracy, and its Correlation Calibration value has a very large spike in correct initial point position, therefore can obtain correct initial point position comparatively accurately.But the shortcoming of this method is also clearly, due to recursion type computing can not be adopted to carry out the calculating of degree of correlation check value, as long as often change the optimized start point calculating location once supposed, in synchronous head Correlation Calibration value a little will update all once.Especially in the system of in real time application, due to the Position Approximate at synchronous head place cannot be determined, from first random sampled point, often change the initial point position once supposed, all will carry out a Correlation Calibration value and calculate.A large amount of soft and hardware resources can be taken like this, thus greatly extend the time finding correct initial point position.In addition, this mode also can cause one " secondary peak ", affects the judgement of optimized start point.
Summary of the invention
For the deficiency of above-mentioned OFDM time-domain synchronizing method, the present invention proposes a kind of OFDM time-domain synchronizing method based on two-stage synchronous head, original traditional ofdm signal time-domain synchronizing method is divided into two-stage: the first order " slightly " is synchronous, utilizes synchronous head T
nthe correlation of middle the first half data and later half data, uses recursive algorithm to find the possible range of ofdm signal optimized start point fast; The second level " carefully " is synchronous, utilizes synchronous head T
nthe middle feature that there is front and back symmetric data structure, calculates the exact position of ofdm signal optimized start point.This method has that hardware spending is little, the feature such as fast operation and starting point registration.
Technical scheme of the present invention is: a kind of ofdm signal time-domain synchronizing method based on two-stage synchronous head sequence, is characterized in that: the step of transmitting terminal transmit band synchronous head frame, its synchronous head is T
nfor { [A
α, B
2 β], [A
α, B
2 β], wherein A
αfor bipolarity pseudo random sequence; B
2 βfor bipolarity symmetric form pseudo random sequence, α and β is the arbitrary integer being greater than 0, N=2 α+4 β; Receiving terminal utilizes synchronous head T
nthe correlation of middle the first half data and later half data, calculates the step of ofdm signal optimized start point scope; Receiving terminal utilizes synchronous head T
nthe middle feature that there is front and back symmetric data structure, calculates the step of ofdm signal optimized start point exact position.
Signal time-domain synchronizing method as above, is characterized in that: the computing formula of described optimized start point scope is as follows:
Calculate M successively afterwards
1(d
2), M
1(d
3), M
1(d
4) ... until M
1(d
h2), find out the point of maximum in all calculated values, just can obtain the Position Approximate of optimized start point; Wherein H2 is that receiving terminal receives number of data points H at every turn and deducts the number of data points that a complete OFDM frame data point quantity adds the synchronous head of an OFDM frame, and H is 2 times of a complete OFDM frame data point quantity.Signal time-domain synchronizing method as above, is characterized in that: described optimized start point exact position d
n1formula be:
Calculate d successively afterwards
n1~ d
n2in scope Correlation Calibration value a little, compare that to find out the maximum point of Correlation Calibration value be exactly ofdm signal optimized start point.
The invention has the beneficial effects as follows: although the first order of the present invention synchronously cannot accurately orient optimized start point position, hardware spending is little, locating speed is fast.Most non-optimal initial point position can be excluded within the fastest time.Remain possible optimized start point position bring into the second level synchronously continue calculate, although the synchronous computing in the second level can not use recursive algorithm, the large speed of hardware spending is slower, but the synchronous computing due to the first order has reduced the scope of possibility optimized start point greatly, and this algorithm can orient the optimized start point position of ofdm signal accurately.Therefore integrate and see, no matter the ofdm signal novel synchronous method that this patent proposes in hardware spending, arithmetic speed or in positioning precision, has certain advantage compared to traditional OFDM time-domain synchronizing method.
Accompanying drawing explanation
Fig. 1 is the frame structure schematic diagram of ofdm signal;
Fig. 2 is the two-stage synchronous head sequential structure write in this patent and first order correlative relationship schematic diagram;
Fig. 3 is the two-stage synchronous head sequential structure write in this patent and second level correlative relationship schematic diagram;
Fig. 4 is each data point its first order corresponding and second level Correlation Calibration value of obtaining in specific embodiments.
Embodiment
Below in conjunction with drawings and the specific embodiments, the present invention is described in further detail.
First, this patent devises a kind of synchronous head and (is synchronous head T
n=[A
α , B
2 β ], [A
α , B
2 β ]): both having comprised can the continuous and identical pseudo random sequence of two of quick position optimized start point scope, i.e. two [A
α, b
2 β ]; Comprise again the symmetrical structure pseudo random sequence accurately can locating optimized start point position, i.e. two [B
2 β ].Its structure is as follows:
Suppose that a length is the bipolarity of α (namely sequence forms by 1 and-1) pseudo random sequence
A
α ={ a
1, a
2, a
3..., a
α-2, a
α-1, a
α; Another length is the bipolarity symmetric form pseudo random sequence B of 2 β
2 β ={ b
1, b
2, b
3..., b
β-2, b
β-1, b
β, b
β, b
β-1, b
β-2..., b
3, b
2, b
1.α and β is the arbitrary integer being greater than 0.Synchronous head T
n={ [A
α , B
2 β ], [A
α , B
2 β ], length
n=
2 α+4 β, real ofdm signal optimized start point is exactly first data point of synchronous head.
The process finding ofdm signal time domain optimized start point is divided into two-stage: the first order adopt in the ofdm signal received lower can complete packet containing the data (OFDM frame structure as shown in Figure 1) of an OFDM frame, suppose the number of data points comprised to be H, H be a complete OFDM frame comprise 2 times of number of data points.And find data starting point d
1(its sampled value is defined as r (d
1), r (d
1+ k) be defined as d
1the sampled value of a kth data point after point), start the first order Correlation Calibration value M calculating this point
1(d
1).Observe synchronous head T
nfirst order correlative relationship (as shown in Figure 2), can computing formula be obtained as follows:
Calculate M successively afterwards
1(d
2), M
1(d
3), M
1(d
4) ... until M
1(d
h2), wherein H2 is that receiving terminal receives number of data points H at every turn and deducts the number of data points that a complete OFDM frame data point quantity adds the synchronous head of an OFDM frame.Find out the point of maximum in all calculated values, just can obtain the Position Approximate of optimized start point.Observe Correlation Calibration value formula we can see, the denominator term in formula and point subitem, after d point at every turn mobile one, only have and put relevant item to that of movement and change, and other all remain unchanged.Need to calculate the value of all items when only having first time to calculate, as long as remove an item that will remove when calculating afterwards at every turn, then calculate an item that will add, other unchanged item is retained just passable.Hardware spending when therefore can use recursive algorithm to reduce computing and elapsed time.
In background introduction before, we discussed, the optimized start point that the first order finds inaccuracy, were only scopes.Therefore in the second level is synchronous, accurately optimized start point to be found.
First the d that the ofdm signal optimized start point scope that the first order obtains is synchronously is supposed
n1~ d
n2(1<n1<n2<H).From d
n1point starts to calculate second level associated check value M
2(d
n1), observe synchronous head T
nsecond level correlative relationship (as shown in Figure 3), obtain second level Correlation Calibration value formula as follows:
Calculate d successively afterwards
n1~ d
n2in scope Correlation Calibration value a little.We can see to observe formula, and the denominator term in formula and point subitem are after d point at every turn mobile one, and all addition items all can change, and therefore cannot use recursive algorithm.After each mobile supposition starting point, need all addition items all to calculate one time.Calculating the maximum point of Correlation Calibration value is exactly ofdm signal optimized start point.
Below enumerate an instantiation:
Be provided with an ofdm signal receive-transmit system, the design of transmitting terminal ofdm signal synchronous head is as follows: at formula T
n=[A
α , B
2 β ], [A
α , B
2 β ] in get
α=100, β=50, then
n=
2 α+4 β=400, namely length is bipolarity (namely sequence forms by 1 and-1) the pseudo random sequence A of 100 data points
100={ a
1, a
2, a
3..., a
98, a
99, a
100; Another length is the bipolarity symmetric form pseudo random sequence B of 100 data points
100={ b
1, b
2, b
3..., b
48, b
49, b
50, b
50, b
49, b
48..., b
3, b
2, b
1, common composition ofdm signal synchronous head T
400={ [A
100, B
100], [A
100, B
100], the length of synchronous head is 400 data points.Real ofdm signal optimized start point is exactly OFDM synchronous head T
400first data point a
1.
If the length of an ofdm signal whole frame is 2000 data points.OFDM system receiving terminal receives 4000 data points at every turn, therefore must comprise a complete OFDM data frame.If receive 4000 data points to be followed successively by [d
1, d
2, d
3..., d
3998, d
3999, d
4000], and the synchronous head starting point of this complete OFDM data frame is inevitable at d
1to d
2400between, this is because a complete OFDM frame comprises 2000 data points, and puts d
24001600 data points afterwards can not comprise a complete OFDM frame.If r is (d
1) be d
1the data value of point, r (d
1+ k) be d in the data sequence received
1kth point (i.e. d after point
1+kpoint) data value.
Utilize OFDM synchronous head T
400front 200 data points and rear 200 identical characteristics of data point, calculate from d
1to d
2400the result of first order Correlation Calibration value:
……………
By formula above and utilize recursive algorithm to obtain from d
1to d
2400correlation Calibration value schematic diagram corresponding to middle each point is as Fig. 4.As can be seen from the figure, from d
1084to d
1323the Correlation Calibration value of these 240 data points is maximum in 2400 points and change is very little.These 240 points are substituted into second level synchronous head computing.
The synchronous computing in the second level, utilizes OFDM synchronous head T
400in former and later two B
100characteristic symmetrical before and after, calculates from a d
1084to a d
1323the result of first order Correlation Calibration value:
……………
By formulae discovery above, obtain from a d
1084to a d
1323corresponding second level Correlation Calibration value schematic diagram as shown in Figure 4.From figure, we can see that Correlation Calibration value has a very high peak value to appear at a d
1208place, therefore puts d
1208it is exactly the optimized start point of ofdm signal frame.Arrive here, the Domain Synchronous of ofdm signal just completes.
Those skilled in the art can carry out various modifications and variations to the embodiment of the present invention, if these amendments and modification are within the scope of the claims in the present invention and equivalent technologies thereof, then these revise and modification also within protection scope of the present invention.
The prior art that the content do not described in detail in specification is known to the skilled person.
Claims (3)
1. based on an ofdm signal time-domain synchronizing method for two-stage synchronous head sequence, it is characterized in that: the step of the OFDM frame of transmitting terminal transmit band synchronous head, its synchronous head is T
nfor [A
α, B
2 β], [A
α, B
2 β], wherein A
αfor bipolarity pseudo random sequence; B
2 βfor bipolarity symmetric form pseudo random sequence, α and β is the arbitrary integer being greater than 0, N=2 α+4 β;
Receiving terminal utilizes synchronous head T
nthe correlation of middle the first half data and later half data, calculates the step of ofdm signal optimized start point scope;
Receiving terminal utilizes synchronous head T
nthe middle feature that there is front and back symmetric data structure, calculates the step of ofdm signal optimized start point exact position.
2. signal time-domain synchronizing method as claimed in claim 1, is characterized in that: the computing formula of described optimized start point scope is as follows:
Calculate M successively afterwards
1(d
2), M
1(d
3), M
1(d
4) ... until M
1(d
h2), find out the point of maximum in all calculated values, just can obtain the Position Approximate of optimized start point; Wherein H2 is that receiving terminal receives number of data points H at every turn and deducts the number of data points that a complete OFDM frame data point quantity adds the synchronous head of an OFDM frame, and H is 2 times of a complete OFDM frame data point quantity.
3. signal time-domain synchronizing method as claimed in claim 1 or 2, is characterized in that: described optimized start point exact position d
n1formula be:
Calculate d successively afterwards
n1~ d
n2in scope Correlation Calibration value a little, compare that to find out the maximum point of Correlation Calibration value be exactly ofdm signal optimized start point.
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Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2008134976A1 (en) * | 2007-05-02 | 2008-11-13 | Huawei Technologies Co., Ltd. | Method and apparatus of establishing a synchronisation signal in a communication system |
| CN101778088A (en) * | 2010-03-12 | 2010-07-14 | 中国科学院声学研究所 | Training sequence frame timing synchronized method based on pseudo-random sequence modulation based |
| CN101883068A (en) * | 2009-05-09 | 2010-11-10 | 电子科技大学中山学院 | Superimposed training sequence time thickness synchronization method |
| CN102143574A (en) * | 2011-04-02 | 2011-08-03 | 重庆邮电大学 | Timing synchronization method suitable for IEEE (Institute of Electrical and Electronic Engineers) 802.16m preamble structure |
| CN102377726A (en) * | 2011-12-08 | 2012-03-14 | 北京交通大学 | Timing synchronization method of OFDM (Orthogonal Frequency Division Multiplexing) system |
-
2014
- 2014-11-20 CN CN201410662708.3A patent/CN104410597B/en active Active
Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2008134976A1 (en) * | 2007-05-02 | 2008-11-13 | Huawei Technologies Co., Ltd. | Method and apparatus of establishing a synchronisation signal in a communication system |
| CN101883068A (en) * | 2009-05-09 | 2010-11-10 | 电子科技大学中山学院 | Superimposed training sequence time thickness synchronization method |
| CN101778088A (en) * | 2010-03-12 | 2010-07-14 | 中国科学院声学研究所 | Training sequence frame timing synchronized method based on pseudo-random sequence modulation based |
| CN102143574A (en) * | 2011-04-02 | 2011-08-03 | 重庆邮电大学 | Timing synchronization method suitable for IEEE (Institute of Electrical and Electronic Engineers) 802.16m preamble structure |
| CN102377726A (en) * | 2011-12-08 | 2012-03-14 | 北京交通大学 | Timing synchronization method of OFDM (Orthogonal Frequency Division Multiplexing) system |
Non-Patent Citations (2)
| Title |
|---|
| 郑娟: "宽带无线OFDM系统同步算法的研究", 《中国博士学位论文全文数据库 信息科技辑》 * |
| 韩艳春: "OFDM系统的同步技术研究", 《中国博士学位论文全文数据库 信息科技辑》 * |
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