CN101312444B - Method and apparatus for acquiring frequency of multi-path signal - Google Patents
Method and apparatus for acquiring frequency of multi-path signal Download PDFInfo
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- CN101312444B CN101312444B CN2007101051833A CN200710105183A CN101312444B CN 101312444 B CN101312444 B CN 101312444B CN 2007101051833 A CN2007101051833 A CN 2007101051833A CN 200710105183 A CN200710105183 A CN 200710105183A CN 101312444 B CN101312444 B CN 101312444B
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Abstract
The invention provides a method for attaining the target frequency of a multi-path signal and a device thereof, wherein the multi-path signal comprises a first path signal and a second path signal. The method comprises adopting a first path to receive the first path signal and adopting a second path to receive the second path signal, determining a target region which is a part of a second cyclic prefix of the second path signal and is overlapped with a first cyclic prefix of the first path signal, and determining the target frequency according to the target area.
Description
Technical field
The present invention relates to a kind of method and device that obtains frequency, and especially, relate to a kind of method and device that obtains the target frequency of multi-path signal.
Background technology
(Orthogonal Frequency Division Multiplexing is a kind of high efficiency multipath modulating/demodulating system technology OFDM) to OFDM, and its principle promptly utilizes a plurality of subcarriers to transmit data simultaneously, to promote message transmission rate.OFDM is the technology of a multipath modulating/demodulating system.As its name suggests, OFDM is divided into several narrow frequency bands with spendable bandwidth, makes data to transmit through these frequency bands abreast.Because the OFDM wireless communication system has high data transmission rate, high bandwidth service efficiency and avoids radio wave to receive advantages such as multipath attenuation, therefore, be widely used in the new wireless communication system from generation to generation.
Yet the OFDM technology still has its shortcoming, for example peak value/average power (peak-to-averagepower ratio) and very responsive to the frequency errors of subchannel (sub-channel).Therefore, in the OFDM wireless communication system, how carrying out the work of frequency restoration, to reach the effect of Frequency Synchronization, is a very important problem.
Traditional multi-path signal Frequency Synchronization method, be add before the data segments in signal a Cyclic Prefix (Cyclic Prefix, CP).After receiving terminal receives this signal, utilize this Cyclic Prefix to estimate and obtain synchronizing frequency for frequency plot.Yet, when Cyclic Prefix is interfered, possibly its frequency of carrying out phase place estimation gained is caused sizable error, cause the serious frequency shift phenomenon.
Therefore, main purpose of the present invention is to provide a kind of method and device that obtains the frequency of multi-path signal, to address the above problem.
Summary of the invention
A preferred embodiment according to the present invention is a kind of method of obtaining the multi-path signal target frequency.Wherein, this multi-path signal comprises one first path signal and one second path signal.At first, this method receives this first path signal and receives this second path signal via one second path via one first path.Then, this method determines a target area, and this target area is the part of one second Cyclic Prefix of second path signal, and one first Cyclic Prefix of this target area and this first path signal overlaps.Afterwards, this method is according to this this target frequency of target area decision.
Another preferred embodiment according to the present invention is a kind of device that obtains the multi-path signal target frequency.Wherein, this multi-path signal comprises one first path signal and one second path signal.This device comprises a receiver module, a regional decision module and a frequency decision module.This receiver module is used for receiving this first path signal and receiving this second path signal via one second path via one first path.This zone decision module is used to determine a target area, and this target area is the part of one second Cyclic Prefix of second path signal, and one first Cyclic Prefix of this target area and this first path signal overlaps.This frequency decision module is used for according to this this target frequency of target area decision.
Can further be understood by following detailed Description Of The Invention and accompanying drawing about advantage of the present invention and spirit.
Description of drawings
Fig. 1 shows multi-path signal comprised in the prior art first path signal and the sketch map of second path signal.
Fig. 2 shows the flow chart that obtains multi-path signal target frequency method according to first preferred embodiment of the present invention.
Fig. 3 shows the example of second path signal of first path signal, second path signal and delay.
Fig. 4 shows the flow chart of the substep S121-S123 that step S12 shown in Figure 2 can comprise.
Fig. 5 shows the flow chart of the substep S131-S135 that step S13 shown in Figure 2 can comprise.
Fig. 6 shows the functional block diagram of obtaining multi-path signal target frequency device according to second preferred embodiment of the present invention.
Fig. 7 shows the detailed functions calcspar of regional decision module shown in Figure 6.
The reference numeral explanation
S11-S135: process step 10: frequency deriving means
12: receiver module 14: regional decision module
16: frequency decision module 141: choice device
142: calculation element 143: regional determination device
1422: the second computing units of 1421: the first computing units
1423: subtrator 1431: setup unit
1432: discrimination unit 1433: comparing unit
21,24: Cyclic Prefix 22: data
23,25A, 25B, 26,27: data segments
24A, 24B: part Cyclic Prefix L
21: circulating prefix-length
L
22: data length P1: first path signal
P2: the second path signal P2 ': second path signal of delay.
Embodiment
Method of the present invention and device are used to obtain the frequency of a multi-path signal.In practical application, this multi-path signal can be an ofdm signal.See also Fig. 1, Fig. 1 shows the example of this multi-path signal.As shown in Figure 1, this multi-path signal comprises one first path signal P1 and one second path signal P2.With the ofdm signal is example, and the Cyclic Prefix 21 of the first path signal P1 is by 23 generations of the data segments of duplicating the data 22 among the first path signal P1.Therefore, the content that comprised of Cyclic Prefix 21 is identical with data segments 23.
On the other hand, to be that the second path signal P2 arrives at time of receiving terminal later for the main difference of the first path signal P1 and the second path signal P2.The first path signal P1 and the second path signal P2 are from the signal of same emission source, and its difference is the difference that effect produced because of multi-path signal, and therefore, the Cyclic Prefix 24 of the second path signal P2 is also identical with the Cyclic Prefix 21 of the first path signal P1.Can know that in like manner Cyclic Prefix 21 also is identical with data segments (combination of 25A and 25B) among the second path signal P2 in theory.In addition, label is that the part of 24A is identical in data segments 25A and the Cyclic Prefix 24, data segments 25B then with Cyclic Prefix 24 in label be that the part of 24B is identical.
Because the part Cyclic Prefix 24B of the second path signal P2 and the data 22 of the first path signal P1 have the overlapping part in time, so the part of Cyclic Prefix 24B can receive the interference of data 22.If directly utilize the frequency of Cyclic Prefix 24 these multi-path signals of estimation, with having serious error.Therefore, mainly adopt undisturbed Cyclic Prefix section (zone shown in label 24A) as a target area with device according to the method for the invention, and then utilize a target frequency of this this multi-path signal of target area decision.
First preferred embodiment according to the present invention is a kind of method of obtaining a target frequency of multi-path signal.See also Fig. 2, Fig. 2 shows the flow chart of this method.As shown in Figure 2, at first, this method execution in step S11 receives this first path signal and receives this second path signal via one second path via one first path.Then, this method execution in step S12 determines a target area.This target area is the part of one second Cyclic Prefix of second path signal, and one first Cyclic Prefix of this target area and this first path signal overlaps.Afterwards, this method execution in step S13 is according to this this target frequency of target area decision.This target frequency can be by the clock answer program decision of carrying out to this target area.
In practical application, can the second path signal P2 be postponed according to the method for the invention, producing the second path signal P2 ' that postpones, and find out this target area by the second path signal P2 ' of the relatively second path signal P2 and this delay.See also Fig. 3, Fig. 3 shows the example of the second path signal P2 ' of the first path signal P1, the second path signal P2 and delay.
In example shown in Figure 3, the second path signal P2 ' of delay is by the length L with the second path signal P2 delayed data 22
22Produce.According to the present invention, the data segments 26 among the second path signal P2 can be regarded as a first area with the combination of target area 24A, and data segments 27 then can be regarded as a second area with the combination of data segments 25A.As shown in Figure 3; Data segments 26 among the second path signal P2 ' that postpones in time domain be with the second path signal P2 in data segments 27 overlap, the target area 24A among the second path signal P2 ' of delay in time domain then be with the second path signal P2 in data segments 25A overlap.Be prone to speech, this first area among the second path signal P2 ' of delay in time domain with the second path signal P2 in this second area overlapping.
The difference that can calculate this first area and this second area according to the method for the invention is to produce a difference signal.As discussed previously, data segments 25A is identical with the content of target area 24A.Therefore, the part corresponding to data segments 25A (that is corresponding to target area 24A) should be substantially equal to zero in this difference signal.Relatively, the data segments 27 in data segments in the first area 26 and the second area does not have inevitable association.Therefore, the part corresponding to data segments 26 (that is corresponding to data segments 27) can't equal zero in this difference signal.Approach zero by the signal energy of judging which section in this difference signal, according to the method for the invention can be by the position of finding out target area 24A in this difference signal.
As shown in Figure 3, the length of this first area, second area and this difference signal all is substantially equal to the length L of Cyclic Prefix 21
21
As shown in Figure 4, the step S12 among Fig. 2 can comprise substep S121-S123.Substep S121 selects a first area and a second area in this second path signal.Wherein, this first area comprises this target area, and this second area comprises the original area corresponding to this target area.Substep S122 calculates the difference of this first area and this second area to produce a difference signal.Substep S123 is then according to this this target area of difference signal decision.Wherein, the signal energy of this target area is less than a default value.
In practical application, substep S122 can calculate one group of first amplitude of this first area and one group of second amplitude of this second area earlier, should organize second amplitude again and deduct this and organize first amplitude to produce this difference signal.
In order can earlier this difference signal to be made as a predeterminable area according to the method for the invention further by the scope that defines target area 24A in this difference signal.This predeterminable area can further be divided into first subregion and second subregion, and compares to the gross energy of first subregion and second subregion.If the gross energy of first subregion is greater than the gross energy of second subregion and its energy difference during greater than a threshold amount of energy; That is to say; The signal strength signal intensity of first subregion is strong when a lot of than second subregion; First subregion that signal strength signal intensity is bigger is made as predeterminable area again, and repeats above-mentioned step, and first subregion is divided into two sub regions again and compares its gross energy.So continue to go on, until the energy difference of two sub regions of dividing less than a threshold amount of energy.The signal strength signal intensity sizableness of two subregions of this moment is approaching.Merge this two subregion and can obtain in this difference signal part corresponding to data segments 26 (that is corresponding to data segments 27).In this difference signal, can define the scope of target area 24A corresponding to the part of data segments 26.
As shown in Figure 5, aforesaid step S13 can be subdivided into substep S131-S135.Substep S131 is made as a predeterminable area with this difference signal.Substep S132 is divided into one first subregion and one second subregion with this predeterminable area.Substep S133 then is that one second gross energy of one first gross energy and this second subregion of relatively this first subregion is to produce an energy difference.If greater than a threshold amount of energy, then this method is carried out substep S134 to this first gross energy, and this first subregion is made as this predeterminable area and iteron step S132-S134 greater than this second gross energy and this energy difference.If this energy difference less than this threshold amount of energy, is then carried out substep S135, this difference signal this first subregion of deletion and this second subregion are to produce this target area certainly.
Second preferred embodiment according to the present invention is a kind of device that obtains the multi-path signal target frequency.This multi-path signal comprises one first path signal and one second path signal.See also Fig. 6, Fig. 6 shows the functional block diagram of this frequency deriving means.As shown in Figure 5, frequency deriving means 10 comprises receiver module 12, regional decision module 14 and frequency decision module 16.Receiver module 12 is used for receiving this first path signal and receiving this second path signal via one second path via one first path.Zone decision module 14 is used to determine a target area, and this target area is a part and this target area and the overlapping of one first Cyclic Prefix in this first path signal of one second Cyclic Prefix of second path signal.Wherein, the length of the length of this second Cyclic Prefix and this difference signal is substantially equal to this prefix length.Frequency decision module 16 is used for according to this this target frequency of target area decision.This target frequency can be by the clock answer program decision of carrying out to this target area.
As shown in Figure 7, in practical application, regional decision module 14 can comprise choice device 141, calculation element 142 and regional determination device 143.Choice device 141 is used for selecting a first area and a second area from this second path signal.This first area comprises this target area, and this second area comprises the original area corresponding to this target area.Calculation element 142 electrical ties are to choice device 141, and the difference that is used to calculate this first area and this second area is to produce a difference signal.Zone determination device 143 electrical ties are to calculation element 142, and according to this this target area of difference signal decision, wherein, the signal energy of this target area is less than a default value.
In addition, as shown in Figure 7, calculation element 142 can comprise first computing unit 1421, second computing unit 1422 and subtrator 1423.First computing unit 1421 is used to calculate one group of first amplitude of this first area.Second computing unit 1422 is used to calculate one group of second amplitude of this second area.Subtrator 1423 electrical ties to the first computing units 1421 and second computing unit 1422, and should organize second amplitude and deduct this and organize first amplitude to produce this difference signal.
Fig. 7 also viewing area determination device 143 can comprise setup unit 1431, discrimination unit 1432 and comparing unit 1433.Setup unit 1431 is used for this difference signal is made as a predeterminable area.Discrimination unit 1432 electrical ties are to setup unit 1431, and are used for this predeterminable area is divided into one first subregion and one second subregion.1433 of comparing units in order to one second gross energy of one first gross energy of this first subregion relatively and this second subregion to produce an energy difference.If comparing unit 1433 result relatively is this first gross energy greater than this second gross energy and this energy difference greater than a threshold amount of energy, then setup unit 1431 can be made as this predeterminable area and operating space subdivision 1432 and comparing unit 1433 again with this first subregion.If this energy difference is less than this threshold amount of energy, then setup unit 1431 can be from this difference signal this first subregion of deletion and this second subregion to produce this target area.
Compared to prior art, will reach device according to the method for the invention and be applied on the multi-path signal (for example ofdm signal), can avoid adopting the Cyclic Prefix that is interfered and the frequency that causes estimating gained has the situation of gross error to take place.Therefore, by method and the device that obtains the multi-path signal target frequency of the present invention, can in multi-path wireless communication system (for example 0FDM wireless communication system), reach the effect of good Frequency Synchronization.
By the detailed description of above preferred embodiment, be to hope to know more to describe characteristic of the present invention and spirit, and be not to come category of the present invention is limited with the above-mentioned preferred embodiment that is disclosed.On the contrary, its objective is that hope can contain in the category of claim of being arranged in of various changes and tool equality institute of the present invention desire application.Therefore, the category of the claim that the present invention applied for should be done the broadest explanation according to above-mentioned explanation, contains the arrangement of all possible change and tool equality to cause it.
Claims (10)
1. method of obtaining a target frequency of a multi-path signal, this multi-path signal comprises one first path signal and one second path signal, and this method comprises the following step:
(a) receive this first path signal via one first path, and receive this second path signal via one second path;
(b) determine a target area, this target area is the part of one second Cyclic Prefix in this second path signal, and this target area and the overlapping of one first Cyclic Prefix in this first path signal; And
(c) according to this this target frequency of target area decision,
Wherein, step (b) is carried out with the following step:
(b1) select a first area and a second area in this second path signal certainly, this first area comprises this target area, and this second area comprises the original area corresponding to this target area;
(b2) capacity volume variance of calculating this first area and this second area is to produce a difference signal; And
(b3) according to this target area of this difference signal decision, wherein, a signal energy of this target area is less than a default value,
Wherein, step (b3) is carried out with the following step:
(b31) this difference signal is made as a predeterminable area;
(b32) this predeterminable area is divided into one first subregion and one second subregion;
(b33) one second gross energy of one first gross energy of this first subregion and this second subregion relatively is to produce an energy difference;
(b34) if this first gross energy greater than this second gross energy and this energy difference greater than a threshold amount of energy, this first subregion is made as this predeterminable area and iteron step (b32)-(b34); And
(b35) if this energy difference less than this threshold amount of energy, this difference signal this first subregion of deletion and this second subregion are to produce this target area certainly.
2. the method for claim 1, wherein step (b2) is carried out with the following step:
One group first amplitude of calculating in this first area;
One group second amplitude of calculating in this second area; And
Should organize second amplitude and this and organize first amplitude and subtract each other, to produce this difference signal.
3. the method for claim 1, wherein the length of this second Cyclic Prefix with a prefix length and this difference signal is substantially equal to this prefix length.
4. the method for claim 1, wherein in step (c), this target frequency is by the clock answer program decision of carrying out to this target area.
5. the method for claim 1, wherein this multi-path signal is an orthogonal frequency-division multiplex singal.
6. device in order to the target frequency that obtains a multi-path signal, this multi-path signal comprises one first path signal and one second path signal, and this device comprises:
One receiver module is in order to receive this first path signal and to receive this second path signal via one second path via one first path;
One regional decision module, in order to determine a target area, this target area is the part of one second Cyclic Prefix of this second path signal, and this target area and the overlapping of one first Cyclic Prefix in this first path signal; And
One frequency decision module, in order to according to this target frequency of this target area decision,
Wherein, this zone decision module comprises:
One choice device is selected a first area and a second area in order to this second path signal certainly, and this first area comprises this target area, and this second area comprises the original area corresponding to this target area;
One calculation element, in order to the capacity volume variance of calculating this first area and this second area to produce a difference signal; And
One regional determination device, in order to according to this target area of this difference signal decision, wherein, a signal energy of this target area is less than a default value,
Wherein, this zone determination device comprises:
One setup unit is in order to be made as a predeterminable area with this difference signal;
One discrimination unit is in order to be divided into this predeterminable area one first subregion and one second subregion; And
One comparing unit is in order to relatively one first gross energy of this first subregion and one second gross energy of this second subregion, to produce an energy difference;
Wherein, If this first gross energy greater than this second gross energy and this energy difference greater than a threshold amount of energy; This setup unit is made as this first subregion this predeterminable area and operates this discrimination unit again and this comparing unit; If this energy difference is less than this threshold amount of energy, this setup unit from this difference signal this first subregion of deletion and this second subregion to produce this target area.
7. device as claimed in claim 6, wherein, this calculation element comprises:
One first computing unit is in order to calculate one group of first amplitude in this first area;
One second computing unit is in order to calculate one group of second amplitude in this second area; And
One subtrator was organized first amplitude and was subtracted each other in order to should organize second amplitude and this, to produce this difference signal.
8. device as claimed in claim 6, wherein, the length that this second Cyclic Prefix has a prefix length and this difference signal is substantially equal to this prefix length.
9. device as claimed in claim 6, wherein, in this frequency decision module, this target frequency is by the clock answer program decision of carrying out to this target area.
10. device as claimed in claim 6, wherein, this multi-path signal is an orthogonal frequency-division multiplex singal.
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|---|---|---|---|---|
| US6549592B1 (en) * | 1998-02-06 | 2003-04-15 | Cisco Technology, Inc | Enhanced synchronization burst for OFDM systems |
| CN1472900A (en) * | 2002-08-01 | 2004-02-04 | 上海交通大学 | Method for estimating carrier, frequency shifts of orthogonal FDM communication system |
| CN1599298A (en) * | 2003-09-18 | 2005-03-23 | 电子科技大学 | OFDM frequence synchronous method at multi-path channel |
| CN1761175A (en) * | 2005-11-14 | 2006-04-19 | 北京北方烽火科技有限公司 | Method for carrying out frame synchronization timing at receiving and of base station of WiMAX system |
| CN1809046A (en) * | 2006-02-14 | 2006-07-26 | 郭更生 | Method and apparatus of implementing multi-symbol OFDM synchronization |
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2007
- 2007-05-24 CN CN2007101051833A patent/CN101312444B/en not_active Expired - Fee Related
Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6549592B1 (en) * | 1998-02-06 | 2003-04-15 | Cisco Technology, Inc | Enhanced synchronization burst for OFDM systems |
| CN1472900A (en) * | 2002-08-01 | 2004-02-04 | 上海交通大学 | Method for estimating carrier, frequency shifts of orthogonal FDM communication system |
| CN1599298A (en) * | 2003-09-18 | 2005-03-23 | 电子科技大学 | OFDM frequence synchronous method at multi-path channel |
| CN1761175A (en) * | 2005-11-14 | 2006-04-19 | 北京北方烽火科技有限公司 | Method for carrying out frame synchronization timing at receiving and of base station of WiMAX system |
| CN1809046A (en) * | 2006-02-14 | 2006-07-26 | 郭更生 | Method and apparatus of implementing multi-symbol OFDM synchronization |
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