CN1753394B - Method of improving despreading spectrum of OFDM system synchronization performance - Google Patents
Method of improving despreading spectrum of OFDM system synchronization performance Download PDFInfo
- Publication number
- CN1753394B CN1753394B CN 200410009597 CN200410009597A CN1753394B CN 1753394 B CN1753394 B CN 1753394B CN 200410009597 CN200410009597 CN 200410009597 CN 200410009597 A CN200410009597 A CN 200410009597A CN 1753394 B CN1753394 B CN 1753394B
- Authority
- CN
- China
- Prior art keywords
- ofdm system
- ofdm
- improve
- orthogonal intersection
- synchronization capability
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Fee Related
Links
- 238000000034 method Methods 0.000 title claims abstract description 45
- 238000001228 spectrum Methods 0.000 title claims description 47
- 238000013507 mapping Methods 0.000 claims description 8
- 125000002015 acyclic group Chemical group 0.000 claims description 7
- 238000012545 processing Methods 0.000 claims description 6
- 230000011218 segmentation Effects 0.000 claims description 6
- 230000007480 spreading Effects 0.000 claims description 5
- 238000006073 displacement reaction Methods 0.000 claims description 3
- 230000001360 synchronised effect Effects 0.000 abstract description 7
- 230000009466 transformation Effects 0.000 abstract 1
- 230000008569 process Effects 0.000 description 11
- 238000005516 engineering process Methods 0.000 description 10
- 238000010586 diagram Methods 0.000 description 7
- 230000005540 biological transmission Effects 0.000 description 5
- 238000004422 calculation algorithm Methods 0.000 description 5
- 230000008901 benefit Effects 0.000 description 3
- 230000000295 complement effect Effects 0.000 description 3
- 238000005314 correlation function Methods 0.000 description 3
- 238000010295 mobile communication Methods 0.000 description 3
- 238000004364 calculation method Methods 0.000 description 2
- 238000006243 chemical reaction Methods 0.000 description 2
- 238000012937 correction Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 230000006855 networking Effects 0.000 description 2
- 238000004088 simulation Methods 0.000 description 2
- 241001269238 Data Species 0.000 description 1
- 101100224604 Schizosaccharomyces pombe (strain 972 / ATCC 24843) dri1 gene Proteins 0.000 description 1
- 102100029469 WD repeat and HMG-box DNA-binding protein 1 Human genes 0.000 description 1
- 101710097421 WD repeat and HMG-box DNA-binding protein 1 Proteins 0.000 description 1
- 238000005311 autocorrelation function Methods 0.000 description 1
- 230000004888 barrier function Effects 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 125000004122 cyclic group Chemical group 0.000 description 1
- 230000006378 damage Effects 0.000 description 1
- 230000007812 deficiency Effects 0.000 description 1
- 238000013461 design Methods 0.000 description 1
- 230000008521 reorganization Effects 0.000 description 1
Images
Classifications
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04J—MULTIPLEX COMMUNICATION
- H04J13/00—Code division multiplex systems
- H04J13/0007—Code type
- H04J13/0055—ZCZ [zero correlation zone]
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04J—MULTIPLEX COMMUNICATION
- H04J13/00—Code division multiplex systems
- H04J13/0003—Code application, i.e. aspects relating to how codes are applied to form multiplexed channels
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04J—MULTIPLEX COMMUNICATION
- H04J13/00—Code division multiplex systems
- H04J13/0007—Code type
- H04J13/004—Orthogonal
Abstract
This invention discloses a method for improving the synchronous performance of the OFDM system, which applies an orthogonal spectrum-spreading code with zero interference window property to spread signal symbols before modulating the OFDM system then de-spreads the information symbols with the orthogonal spectrum-spread code after carrying out the quick Foucault transformation at the receiving end.
Description
Technical field
The present invention relates to a kind of utilization and have zero " window" (Interference Free Window, abbreviation IFW) orthogonal intersection of characteristic improves OFDM (Orthogonal Frequency DivisionMultiplexing, OFDM) method of system synchronization performance belongs to the mobile communication technology field.
Background technology
OFDM is the high speed transmission technology under a kind of wireless environment, it can satisfy at a high speed and the requirement of anti-interference two aspects simultaneously, not only can improve band efficiency greatly, and higher data throughput is provided, can also effectively suppress multipath and disturb, have very big advantage in the high-speed mobile communications field.Therefore, the general estimating OFDM technology of people will become one of core technology of the 4th third-generation mobile communication (4G).
The basic thought of OFDM technology is in frequency domain given channel to be divided into many orthogonal sub-channels, uses a subcarrier to modulate on each subchannel, and each subcarrier parallel transmission.Owing to adopt the notion of orthogonal frequency to distinguish different carrier wave branch roads, therefore allow each carrier wave frequency range overlapped, thereby significantly improved the availability of frequency spectrum.Fig. 1 is the basic block diagram of a typical ofdm system.The data flow of input becomes parallel low rate data streams through serial/parallel conversion.Each bar parallel data stream is respectively by different carrier frequency modulation.The modulation and demodulation of OFDM adopt a pair of IFFT/FFT (anti-fast fourier transform/fast fourier transform) to realize that it is simple that this process of achieving becomes.
Though the OFDM technology has lot of superiority, it also exists a lot of technological difficulties to overcome when specific implementation.It is very sensitive to carrier frequency offset and phase noise that wherein topmost technological difficulties are embodied in ofdm system, very high to synchronous requirement.This is because the deviation of carrier frequency and noise can make to produce between the subchannel to be disturbed, thereby can not satisfy the requirement of OFDM technology antithetical phrase interchannel strict orthogonal.If each subchannel can not be accomplished strict orthogonal, will produce strong interchannel interference, the performance of whole OFDM system is seriously descended.At present, people have proposed multiple OFDM synchronized algorithm, as ESPRIT synchronized algorithm and ML algorithm for estimating etc. for solving ofdm system to synchronous demanding problem.But these algorithms cut both ways, and can not tackle the problem at its root.And use these algorithms can increase the computational burden of whole system undoubtedly.
Current, it is found that some adopts the orthogonal intersection of specific coding mode to have the characteristic of zero " window", for example LAS sign indicating number, CCK sign indicating number etc.So-called zero " window" claims zero correlation window again, the auto-correlation function that is meant its address code is desirable, in the cross-correlation function in certain deviation range (in the window) also be desirable, promptly do not pay the peak fully, described in the above window only has the sparse peak of paying outward, and just the correlation function of LAS-CDMA address code as shown in Figure 2 is such.We claim apart from initial point nearest one to tackle peak-to-peak interval be zero " window", every signal that drops on other address code in zero " window" can not produce interference.This characteristic is applied among the ofdm system, just might solve its require synchronously high, realize the big technical barrier of difficulty.But, just known to the applicant, still in ofdm system, do not use the technical scheme of orthogonal intersection zero " window" characteristic at present.
Summary of the invention
The objective of the invention is to blank at prior art, the orthogonal intersection that provides a kind of utilization to have zero " window" characteristic carries out spread spectrum/de-spreading operation, be formed on the zero " window" of arranging on the frequency, overcome the phase mutual interference of adjacent orthogonal subcarrier thus, improve the method for ofdm system net synchronization capability.
For realizing above-mentioned goal of the invention, the present invention adopts following technical scheme:
A kind of method that is used to improve the ofdm system net synchronization capability, on chnnel coding, adopt orthogonal intersection with zero " window" characteristic, the acyclic autocorrelation sequence of described orthogonal intersection and acyclic cross-correlation sequence have the window of a zero correlation at least in certain displacement range, it is characterized in that:
Before the transmitting terminal of ofdm system carries out anti-fast fourier transform, utilize described orthogonal intersection that information symbol is carried out spread spectrum, and carry the chip of different orthogonal spreading code with the different sub carrier of OFDM respectively; After the receiving terminal of ofdm system carries out fast fourier transform, go out described information symbol with described orthogonal intersection despreading.
Described orthogonal intersection is LAS sign indicating number or CCK sign indicating number.
Transmitting terminal at described ofdm system, be divided at least one group behind the emission information via coding, each modulation bit number of organizing according to an OFDM subcarrier is carried out segmentation, be mapped as complex symbol according to the needed bit constellation mapping ruler of OFDM subcarrier-modulated every section.
Perhaps, transmitting terminal at described ofdm system has at least one group of user profile, after each is organized user profile and encodes respectively, every group of user profile is carried out segmentation according to the modulation bit number of an OFDM subcarrier, be mapped as complex symbol according to the needed bit constellation mapping ruler of OFDM subcarrier-modulated every section.
At the transmitting terminal of described ofdm system, data subcarriers all among the OFDM is divided into groups, every group of sub-carrier number is the length of described orthogonal intersection, and the subcarrier in same group is adjacent on frequency.
At the receiving terminal of described ofdm system, the baseband complex signal that receives is carried out after the fast fourier transform, at first carry out frequency domain equalization and handle, carry out the despreading processing with described orthogonal intersection again.
Described frequency domain equalization is handled the pilot sub-carrier mode that can adopt ofdm system to use, and also can adopt FSm code word in the cdma system to do pilot channel and carry out channel estimating and compensation.
The method that the orthogonal intersection that utilization of the present invention has a zero " window" characteristic improves the ofdm system net synchronization capability has made full use of the zero " window" characteristic of certain orthogonal spreading code, effectively overcome of the influence of factors such as carrier frequency shift, noise, for further applying of ofdm system established technical foundation to the ofdm system net synchronization capability.In addition, this method has also further been widened the range of application with orthogonal intersection of zero " window" characteristic.
Description of drawings
The present invention is further illustrated below in conjunction with the drawings and specific embodiments.
Fig. 1 is the basic block diagram of an existing typical ofdm system.
Fig. 2 is the correlation function schematic diagram of LAS-CDMA address code, has shown the zero " window" that this orthogonal intersection provided among the figure.
In the ofdm system of Fig. 3 for employing the method for the invention, the schematic diagram of transmitting terminal band spectrum modulation process.
In the ofdm system of Fig. 4 for employing the method for the invention, the schematic diagram of receiving terminal despreading process.
Fig. 5 is the structural representation that is used to verify the system emulation platform of the method for the invention usefulness.
Fig. 6 a, Fig. 6 b, Fig. 6 c common ofdm system when being respectively frequency deviation fre_off=0, MC-CDMA behind the M sequence spread spectrum, the received signal planisphere of MC-CDMA behind the LAS-Code spread spectrum.
Fig. 7 a, Fig. 7 b, Fig. 7 c common ofdm system when being respectively frequency deviation fre_off=0.1, MC-CDMA behind the M sequence spread spectrum, the received signal planisphere of MC-CDMA behind the LAS-Code spread spectrum.
Fig. 8 a, Fig. 8 b, Fig. 8 c common ofdm system when being respectively frequency deviation fre_off=0.25, MC-CDMA behind the M sequence spread spectrum, the received signal planisphere of MC-CDMA behind the LAS-Code spread spectrum.
Fig. 9 a, Fig. 9 b, Fig. 9 c common ofdm system when being respectively frequency deviation fre_off=0.5, MC-CDMA behind the M sequence spread spectrum, the received signal planisphere of MC-CDMA behind the LAS-Code spread spectrum.
Embodiment
Before the method for the invention is further specified, at first the employed orthogonal intersection with zero " window" characteristic of this method is described.The front is mentioned, have the orthogonal intersection of zero " window" characteristic common two kinds-LAS sign indicating number and CCK sign indicating number arranged.Wherein the LAS sign indicating number is ZL 00801970.3 by Mr. Li Daoben in the patent No., and name is called in the invention of " a kind of spread spectrum multiple access coding method with zero correlation window " and at first proposes, and with its encoding scheme as the LAS-CDMA system.This LAS sign indicating number is made of LS sign indicating number and LA sign indicating number, and wherein the LS sign indicating number is basic multi-user's access sequence family, and expansion access sequence family quantity plays in LA family.The LS sign indicating number is synthetic by C sign indicating number and S sign indicating number, and the C sign indicating number has identical auto-correlation peak and complementary peak external characteristic with the S sign indicating number, and the outside, LS sign indicating number auto-correlation peak that synthetic back forms be complete zero, in the LS sign indicating number family between each sequence cross-correlation be zero entirely.The LA sign indicating number is three level sign indicating numbers, and it is by an orthogonal code with L orthogonal intersection (get+1 and-1 value), inserts a string 0 formation that is uneven in length again between each code element.Have zero correlative window characteristic by LS sign indicating number and the compound LAS sign indicating number that constitutes of LA sign indicating number, the width of this zero correlation window can design in advance.About further specifying of this encoding scheme and zero correlative window characteristic thereof, see also this patent specification.CCK sign indicating number (complementary code keying, complementary code keying) is another orthogonal intersection with zero correlative window characteristic, and it mainly uses in wireless local area network technology, and has become the part of IEEE802.11B standard.Comparatively speaking, the zero correlative window characteristic of LAS sign indicating number is better than CCK sign indicating number, because its zero correlation window not only quantity is many, and width is controlled, the most important thing is that the number of codewords that satisfies the zero correlation window condition is far longer than the CCK sign indicating number, this application for reality has direct meaning, guarantees that promptly available number of users or user's data transmission rate are far longer than the CCK sign indicating number, therefore in the embodiment below, said orthogonal intersection with zero correlative window characteristic is an example with the LAS sign indicating number all.
In ofdm system, use different subcarriers to carry different information symbols.In order to make full use of the zero correlative window characteristic of LAS sign indicating number, we allow the chnnel coding of ofdm system adopt above-mentioned LAS sign indicating number, carry the chip (CHIP) of different LAS orthogonal intersections with the different subcarrier of OFDM.Like this, originally the chip in the LAS-CDMA system of arranging on the time shaft just arranges it by the OFDM method on frequency axis, and the zero correlation window on the time domain that the LAS sign indicating number is had also distributes on frequency domain thereupon.The problem that ofdm system causes owing to sub-carrier frequencies is non-orthogonal has just become the phase mutual interference between the different sub carrier of frequency domain here, and this interference is based on the interference of adjacent sub-carrier.Owing to introduced the LAS sign indicating number with zero " window" characteristic in the chnnel coding process, its zero correlation window just can overcome the phase mutual interference of adjacent sub-carrier in the arrangement of frequency domain, thereby improves the net synchronization capability of ofdm system.The basic principle of the method for the invention that Here it is.
The method of the invention is put it briefly, and is exactly at first at transmitting terminal, increases with the CDMA orthogonal intersection with zero " window" to come information symbol is carried out spread spectrum before the OFDM modulation; After carrying out the FFT conversion, receiving terminal goes out information symbol then with this orthogonal intersection despreading.
In order to be illustrated more clearly in the implementation procedure of the method for the invention, below said process is divided into two stages of transmitting terminal band spectrum modulation and receiving terminal despreading specifically to be illustrated.
Here, the length that at first defines the LAS orthogonal intersection is 2N, and N is a natural number.N frequency expansion sequence is FS1, FS2 ..., FSN, the modulation bit number of each OFDM subcarrier is M, M also is a natural number.
In the ofdm system of Fig. 3 for employing the method for the invention, the schematic diagram of transmitting terminal band spectrum modulation process.
As shown in Figure 3,, be divided into the N group behind the emission information via coding, be designated as S respectively at transmitting terminal
1, S
2..., S
N, carry out segmentation to every group with the length M bit, be divided into section into j, every section M bit is mapped as complex symbol according to the needed bit constellation mapping ruler of OFDM subcarrier-modulated: S
11, S
12..., S
21, S
22..., S
N1, S
N2... S
Ij, S wherein
IjRepresent that it is that i organizes j symbol.Above-mentioned process shown in the figure also can have another implication, be after N group different user information is encoded respectively, every group of user profile to be carried out segmentation according to the length M bit, be divided into section into j, and carry out bit constellation mapping with same way as noted earlier, equally also can obtain complex symbol: S
11, S
12..., S
21, S
22..., S
N1, S
N2... S
Ij, S wherein
IjBe i user's j symbol.
After finishing the bit constellation mapping, utilize above-mentioned LAS orthogonal intersection to carry out spread spectrum to each complex symbol, the used frequency expansion sequence of i group code is FS
iN is organized frequency expansion sequence addition, obtain modulating data sequence: D
1, D
2..., D
k..., D wherein
i=S
I1FS
1+ S
I2FS
2+ ...+S
INFS
N=(d
1, d
2..., d2
N).Data subcarriers all among the OFDM is divided into groups: C
1, C
2..., C
k..., every group of sub-carrier number is frequency expansion sequence length 2N:C
I1, C
I2..., C
I2N, and the subcarrier in same group is adjacent on frequency.Use the modulating data sequence D
1, D
2..., D
k... respectively the subcarrier of respectively organizing among the OFDM is modulated, wherein d
IkBe modulated to C
IkOn.The K here represents the subcarrier of all transmission data of OFDM is divided into the K section, every section LAS code word that just in time transmits the some modulating datas of carrying.For example, the length of LAS code word is 32, and OFDM one has 256 subcarriers transmission data, we just can be divided into 8 sections to 256 subcarriers so, K=8, every section length 32 that 32 subcarriers just in time are the LAS code words, and every section LAS number of codewords has 16, can transmit 8 * 16=128 symbol simultaneously so in an OFDM symbol period.
In the ofdm system of Fig. 4 for employing the method for the invention, the schematic diagram of receiving terminal despreading process.
Receiving terminal at first carries out frequency offset correction, clock synchronization, frame synchronization, goes conventional treatment such as circulation prefix processing the baseband complex signal that receives.Calculate carrying out FFT through the complex signal after the above-mentioned processing, carry out frequency domain equalization then and handle, obtain the data drik of each subcarrier-modulated, the subcarrier number of its subscript and transmitting terminal is consistent.With frequency expansion sequence FSj to i group of received data Dri=(dri1, dri2 ..., dri2N) carry out despreading and obtain Srij=dri1FSj1+dri2FSj2+...+dri2NFSj2N.Despreading obtains N complex data: Srij to every group of received data with N group frequency expansion sequence, i=1, and 2 ..., j=1,2 ..., N.Then data sequence Srij is carried out subsequent treatment such as bit map decode.Data after the processing promptly become reception information after reorganization.
In the process of above-mentioned band spectrum modulation and despreading, bit constellation mapping, frequency offset correction, clock synchronization, frame synchronization, to go operation such as Cyclic Prefix all be the operation of existing moving communicating field routine.Frequency domain equalization can adopt the employed pilot sub-carrier mode of ofdm system, also can adopt FSm code word in the cdma system to do pilot channel and carry out channel estimating and compensation, the pilot channel of this operation and general CDMA or the routine operation of frequency pilot sign are the same, have not just given unnecessary details at this.
Operation by above-mentioned band spectrum modulation and despreading realizes that the key that the net synchronization capability of ofdm system improves is that frequency expansion sequence has zero " window" characteristic, and promptly its acyclic autocorrelation sequence and acyclic cross-correlation sequence will have the window of a zero correlation in certain displacement range.If Rij (n) is the acyclic cross-correlation sequence of frequency expansion sequence i and j, then Rij (n) should satisfy: Rij (n)=0, work as n=-L, and-L+1 ... ,-1,1,2 ..., L, L are natural number, and are the bigger the better satisfying under the prerequisite of number of codewords.The LAS orthogonal intersection promptly is the desirable frequency expansion sequence that satisfies above-mentioned condition.
In the process of above-mentioned spread spectrum/despreading, system synchronization need be synchronized to and can make just in the zero window skew that correlation is zero after the despreading.In ofdm system, this point just can be accomplished by OFDM's itself synchronously.Say simply, be exactly transmitting terminal be the corresponding relation of knowing the chip of LAS sign indicating number and subcarrier certainly, but receiving terminal needs also to know that this corresponding relation can despreading.And the frame synchronization of ofdm system itself requires to provide this synchronous.
The method that the orthogonal intersection that utilization of the present invention has a zero " window" characteristic improves the ofdm system net synchronization capability not only has theoretic reasonability, has confirmed also that by simulation calculation it has the gratifying effect of improving the ofdm system net synchronization capability.
Fig. 5 is the structural representation that is used to verify the system emulation platform of the method for the invention usefulness.
Analogue system comprises three kinds: the ofdm system of two kinds of spread spectrums and a kind of common ofdm system.The frequency expansion sequence of two kinds of spread spectrum systems is respectively M sequence and LAS-Code frequency expansion sequence; Common ofdm system does not then have spread spectrum and two modules of despreading.Obtain the result of simulation calculation by the planisphere of contrast reception.
The used parameter of emulation is:
Frequency deviation/subcarrier spacing (4 kinds): fre_off (being ε)=0; 0.10; 0.25; 0.5
Modulation system: BPSK
M sequence length: 7
M sequence eigenpolynomial: (1,7) is 1+x
6
Spreading ratio: 64
Number of users: 16
Sub-carrier number: 64
Emulation is counted: 200
The code character of LAS-Code: (1,3,5,7,9,11,13,15,17,19,21,23,25,27,29,31) here, zero correlation window is 7.
Common ofdm system when Fig. 6 a, Fig. 6 b, Fig. 6 c have provided frequency deviation fre off=0 respectively, MC-CDMA behind the M sequence spread spectrum, the received signal planisphere of MC-CDMA behind the LAS-Code spread spectrum, wherein Fig. 6 a is common ofdm system, Fig. 6 b is MC-CDMA behind the M sequence spread spectrum, and Fig. 6 c is MC-CDMA behind the LAS-Code spread spectrum.
As can be seen, when not having frequency deviation, the MC-CDMA behind common ofdm system and the LAS-Code spread spectrum does not all introduce interference, and the MC-CDMA behind the process M sequence spread spectrum will introduce the interference between certain user.But the interference here is still very little and sustainable.Can't produce error code.
Fig. 7 a, Fig. 7 b, Fig. 7 c common ofdm system when having provided frequency deviation fre_off=0.1 respectively, MC-CDMA behind the M sequence spread spectrum, the received signal planisphere of MC-CDMA behind the LAS-Code spread spectrum, wherein Fig. 7 a is common ofdm system, Fig. 7 b is MC-CDMA behind the M sequence spread spectrum, and Fig. 7 c is MC-CDMA behind the LAS-Code spread spectrum.
Fig. 8 a, Fig. 8 b, Fig. 8 c common ofdm system when having provided frequency deviation fre_off=0.25 respectively, MC-CDMA behind the M sequence spread spectrum, the received signal planisphere of MC-CDMA behind the LAS-Code spread spectrum, wherein Fig. 8 a is common ofdm system, Fig. 8 b is MC-CDMA behind the M sequence spread spectrum, and Fig. 8 c is MC-CDMA behind the LAS-Code spread spectrum.
In frequency deviation is 0.1 and 0.25 o'clock, and the received signal of all ofdm systems can produce very big rotation, and received signal has the phenomenon of dispersing simultaneously.This phase place rotation can tolerate that because do not produce error code, methods such as use equilibrium just can be corrected it.But dispersing of received signal then is insupportable, because can cause the generation of error code like this.This situation is the most serious to common ofdm system influence, and improved this problem to a certain extent through the MC-CDMA system behind the M sequence spread spectrum, but, like this, exist in system under the situation of noise and error code also relatively easily occurs than obviously serious many under the situation of no frequency deviation.But then obviously improved this performance greatly through the MC-CDMA system after the LAS-Code spread spectrum, received signal is dispersed hardly.Illustrate that thus there is stronger anti-system frequency deviation ability in the LAS-coded-OFDM system.
Fig. 9 a, Fig. 9 b, Fig. 9 c common ofdm system when having provided frequency deviation fre_off=0.5 respectively, MC-CDMA behind the M sequence spread spectrum, the received signal planisphere of MC-CDMA behind the LAS-Code spread spectrum, wherein Fig. 9 a is common ofdm system, Fig. 9 b is MC-CDMA behind the M sequence spread spectrum, and Fig. 9 c is MC-CDMA behind the LAS-Code spread spectrum.
Frequency deviation be 0.5 o'clock be a kind of limiting condition, effect comparison in this case clearly, the planisphere of LAS-MC-CDMA system has only few dispersing, this specific character makes the anti-frequency bias properties of LAS-OFDM system splendid.This is because the benefit that the zero relevant window of LAS-Code is brought, and this is that other frequency expansion sequences institutes are ungratified.
Because the characteristics of this method are to use LAS orthogonal intersection spread spectrum before the IFFT of transmitting terminal OFDM, go out symbol with the despreading of LAS orthogonal intersection then after receiving end FFT.The advantage of OFDM is preserved, and the destruction of the orthogonality of the subcarrier that causes owing to reasons such as high-speed mobile is then eliminated by the LAS orthogonal intersection despreading of next stage.LAS orthogonal intersection despreading simultaneously can also further reduce The noise, promptly can also obtain the gain of general CDMA, keeps the characteristics of OFDM technology simultaneously.In addition,, can also come networking, can remedy the deficiency of OFDM aspect networking like this with the characteristic of CDMA because OFDM adds CDMA.
Though above described the present invention by embodiment, those of ordinary skills know, the present invention has many distortion and variation and does not break away from spirit of the present invention, appended claim will comprise these distortion and variation.
Claims (9)
1. method that is used to improve the ofdm system net synchronization capability, on chnnel coding, adopt orthogonal intersection with zero " window" characteristic, the acyclic autocorrelation sequence of described orthogonal intersection and acyclic cross-correlation sequence have the window of a zero correlation at least in certain displacement range, it is characterized in that:
Before the transmitting terminal of ofdm system carries out anti-fast fourier transform, utilize described orthogonal intersection that information symbol is carried out spread spectrum, and carry the chip of different orthogonal spreading code with the different sub carrier of OFDM respectively;
After the receiving terminal of ofdm system carries out fast fourier transform, go out described information symbol with described orthogonal intersection despreading.
2. the method that is used to improve the ofdm system net synchronization capability as claimed in claim 1 is characterized in that:
Described orthogonal intersection is the LAS sign indicating number.
3. the method that is used to improve the ofdm system net synchronization capability as claimed in claim 1 is characterized in that:
Described orthogonal intersection is the CCK sign indicating number.
4. the method that is used to improve the ofdm system net synchronization capability as claimed in claim 1 is characterized in that:
Transmitting terminal at described ofdm system, be divided at least one group behind the emission information via coding, each modulation bit number of organizing according to an OFDM subcarrier is carried out segmentation, be mapped as complex symbol according to the needed bit constellation mapping ruler of OFDM subcarrier-modulated every section.
5. the method that is used to improve the ofdm system net synchronization capability as claimed in claim 1 is characterized in that:
Transmitting terminal at described ofdm system has at least one group of user profile, after each is organized user profile and encodes respectively, every group of user profile is carried out segmentation according to the modulation bit number of an OFDM subcarrier, be mapped as complex symbol according to the needed bit constellation mapping ruler of OFDM subcarrier-modulated every section.
6. the method that is used to improve the ofdm system net synchronization capability as claimed in claim 1 is characterized in that:
At the transmitting terminal of described ofdm system, data subcarriers all among the OFDM is divided into groups, every group of sub-carrier number is the length of described orthogonal intersection, and the subcarrier in same group is adjacent on frequency.
7. the method that is used to improve the ofdm system net synchronization capability as claimed in claim 1 is characterized in that:
At the receiving terminal of described ofdm system, the baseband complex signal that receives is carried out after the fast fourier transform, at first carry out frequency domain equalization and handle, carry out the despreading processing with described orthogonal intersection again.
8. the method that is used to improve the ofdm system net synchronization capability as claimed in claim 7 is characterized in that:
Described frequency domain equalization is handled the pilot sub-carrier mode that adopts ofdm system to use.
9. the method that is used to improve the ofdm system net synchronization capability as claimed in claim 7 is characterized in that:
FSm code word in the described frequency domain equalization processing employing cdma system is done pilot channel and is carried out channel estimating and compensation.
Priority Applications (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 200410009597 CN1753394B (en) | 2004-09-21 | 2004-09-21 | Method of improving despreading spectrum of OFDM system synchronization performance |
| PCT/CN2005/001481 WO2006032191A1 (en) | 2004-09-21 | 2005-09-16 | A method of spreading and de-spreading for improving synchronization performance of ofdm system |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 200410009597 CN1753394B (en) | 2004-09-21 | 2004-09-21 | Method of improving despreading spectrum of OFDM system synchronization performance |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN1753394A CN1753394A (en) | 2006-03-29 |
| CN1753394B true CN1753394B (en) | 2010-04-28 |
Family
ID=36089841
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN 200410009597 Expired - Fee Related CN1753394B (en) | 2004-09-21 | 2004-09-21 | Method of improving despreading spectrum of OFDM system synchronization performance |
Country Status (2)
| Country | Link |
|---|---|
| CN (1) | CN1753394B (en) |
| WO (1) | WO2006032191A1 (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN108964827A (en) * | 2018-08-17 | 2018-12-07 | 盐城工学院 | It is a kind of based on the frequency shift keyed near radio network using CDMA technology |
| CN109217968A (en) * | 2018-08-17 | 2019-01-15 | 盐城工学院 | A kind of near radio network using CDMA technology based on phase-shift keying (PSK) technology |
Families Citing this family (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101355539B (en) * | 2007-07-24 | 2012-05-09 | 重庆无线绿洲通信技术有限公司 | Transmission method for multi-carrier synchronization CDMA |
| CN101692664B (en) * | 2009-10-13 | 2012-02-08 | 清华大学 | Multi-carrier wireless transmission method for adopting discontinuous carrier wave interference code |
| CN107276951B (en) * | 2016-04-08 | 2021-08-06 | 深圳光启合众科技有限公司 | Carrier synchronization method and device |
| CN107276740B (en) * | 2016-04-08 | 2020-01-07 | 深圳光启合众科技有限公司 | Timing synchronization method, device and system |
| CN111835668B (en) * | 2020-08-05 | 2023-03-31 | 成都盟升科技有限公司 | Simplified non-coherent despreading and demodulating method for MSK spread spectrum system |
| CN112671683B (en) * | 2020-12-16 | 2023-07-25 | 清华大学 | Signal modulation and demodulation method and system for segmented continuous frequency modulation wave |
Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1391408A (en) * | 2001-06-11 | 2003-01-15 | 华为技术有限公司 | Method for selecting synchronous code in synchronizing system of mobile communication |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| KR20050013611A (en) * | 2002-06-25 | 2005-02-04 | 코닌클리즈케 필립스 일렉트로닉스 엔.브이. | Mt-cdma using spreading codes with interference-free windows |
| DE10239810A1 (en) * | 2002-08-29 | 2004-03-11 | Siemens Ag | Method and transmission device for transmitting data in a multi-carrier system |
-
2004
- 2004-09-21 CN CN 200410009597 patent/CN1753394B/en not_active Expired - Fee Related
-
2005
- 2005-09-16 WO PCT/CN2005/001481 patent/WO2006032191A1/en active Application Filing
Patent Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1391408A (en) * | 2001-06-11 | 2003-01-15 | 华为技术有限公司 | Method for selecting synchronous code in synchronizing system of mobile communication |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN108964827A (en) * | 2018-08-17 | 2018-12-07 | 盐城工学院 | It is a kind of based on the frequency shift keyed near radio network using CDMA technology |
| CN109217968A (en) * | 2018-08-17 | 2019-01-15 | 盐城工学院 | A kind of near radio network using CDMA technology based on phase-shift keying (PSK) technology |
| CN109217968B (en) * | 2018-08-17 | 2020-04-28 | 盐城工学院 | Short-distance wireless network based on phase shift keying technology and adopting CDMA technology |
Also Published As
| Publication number | Publication date |
|---|---|
| WO2006032191A1 (en) | 2006-03-30 |
| CN1753394A (en) | 2006-03-29 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CN101039295B (en) | Method for improving synchronization performance of OFDM system using low correlated code | |
| Yang et al. | Multicarrier DS-CDMA: A multiple access scheme for ubiquitous broadband wireless communications | |
| US8804478B2 (en) | Apparatus and method for transmitting data using a plurality of carriers | |
| US11025471B2 (en) | Method and system for providing code cover to OFDM symbols in multiple user system | |
| CN110266622B (en) | Orthogonal multi-carrier M-element chaotic phase modulation spread spectrum underwater acoustic communication method | |
| CN101321146B (en) | Peak-to-average ratio restraining method and device in multi-carrier orthogonal frequency division multiplexing system | |
| WO2007122828A1 (en) | Pilot signal transmitting method and wireless communication apparatus | |
| JP2005533429A (en) | Time-frequency interleaved MC-CDMA for quasi-synchronous systems | |
| KR100873600B1 (en) | Transmitter apparatus and communication system | |
| CN101534278B (en) | Time-frequency expansion Orthogonal Frequency Division Multiplexing transmitting and receiving device, method and system | |
| CN110518935A (en) | Underwater sound communication system and PAPR suppressing method based on MC-CDMA | |
| CN113315541B (en) | Pseudo-random phase sequence spread spectrum modulation method | |
| CN1992689B (en) | Method for improving inter-carrier interference of OFDM system | |
| CN105516045A (en) | OFDM (Orthogonal Frequency-Division Multiplexing) training sequence construction method and synchronization method | |
| CN1753394B (en) | Method of improving despreading spectrum of OFDM system synchronization performance | |
| Adhikary et al. | Constructions of cross Z-complementary pairs with new lengths | |
| Kumbasar et al. | Better wavelet packet tree structures for PAPR reduction in WOFDM systems | |
| CN108206801A (en) | Frequency spreading device for cyclic frequency shift orthogonal frequency division multiplexing | |
| CN102065035B (en) | Channel estimation method of multi-band orthogonal frequency-division multiplexing ultra-wideband system | |
| CN105049396B (en) | The PTS OFDM methods eliminated based on clipped noise and subcarrier interference | |
| CN109617568B (en) | Orthogonal complementary sequence set-based multi-system spread spectrum OFDM modulation method | |
| CN108616475B (en) | Subcarrier index differential modulation method for OFDM system | |
| CN104954312A (en) | OFDM (orthogonal frequency division multiplexing) modulation based frame synchronization signal generation method for power-line carrier communication system | |
| Khan et al. | Combined OTFS and OCDM for Unprecedented Performance: A Paradigm Shift in Wireless Communication | |
| CN1352505A (en) | Method for transmitting diversity in orthogonal multiple carrier wave system |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| C06 | Publication | ||
| PB01 | Publication | ||
| C10 | Entry into substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| C14 | Grant of patent or utility model | ||
| GR01 | Patent grant | ||
| ASS | Succession or assignment of patent right |
Owner name: BEIJING FOUNDER BROADBAND NETWORK TECHNOLOGY CO., Free format text: FORMER OWNER: FANGZHENG COMMUNICATION TECHNOLOGY CO., LTD. Effective date: 20100907 |
|
| C41 | Transfer of patent application or patent right or utility model | ||
| COR | Change of bibliographic data |
Free format text: CORRECT: ADDRESS; FROM: 100083 10/F, SILVER NETWORK CENTER, NO.113, ZHICHUN ROAD, HAIDIAN DISTRICT, BEIJING TO: 100871 5/F, FANGZHENG BUILDING, ZHONGGUANCUN, NO.298, CHENGFU ROAD, HAIDIAN DISTRICT, BEIJING |
|
| TR01 | Transfer of patent right |
Effective date of registration: 20100907 Address after: 100871 Beijing, Haidian District Road, building No. 298, founder of the building, Zhongguancun, layer 5 Patentee after: Beijing PKU Founder Broadband Network Technology Co., Ltd. Address before: 100083, Beijing, Zhichun Road, Haidian District No. 113 silver net center, 10 floor Patentee before: Fangzheng Communication Technology Co., Ltd. |
|
| C56 | Change in the name or address of the patentee |
Owner name: FOUNDER BROADBAND NETWORK SERVICE CO., LTD. Free format text: FORMER NAME: BEIJING PKU FOUNDER BROADBAND NETWORK TECHNOLOGY CO., LTD. |
|
| CP03 | Change of name, title or address |
Address after: North Building 100088 Beijing city Haidian District Institute of Road No. 15 5 floor Patentee after: Founder Broadband Network Service Co., Ltd. Address before: 100871 Beijing, Haidian District Road, building No. 298, founder of the building, Zhongguancun, layer 5 Patentee before: Beijing PKU Founder Broadband Network Technology Co., Ltd. |
|
| C56 | Change in the name or address of the patentee | ||
| CP01 | Change in the name or title of a patent holder |
Address after: North Building 100088 Beijing city Haidian District Institute of Road No. 15 5 floor Patentee after: FOUNDER BROADBAND NETWORK SERVICE CO., LTD. Address before: North Building 100088 Beijing city Haidian District Institute of Road No. 15 5 floor Patentee before: Founder Broadband Network Service Co., Ltd. |
|
| CF01 | Termination of patent right due to non-payment of annual fee | ||
| CF01 | Termination of patent right due to non-payment of annual fee |
Granted publication date: 20100428 Termination date: 20190921 |