CN103763294B - A kind of method of sign synchronization precision in raising ofdm system - Google Patents
A kind of method of sign synchronization precision in raising ofdm system Download PDFInfo
- Publication number
- CN103763294B CN103763294B CN201410030641.1A CN201410030641A CN103763294B CN 103763294 B CN103763294 B CN 103763294B CN 201410030641 A CN201410030641 A CN 201410030641A CN 103763294 B CN103763294 B CN 103763294B
- Authority
- CN
- China
- Prior art keywords
- valid data
- time delay
- sign synchronization
- average
- ofdm system
- 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
Landscapes
- Synchronisation In Digital Transmission Systems (AREA)
Abstract
The invention discloses a kind of method for improving sign synchronization precision in ofdm system, the method includes：Valid data are selected from the data for receiving, wherein valid data detect the short lead data of the time domain after frame data for receiving terminal；Channelling mode identification is carried out to the valid data, the subchannel that useful signal is located is identified；For described channelling mode recognition result, corresponding threshold calculations function is given；The valid data are entered with line delay auto-correlation computation and obtains time delay autocorrelation result, and calculate the average of the time delay autocorrelation result；Calculate the average energy of described valid data；The average energy of the average and the valid data of the time delay autocorrelation result is substituted into into threshold calculations function, the sign synchronization threshold value of the receiving frame is obtained；The time delay autocorrelation result is compared with the sign synchronization threshold value, the scope of precise synchronization point is obtained.The present invention improves in ofdm system sign synchronization precision and with wider range of application.
Description
Technical field
The present invention relates to OFDM technology field, especially a kind of method for improving sign synchronization precision in ofdm system.
Background technology
Used as the newest standards in WLAN, it not only increases carrier wave efficiency to 802.11ac, and substantially increases and be
The stability of system.802.11ac also ensure that the compatibility with previous version (includes while performance boost is ensured
802.11a\n)。
In 802.11ac, OFDM frames have four kinds of forms, and every kind of form most starts all to be short leading (STF), followed by length
Leading (LTF).Short leading effect is to carry out frame to detect to determine whether to receive frame data, and completes sign synchronization to determine
The original position of long preambles, such that it is able to transmission information is demodulated and is received.It is short it is leading have 10 cycles, each cycle is long
Spend 0.8 μ s；Long preambles Cyclic Prefix is 1.6us, and two symbol periods for repeating are 3.2us, altogether long 8us.802.11ac support
Various channel widths, including 20MHz channels, 40MHz channels, 80MHz channels, 160MHz channels and 80+80MHz channels.It is useful
Inromation bandwidth can be attached to any one 20MHz subchannel, the 40MHz letters of these channels when less than channel width
In road, 80MHz subchannels or 160MHz subchannels.
Prior art mainly carries out sign synchronization using the periodicity and dependency of short leading and long preambles, probably has as follows
Several method：(1) computing cross-correlation is carried out using locally stored long preamble and receiving sequence, before can finding out each length
Lead the starting point in cycle, but due to the long preambles cycle it is longer, it is computationally intensive and time delay is longer, easily affect channel estimation；(2)
Computing cross-correlation is carried out using locally stored long preamble Cyclic Prefix and receiving sequence, as Cyclic Prefix is half week
The long preambles symbol of phase, so dependency is poor, it is larger by short leader sequence and influence of noise；(3) using long preamble
Periodically enter line delay auto-correlation computation, and the starting point that Energy maximum value can obtain long preambles calculated by sliding window,
It is but amount of calculation further increases and impracticable.(4) cross-correlation is carried out using locally stored short preamble cycle and receiving sequence
Computing, can find out the starting point of each short preamble cycle, but be not easy to determine short leading end position；(5) using short
The periodicity of targeting sequencing enters line delay auto-correlation computation, as short leader sequence is poor with the dependency of long preambles, works as correlation
Value can provide synchronous point when reducing to a certain extent, but the point receives multipath channel and influence of noise larger very inaccurate.
In sum, from from the point of view of amount of calculation and sequential time delay, short leading cross-correlation is mainly adopted at present and from phase
The method that pass combines improves the precision of sign synchronization.Under auto-correlation and cross correlation results are as shown in Fig. 2 autocorrelation result starts
The position of drop is the end position in short leading last cycle, when autocorrelation result drops below certain threshold value,
Can determine it is short it is leading be over, last cross-correlation peak value be long preambles original position.
The method of above-mentioned raising sign synchronization precision has three：1st, do not account for short leading related to long preambles
Property.According to the theory of maximum likelihood, during for approximate Gaussian distribution, threshold value should be selected in the midpoint of two theoretical values, institute
Determined on the basis of it there is a constant with threshold value.2nd, effect of noise is not accounted for.As sequence period is limited, enter
During line delay autocorrelation calculation, the correlated results of noise is not 0, but in approximate Gaussian distribution, standard deviation is less.With making an uproar
The increase of sound, the standard deviation increase of correlated results, affects the judgement of short leading end position.3rd, the shadow of channel width is not accounted for
Ring.As it was previously stated, the bandwidth of useful signal is often below channel width, so as to the noise outside effective signal bandwidth is to related knot
Fruit produces interference, affects the judgement of short leading end position.
Due to the presence of the problems referred to above, symbol synchronization point skew accurate synchronization one short preamble cycle of point is often resulted in.It is right
This, the method for having document to propose auto-correlation adjusting thresholds so that threshold value is adjusted according to the energy variation for receiving signal or according to AGC
System provides auto-correlation threshold value.These improved methods do not account for channel width, while threshold value is only linear with the relation of energy,
The change of noise size can not be reflected.Therefore need to calculate the optimal of sign synchronization according to different channelling modes and influence of noise
Threshold value.
The content of the invention
(1) technical problem to be solved
It is an object of the invention to provide a kind of method for improving sign synchronization precision in ofdm system.
(2) technical scheme
To reach above-mentioned purpose, the invention provides a kind of method for improving sign synchronization precision in ofdm system, the party
Method includes：Valid data are selected from the data for receiving, wherein valid data are detected after frames received evidence for receiving terminal
The short lead data of time domain；Channelling mode identification is carried out to the valid data, the subchannel that useful signal is located is identified；Pin
To described channelling mode recognition result, corresponding threshold calculations function is given；Line delay auto-correlation is entered to the valid data
Computing obtains time delay autocorrelation result, and calculates the average of the time delay autocorrelation result；Calculate the average of described valid data
Energy；The average energy of the average and the valid data of the time delay autocorrelation result is substituted into into threshold calculations function, is obtained
The sign synchronization threshold value of the receiving frame；The time delay autocorrelation result and the average energy are compared, the ratio for obtaining
It is compared with the sign synchronization threshold value, obtains the scope of precise synchronization point.
It is in such scheme, described that channelling mode identification is carried out to the valid data, identify the son that useful signal is located
In the step of channel, the channelling mode identification to be referred to and identify that the son that signal is located is believed according to the difference of each sub-channel energy
Road.
It is in such scheme, described for described channelling mode recognition result, provide the step of corresponding threshold calculations function
In rapid, it is, according to channelling mode recognition result, to obtain corresponding threshold calculations function.
It is in such scheme, described the valid data are entered with line delay auto-correlation computation to obtain time delay autocorrelation result, and
In the step of calculating the average of the time delay autocorrelation result, the time delay auto-correlation computation, its delay length are short by leading one
The individual cycle.
In such scheme, the step of the average energy of the valid data described in the calculating in, the valid data it is flat
Energy is the average energy in short leading a cycle.
In such scheme, the step of the average energy of the valid data described in the calculating in, be the reality to valid data
Portion and imaginary part distinguish it is squared sue for peace again, finally calculate.
(3) beneficial effect
As above-mentioned technical proposal is used, the present invention has following advantages compared with prior art：The symbol of the present invention is same
Step threshold value calculation method, from actually considering a problem, has considered noise and channel width for time delay autocorrelation calculation and energy
The impact that amount is calculated, gives accurate threshold value calculation method, has reached higher synchronization accuracy, and which can be applied not only to
In 802.11ac, other similar ofdm systems with targeting sequencing can be used, with wider range of application.
Description of the drawings
HT-MIXED FORMAT PPDU form schematic diagrams of the Fig. 1 for 802.11ac.
Fig. 2 is short leader sequence time delay auto-correlation and cross-correlation curve.
The method flow diagram for improving sign synchronization precision in ofdm system that Fig. 3 is provided for the present invention.
Fig. 4 is the method flow diagram for improving sign synchronization precision in ofdm system according to the embodiment of the present invention.
Fig. 5 is the sign synchronization result and other comparative result figures using the present invention.
Specific embodiment
To make the object, technical solutions and advantages of the present invention become more apparent, below in conjunction with specific embodiment, and reference
Accompanying drawing, the present invention is described in more detail.
The invention provides a kind of method for improving sign synchronization precision in ofdm system, the method is first by channel mould
Formula identification determines specific threshold function table, is calculated accurate symbol by threshold function table by correlation and energy value afterwards
Synchronization threshold, determines the scope of symbol synchronization point by auto-correlation computation result and the threshold value, by the accurate of sign synchronization threshold value
Calculate the precision for improving sign synchronization.
As shown in figure 3, the method flow diagram for improving sign synchronization precision in ofdm system that Fig. 3 is provided for the present invention, should
Method is comprised the following steps：
Step 1：Valid data are selected from the data for receiving, wherein valid data detect receiving frame for receiving terminal
The short lead data of time domain after data.
Step 2：Channelling mode identification is carried out to the valid data, the subchannel that useful signal is located is identified；Wherein
The channelling mode identification refers to the subchannel that signal place is identified according to the difference of each sub-channel energy.
Step 3：For described channelling mode recognition result, corresponding threshold calculations function is given；It is wherein described to be directed to
Described channelling mode recognition result, provides corresponding threshold calculations function, is, according to channelling mode recognition result, to obtain correspondence
Threshold calculations function.
Step 4：The valid data are entered with line delay auto-correlation computation and obtains time delay autocorrelation result, and calculate the time delay
The average of autocorrelation result；Wherein described time delay auto-correlation computation, its delay length are short leading a cycle.
Step 5：Calculate the average energy of described valid data；The average energy of wherein described valid data is short leading
Average energy in a cycle, the average energy of the valid data described in the calculating is the real part to valid data and void
Portion distinguish it is squared sue for peace again, finally calculate.
Step 6：The average energy of the average and the valid data of the time delay autocorrelation result is substituted into into threshold calculations
Function, obtains the sign synchronization threshold value of the receiving frame.
Step 7：The time delay autocorrelation result and the average energy are compared, the ratio for obtaining and the symbol
Synchronization threshold is compared, and obtains the scope of precise synchronization point.
The invention will be further described for shown embodiment below in conjunction with the accompanying drawings.
Embodiment one：In a kind of raising ofdm system, the method for sign synchronization precision, is applied to ofdm system sign synchronization
In the calculating of threshold value, by taking the HT-MIXED FORMAT PPDU of 802.11ac as an example, the docking collection of letters number is needed to carry out in receiving terminal
It is during the calculating of sign synchronization threshold value, as follows according to the flow processing shown in accompanying drawing 4.
The first step, by selecting valid data in the data for receiving.The valid data are determined and are connect to complete frame detection
Receive part short lead data of the frames received according to after.In this example, it is assumed that there was only 3 symbol lengths after completing frame detection
Short leading time domain data.
Valid data are carried out channelling mode identification by second step, it is indicated that the subchannel that useful information is located.
Specifically, for receive channel in each 20MHz bandwidth subchannel i, design passband to should subchannel i and
Digital band-pass filter f of the pass band width for 20MHzi；And to each wave filter fiValid data after Filtering Processing calculate energy
Ei.If EiMore than certain threshold value TE, then the subchannel is with information.So as to obtain the channelling mode of receiving frame.
3rd step, to described channelling mode recognition result, provides corresponding threshold calculations function；Channelling mode identification
As a result need not identify useful information in which subchannel, it is only necessary to know and occupy several sub-channels.Table one is listed
The corresponding threshold calculations function of local channel pattern：
Table one：The corresponding threshold calculations function of local channel pattern
In table one, 20MHz/20MHz represents information of the 20MHz transmissions with a width of 20MHz；20MHz/40MHz tables
Show information of the 40MHz transmissions with a width of 20MHz, the 20MHz information may occupy the upper side band of 40MHz channels, also may be used
The lower sideband of the 40MHz channels can be occupied, but corresponding threshold calculations function is identical.In formula, C0Represent auto-correlation
The average of computing；E0Represent average energy.
In actual applications, in order to reduce amount of calculation, can be approximately normal by a certain section of the fragmentation threshold computation function
Number corresponds to a constant by two sections, obtains the simplified function of threshold calculations function.
Described valid data are entered line delay auto-correlation computation, and obtain the average of auto-correlation computation result by the 4th step.
Computing formula isWherein r represents reception signal；R (k) is receive signal k-th
Sampled point；Likewise, r (k-n) is kth-n sampled point, r (k-Ls-n) is kth-Ls-n sampled point；Ls is short by leading one
The length in individual cycle；()*Expression takes conjugation to signal；CkTo adopt the autocorrelation result obtained during k-th sampled point.
Described valid data are calculated average energy by the 5th step.Formula is
Parameter physical significance is with the 4th step.
6th step, substitutes into threshold calculations function to described auto-correlation computation result and average energy, obtains the receiving frame
Sign synchronization threshold value.Specifically, it is exactly by calculated autocorrelation result meansigma methodss C0With average energy E0Substitute into threshold
Value is calculated in function or simplified function, so as to obtain threshold value T0。
7th step, detects reception signal point K0The auto-correlation computation result at place and average energy E0Ratio less than should
Threshold value T0When, it may be determined that symbol synchronization point is in [K0- Ls, K0- 1] in the range of.
A kind of application in practice of method for improving sign synchronization precision in ofdm system is embodiment described above provides,
Which can be limited in amount of available data and the threshold value that sign synchronization is given in signal, comparing result such as Fig. 5 is received by noise jamming
Shown, Fig. 5 is the sign synchronization result and other comparative result figures using the present invention.Simulated environment is flat for IEEE 802.11ac
Platform, 20MHz/20MHz bandwidth, 40MHz samplings, using TGac_D channel models, the multipath channel root-mean-square time delay is 50ns, is imitated
True 4000 bag is counted.Due to the impact of multipath channel, define synchronous point and be correctly together less than 5 points with exact point deviation
Beans-and bullets shooter.In figure, transverse axis is signal to noise ratio, and the longitudinal axis is accurate synchronization point probability.Wherein Met1 represents long preambles Cyclic Prefix cross-correlation side
The synchronized result of method；Met2 is the method that short leading auto-correlation is combined with cross-correlation, and threshold value is according to energy value linear change；
The method of the method application this patent that Met3 is combined with cross-correlation to short leading auto-correlation improves the precision of sign synchronization.
According to the disclosed embodiments, those skilled in the art can realize or using the present invention.Due to this synchronization side
Method carries out auto-correlation and energy calculation using short leading periodicity, in TGac standard channels, even if data available is seldom
Can realize, be especially suitable for applying in the sign synchronization threshold calculations of 802.11ac.
Above-described embodiment technology design only to illustrate the invention and feature, its object is to allow person skilled in the art
Scholar will appreciate that present disclosure and implement according to this, can not be limited the scope of the invention with this.It is all according to the present invention
Equivalence changes or modification that spirit is made, should all be included within the scope of the present invention.
Claims (5)
1. it is a kind of improve ofdm system in sign synchronization precision method, it is characterised in that the method includes：
Select valid data from the data for receiving, wherein valid data for receiving terminal detect frames received according to after when
The short lead data in domain；
Channelling mode identification is carried out to the valid data, the subchannel that useful signal is located is identified；
For described channelling mode recognition result, corresponding threshold calculations function is given；
The valid data are entered with line delay auto-correlation computation and obtains time delay autocorrelation result, and calculate the time delay autocorrelation result
Average；
Calculate the average energy of described valid data；
The average energy of the average and the valid data of the time delay autocorrelation result is substituted into into threshold calculations function, is somebody's turn to do
The sign synchronization threshold value of receiving frame；And
The time delay autocorrelation result and the average energy are compared, the ratio for obtaining is entered with the sign synchronization threshold value
Row compares, and obtains the scope of precise synchronization point.
2. it is according to claim 1 improve ofdm system in sign synchronization precision method, it is characterised in that it is described to institute
Stating valid data carries out channelling mode identification, the step of identify the subchannel that useful signal is located in, the channelling mode is known
The subchannel that signal place is identified according to the difference of each sub-channel energy is not referred to.
3. it is according to claim 1 improve ofdm system in sign synchronization precision method, it is characterised in that it is described to institute
State valid data and enter line delay auto-correlation computation and obtain time delay autocorrelation result, and calculate the average of the time delay autocorrelation result
In step, the time delay auto-correlation computation, its delay length are short leading a cycle.
4. it is according to claim 1 improve ofdm system in sign synchronization precision method, it is characterised in that the calculating
In the step of average energy of described valid data, the average energy of the valid data is flat in short leading a cycle
Equal energy.
5. it is according to claim 1 improve ofdm system in sign synchronization precision method, it is characterised in that the calculating
In the step of average energy of described valid data, be the real part to valid data and imaginary part distinguish it is squared sue for peace again, most
After calculate.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201410030641.1A CN103763294B (en) | 2014-01-22 | 2014-01-22 | A kind of method of sign synchronization precision in raising ofdm system |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201410030641.1A CN103763294B (en) | 2014-01-22 | 2014-01-22 | A kind of method of sign synchronization precision in raising ofdm system |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN103763294A CN103763294A (en) | 2014-04-30 |
| CN103763294B true CN103763294B (en) | 2017-04-05 |
Family
ID=50530456
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN201410030641.1A Expired - Fee Related CN103763294B (en) | 2014-01-22 | 2014-01-22 | A kind of method of sign synchronization precision in raising ofdm system |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN103763294B (en) |
Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101325575A (en) * | 2008-05-28 | 2008-12-17 | 苏州中科半导体集成技术研发中心有限公司 | Method for implementing frame synchronization of OFDM system |
| CN103200144A (en) * | 2013-03-28 | 2013-07-10 | 灵芯微电子科技（苏州）有限公司 | Synchronizing method used for MIMO-OFDM system |
-
2014
- 2014-01-22 CN CN201410030641.1A patent/CN103763294B/en not_active Expired - Fee Related
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101325575A (en) * | 2008-05-28 | 2008-12-17 | 苏州中科半导体集成技术研发中心有限公司 | Method for implementing frame synchronization of OFDM system |
| CN103200144A (en) * | 2013-03-28 | 2013-07-10 | 灵芯微电子科技（苏州）有限公司 | Synchronizing method used for MIMO-OFDM system |
Non-Patent Citations (3)
| Title |
|---|
| 基于IEEE 802.11n无线局域网标准的同步技术研究;方元;《万方学位论文数据库》;20121130;全文 * |
| 基于IEEE802.11n无线局域网***的符号同步;方元;《电子设计工程》;20130731;全文 * |
| 基于IEEE802.11n的MIMO-OFDM算法研究;鉴海防;《万方学位论文数据库》;20101231;全文 * |
Also Published As
| Publication number | Publication date |
|---|---|
| CN103763294A (en) | 2014-04-30 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CN110224968B (en) | Frame timing synchronization method and device in OFDM communication system | |
| CN104125190B (en) | Ofdm system timing synchronization implementation method suitable for low signal-to-noise ratio channel circumstance | |
| CN105991498B (en) | The generation method and method of reseptance of leading symbol | |
| CN104022996B (en) | Channel estimation-based timing synchronization method for orthogonal frequency division multiplexing (OFDM) system | |
| CN101951356B (en) | Synchronization method of orthogonal frequency division multiplexing-ultra wideband (OFDM-UWB) system based on peak detection | |
| CN1308427A (en) | Signal structure, detection and estimation of timing sync and access of upstream link | |
| CN103023853B (en) | Orthogonal frequency division multiplexing received frame synchronizing method for co-training sequence mutual-correlation information | |
| CN105991500B (en) | The method of reseptance and device of leading symbol | |
| CN104717174B (en) | A kind of OFDM anti-interference synchronous methods under complexity multipath channel | |
| CN107070831A (en) | The receiving handling method of leading symbol in physical frame | |
| CN103259756A (en) | Method of symbol timing synchronization and carrier synchronization applied to OFDM system | |
| CN114268528B (en) | Frame capturing synchronization method and device | |
| CN102185819A (en) | OFDM (Orthogonal Frequency Division Multiplexing) time synchronization algorithm based on conjugate symmetric sequence | |
| CN103889069B (en) | A kind of accidental access signal method of sending and receiving applied to large coverage | |
| CN103095624A (en) | Frame synchronization method | |
| CN106789825A (en) | A kind of ofdm system sychronisation and method based on sliding window peakvalue's checking | |
| CN102377726B (en) | Timing synchronization method of OFDM (Orthogonal Frequency Division Multiplexing) system | |
| CN101242389B (en) | A frame synchronization method | |
| CN110430156B (en) | Frame synchronization method and system for burst OFDM data transmission | |
| CN104270333B (en) | Produce the method and OFDM synchronous method of OFDM synchronous training sequences | |
| CN105024966B (en) | The symbol timing synchronization method of ofdm system | |
| CN103763294B (en) | A kind of method of sign synchronization precision in raising ofdm system | |
| CN108600142A (en) | A kind of synchronous method in FBMC/OQAM systems | |
| CN110278173B (en) | Timing synchronization method under low signal-to-noise ratio environment in OFDM system | |
| CN104901918B (en) | The method and synchronous method of OFDM data sequence are generated based on Chirp signal |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| C06 | Publication | ||
| PB01 | Publication | ||
| C10 | Entry into substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| GR01 | Patent grant | ||
| GR01 | Patent grant | ||
| 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: 20170405 Termination date: 20180122 |