CN105139692A - Correlation receiving-based vehicle wireless distance measurement method - Google Patents

Abstract

The invention belongs to the technical field of wireless distance measurement and positioning, and particularly relates to a correlation receiving-based vehicle wireless distance measurement method. The method mainly comprises the four steps: A, an IEEE802.11p protocol receiving signal is subjected to correlation calculation and normalization processing; B, grouped summation is carried out on statistical results, and a time delay estimation sequence is obtained; C, signal propagation time delay is found out in the time delay estimation sequence; and D, the distance is calculated and obtained through the propagation time delay. Correlation summation is firstly applied to wireless positioning of the IEEE802.11p protocol, the positioning precision is high, stability is good, and the vehicle distance measurement precision can be improved in a multipath, non-line of sight and high-doppler frequency shift environment.

Description

A kind of automobile wireless distance-finding method based on correlation reception

Technical field

The invention belongs to wireless distance finding, field of locating technology, can be used for using the high precision wireless of the vehicle of IEEE802.11p agreement to locate in car networking, specifically a kind of automobile wireless distance-finding method based on correlation reception.

Background technology

" traffic safety and emergency guarantee " is one of the six large major fields and preferential theme thereof of " National Program for Medium-to Long-term Scientific and Technological Development (2006-2020) " transportation, also be five great science and technology research and development special projects in " communications and transportation " 12 " development plan " simultaneously, one of six large Popularization and application of achievements in scientific research major fields, by these ITS (IntelligentTransportSystem, intelligent transportation system) investigation and application, traffic hazard and event prevention will be strengthened, for vehicle driving creates the traffic circulation environment of safety and comfort more.

The achievement in research of traffic safety mostly concentrates on the range observation of Adjacent vehicles both at home and abroad at present, the nearest front vehicle of the normal car of now divorced can detect the exception of front truck, but may detect reflective information hardly thus cannot know the existence of potential danger in time due to the vehicle at the stop rear again of signal.As long as research shows that rear car driver receives early warning signal in first 0.5 second causing danger to collide with front truck, the generation of about 60% traffic hazard just can be avoided.If the distance of Adjacent vehicles can only be obtained, vehicle pileup collision thoroughly cannot be solved, only obtain the accurate distance information of many cars at a distance, and carry out according to the relative speed of a motor vehicle, acceleration, distance etc. the early warning that associating judgement just likely realizes the collision of many vehicle pileups, thus reduce the incidence of the especially a chain of rear-end impact accident of traffic accident.The accurate distance information how obtaining non-adjacent vehicle avoids vehicle pileup to collide key issue urgently to be resolved hurrily.

IEEE802.11p standard organizes proposition, specially to the correction of IEEE802.11 standard, to provide wireless access capability to be supported in the application in intelligent transportation system under car networked environment by IEEE in 2010.Original IEEE802.11 standard is mainly used in LAN (Local Area Network), and therefore it is inapplicable under the vehicle environment of high doppler shift, multipath, fast-fading.Specially for car networked environment has carried out serial amendment in the Physical layer and media access control layer of IEEE802.11p, such as: the duration increasing symbol, protection interval etc.IEEE802.11p adopts OFDM (OrthogonalFrequencyDivisionMultiplexing, OFDM) modulation technique, wherein lead code (Preamble) comprises 10 short training sequences (shortpreamble) and two long training sequences (longpreamble).

The method for synchronizing time that the employing that patent of the present invention proposes just on the basis of IEEE802.11p standard 10 short training sequences carry out based on correlation reception technology, thus be multiplied by according to this time delay the range information that electromagnetic speed can obtain between vehicle.The method can realize the precision distance measurement under multipath, non-direct-view, high doppler shift environment, thus provides important distance parameter for vehicle pileup anti-collision warning.

Summary of the invention

The object of this invention is to provide a kind of automobile wireless distance-finding method based on correlation reception technology, can only realize to overcome existing vehicle odometry the problem that Adjacent vehicles range finding cannot carry out many vehicle pileups anti-collision warning.The precision of vehicle odometry particularly can be improved under multipath, non-direct-view, high doppler shift environment.

A kind of automobile wireless distance-finding method based on correlation reception mainly comprises following four steps:

A. carry out correlation computations to received signal and normalized: in IEEE802.11p agreement with the conjugate of short training sequence for template signal and Received signal strength carry out correlation computations, and its result P (d) is normalized divided by signal energy R (d) again, result is M (d), and circular is:

$P\left(d\right)={\mathrm{\Σ}}_{m=0}^{L-1}r(d+m)\×t^{*}(1+m),$

$R\left(d\right)={\mathrm{\Σ}}_{m=0}^{L-1}|r(d+m){|}^2,$

$M\left(d\right)=\frac{{\left|P\left(d\right)\right|}^2}{R^2\left(d\right)},$

Wherein, * represents the conjugate operation of plural number, and the Received signal strength that r (d+m) is IEEE802.11p, the short training sequence that t (1+m) is IEEE802.11p, L=16 is the length of a short training symbols.

B. carry out classification & sum to statistics: be one group to M (d) to be spaced apart 9 samples of L=16, carry out summation respectively and obtain time delay estimated sequence G (t), circular is:

$G\left(t\right)={\mathrm{\Σ}}_{d=1}^{9}M(t+(d-1)\×L).$

C. from time delay estimated sequence, find signal transmission delay: from time delay estimated sequence M (d), find the subscript that maximum sample is corresponding, this subscript value deducts be multiplied by signal sampling interval T again _s, its result is the propagation delay of signal t in IEEE802.11p standard _svalue be 1 microsecond, circular is:

${\hat{T}}_{est}=\left(\mathrm{argmax}\right(G\left(t\right))-(\frac{L}{2}+1))\×T_s.$

D. distance is calculated according to propagation delay: propagation delay be multiplied by electromagnetic wave propagation speed C, result is the estimated distance between vehicle circular is:

$\hat{D}={\hat{T}}_{est}\×C.$

The present invention contrasts prior art and has following remarkable advantage:

1. achieve the method for being carried out measuring vehicle distance by signal correction, thus the collaborative early warning between many vehicles can be realized.

2., under the environment such as multipath, high doppler shift, the method distance accuracy is better than other conventional methods.

Accompanying drawing explanation

Fig. 1 is overview flow chart of the present invention.

Fig. 2 is Received signal strength correlation computations and normalization.

Fig. 3 is time delay estimated sequence oscillogram.

Embodiment

Below in conjunction with accompanying drawing, embodiments of the present invention are described.In embodiment, the propagation delay of putative signal is 191 sampled points, and now the subscript of classification & sum maximal value should be 191+9=200 in theory.

Fig. 1 is the overview flow chart of the automobile wireless distance-finding method based on correlation reception of the present invention, and distance-finding method specific implementation is:

A. carry out correlation computations to received signal and normalized: in IEEE802.11p agreement with the conjugate of 160 of short training sequence samples for template signal and Received signal strength carry out correlation computations, and its result P (d) is normalized divided by signal energy R (d) again, result is M (d), and circular is:

$P\left(d\right)={\mathrm{\Σ}}_{m=0}^{15}r(d+m)\×t^{*}(1+m),$

$R\left(d\right)={\mathrm{\Σ}}_{m=0}^{15}{\left|r(d+m)\right|}^2,$

$M\left(d\right)=\frac{{\left|P\left(d\right)\right|}^2}{R^2\left(d\right)}.$

When bit signal to noise ratio (S/N ratio) is 30 decibels, its simulation result as shown in Figure 2.

B. carry out classification & sum to statistics: be one group to M (d) to be spaced apart 9 samples of 16, carry out summation respectively and obtain time delay estimated sequence G (t), circular is:

$G\left(t\right)={\mathrm{\Σ}}_{d=1}^{9}M(t+(d-1)\×16),$

When bit signal to noise ratio (S/N ratio) is 30 decibels, its simulation result as shown in Figure 3.

C. from time delay estimated sequence, find signal transmission delay: as can be seen from Figure 3 in time delay estimated sequence M (d) maximal value corresponding under be designated as 200, be multiplied by sampling interval 1 microsecond of signal again, its result is propagation delay 191 microsecond of signal.

D. distance is calculated according to propagation delay: propagation delay 191 microsecond is multiplied by electromagnetic wave propagation speed 3 × 10 ⁸, result is the distance between vehicle.

Claims (1)

1. one kind is characterized in that comprising the following steps based on the automobile wireless distance-finding method of correlation reception:

A. correlation computations is carried out to received signal and normalized: in IEEE802.11p agreement, with the conjugate of short training sequence for template signal and Received signal strength carry out correlation computations, and by its result P (d) again divided by signal energy R (d), obtaining result is M (d), and circular is:

$P\left(d\right)=\underset{m=0}{\overset{L-1}{\Σ}}r(d+m)\×t^{*}(1+m)$

$R\left(d\right)=\underset{m=0}{\overset{L-1}{\Σ}}|r(d+m){|}^2$

$M\left(d\right)=\frac{|P\left(d\right){|}^2}{R^2\left(d\right)}$

Wherein, * represents the conjugate operation of plural number, the Received signal strength that r (d+m) is IEEE802.11p agreement, the short training sequence that t (1+m) is IEEE802.11p agreement, and L=16 is the length of a short training symbols;

B. carry out classification & sum to statistics: be one group to M (d) to be spaced apart 9 samples of L=16, carry out summation respectively and obtain time delay estimated sequence G (t), circular is:

$G\left(t\right)={\mathrm{\Σ}}_{d=1}^{9}M(t+(d-1)\×L);$

C. from time delay estimated sequence, find signal transmission delay: from time delay estimated sequence M (d), find the subscript that maximum sample is corresponding, this subscript value deducts be multiplied by signal sampling interval T again _s, its result is the propagation delay of signal t _svalue be 1 microsecond, circular is:

${\hat{T}}_{est}=\left(\mathrm{argmax}\right(G\left(t\right))-(\frac{L}{2}+1\left)\right)\×T_S;$

D. distance is calculated according to propagation delay: propagation delay be multiplied by electromagnetic wave propagation speed C, result is the distance between vehicle circular is:

$\hat{D}={\hat{T}}_{est}\×C.$