CN103607723B - A kind of wireless communication link method of estimation towards high-speed railway wire community - Google Patents

Abstract

The invention discloses a kind of wireless communication link method of estimation towards high-speed railway wire community belonging to wireless mobile telecommunication technology field.The method includes following steps: 1) propose a set of criteria for classification for high-speed railway characteristic communication environments；2) the large scale path loss under all kinds of scenes and shadow fading are modeled, set up a set of standardization propagation model storehouse towards high-speed railway；3) coverage prediction method towards railway wire community is proposed.The present invention can be on the premise of not measuring by early stage, predict the coverage of high-speed railway community more accurately, optimize the network arrangement scheme of high-speed railway, base station, minizone spacing is reasonably set, and then reduces the input to high-speed railway wireless communication infrastructure greatly.

Description

A kind of wireless communication link method of estimation towards high-speed railway wire community

Technical field

The invention belongs to wireless mobile telecommunication technology field, particularly to a kind of wireless towards high-speed railway wire community Communication link method of estimation.

Background technology

In mobile Communication System for High Speed Railway, the setting of cell base station and planning depend on wireless signal at railway Attenuation in characteristic environment.Along with the increase of distance, electromagnetic wave can be by electrolyte during free space transmission Absorption loss, the relevant and cancellation phenomenon blocking the signal being lost and being caused by anti-, scattered wave of ground obstacle.This The intensity of wireless channel at a little effect strong influence receivers.If the wireless signal strength of receiving terminal is less than the thresholding of system Level, arises that call drop phenomenon between train and base station, for this Safety-Critical System such a for high-speed railway, and meeting Cause huge potential safety hazard.

In order to ensure the reliability of high-speed railway wireless coverage completely, it is necessary to arrange substantial amounts of base station along the line at rail, logical Cross the cell structure setting up chainlike distribution formula, it is achieved the good covering of wireless signal in train operation completely.Between bigger base station Away from will be unable to meet minimum covering level and the high standard requirement of overall situation covering measures under high-speed railway Safety-Critical System；And relatively Little base station spacing will result in huge fund waste, increases subsequent network maintenance cost greatly, reduces high-speed railway simultaneously The antijamming capability of wireless communication system.So, reasonable, a link budget side accurately towards high-speed railway radio communication Method is for promoting high-speed railway network performance, it is ensured that it is most important that high-speed railway runs safety.

For the method for high-speed railway cellular link budget, the past generally uses beehive network in public network Under MPS process Probabilistic estimation, combine with the channel model (i.e. Hata model) of tradition public network communication environment Way.Wherein Hata model is only capable of predicting city, suburb, rural three class scenes, it is impossible to contain warp in high-speed railway radio communication The scenes such as the overpass that often relates to, cutting, river, station.When using Radio Link based on Hata model to estimate, its prediction Often there is bigger error with the channel test under railway characteristic environment in effect.And mostly tradition public network is based on cellular network Network structure, this class formation is many assumes a disc by cell coverage area, and the community in railway wireless communication is wire Community, traditional MPS process probability forecasting method can cause covering measures to owe to estimate phenomenon in Railway Environment, it is impossible to rationally Prediction railway wireless link situation of change.

In sum, a set of standardization propagation model storehouse containing railway characteristic communication environments, join with brand-new towards The covering measures Forecasting Methodology of railway wire community, it is possible to the link budget well solving high-speed railway wireless communication system is difficult Topic.

Summary of the invention

The problem existed for above-mentioned prior art, the present invention proposes a kind of channel radio towards high-speed railway wire community Letter link method of estimation, it is characterised in that the method includes following steps:

1) a set of criteria for classification for high-speed railway characteristic communication environments is proposed；

2) the large scale path loss under all kinds of scenes and shadow fading are modeled, set up a set of towards high-speed railway Standardization propagation model storehouse；

3) based on step (2), the coverage prediction method towards railway wire community is proposed.

Criteria for classification described in step 1) is: high-speed railway communication environments is divided into 7 classes: city, suburb, rural area, overpass, Cutting, station, river.

Step 2) described large scale path loss is modeled, formula is as follows:

PL_Proposed(dB)=Δ₁+74.52+26.16log₁₀(f=930)

-13.82log₁₀(h_b)-3.2(log₁₀(11.75h_m))²

+[44.9-6.55log₁₀(h_b)+Δ₂]log₁₀(d)

Wherein, f is signal frequency (MHz), h_bAnd h_mFor base station and the height (m) of mobile portable antennas distance rail level, d is base Stand and the spacing (km) of mobile station, Δ₁And Δ₂For constant term and the modifying factor of path loss index item.

Described being modeled two modifying factors, formula is as follows:

Δ_i=p·log₁₀(h_b)+q

Wherein, i=1,2 refer to two modifying factors respectively, p and q is to measure, according to reality, the fitting parameter obtained, and is used for Δ is described₁And Δ₂Change, in different environment, p and q is respectively equal to different values.

Step 2) described shadow fading obeys the Gaussian Profile of 0 average, is modeled shadow fading, and formula is as follows:

${\mathrm{\σ}}_j\left(\mathrm{dB}\right)~N[{{\mathrm{\μ}}_{\mathrm{\σ}}}_j,{{\mathrm{\σ}}_{\mathrm{\σ}}}_j]$

Wherein, j=1,2,3,4,5,6,7 represent 7 class high-speed railway communication environments respectively.

Step 2) described in high-speed railway standardization propagation model storehouse degree of fitting judgement evaluation index be:

$\begin{array}{c}R-\mathrm{Square}=1-\frac{\underset{n-1}{\overset{N}{\mathrm{\Σ}}}{w}_n{(y_n-{\hat{y}}_n)}^2}{\underset{n-1}{\overset{N}{\mathrm{\Σ}}}{w}_n{(y_n-{\stackrel{\‾}{y}}_n)}^2}\\ \mathrm{RMSE}=\sqrt{\frac{1}{N-1}\underset{n-1}{\overset{N}{\mathrm{\Σ}}}{(y_n-{\stackrel{\‾}{y}}_n)}^2}\end{array}$

Wherein, R-Square is the coefficient of determination, and RMSE is root-mean-square error, and N is number of samples, w_nFor weight factor, y_nFor Test sample,For estimate,Mean value for test value；Closer to 1, the coefficient of determination shows that degree of fitting is the best, root mean square is by mistake Difference is the least shows that the error of model is the least.

Described step 3) comprises the following steps:

31) the up or down line link foundation as link budget is determined；

32) determining ambient noise thresholding N, formula is as follows:

N=k·T_tem·BW

Wherein, BW is system bandwidth, and Tem is environment temperature, and k is Boltzmann constant；

33) determining receiver sensitivity RS, formula is as follows:

RS=N+NF+SNR_min

Wherein, NF is receiver noise figure, and SNRmin is minimum signal to noise ratio needed for receiver, and k is Boltzmann constant；

34) determining reception level threshold T under Safety-Critical System, formula is as follows:

T=RS+ protection value

Wherein, protection value be multipath fading protection value, high-speed mobile protection value, aging protection value, phone noise protection value, Interference protection value, row control protection value sum；

35) determining shadow fading nargin M, formula is as follows:

$O=\frac{1}{2}+\frac{1}{2}\·\mathrm{erf}\left(\frac{M}{\mathrm{\σ}\sqrt{2}}\right)$

Wherein, O is edge communications failure-free probability, and σ is the standard deviation of shadow fading in wire community；

36) determining overall situation covering measures U, formula is as follows:

$U=\frac{1}{2}-\frac{1}{2}\mathrm{erf}\left(a\right)-\frac{1}{2}\·\exp \left(\frac{1-4\mathrm{ab}}{{4b}^2}\right)\·[\mathrm{erf}(\frac{1}{2b}-a)-1]$

Wherein:, $a=-\frac{M}{\mathrm{\σ}\sqrt{2}},b=\frac{10n{\log }_{10}\left(e\right)}{\mathrm{\σ}\sqrt{2}},$ N is path loss index；

37) average reception level at maximum communication distance D is determinedFormula is as follows:

$\stackrel{\‾}{P_{\mathrm{RX}}\left(D\right)}=M+T$

Wherein, T is for receiving level threshold；

38) determining maximum communication distance D, formula is as follows:

$D={10}^{\frac{P_{\mathrm{TX}}+G_{\mathrm{TX}}+G_{\mathrm{RX}}-L_{\mathrm{TX}}-L_{\mathrm{RX}}-{\mathrm{PL}}_0-\stackrel{\‾}{P_{\mathrm{RX}}\left(D\right)}}{10n}}$

Wherein, P_TXFor launching power, G_TX/G_RXFor transmitting/receiving antenna gain, L_TX/L_RXFor transmitting/receiving end overall loss, PL₀For Constant term in large scale path loss model, it may be assumed that

Δ₁+74.52+26.16log₁₀(f=930)-13.82log₁₀(h_b)-3.2(log₁₀(11.75h_m))²。

Described step 31) link budget according to for selecting the minimum link of loss.

Described step 31) to step 34) by the adjustment to real system parameter, it is possible to it is generalized to non-railway wireless communication System.

The beneficial effect of the invention: the method overcome conventional wireless propagation model storehouse big at Railway Environment application error, and Planar MPS process probability Estimation cannot be applicable to the limitation of wire community, well solves under high-speed railway typical environment special The wireless communication link estimation problem of colo(u)r streak shape community, improves the degree of accuracy and the science of railway wire community wireless link budget Property, and then the design of optimization Railroad Communication System, there is the strongest applicability and practicality, for high-speed railway cordless communication network Design provides important evidence.

Accompanying drawing explanation

Fig. 1 is a kind of wireless communication link method of estimation flow chart towards high-speed railway that the present invention proposes；

Fig. 2 is to damage the path proposed on " Zhengzhou-Xi'an " high-speed railway circuit with the coefficient of determination (R-Square) Consumption model library is verified；

Fig. 3 is to damage the path proposed on " Beijing-Shanghai " high-speed railway circuit with the coefficient of determination (R-Square) Consumption model library is verified；

Fig. 4 be with root-mean-square error (RMSE) on " Zhengzhou-Xi'an " high-speed railway circuit to the path loss proposed Model library is verified；

Fig. 5 be with root-mean-square error (RMSE) on " Beijing-Shanghai " high-speed railway circuit to the path loss proposed Model library is verified；

Fig. 6 is that shadow fading nargin affects situation to cell edge outage probability；

Fig. 7 is channel quality and the impact on railway wire community entirety covering measures of the shadow fading nargin；

Fig. 8 is that channel quality communicates with cell edge the failure-free probability impact on railway wire community entirety covering measures；

Fig. 9 be estimate that high-speed railway wire community is maximum can the flow chart of communication distance；

Figure 10 be base station antenna height on maximum under urban settings can the impact of communication distance；

Figure 11 be base station antenna height on maximum under the scene of suburb can the impact of communication distance；

Figure 12 be base station antenna height on maximum under the scene of rural area can the impact of communication distance；

Figure 13 be base station antenna height on maximum under overpass scene can the impact of communication distance；

Figure 14 be base station antenna height on maximum under cutting scene can the impact of communication distance；

Figure 15 be base station antenna height on maximum under the scene of station can the impact of communication distance；

Figure 16 be base station antenna height on maximum under river scene can the impact of communication distance.

Detailed description of the invention

Below in conjunction with the accompanying drawings and the method is elaborated by part railway system actual parameter.

It is illustrated in figure 1 a kind of wireless communication link method of estimation flow chart towards high-speed railway that the present invention proposes. First, based on China's 4 high-speed railway circuits (Wuhan-Guangzhou, Zhengzhou-Xi'an, Shijiazhuang-Taiyuan, Beijing-Tianjin) and 8 Individual high speed railway station (Beijing South Station, station, Zhengzhou, Wuhan Railway Station, Changsha Station, northern station, Xi'an, northern station, Shijiazhuang, station, Taiyuan, Tianjin Stand) field test and investigate on the basis of, a set of criteria for classification for high-speed railway characteristic communication environments is proposed.Will be at a high speed Railway communication environments is divided into 7 classes:

1) city: this scene refers in particular to the ground that typical large and medium-sized urban district, i.e. population are the densest, industry and commerce is more flourishing District.Rail level can be parallel to earth's surface, may also be on the overpass of 5-20 rice.Radially effective coverage, rail level both sides, longitudinally 80% little The building of 5-20 floor (exceeding rail level 10-40 rice) are had in district.High-rise building can cause a large amount of strong reflection, dissipate the appearance in footpath.This type of Instead, scattering composition because of its Secondary Emission point high, less to the diffraction loss of any barrier, to receiving end signal intensity effect relatively Greatly.

2) suburb: this scene refers in particular to typical micropolis, township, town, village, and non-flat forms, the suburb of non-open area Wild.Rail level is parallel to earth's surface.Radially effective coverage, rail level both sides, longitudinal 60%-80% community in have the building of 1-5 layer with similar The vegetation of height.Exist appropriate in suburb, equally distributed anti-, scattering object.Direct projection footpath, ground return footpath, environment are anti-, scattering Footpath all occupies certain weight proportion.

3) rural area: this scene refers in particular to region outside of the city open on typical case's Image of Flat Ground.Rail level is parallel to earth's surface.Rail level both sides Radially there is no building in the community of effective coverage, longitudinal direction 80%, only have the shortest (less than 2 meters) crops and vegetation.Rural area is opened In wealthy ground anti-, scattering object is less, direct wave and ground-reflected wave are occupied an leading position.Channel transfer matrices convergence sparse matrix is tied Structure.

4) overpass: this scene is refered in particular in non-city, non-mountain area, area, non-river rail level are placed in high overhead of 10-30 rice Region on bridge.It is low-rise buildings in the community of radially effective coverage, rail level both sides, longitudinally 80%, has part trees, shaft tower high In bridge floor 0-10 rice.Overpass bridge floor can stop anti-, the scattered wave of major part earth's surface scattering object.And smooth bridge floor can produce Stronger bridge floor back wave.Exceed the number of bridge floor, house can cause at receiving terminal that near-end is anti-, scattering, occurs that multipath sub-clustering is existing As.

5) cutting: this scene is refered in particular in uneven area as ensureing smooth the dug U-type groove region of rail level.Cutting both sides Cliff mostly is symmetrical structure, gradient 30 °, degree of depth 2-20 rice, the many coverings in surface vegetation.The outer both sides of cutting are suburb, township environment, There is a small amount of slight slope.Suburb, rural environments it mostly is outside cutting.There is fragmentary little slight slope.The zanjon shape structure of cutting makes outside cutting Anti-, scattered wave be difficult to arrive receiving terminal.Cutting both sides cliff can cause at receiving terminal that substantial amounts of near-end is anti-, scattered wave.

6) station: this scene refers in particular to the large, medium and small type passenger station occurred in railway line.Long 400-800 is had above station Rice, wide 100-500 rice, the canopy of high 50-80 rice.Large and medium-sized station canopy is closed, and small station canopy mostly is at platform Semi-enclosed canopy.Base station is stood at the outer 100-500 rice of awning more.The transmission of radio wave can be caused additionally by station top Diffraction loss.Its internal enclosed structure can cause intensive reflection effect in subregion.

7) river: this scene refers in particular to there is sheet (more than 5 square kilometres) Lake Water in rail both sides radially effective coverage Territory, or the river having 50-200 rice wide passes from below through rail (now rail is many as on overpass).Rail both sides mostly are allusion quotation Type suburb, rural environments.Level can cause the appearance of a large amount of mirror-reflection.Simultaneously because the absorption loss of the water surface is different from ground Table, its reflectance factor is relatively big, and wireless loss is affected by bigger.

The division of above-mentioned scene is based on following criterion:

1) division of scene depends on serviced wireless system.

2) not only radio transmission mechanism is to propagate the foundation of scene partitioning, the arranging net of wireless communication system, configures and performance Demand should be all the reference factor propagating scene partitioning.

3) scene classification is without containing all possibilities；But must response feature change.

4) scene has exclusiveness each other.

5) in addition to the scene of station, the characteristic feature (such as cutting, overpass) in remaining scene exceedes community track section 80%。

6) topography and geomorphology being classified based in rail radially effective coverage and the scattering object of scene is distributed.Effective coverage is radially A length of it is represented by d_h=(D2) tan (θ), wherein θ is rail and the angle on radiation pattern main lobe border.

Secondly, in above-mentioned 7 class scenes, use the survey that GSM-R existing network BCCH signal combines with vehicle-mounted field test instrument Method for testing, obtains in all kinds of high-speed railway environment and receives signal testing sample value more than 23,000,000, under all kinds of scenes Large scale path loss and shadow fading be modeled, it is proposed that a set of standardized high-speed railway propagation model storehouse.This mould The type scope of application is as follows:

1) frequency: 930MHz；

2) mulching method: wire covers；

3) antenna form: omnidirectional, orientation；

4) effectively base station antenna height (distance rail level) 20-40m；

5) effectively mobile station base station height 4m, only for car antenna；

6) Prediction distance scope 0.5-8km；

7) earth curvature is not considered；

8) change of track grade and radius of curvature is not considered.

This model includes large scale path loss is modeled and is modeled shadow fading.

In the modeling to large scale path loss, use the Hata model basal expression as path loss PL of classics Formula is as follows:

PL_Hata(dB)=74.52+26.16log₁₀(f)

-13.82log₁₀(h_b)-3.2(log₁₀(11.75h_m))²(1)

+[44.9-6.55log₁₀(h_b)]log₁₀(d)

Wherein, f is signal frequency (MHz), h_bAnd h_mFor base station and the height (m) of mobile portable antennas distance rail level, d is base Stand and the spacing (km) of mobile station.Classical Hata model cannot be applicable to railway wireless communication environments, so, at the base of above formula One path loss prediction algorithm revised is proposed on plinth, as follows:

PL_Proposed(dB)=Δ₁+74.52+26.16log₁₀(f=930)

-13.82log₁₀(h_b)-3.2(log₁₀(11.75h_m))²(2)

+[44.9-6.55log₁₀(h_b)+Δ₂]log₁₀(d)

Wherein, Δ₁And Δ₂For constant term and the modifying factor of path loss index item, it is respectively used to the boosting algorithm degree of accuracy With the reaction high-speed railway characteristic environment impact on path loss index.Note, owing to this algorithm leads to for high-speed railway GSM-R Communication system, therefore frequency limit is at 930MHz.

Being modeled two modifying factors in above-mentioned correction term in conjunction with substantial amounts of field test, modeling method uses base In the linear regression theory of least square method, probe into height of transmitting antenna to modifying factor Δ₁And Δ₂Impact, formula is as follows:

Δ_i=p·log₁₀(h_b)+q (3) wherein i=1,2 refers to two modifying factors respectively.

For the shadow fading (dB) of signal under high-speed railway environment, obey the Gaussian Profile of 0 average, by a large amount of communities Joint test, the standard deviation of 0 average Gaussian Profile is carried out quadratic fit modeling, find standard deviation under jth class environment also Gaussian distributed, can portray with following formula:

${\mathrm{\σ}}_j\left(\mathrm{dB}\right)~N[{{\mathrm{\μ}}_{\mathrm{\σ}}}_j,{{\mathrm{\σ}}_{\mathrm{\σ}}}_j]---\left(4\right)$

On the basis of a large amount of tests, equation (2) and (4) are utilized to obtain high-speed railway propagation model under all kinds of scenes Storehouse, concludes in Table 1:

Table one high-speed railway branch Jing Chuanbomoxingku

In order to verify proposed high-speed railway propagation model storehouse, use " coefficient of determination (R-Square) " and " root mean square Error (RMSE) " adjudicate evaluation index as degree of fitting, the method for estimation of the two is as follows:

$\begin{array}{c}R-\mathrm{Square}=1-\frac{\underset{n-1}{\overset{N}{\mathrm{\Σ}}}{w}_n{(y_n-{\hat{y}}_n)}^2}{\underset{n-1}{\overset{N}{\mathrm{\Σ}}}{w}_n{(y_n-{\stackrel{\‾}{y}}_n)}^2}\\ \mathrm{RMSE}=\sqrt{\frac{1}{N-1}\underset{n-1}{\overset{N}{\mathrm{\Σ}}}{(y_n-{\stackrel{\‾}{y}}_n)}^2}\end{array}---\left(5\right)$

Wherein, N is number of samples, w_nFor weight factor, y_nFor test sample,For estimate,Putting down for test value Average.Closer to 1, the coefficient of determination shows that degree of fitting is the best, root-mean-square error is the least shows that the error of model is the least.Respectively " Zheng State-Xi'an " and " Beijing-Shanghai " two rail tracks on proposed model is verified, effect is as shown in Figure 2-5.Can see Go out proposed models and theory optimal solution (i.e. regression fit line in figure) performance and closely, and be much better than public network Radio Link The Hata model that budget is used.

Next, the method for estimation of shadow fading nargin in link budget under proposition high-speed railway characteristic environment.Shadow fading Nargin is the pre-made allowance in link budget as shadow fading protection, is used for estimating that maximum can communication distance.If do not examined Consider the shadow fading change with distance, the most only need to be at cell edge propagation loss prediction, i.e. calculating maximum can examine during communication distance Consider shadow fading nargin.Cell edge outage probability determines the shadow fading margin value that system should be arranged.High Speed Railway The outage probability of shape cell edge can be expressed as:

$\begin{array}{c}O\left(D\right)=P(P_r\left(D\right)<T)\\ =\underset{-\&infin;}{\overset{T}{\&Integral;}}\frac{1}{\sqrt{2\mathrm{\&pi;}}\mathrm{\&sigma;}}\exp \left(\frac{{(r-\stackrel{\&OverBar;}{P_r\left(D\right)})}^2}{2{\mathrm{\&sigma;}}^2}\right)\mathrm{dr}---\left(6\right)\\ =\frac{1}{2}+\frac{1}{2}\&CenterDot;\mathrm{erf}\left(\frac{T-\stackrel{\&OverBar;}{P_r\left(D\right)}}{\mathrm{\&sigma;}\sqrt{2}}\right)\end{array}$

Wherein, P (P_r(D) < Τ) it is at wire cell edge D, to receive the level probability less than threshold level T, σ is wire The standard deviation of shadow fading in community.

In order to reduce (or control) edge outage probability, it is necessary to introduce shadow fading nargin M in link budget.Limit, community The local average of received signal strength and the difference of system I received signal strength T at edge D, it is simply that institute in link budget Need the surplus compensating/reserving, i.e. shadow fading nargin:

$M=\stackrel{\&OverBar;}{P_r\left(D\right)}-T---\left(7\right)$

Understanding from above-mentioned derivation, edge outage probability can be expressed as:

$\begin{array}{c}O=\frac{1}{2}+\frac{1}{2}\&CenterDot;\mathrm{erf}\left(\frac{T-\stackrel{\&OverBar;}{P_r\left(D\right)}}{\mathrm{\&sigma;}\sqrt{2}}\right)\\ =\frac{1}{2}+\frac{1}{2}\&CenterDot;\mathrm{erf}(-\frac{M}{\mathrm{\&sigma;}\sqrt{2}})---\left(8\right)\\ =\frac{1}{2}-\frac{1}{2}\&CenterDot;\mathrm{erf}\left(\frac{M}{\mathrm{\&sigma;}\sqrt{2}}\right)\end{array}$

Accumulated probability density function (CDF) in conjunction with 0 average Gaussian Profile:

The edge outage probability of railway wire community and the accumulated probability density function of average Gaussian Profile can be drawn Relation:

O (x)=F (-x) (10)

Can be derived that on the basis of above-mentioned analysis, shadow fading possesses randomness, it is impossible to measure that it is the most interval, is only capable of Its feature being described by the way of probability threshold, therefore the communication overlay Quality Down caused due to shadow fading, also should use The mode of probability is measured.Fig. 6 shows that the impact on cell edge outage probability of the shadow fading nargin, three horizontal lines mark out Outage probability is situation when 0.1,0.05 and 0.01.This figure shows: under 4dB standard deviation, and system shadow fading is remaining for 5dB Time cell edge outage probability be 0.1, and shadow fading remaining be 0.01 for the outage probability of cell edge during 9dB.Therefore, During the link budget of follow-up railway wire community, cell edge outage probability must set previously according to system requirements. Make excessive demands the characteristic of system in view of railway security, cell edge outage probability can not be too high.If uniting a typical railroad scene In meter is interval, in the case of not considering multipath fading, it is desirable to the outage probability of system is less than a%, then railway branch scape shade declines Nargin M that falls (dB) design reference value is concluded in table two:

Table two high-speed railway branch scape shadow fading margin design reference value

a%

City

Suburb

Rural area

Overpass

Cutting

Vehicle-mounted

River

10%

4.3dB

5.2dB

3.8dB

3.6dB

4.8dB

3.5dB

4.5dB

5%

5.5dB

6.6dB

4.8dB

4.7dB

6.2dB

4.5dB

5.8dB

1%

7.7dB

9.4dB

6.8dB

6.6dB

8.7dB

6.4dB

8.3dB

Finally, utilize above-mentioned conclusion, the covering measures budget method of mover iron route shape community, and determine on this basis The largest coverage distance of railway community.Understand for the ease of subsequent algorithm, first part concept is defined.Local communication is good Signal P is received at the r of distance base station on probability, i.e. railway line_RX(r) probability higher than threshold signal T.Edge communications failure-free probability, In railway line, i.e. at edge, base station D, receive signal P_RX(D) probability higher than threshold signal T, with outage probability before one by one Corresponding.Railway line communication overlay probability, any position that i.e. railway base station covers in railway line receives signal higher than thresholding The probability of signal T.The value of accumulated probability, i.e. certain stochastic variable is less than the probability of a threshold value.Conventional CDF represents.

Communication failure-free probability at local position r can be expressed as

$\begin{array}{c}O\left(r\right)=P(P_{\mathrm{RX}}\left(r\right)>T)\\ =1-\underset{-\&infin;}{\overset{T}{\&Integral;}}\frac{1}{\sqrt{2\mathrm{\&pi;}}\mathrm{\&sigma;}}\exp \left(\frac{{(P_{\mathrm{RX}}\left(r\right)-\stackrel{\&OverBar;}{P_{\mathrm{RX}}\left(r\right)})}^2}{2{\mathrm{\&sigma;}}^2}\right)d\left(P_{\mathrm{RX}}\left(r\right)\right)---\left(11\right)\\ =\frac{1}{2}+\frac{1}{2}\&CenterDot;\mathrm{erf}\left(\frac{T-\stackrel{\&OverBar;}{P_{\mathrm{RX}}\left(r\right)}}{\mathrm{\&sigma;}\sqrt{2}}\right)\end{array}$

R=D, above formula is made to become edge communications failure-free probability.If P is [P_Rx(r) > Τ] represent acceptance at rail circuit distance r Power P_RxR () more than the probability of system threshold level T, then the railway wire circuit covering measures of an a length of D is represented by

$\begin{array}{c}U=\frac{1}{D}\&Integral;P[P_{\mathrm{RX}}\left(r\right)>T]\mathrm{dr}\\ =\frac{1}{D}\underset{0}{\overset{D}{\&Integral;}}P[P_{\mathrm{RX}}\left(r\right)>T]\mathrm{dr}\end{array}---\left(12\right)$

Can derive further:

$\begin{array}{c}U=\frac{1}{D}\underset{0}{\overset{D}{\&Integral;}}P[P_{\mathrm{RX}}\left(r\right)>T]\mathrm{dr}\\ =\frac{1}{D}\underset{0}{\overset{D}{\&Integral;}}[\frac{1}{2}-\frac{1}{2}\&CenterDot;\mathrm{erf}\left(\frac{T-[P_{\mathrm{TX}}-({\mathrm{PL}}_0+10n{\log }_{10}(r/r_0))]}{\mathrm{\&sigma;}\sqrt{2}}\right)]\mathrm{dr}\\ =\frac{1}{D}\underset{0}{\overset{D}{\&Integral;}}[\frac{1}{2}-\frac{1}{2}\&CenterDot;\mathrm{erf}\left(\frac{T-P_{\mathrm{TX}}+{\mathrm{PL}}_0+10\mathrm{nlo}{g}_{10}(D/r_0)+10n{\log }_{10}(r/D)}{\mathrm{\&sigma;}\sqrt{2}}\right)]\mathrm{dr}\\ =\frac{1}{2}-\frac{1}{2D}\underset{0}{\overset{D}{\&Integral;}}\left[\mathrm{erf}(\frac{T-P_{\mathrm{TX}}+{\mathrm{PL}}_0+10n{\log }_{10}(D/r_0)}{\mathrm{\&sigma;}\sqrt{2}}+\frac{10n{\log }_{10}(r/D)}{\mathrm{\&sigma;}\sqrt{2}})\right]\mathrm{dr}\end{array}---\left(13\right)$

Wherein n is path loss index, for the ease of follow-up expression, makes:

$\begin{array}{c}a=\frac{T-P_{\mathrm{TX}}+{\mathrm{PL}}_0+10{n\log }_{10}(D/r_0)}{\mathrm{\&sigma;}\sqrt{2}}\\ b=\frac{10n{\log }_{10}\left(e\right)}{\mathrm{\&sigma;}\sqrt{2}}\end{array}---\left(14\right)$

Then above formula can be with abbreviation:

$U=\frac{1}{2}-\frac{1}{2D}\underset{0}{\overset{D}{\&Integral;}}\left[\mathrm{erf}(a+b\ln \left(\frac{r}{D}\right))\right]\mathrm{dr}---\left(15\right)$

Replace above formula: t=a+bln (r/D), then above formula integration can abbreviation be finally following closed solutions:

$\begin{array}{c}U=\frac{1}{2}-\frac{1}{2D}\underset{-\&infin;}{\overset{a}{\&Integral;}}\exp \left(\frac{t-a}{b}\right)\&CenterDot;\mathrm{erf}\left(t\right)\mathrm{dr}\\ =\frac{1}{2}-\frac{\exp (-a/b)}{2}\&CenterDot;[\exp \left(\frac{1}{4b^2}\right)\mathrm{erf}(\frac{1}{2b}-t)+\exp \left(\frac{t}{b}\right)\mathrm{erf}\left(t\right)={|}_{t=-\&infin;}^{t=a}\\ =\frac{1}{2}-\frac{1}{2}\mathrm{erf}\left(a\right)-\frac{1}{2}\&CenterDot;\exp \left(\frac{1-4\mathrm{ab}}{4b^2}\right)\&CenterDot;[\mathrm{erf}(\frac{1}{2b}-a)-1]\end{array}---\left(16\right)$

Wherein:

$\begin{array}{c}a=\frac{T-P_{\mathrm{TX}}+{\mathrm{PL}}_0+10{n\log }_{10}(D/r_0)}{\mathrm{\&sigma;}\sqrt{2}}\\ b=\frac{10n{\log }_{10}\left(e\right)}{\mathrm{\&sigma;}\sqrt{2}}\end{array}---\left(17\right)$

Derivation to shadow fading nargin before in conjunction with, it can be deduced that:

$a=-\frac{M}{\mathrm{\&sigma;}\sqrt{2}}---\left(18\right)$

It is the most general that Fig. 7 and Fig. 8 respectively illustrates shadow fading nargin and edge communications under different channel qualities (σ/n) The rate impact on railway wire community entirety covering measures, meanwhile, for the ease of comparison, the relation curve of planar public network is also Draw in the drawings.It can be seen that the covering measures of railway wire community and planar community exist larger difference, traditional Planar MPS process Forecasting Methodology is not suitable for railway wire community and characteristic communication environments.Furthermore, it is possible to find, when σ/n relatively Time big, wire cell edge covering measures can preferably react overall situation covering measures；But when the overall situation less, the highest for σ/n Covering measures does not ensures that preferable edges cover probability.This explanation, although railway wire line traffic covering measures is higher than Planar community, but:

1) σ/n less under Railway Environment constrains the degree of accuracy utilizing edge outage probability to estimate overall situation covering measures.

2) acceptance criteria based on overall situation covering measures is not suitable for Railway Environment.

3) examination of railway wireless network is it should be emphasized that wire cell edge, checks and accepts covering of being caused reducing global measuring The phenomenon of lid probability " virtual height ".

In order to be suitable for railway characteristic environment and the demand of wire community, utilize said method, to system threshold level T, limit The reasonable definition of edge communication failure-free probability (or vice versa: edge outage probability) O, it is possible to obtain the overall situation under present railway community is covered Lid probability, in conjunction with radio propagation channel model library, the anti-maximum communication distance solving railway wire community.

Concrete grammar step is as follows:

Step 1: determine the upper or downlink foundation as link budget.

The core parameter of high-speed railway GSM-R system is as shown in Table 3:

Table three high-speed railway GSMs-R system parameter

Parameter	Base station	Vehicle-mounted mobile platform
			Launch power (dBm)	43	39
Thermal noise (dBm)	-121	-121
			Noise pattern (dB)	5	7
Minimum SNR(dB)	6	10
			Receiver sensitivity (dBm)	-110	-104

Railway is identical due to the loss uplink and downlink of the devices such as GSM-R link center tap, cable, coupler, circulator, therefore The maximum link loss that GSM-R up-link can bear is: 39-(-110)=149dB；GSM-R downlink can bear Maximum link loss is: 43-(-104)=147dB.Link budget is because selecting the link of loss minimum, i.e. downlink.Meanwhile, Uplink budget lacks feasibility: downlink can meet Li Shi sampling criterion calls based on the test of BCCH signal； And up-link is only capable of testing based on Abis interface, it is impossible to provide and test data accurately.Therefore suggestion: the link of GSM-R system Budget is based on downlink.Step 2: determine ambient noise thresholding N.

Known system bandwidth BW, environment temperature Tem, Boltzmann constant k.Wherein GSM-R system bandwidth 200kHz.Typical case Under environment, Tem is 290 Kelvins (about 16.9 degrees Celsius), then ambient noise thresholding N is:

N=k·T_tem·BW

=(1.38×10^-23)×290×(200×10³)

=8.004×10^-16W (19)

=-120.97dBm

Step 3: determine receiver sensitivity RS.

Known receiver noise figure NF, minimum signal to noise ratio snr min, Boltzmann constant k needed for receiver.Wherein GSM-R Receiver noise figure is 7dB, and signal to noise ratio is 10dB, then receiver sensitivity RS is:

RS=N+NF+SNR_min=-121+7+10=-104dBm (20)

Step 4: determine reception level threshold T under Safety-Critical System.

Consider that railway security makes excessive demands the requirement of system, on the basis of receiver sensitivity, introduce protection.Consider that multipath declines Fall protection (3dB), high-speed mobile protection (3dB), aging protection (3dB), electrification noise protection (3dB), interference protection (3dB), Row control protection (3dB).Therefore reception level threshold T of railway GSM-R system is:

T=RS+(3+3+3+3+3+3)

=-104+18 (21)

=-86dBm

Step 5: determine shadow fading nargin M.

Known edge communications failure-free probability O, then shadow fading nargin M can determine by the following method:

$O=\frac{1}{2}+\frac{1}{2}\&CenterDot;\mathrm{erf}\left(\frac{M}{\mathrm{\&sigma;}\sqrt{2}}\right)---\left(22\right)$

Step 6: determine overall situation covering measures U.

$U=\frac{1}{2}-\frac{1}{2}\mathrm{erf}\left(a\right)-\frac{1}{2}\&CenterDot;\exp \left(\frac{1-4\mathrm{ab}}{{4b}^2}\right)\&CenterDot;[\mathrm{erf}(\frac{1}{2b}-a)-1]---\left(23\right)$

Wherein:, $a=-\frac{M}{\mathrm{\&sigma;}\sqrt{2}},b=\frac{10n{\log }_{10}\left(e\right)}{\mathrm{\&sigma;}\sqrt{2}},$ N is path loss index.

Step 7: determine the average reception level at maximum communication distance

Known reception level threshold T and shadow fading nargin M.The average reception level of Gu great Tong XinjulichuFor:

$\stackrel{\&OverBar;}{P_{\mathrm{RX}}\left(D\right)}=M+T$

Step 8: determine maximum communication distance D.

Known transmitting power P_TX, transmit/receive antenna gain G_TX/G_RX, transmit/receive end overall loss L_TX/L_RX, large scale path is damaged In consumption model

Δ₁+74.52+26.16log₁₀(f=930)-13.82log₁₀(h_b)-3.2(log₁₀(11.75h_m))²Item PL₀；

Therefore maximum communication distance is:

$D={10}^{\frac{P_{\mathrm{TX}}+G_{\mathrm{TX}}+G_{\mathrm{RX}}-L_{\mathrm{TX}}-L_{\mathrm{RX}}-{\mathrm{PL}}_0-\stackrel{\&OverBar;}{P_{\mathrm{RX}}\left(D\right)}}{10n}}$

This distance is the use value of base station spacing in wireless network.

In above-mentioned steps, front four steps, by the adjustment to real system parameter, also extend to non-railway wireless communication system System.On this basis the calculation process of rear three steps can be summarized with Fig. 8.

Embodiment 1

In order to the most clearly illustrate the using method of proposed link budget algorithm, introduce more specifically railway system System does example.Wherein, the device loss parameter of railway downlink is shown in Table four:

The device loss parameter of table four railway downlink

Remaining high-speed railway link budget parameter is concluded in table five:

Table five high-speed railway wire link budget parameter collects

On the basis of said system parameter is arranged, integrating step 1-8, it is possible to obtain under high-speed railway environment, each is propagated Maximum communication distance in scene and the graph of a relation of base station height, result such as Figure 10-16.Wherein, in figure three black lines by up to The lower railway wire cell edge communication failure-free probability of expression respectively is 90%, 95%, and the situation of 99%.There it can be seen that 90% limit Under edge communication failure-free probability, the base station range of community is maximum.Additionally, the MPS process under all kinds of featurettes of high-speed railway Scope is mostly up to 10km, much larger than the 3km base station spacing in actual existing network, and by the height of antenna for base station distance rail level Affect bigger.Existing network is badly in need of using rational link method of estimation to be optimized, and the network of follow-up high-speed railway circuit is built Vertical also it be necessary to link algorithm for estimating the most accurately and be designed.

The above, only this method preferably detailed description of the invention, but the protection domain of this method is not limited thereto, Any those familiar with the art in the technical scope that this method describes, the change that can readily occur in or replacement, All should contain within the protection domain of this method.Therefore, the protection domain of this method should be with scope of the claims It is as the criterion.

Claims (8)

1. the wireless communication link method of estimation towards high-speed railway, it is characterised in that the method includes following steps:

1) a set of scene classification standard for high-speed railway characteristic communication environments is proposed；

2) large volumes of channels measurement has been carried out, it is thus achieved that magnanimity high-speed railway wireless channel test data, to the big chi under all kinds of scenes Degree path loss and shadow fading are modeled, and set up a set of standardization propagation model towards high-speed railway wire cell structure Storehouse；

3) propose and utilize cell edge covering measures and shadow fading probability density function to carry out shadow fading loss to estimate The method of meter；

4) high-speed railway wire cell structure is combined, it is proposed that estimated community overall situation covering measures by cell edge covering measures Method；

5) based on step (2) (3) (4), the overall coverage prediction towards railway wire community and link method of estimation are proposed；Described Step 3) in detailed process be according to channel model parameters, determine shadow fading accumulated probability distribution function and standard deviation；? Eventually, in conjunction with cell edge covering measures requirement, determining shadow fading loss M, the anti-solution formula of M value is as follows:

$O=\frac{1}{2}+\frac{1}{2}\&CenterDot;erf\left(\frac{M}{\mathrm{\&sigma;}\sqrt{2}}\right)$

Wherein, O is edges cover probability, and σ is the standard deviation of shadow fading in wire community；

Described step 4) in detailed process be according to channel model parameters, in conjunction with established based on cell edge covering measures Shadow fading loss design result, determines railway wire community overall situation covering measures U, and formula is as follows:

$U=\frac{1}{2}-\frac{1}{2}erf\left(a\right)-\frac{1}{2}\&CenterDot;\exp \left(\frac{1-4ab}{4b^2}\right)\&CenterDot;\&lsqb;erf(\frac{1}{2b}-a)-1\&rsqb;$

Wherein:N is path loss index；

Step 5) comprise the following steps:

51) the up or down line link foundation as link budget is determined；

Link budget selects the link that loss is minimum；

52) determining ambient noise thresholding N, formula is as follows:

N=k T_tem·BW

Wherein, BW is system bandwidth, and Tem is environment temperature, and k is Boltzmann constant；

53) determining receiver sensitivity RS, formula is as follows:

RS=N+NF+SNR_min

Wherein, NF is receiver noise figure, and SNRmin is minimum signal to noise ratio needed for receiver, and k is Boltzmann constant；

54) determining reception level threshold under Safety-Critical System, formula is as follows:

T=RS+ protection value

Wherein, protection value is multipath fading protection value, high-speed mobile protection value, aging protection value, phone noise protection value, interference Protection value, row control protection value sum；

55) shadow fading nargin M is determined；

56) overall situation covering measures U is determined；

57) average reception level at maximum communication distance D is determinedFormula is as follows:

$\stackrel{\&OverBar;}{P_{RX}\left(D\right)}=M+T$

Wherein, T is for receiving level threshold；

58) determining maximum communication distance D, formula is as follows:

$D={10}^{\frac{P_{TX}+G_{TX}+G_{RX}-L_{TX}-L_{RX}-{\mathrm{PL}}_0-\stackrel{\&OverBar;}{P_{RX}\left(D\right)}}{10n}}$

Wherein, P_TXFor launching power, G_TX/G_RXFor transmitting/receiving antenna gain, L_TX/L_RXFor transmitting/receiving end overall loss, PL₀For big chi Constant term in degree path loss model, it may be assumed that

Δ₁+74.52+26.16log₁₀(f=930)-13.82log₁₀(h_b)-3.2(log₁₀(11.75h_m))²。

A kind of wireless communication link method of estimation towards high-speed railway the most according to claim 1, it is characterised in that step Rapid 1) described scene classification standard is: high-speed railway communication environments is divided into 7 classes: city, suburb, rural area, overpass, cutting, Station, river.

A kind of wireless communication link method of estimation towards high-speed railway the most according to claim 1, it is characterised in that step Rapid 2) described large volumes of channels measurement has been carried out, it is thus achieved that the magnanimity high-speed railway wireless channel test number under high-speed railway wire community According to, large scale path loss is modeled, formula is as follows:

PL_Proposed(dB)=Δ₁+74.52+26.16log₁₀(f=930)

-13.82log₁₀(h_b)-3.2(log₁₀(11.75h_m))²

+[44.9-6.55log₁₀(h_b)+Δ₂]log₁₀(d)

Wherein, f is signal frequency (MHz), h_bAnd h_mFor base station and mobile portable antennas distance rail level height (m), d be base station and The spacing (km) of mobile station, Δ₁And Δ₂For constant term and the modifying factor of path loss index item.

A kind of wireless communication link method of estimation towards high-speed railway the most according to claim 3, it is characterised in that right Two modifying factors are modeled, and formula is as follows:

Δ_i=p log₁₀(h_b)+q

Wherein i=1,2 refer to two modifying factors respectively, p and q is to measure, according to reality, the fitting parameter obtained, and is used for describing Δ₁And Δ₂Change, in different environment, p and q is respectively equal to different values.

A kind of wireless communication link method of estimation towards high-speed railway the most according to claim 1, it is characterised in that step Rapid 2) described large volumes of channels measurement has been carried out, it is thus achieved that the magnanimity high-speed railway wireless channel test number under high-speed railway wire community According to, data analysis points out that shadow fading obeys the Gaussian Profile of 0 average, is modeled shadow fading, and formula is as follows:

${\mathrm{\&sigma;}}_j\left(dB\right)~N\&lsqb;{\mathrm{\&mu;}}_{{\mathrm{\&sigma;}}_j},{\mathrm{\&sigma;}}_{{\mathrm{\&sigma;}}_j}\&rsqb;$

Wherein, j=1,2,3,4,5,6,7 represent 7 class high-speed railway communication environments respectively.

A kind of wireless communication link method of estimation towards high-speed railway the most according to claim 1, it is characterised in that step Rapid 2) the degree of fitting judgement evaluation index in the standardization propagation model storehouse of the high-speed railway described in is:

$R-Square=1-\frac{\underset{n=1}{\overset{N}{\&Sigma;}}{w}_n{(y_n-{\hat{y}}_n)}^2}{\underset{n=1}{\overset{N}{\&Sigma;}}{w}_n{(y_n-{\stackrel{\&OverBar;}{y}}_n)}^2}$

$RMSE=\sqrt{\frac{1}{N-1}\underset{n=1}{\overset{N}{\&Sigma;}}{(y_n-{\stackrel{\&OverBar;}{y}}_n)}^2}$

Wherein, R-Square is the coefficient of determination, and RMSE is root-mean-square error, and N is number of samples, w_nFor weight factor, y_nFor test Sample,For estimate,Mean value for test value；Closer to 1, the coefficient of determination shows that degree of fitting is the best, root-mean-square error is more Little show that the error of model is the least.

A kind of wireless communication link method of estimation towards high-speed railway the most according to claim 1, it is characterised in that institute State step 51) link budget according to for selecting the minimum link of loss.

A kind of wireless communication link method of estimation towards high-speed railway the most according to claim 1, it is characterised in that institute State step 51) to step 54) by the adjustment to real system parameter, it is possible to it is generalized to non-Measurement of Railway Radio Communication System wire little District.