Realistic Propagation Simulation of Urban
Mesh Networks
Vinay Sridhara Stephan Bohacek
vsridhara@https://www.doczj.com/doc/633010012.html, bohacek@https://www.doczj.com/doc/633010012.html,
Department of Electrical and Computer Engineering
University of Delaware
Newark,DE19716
Abstract
Simulation plays an important role in the veri?cation of mobile wireless networking protocols.Recently several cities have either begun deploying or are completing plans to deploy large-scale urban mesh networks(LUMNets).
On the other hand,the networking research community has little expertise in simulating such networks.While the protocols are simulated reasonably realistically,the propagation of wireless transmissions and the mobility of nodes are not.Today,simulations typically model propagation with either the free-space model or a"two-ray"
model that includes a ground re?ection.Such models are only valid in open space where there are no hills and no buildings.Since wireless signals at the frequencies used for mobile wireless networking are partly re?ected off of buildings and partly is transmitted into the building,the presence of buildings greatly in?uences propagation.
Consequently,the open-space propagation models are inaccurate in outdoor urban areas.Indoors,the open-space models are not even applicable.This paper presents guidelines for simulating propagation in such urban settings.
Furthermore,extensive background discussion on propagation is also included.The techniques for propagation are validated against propagation measurements.The techniques discussed are implemented in a suite of tools that are compatible with protocol simulators and are freely available for use.
Stephan Bohacek is the corresponding author.His address is University of Delaware,Dept.of Electrical and Computer Engineering,Newark, DE19716,USA,302-831-4274,bohacek@https://www.doczj.com/doc/633010012.html,.
I.I NTRODUCTION
Recently,there has been interest in developing protocols for urban mesh networks such as the ones to be deployed in Philadelphia[1],San Francisco[2],Taipei[3],Minneapolis[4],Anaheim,California,and Tempe, Arizona.Simulation is the common technique to determine the performance of these protocols.However,today, most simulations use the trivial disk propagation model(i.e.,the signal propagates exactly R meters and no further)or a highly idealized propagation model such as the free-space or the two-ray model.Due to the presence of buildings,propagation in urban environments is far more complicated than the propagation presented by these simple models.Consequently,channel variability,which is a key aspect of wireless networking,is not well modeled in today’s simulations.The result is that many insights gained from the free-space environment do not necessarily hold in the urban environment,casting doubt on the applicability of the conclusions drawn from today’s simulations. While the reasons that realistic propagation models are typically not included into network simulations is not well documented,it seems that the typical reasons include the belief that propagation modeling is computationally intractable and that propagation cannot be realistically modeled due to small-scale fading and delay spread.To the contrary,this paper demonstrates the feasibility of including realistic propagation into network simulation.To this end,a simulator has been developed in accordance with the guidelines set forth in this paper[5].This simulator is validated in three scenarios and it is shown that when used with packet level simulation,realistic propagation has a dramatic impact on simulation results.Furthermore,while realistic propagation is computationally intensive,the computational complexity of the approach taken here results in the propagation aspects of the typical simulation taking approximately as long as the processing of the discrete events by the packet simulator.Consequently,this paper provides techniques and methods for greatly improving the quality of simulations.
In order to justify the simulation strategy used,an overview of the key features of propagation in an urban environment is presented.This nonmathematical discussion of propagation also provides networking researchers with an intuition of propagation in urban environments.For example,some of the myths that can be found in the networking literature are dispelled,and issues that are neglected in the networking literature,such as the importance of building materials,are discussed.
The remainder of this paper proceeds as follows.In the next section,stochastic models of propagation are discussed.While stochastic models are often used in communication theory,their applicability to networking is
limited,and,as will be discussed,they should be used with care.In contrast,the propagation simulator discussed here is deterministic.Section III discusses several characteristics of propagation.Speci?cally,the subsections of Section III discuss transmissions through walls,re?ections off of walls,multipath fading,diffraction,scattering,time-varying channels,and delay spread.Section IV discusses computational issues,discusses details of the UDelModels’propagation simulator,and presents validation of the simulator.Section V provides some discussion on the impact that realistic simulation has on the performance of networking protocols.As one might expect,traditional simulations that use random way-point mobility and free-space propagation yield very different results than the simulations carried out using realistic mobility and propagation.It is important to note that realistic simulation of wireless networks is an ongoing effort and that as the computational capabilities increase,more detailed and accurate simulations are possible.Some areas that will bene?t from further effort and improved accuracy are discussed in Section VI.Related work on propagation simulation is provided in Section VII and?nally,concluding remarks can be found in Section VIII.
II.S TOCHASTIC M ODELS OF P ROPAGATION
One of the most important aspects of propagation is the channel gain(other characteristics are discussed below). The objective of propagation simulation is to determine the channel gain(and other channel characteristics).The physical layer model then uses these channel characteristics to determine the probability of transmission error. The relationship between the received signal power P received and transmitter signal power P transmitted is P received= K×H×P transmitter,where K is a constant that depends on the wavelength and the antennas,and H is the channel gain.It is common for this relationship to be speci?ed in dB1and dBm(dB milliWatts),i.e.,
P received[dBm]=10log10K+H[dB]+P transmitter[dBm].
To get an idea of common values,consider the typical802.11b transmissions.In this case,the transmission power is15dBm and10log10K=?41dB.Furthermore,the sensitivity of commercially available802.11b receiver cards is approximately-93dBm when receiving at1Mbps.Thus,if the channel gain is lower than-67dB,then it is not possible to decode the transmission with marginal reliability.It is also common to require an extra gain 1For the remainder of the paper,we specify channel gains in dB.
margin to allow for the signal to be decoded reliably(not simply marginally reliability),to account for losses due to connectors and other analogue circuits,and to allow for overly optimistic sensitivity speci?cations.The gain margin depends on the transmitter/receiver manufacturers and system design,and can range from3dB up to9dB, which require the802.11b communication channel gains to be above-64dB and-58dB respectively.
The propagation of wireless signals can be accurately modeled by Maxwell’s Equations.However,it is beyond today’s computational abilities to simulate large urban regions using these equations.For this reason,there has been extensive research effort on developing techniques that provide computationally tractable estimates of the channel gain and other characteristics.In general,the techniques can be classi?ed into deterministic and stochastic models. Furthermore,they can be divided into site speci?c approaches(i.e.,detailed information about the environment is included into the propagation model)and non-site speci?c approaches.As discussed next,for simulation of urban mesh networks,deterministic site speci?c propagation models are appropriate.
We can easily rule-out deterministic non-site speci?c approaches such as the Okumura-Hata model[6]or COST 231[7].Such models provide a relationship between the channel gain and the distance between the receiver and transmitter.However,these models only provide an average behavior and do not model the variability of the channel. On the other hand,non-site speci?c stochastic models can account for channel variability and hence are widely used in communication theory.However,there are many pitfalls to stochastic models which often make them not applicable to urban mesh network simulation.Consider the well established lognormal shadowing model[8].This model speci?es that the received signal power obeys
P received=K
×Y×P transmission,(1)
where K is a constant,d is the distance between the transmitter and receiver,αis the attenuation factor,P transmission is the transmitted power,and Y is a lognormally distributed random variable that accounts for shadowing.This model dictates that if a transmitter and receiver are placed at randomly selected locations,then the relationship between distance,transmitted power and received power obeys(1).While the model has been veri?ed through experimentation,the model focuses only on a single link.On the other hand,in networking,the interest is on a large number of links,speci?cally,the focus is on the graph formed by links.If the relationship between received and transmitted signal strength merely obeys(1),then the graph formed by links would be a type of a random
Strongest signal
Weakest signal
Fig.1.Left,channel gain generated by a correlated lognormal model.Right,channel gains generated by ray-tracing in an urban area.The rectangle shapes are buidlings and the shaded boxes inside the rectangles represent channel gain to locations on the?rst?oor of the building. In both the left and right frames,the star marks the location of the transmitter.
graph,whereas an urban setting induces a graph with deterministic components.Consider the left and right frames in Figure1.The left-hand frame shows the channel gains(including correlations as described in[9]and[10])when a lognormal shadow fading model is used,while the right-hand shows the channel gains in an urban area that is found through the techniques described in the next sections.While it is reasonable to assume that even in the urban setting,if two arbitrary locations are selected,then the signal strength will follow the lognormal distribution(i.e., (1)is valid),it is quite clear that channel gain is not random.Rather,the channel gain is greatly in?uenced by the map of the urban area.For example,the signal propagates far down the streets,while it propagates poorly into or through/over buildings.To see the implication of this,consider the least-hop path shown in Figure2.In this example,only the?rst and last hop are able to propagate between indoor and outdoor,while other hops follow streets(outdoor to outdoor propagation).Thus,we see that the propagation results in routes in urban areas that are not random,but are dependant on the structure of the city.For this reason,we do not use non-site speci?c models, and focus on site-speci?c models where the layout of the city and buildings in?uences the propagation.Currently, the UDelModels’propagation simulator is deterministic.However,future work will include appropriate stochastic elements.
Fig.2.Routing in an Urban ad The shortest hop path travels along the road,it does not follow the shortest geometric route(i.e.,a straight line).
III.C HARACTERISTICS OF U RBAN P ROPAGATION
A.Overview
In the next subsections,several characteristics of propagation are brie?y discussed.The objective is to provide intuition of propagation in urban environments.While there are mathematical models of propagation,we do not provide any mathematical details.An excellent reference that contains mathematical details is[11].
Remark1:We typically focus on the propagation for a particular transmitter and receiver.However,due to reciprocity(e.g.[12]),the channel between two antennas does not depend on which one is the transmitter and which is the receiver.To some degree,the symmetry of channels contradicts the observed asymmetry of links(e.g., [13]and[14]).It is important to note that the observed asymmetry of links is not due to the channel but due to difference in the analogue electronics in the transmitters and receivers.These differences may result in unequal transmit powers and unequal receiver attenuation.In some cases,these differences can be reduced by calibrating the transmit powers.It is also possible that one node experiences more interference than another node.In this case, the probability of error-free packet transmission depends on which node is the transmitter.
B.Transmissions
In urban mesh networks,re?ections off of objects such as buildings and the ground and transmission into buildings play a primary role in the magnitude of the received signal strength.Diffraction and scattering are also important, but from numerical experiments it can be shown that they play a secondary role.When the object that the signal is hitting is much larger than the wavelength,then the behavior of the signal can be accurately modeled as a ray that
is partially re?ected off of the object,partially transmitted through the object,and partially absorbed by the object.
If this ray model is accurate,then there are well known formulas that describe the behavior(e.g.,see[11]).In gen-
eral,the re?ection can be written in terms of six components,H⊥Transmit(θIncidence,εr,ε00r,w,f),H⊥Re?ect(θIncidence,εr,ε00r,w,f),
H⊥Absorb(θIncidence,εr,ε00r,w,f),H k Transmit(θIncidence,εr,ε00r,w,f),H k Re?ect(θIncidence,εr,ε00r,w,f),and H k Absorb(θIncidence,εr,ε00r,w,f) whereθIncidence is the angle between the ray and the material,ε0r andε00r are the real and imaginary part of the
relative dielectric constant of the material,w is the width of the material,f is the frequency of the signal,and the superscript denotes the polarization.
Instead of detailing how each of these factors impacts the propagation,we will consider an example.We examine
the received signal strength on one side of a wall with a transmitter on the other side as shown in left-hand frame
of Figure3.We consider the received signal strength in two locations,speci?cally,one at the same height as the transmitter and one elevated from the transmitter.We assume that the signal strength decays according to free-space propagation and then intersects the wall and suffers insertion loss H k Transmit(where we assume that the wireless
signal is vertically polarized,hence the k superscript).We take the frequency to be2.4GHz,as in802.11b/g.
Three types of wall materials are examined,namely,brick(ε0r=3.9,ε00r=0.001,w=10cm.),concrete(ε0r=5,
ε00r=0.2,w=20cm.),and glass(ε0r=5.8,ε00r=0.003,w=2.5cm.).The behavior for these materials is shown
in the right three frames of Figure3.
Many aspects of transmission through material can be observed in Figure3.First,notice how in the case where
the receiver and transmitter are at the same height,the channel gain increases as the distance between the transmitter
and received decreases.This agrees with the intuition from free-space propagation.The impact of the material can
be seen by noticing the variation in the received signal strength for different materials.For reference purposes,
consider that without the wall,when the transmitter is about5m from the wall,the channel gain is-14dB.from
the wall and a receiver that is at the same height as the transmitter.Thus,when the angle of incidence is0,the wall
reduces the channel gain by0dB(for glass)to6dB(for concrete).The impact of the angle of incidence can be emphasized by considering the channel gain when the transmitter and receiver are not at the same height.As can be
seen,this results in the signal strength?rst increasing and then decreasing as the distance between the transmitter
and receiver increases;this is in con?ict with the behavior in free-space.The key characteristic of propagation at
work here is that when the ray hits the wall at a grazing angle,only a small amount of signal power is transmitted
distance from wall
brick
concrete glass
c
h
a
n
n
e
l
g
a
i
n
(
d
B
)
Fig.3.Transmission through a wall.The?gure depicts the attenuation of the signal when transmitted through walls of different kinds of materials.It also depicts the nature of attenuation due to relative heights of the transmitter and the receiver.
through the wall.The point where the signal strength switches from increasing with the transmitter-receiver distance to decreasing with transmitter-receiver distance depends on the material,the thickness of the material,and the height of the receiver.
Remark2:One interesting implication of Figure3is that if an urban mesh network uses relays mounted on lampposts,then the lamppost are quite close to buildings.Thus,relays mounted on a lamppost on the far side of the street will provide better coverage of a building than a relay mounted on a lamppost on the near side of the street.We concluded that,in some cases,the angle of incidence can be more important than the transmitter-receiver distance.
Figure3shows variation of the channel gain due to the different building materials.The dependence on material poses a serious challenge for simulation.First,walls are typically not made of a single material,but of layers of material.It is,however,possible to extended the method to accommodate layers of different material(e.g.,see[15]) at the expense of computational complexity.A second and more serious problem is that it is not realistic to know the construction material for each building.This dependence on construction materials emphasizes the dif?culty of accurate prediction of channel gains and demonstrates why realistic simulation is more reasonable than accurate simulation.In the UDelModels,it is possible to specify different building materials,but it is assumed that the material is homogeneous for each building.
C.Re?ections
Re?ections are complementary to transmissions.However,it is important to note that some power is absorbed by the material,hence,the power transmitted through a wall and the power re?ected off of a wall do not necessarily
sum to the power of the incident signal and,depending on the material and angle of incidence,a signi?cant amount of energy can be absorbed.
To get an understanding of the impact of re?ections,we consider propagation down a building lined street,as shown in Figure4.Here the signal is repeatedly re?ected off of walls and,in a sense,focused down the street.This effect is sometimes referred to as propagation down an urban canyon.A similar effect can also arise in hallways and tunnels.The result is that the received signal strength is stronger when propagating down a street than it would be with the same transmitter-receiver distance but in free-space.
Figure4shows the channel gain down an urban canyon for the same set of materials considered above and the free-space approximation.Note that free-space predicts a substantially smaller received signal strength than the simulated received signal.For example,when the receiver-transmitter distance is300m.,the difference between the free-space and the model that accounts for re?ection ranges from13dB to5dB,depending on the material and the distance between the walls.Figure4also shows approximations of the channel gain given by1/dα,where, for a canyon width of7m.,α=1.38and a canyon width of35m.,α=1.47.It should be pointed out that it is often assumed thatα∈[2,4],however,as this simple example demonstrates,it is possible that for some paths we haveα<2.That is,while buildings may block communication,they may also enhance communication.
Note the lack of smoothness when the walls are made of brick and the width is35m(e.g.d=50).This is due to the wide variation in the re?ection coef?cient as the angle of incidence varies.Indeed,depending on the material and the width of the material,there may be some angles of incidence where no signal is re?ected.Such angles are called Brewster angles.In some settings,the wide variation of the re?ected signals strength as a function of incident angle results in large?uctuations in the total received signal strength for small movements of the receiver or transmitter antenna.This amounts to further sensitivity of communication on building materials.
D.Multipath Fading
It is well known that wireless signals can experience small-scale fading or multipath fading.Such fading results from the constructive and destructive interference of signals that follow different paths from the transmitter to the receiver.As a result,when the wavelength is small,a small displacement of the transmitter or the receiver will cause a change in the interference and hence a change in the received signal strength.While fast-fading is a signi?cant problem in many wireless systems,it is typically not relevant in wide bandwidth communications such as those often
010*******
010*******d c h a n n e l g a i n (d B )width = 7 m
width = 35 m Fig.4.Propagation down a street.The ?gure depicts the effect of propagation down an urban canyon for different wall materials,different attenuation exponents,and for the free space
used for data communications (e.g.,802.11).The reason is that the received signal strength is essentially averaged over the bandwidth,which,by de ?nition,is wide.The left-hand frame in Figure 5shows an example of the signal strength at various frequencies.Note that at some frequencies,the signal strength is quite low,even 40dB less than the mean signal strength of 0dB.A narrow bandwidth communication will experience such degradations in signal strength.However,when averaged over a suf ?ciently wide bandwidth,the average signal does not experience degradation.For example,the middle frame in Figure 5shows how the signal strength varies for small changes in position.Note that the narrow bandwidth signal experiences rapid and large ?uctuations,while the wide bandwidth case experiences much smaller variations.
In general,the wider the bandwidth,the less susceptible to fast fading.However,variation in signal strength also depends on the environment.The right-hand frame of Figure 5shows the variance of the received signal strength over a circle with one meter radius as a function of the bandwidth.Each curve is for a slightly different environment,but in all cases it is for propagating down the urban canyon as shown in the left-hand frame of Figure 4.Note that in general,the variance decreases as the bandwidth increases.However,the variance of the narrow bandwidth case and the rate that the variation decreases with the bandwidth depends on the environment.In all cases,the variance is quite small when the bandwidth exceeds 10MHz,while 802.11b has a bandwidth of 22MHz.It should be noted that there are other factors besides multipath re ?ections that could cause large changes in signal strength over small
020*********
-50-30-10
10Frequency ?2.4 GHz (MHz)
024680123
S i g n a l S t r e n g t h Position (m)V a r i a n c e o f S i g n a l S t r e n g t h
d=300 m width = 7 m d=100 m width = 7 m Narrow band Bandwidth (MHz)
Fig.5.Fast fading in narrow band and wide band communication scenarios.Left:the signal strength as a function of frequency for a narrow band signal propagating down an urban canyon.Middle:signal strength of a narrow and wide band signal as a function of receiver position perturbation when propagating down an urban canyon.Right:variance in signal strength due to change in receiver position as a function of bandwidth for when propagating down a urban canyon as shown in Figure 4.
changes in position,e.g.changes in antenna orientation.
E.Diffraction
While re ?ections and transmission play an important role in propagation,diffraction is also signi ?cant and should not be neglected.Diffraction allows the signal to "bend"around corners and over/around buildings.However,the diffracted signal will not be as strong as the original signal;the sharper the bend,the weaker the signal.Consider the examples in Figure 6,which use the Uniform Diffraction Theory [16],[17].The left-hand frames show the diffraction around a corner.The second from the left frame compares free-space propagation around the corner to free-space propagation with the added loss due to diffraction.The right-hand frames show diffraction over a building where two diffractions are required.In both cases,as h increases,the signal must make a sharper bend (i.e.,the diffraction angle increases)and,hence,more loss is incurred.It is important to note that the signal strength decreases quickly as h increases.From the right-hand frames in Figure 6,it can be seen that diffracting over a building that is only 5m.higher than the transmitter and receiver results in a channel gain that is too small for typical 802.11communication (recall the discussion in Section II),while diffracting around a single corner (left hand plots of Figure 6)might result in a suf ?ciently large channel gains for most 802.11communications.Indeed,our simulations indicate that for 802.11,diffracting around two corners results in loss that is typically too great for 802.11.
While diffracting around two or more corners leads to large losses,802.11might be able to communicate
70605040302002040
12090
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h (m)C h a n n e l g a i n (d B )With diffraction
Free-space only h (m)C h a n n e l g a i n (d B )0102030
40Fig.6.Diffraction around a corner (left)and over a building (right).As h increases,the signal strength decreases.The dashed lines show the signal strength if the loss was only due to free space propagation while the solid line shows the signal strength when the loss due to diffraction is also included.
effectively around a single corner.Consequently,a signi ?cant portion of the coverage area of 802.11is due to https://www.doczj.com/doc/633010012.html,ing the UDelModels’propagation simulator,it is possible to quantify the impact of diffraction.Table I shows the number of locations to which a particular transmitter is able to communicate when only line-of-sight is used,when line-of-sight and re ?ections/transmissions are used,and when all the components are used,namely,line-of-sight,re ?ections/transmissions and diffraction.The table also shows the difference in the coverage when different numbers of iterations are used.By the number of iterations,we mean the maximum number of re ?ections,transmissions,or diffractions that each ray may experience.We see that about 22%of the locations are missed if diffraction is not used.However,if only line-of-sight is considered,then 78%of the locations are missed.For these calculations,a map of the Paddington area of London was used and the transmitter and receivers were located
1.5m above the ground or above the ?oor.If the transmitter was higher (e.g.,a mobile phone base station),or transmissions with smaller channel gains can be received,then it is possible that diffraction could play a larger role than is illustrated in this example.
F .Scattering
Scattering is often used to refer to the impact of smaller unmodeled objects on the propagation,e.g.,lampposts,trees,vehicles,people,and of ?ce furniture.Scattering also accounts for the unevenness of building walls (e.g.,windows,doors,or facades).Without detailed knowledge of the location and dimension of small objects and without details of building walls,it is dif ?cult to include the effects of these types of scatterers into propagation simulation.Furthermore,the inclusion of such details greatly increases the computational complexity of propagation
TABLE I
C OVERAGE AN
D COMPUTATION TIME
simulation.As a result,relatively little work has focused on including scattering into propagation prediction.One exception is[18]where the impact of scatterers was examined.It was found that in dense urban environments,such scattering does not dominate.More speci?cally,at short distances,scatterers have little impact,but may have a some impact at greater distances(e.g.,in some cases the difference between prediction and measurements decreased from6dB to3dB when scatterers were included).On the other hand,in areas where building density is low(e.g., suburban areas),scatterers such as lampposts,tress,and vehicles may dominate the propagation.This is one reason why this paper focuses on the urban setting.
Scattering can also occur when a wireless signal propagates through vegetation.Indeed,if the vegetation is large and dense,the scattered signal dominates over the direct,non-scattered signal.Even when the vegetation is thin,as it usually is in urban areas,the vegetation can cause loss.At2.4GHz,vegetation causes a loss of approximately
0.2dB per meter of vegetation[19].It is also common to model diffraction over vegetation[20].
G.Time-Varying Channel Gain
While the variability of channel gain is greatly affected by the movement of the transmitter or receiver,the channel gain can also change when the transmitter and receiver are?xed,but objects in the environment move. The right-hand frame of Figure7shows the channel gain as a function of time for a receiver and transmitter as observed along a sidewalk during rush-hour in the city center of Philadelphia.As shown in the left-hand frame of Figure7,the transmitter was5.4m above the sidewalk,while the receiver was only1.2m above the sidewalk. While time-varying propagation is dif?cult to model,in[21],a diffusion-based model was developed that accurately models the variability shown in Figure7.However,more work is required to develop models in general settings.
30405060050100
observed data Time (s)
-C h a n n e l G a i n (d B
)
Fig.7.Left,experimental setup for measuring the time varying nature of propagation in a busy street in Philadelphia.Right,an observed time-series of the channel gain.
It should be noted that the time-varying propagation is due to mobility in the environment.
H.Delay Spread
As noted in sections III-B,III-C and III-E,the wireless signal may follow several different paths from the transmitter to the receiver.While one impact of multiple paths is that the signal may experience multipath fading,another result is that the multiple copies of the wireless transmission will be received at different points of time.Essentially,these multiple copies will interfere with each other.When this self-interference is considered as noise,it is clear that the effective SNR is decreased by the presence of these delayed copies.Since the traditional calculation of SNR considers delayed copies of the transmission as useful signal power,the traditional SNR might not be a good indicator of probability of transmission error.
A channel where multiple copies of the signal arrive at different times is said to have delay-spread.While there is no ideal metric of delay-spread,two common measures are the mean delay spread and the RMS delay spread (see
[8]page 199for de ?nitions).To explore the impact of delay-spread,consider Figure 8,which shows the relationship between SNR and bit-error probability for different amounts of delay spread for a simple 802.11b receiver and for a 802.11a receiver.Note that the bit-error probability of 802.11b is greatly affected by the delay-spread.Also,it is can be seen that for an RMS delay-spread of above 60ns.,which is quite common in an urban setting,the impact of the delay is quite severe.From measurements,it has been found that indoors,the RMS delay-spread is typically less than 50ns.,but outdoors,it can exceed 500ns.The dependence of delay-spread on the communication environment has been widely observed (e.g,[13]and [22]).It should be noted that the delay-spread typically increases with the distance between the transmitter and receiver [23].And therefore,roof-top con ?gurations such as those studied
in[13],which are able to propagate considerable distances due to the lack of obstructions at higher heights,are likely to experience large delay-spread values.As pointed out in[13],to predict the transmission error probability, in some cases,both delay-spread and SNR are required.
Incorporating the effects of delay-spread into wireless simulation poses signi?cant dif?culties.First,the mapping from RMS or mean delay-spread to transmission error probability is not well de?ned.It is possible to have a channel with high RMS delay-spread that yields lower transmission error probability than the one that has a lower RMS delay-spread and conversely.Second,RAKE receivers can be incorporated into receivers that can greatly mitigate the effects of delay-spread.However,the implementation of the RAKE receiver has a signi?cant impact on the performance.For example,[24]shows that high performance RAKE receivers can mitigate the impact of delay-spread,while less effective RAKE receivers will perform poorly when the delay-spread is large.Thus,it is dif?cult to make any conclusions about the effect of delay-spread on future mesh networks based on current receivers.
In anticipation of receivers more suitable for outdoor use,another alternative is to neglect delay-spread.Not only is such an approach reasonable when the inclusion of algorithms that mitigate the effect of delay-spread into802.11b receivers is anticipated,but also because other physical layers based on OFDM greatly mitigate the impact of delay-spread.Consider Figure8,which shows the relationship between SNR and bit-error probability for different values of RMS delay-spread when802.11a is used.Note that the impact of delay-spread is not discernible.Schemes such as802.11g and802.16use OFDM and hence are also relatively immune to delay-spread.In summary,while delay-spread can have a signi?cant impact on transmission error,there are a number of physical layer schemes that can mitigate these effects,and,considering the rapid migration between physical layers(e.g.,from802.11b to802.11g), it seems likely that when there is a need(i.e.,when outdoor mesh networks are?nally deployed)such schemes will become wide-spread.Therefore,depending on the assumptions made about the network being simulated,realistic simulation of future urban mesh networks does not necessarily require consideration of delay-spread.
IV.C OMPUTATIONAL T ECHNIQUES
A.Overview
While much is known about propagation,a major obstacle to simulation of propagation is the computational complexity.This complexity forces a trade-off between computational complexity and accuracy.The dif?culty to
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10-2100
Es/No (dB)B i t E r r o r P r o b a b i l i t y 802.11b -0.7ns 802.11b -13ns 802.11b -26.4ns 802.11b -58ns 802.11a -0.7ns to 220ns
Fig.8.Bit-error probabilities as a function of delay-spread and SNR.Simulation of 802.11b at 1Mbps (without a RAKE receiver)and 802.11a at 6Mbps.The different curves for 802.11b correspond to different RMS-delay spreads.For a delay-spread of 7ns to 220ns,802.11a gave the same relationship between SNR and bit-error rate,hence this relationship is shown with a single curve.
specify the details of the environment (e.g.,wall materials and exact dimensions and structure of buildings)also forces a trade-off with accuracy.It is important to note that the propagation must be determined from every location that a transmitter/receiver could be located to every other possible location that a transmitter/receiver could be located.The simulation of a 1km ×1km urban region often requires hundreds of thousands of locations.Hence,the computation to determine the signal strength from a single location,which is in itself computationally dif ?cult,must be repeated hundred of thousands of times.In this section,techniques to ef ?ciently simulate propagation are discussed.The techniques described are part of the UDelModels simulation package.In the next subsection,outdoor propagation is discussed,and is followed by a discussion on indoor propagation simulation.
B.Outdoor Propagation
Once the map of buildings,bandwidth,and building materials have been de ?ned,propagation can be estimated.As noted above,extreme care must be taken to reduce the computation.A signi ?cant computational savings can be achieved if it is assumed that all walls are vertical.In this case,the 3-D ray tracing problem reduces to a two stage problem,each of which are much smaller than the 3-D problem.The ?rst stage is illustrated in the left-hand plot in Figure 9,where two vertical plane paths are shown (the path that diffracts around the smaller building is not shown).The ?rst stage is a 2-D ray-tracing.Once the vertical plane paths are found,the 3-D ray paths restricted to the vertical plane paths can easily be computed.The right-hand frame in Figure 9shows the paths of rays in the vertical planes.One vertical plane path has three ray paths,one that diffracts over a building,one
Fig.9.Left:a top-view of the scene on the right.The lines shown are found from2-D ray-tracing.Right::Two vertical plane paths(found from2-D ray-tracing)and5ray paths.
that re?ects off of the ground and passes through a building,and one that passes straight through a building.The other vertical plane path has two ray paths,one re?ecting off of the wall of a building and one re?ecting off of the wall of building and undergoing a ground re?ection.While Figure9shows each vertical plane paths having two or three ray paths,in general,in one vertical plane path there are many ray paths that may include re?ection off of the ground,and transmissions through buildings or diffractions over buildings.The UDelModels’propagation simulator only considers three types of ray paths,direct paths(no ground re?ections and no diffractions over buildings),ground re?ected paths with no diffraction,and paths that include no transmissions through buildings but rather diffract over buildings.Note that diffractions and transmissions through buildings result in signi?cant loss, and hence neglecting ray paths with multiple diffractions or diffractions and transmissions into buildings has little impact on accuracy.This method of3-D ray-tracing is known as vertical plane launching[25],and is known to yield accurate propagation estimates in real cities,where all walls are not necessarily vertical[26].
A straightforward implementation of even2-D ray-tracing is computationally dif?cult.Instead,a technique that is more appropriately called beam tracing can be performed.Like ray tracing,the goal of beam tracing is to determine the paths from the transmitter to receiver.Beam tracing begins with the source broadcasting the signal in all directions.This transmission is not modeled as a large number of rays,but as a small number of beams.When a beam intersects a building,two beams are generated,one is re?ected off of the building and one is transmitted into the building.If only a part of the beam intersects the building,then multiple beams are generated,in particular, one that re?ects off of the building,one that transmits into the building,one that passes by the building,as well
as several beams that account for the diffracted signal.Each diffracted beam models a particular range of angles of diffraction.The strength of the diffracted beam is the average strength for the diffraction angles that the beam models.Note that smaller the range of angles for each beam,the more accurate the diffraction model is.But this generates more beams,increasing the computational complexity of the process.Finally,if the receiver is found to be included within the span of a beam,the vertical plane path is found and the3-D rays from transmitter to receiver are determined.Once a3-D ray is found,the3-D ray information,speci?cally,signal strength,phase,delay,angle of departure from the transmitter,and angle of arrival at the receiver are recorded.
The beam tracing computation can be further simpli?ed by dividing the2-D space into a grid and the determining the propagation between the center points of each square.Each square of the grid is called a?oor-tile.Outdoors and indoors are discretized in this manner.To reduce the number of?oor tiles,the entire space is not discretized. Rather,?oor-tiles are placed only along the center-lines of sidewalks,roads,and hallways.For rooms,?oor tiles are placed in every location that a mobile node can be located.Similarly,the walls of buildings are also divided into wall-tiles.Since the beam tracing is in2-D,the wall-tiles are segments(1-D tiles).The smaller the size of these tiles(?oor-tiles and wall-tiles)more accurate the simulation results,but also the more computationally expensive. The computation is divided into two parts,preprocessing and beam tracing.During preprocessing,ray neighbors for each tile are found.A tile’s ray neighbors are all the tiles that could be directly reached(i.e.,without re?ection, transmission through a wall,or diffraction)by a ray emanating from the tile.Once the ray neighbors are found, beam tracing can be performed ef?ciently.Figure10illustrates how the beam tracing with wall tiles is performed. The process of beam tracing Figure10is carried out in a breadth?rst manner2with each beam continued to be re?ected,transmitted until either the beam exits the modeled area or until the estimated channel gain of the beam falls below a threshold.Each time a beam is generated,the?oor-tiles it covers are determined and the3-D ray information is recorded.Note that the3-D ray information allows one to interpolate the signal strength between grid points as well as determine the delay-spread,the Doppler spread(once velocity is known),as well as simulate directional antennas.It is possible to determine the receiver power over a particular bandwidth by integrating the signal strengths in a way that accounts for phase(i.e.,accounting for constructive/destructive interference).The 3-D ray information requires a signi?cant amount of information be saved.A considerable amount of savings is 2Here,breadth?rst means that all the k th re?ections are found before the(k+1)th re?ections are found.
Fig.10.Beam Tracing.Suppose a beam strikes the wall tile marked A.The re?ection of this beam is modeled as a beam emanating from the virtual source as shown.This beam is between and is de?ned by the two rays marked1and2.These rays are used to select the?oor tile ray-neighbors that this beam strikes(since ray-neighbors are precomputed,this selection is computationally ef?cient).Similarly,the rays1and 2are used to select the set of A’s wall tile ray-neighbors that the beam strikes.One such wall tile is shown in the upper right and is marked B.The beam that strikes tile B is de?ned by the rays marked3and4.These rays de?ne the beam that is transmitted through tile B and can be used to?nd the beam that is re?ected off of B.This process of re?ection and transmission is repeated until the beam’s strength is small enough that it can be neglected(e.g.,-110dB).
achieved by simply recording the received power over a bandwidth and RMS delay-spread(which is merely two integers).Of course,this approach cannot be used if directional antennas are simulated or Doppler spread included. Another important computational saving is achieved by recognizing that the communication is not possible between most locations,hence the propagation matrix is https://www.doczj.com/doc/633010012.html,putational savings are possible by using techniques to store sparse matrices.However,since the resulting data is large,and since simulation requires the determination of a large number of channel gains,it is important that the sparse matrix techniques support fast access.
C.Indoor Propagation
Beam tracing can be performed indoors as well as outdoors.However,the computational complexity depends on the number of walls.Since building interiors have a large number of walls,beam tracing inside all the buildings within a large region of a city exceeds today’s computational abilities.Fortunately,it has been found that a realistic estimate of indoor propagation can be performed without using beam tracing.Speci?cally,the attenuation factor (AF)model has been shown to provide realistic channel gain estimates,with the error found to be within4dB[8]. The AF model assumes that communication indoors takes a straight line path(i.e.,no re?ections off of interior walls). Furthermore,transmissions through each interior wall and transmissions through each?oor result in attenuation. While the amount of attenuation depends on the building,a value of4dB per wall(for an of?ce building)has been shown to work well[8].Realistic attenuation for passing through1?oor is30dB,passing through2?oors is35dB,
passing through3?oors is39dB and passing through4or more?oors is40dB[8].In summary,outdoors,rays make re?ections off of buildings,diffractions over and around buildings,and transmissions into buildings.Once inside a building,the ray will continue in the same direction,experiencing further attenuation for any interior wall or?oor that it passes through.When a ray strikes an exterior wall from the inside,it is both re?ected back inside and transmitted outside.
https://www.doczj.com/doc/633010012.html,putational Complexity
Determining the propagation matrix of a region of an urban area is a feasible but highly computationally complex task.The complexity is both in terms of memory usage and processing time.Processing times for a1km×1km urban region is often on the order of tens of processor days.But the process is highly parallelizable and nearly scales with the number of processors used(i.e.,75processor days takes about5days on15processors).Of course,the entire channel gain matrix for each city only needs to be found once.Table II outlines the memory requirements and the processing time for two cities.These two cities represent two ends of the spectrum.Paddington is a dense city with relatively small buildings,whereas the University of Delaware campus has much more open space and larger buildings.Note that the campus map is signi?cantly larger than Paddington,but only has slightly more buildings. The memory requirement is dominated by the lists of ray neighbors.In Table II,the wall tiles were2meters long and?oor tiles were1m×1m.While the number of wall and?oor tiles scales linearly with the reciprocal of the size of the tiles(i.e.,if the wall tiles are twice as long,there are half as many)3,the total ray neighbors scale quadratically.For the simulations shown in Table II,there are between20,000to40,000exterior?oor tiles,and 80,000to100,000interior?oor tiles.As expected,sidewalks and roads utilize little area outdoors,but indoors, hallways and of?ces?ll large areas.
As shown in Table II,there are on the order of10to100million ray neighbors for a city of size about1km×1km. Since each list entry requires40B,the memory requirement approaches4GB.Assuming suf?cient memory resources, the computation time for the preprocessing stage is relatively short;the cities shown in Table II took a single day on an AMD Athlon64FX55with8GB RAM.
Once the ray neighbors are found,the propagation characteristics between each pair of?oor tiles can be found. From a single source,the propagation characteristics to all destinations can be found at the same time.Table 3Recall that the?oor tiles cover sidewalks,roads,hallways,and of?ces only.
快速入门 说明：本篇快速入门为一套完整的SimTrade实际业务操作，交易方式为L/C + CIF，由于不同交易方式下贸易流程不尽相同，本例中的数据资料(加横线部份)仅供参考，请依具体情况来完成实际操作。 (一) 交易准备阶段 1 学生以出口商角色登录，输入用户名(如xyz)，在"选择用户类型"下拉框中选择"出口商"，点"登录系统"，进入出口商业务主页面； 2 创建公司。点"资料"，可查看公司注册资金、帐号、单位代码、邮件地址等信息，还可以修改登陆密码，其它资料逐项填写如下： 公司全称(中文)：宏昌国际股份有限公司 公司全称(英文)：GRAND WESTERN FOODS CORP. 公司简称(中文)：宏昌
公司简称(英文)：GRAND 企业法人(中文)：刘铭华 企业法人(英文)：Minghua Liu 电话：86-25-23501213 传真：86-25-23500638 邮政编码：210005 网址：https://www.doczj.com/doc/633010012.html, 公司地址(中文)：南京市北京西路嘉发大厦2501室 公司地址(英文)：Room2501,Jiafa Mansion, Beijing West road, Nanjing 210005, P.R.China 公司介绍：我们是一家专营食品的公司，长期以来致力于提高产品质量，信誉卓著，欢迎来函与我公司洽谈业务！ 可自由添加图片 注意事项：最好使用GIF或JPG格式的图片，尺寸建议在120*120(像素)左右。 填写完毕后，点"确定"； 3 以同样方法登陆其他四个角色(进口商、工厂、出口地及进口地银行)，分别创建基本资料。 (1)进口商资料如： 公司全称：Carters Trading Company, LLC 公司简称：Carters 企业法人：Carter 电话：0016137893503 传真：0016137895107 网址：https://www.doczj.com/doc/633010012.html, 公司地址(注意应根据所属国家来填写)：P.O.Box8935,New Terminal, Lata. Vista, Ottawa, Canada 公司介绍：We are importers in all items enjoying good reputation！ (2)工厂资料如： 公司全称：冠驰股份有限公司 公司简称：冠驰 企业法人：张弛 电话：86-25-29072727 传真：86-25-29072626 邮政编码：210016 网址：https://www.doczj.com/doc/633010012.html, 公司地址：南京市中正路651号3楼 公司介绍：我公司为信誉卓著的厂商，产品深受客户喜爱，欢迎与我公司洽谈业务，我们
第 1 页 共 10 页 图 1 图2 圆梦2015·高三数学（理）仿真模拟三 一、选择题：本大题共8小题，每小题5分，满分40分．在每小题给出的四个选项中，只有一项是符合题目要求的． 1．已知函数lg y x =的定义域为A ,{} 01B x x =≤≤,则A B =（ ） A ．()0,+∞ B ．[]0,1 C ．(]0,1 D ．[)0,1 2．设i 为虚数单位,若复数() ()2231i z m m m =+-+-是纯虚数,则实数m =（ ） A ．3- B ．3-或1 C ．3或1- D ．1 3 ．设函数sin 2y x x =的最小正周期为T ,最大值为A ，则（ ） A ．T π= ,A = B . T π=,2A = C ．2T π= ,A = D ．2T π=,2A = 4．某由圆柱切割获得的几何体的三视图如图1所示,其中俯视图是 中心角为60?的扇形,则该几何体的体积为（ ） A ． 3 π B ．23π C ．π D ．2π 5．给定命题p ：若20x ≥，则0x ≥； 命题q :：已知非零向量,,a b 则 “⊥a b ”是“-+=a b a b ”的充要条件. 则下列各命题中,假命题的是（ ） A ．p q ∨ B ． ()p q ?∨ C ．()p q ?∧ D ．()()p q ?∧? 6．已知函数()222,02,0 x x x f x x x x ?+≥=?-）的比值a b ,称这些比值中的最小值为这个 数表的“特征值”.当2n =时, 数表的所有可能的“特征值”最 大值为（ ） A ．3 B ． 43 C ．2 D ．32
单项选择题（5X2=10分） 1. 海运提单和航空提单（ C ） A.均为物权凭证 B.均为可转让的物权凭证 C.前者作物权凭证，后者不可转让，不作物权凭证 D.前者不作物权凭证，后者作物权凭证 2. CIF合同的货物在刚装船后因火灾被焚，应由（D） A. 卖方负担损失 B. 卖方请求保险公司赔偿 C. 买方委托卖方向保险公司索赔 D.买方负担损失并请求保险公司赔偿 3.关于接受的生效，英美法系实行的原则是（A） Ａ．投邮生效Ｂ．签署日生效 Ｃ．到达生效Ｄ．双方协商 4.海运提单之所以能够向银行办理抵押贷款，是因为（D ） A.海运提单是承运人签发的货物收据 B.海运提单可以转让 C.海运提单是运输契约的证明 D.海运提单具有物权凭证的性质 5.为防止运输途中货物被窃，应该投保（C ）。 A. 一切险、偷窃险 B. 水渍险 C. 平安险、偷窃险 D. 一切险、平安险、偷窃险 6.汇票根据（B ）不同，分为银行汇票和商业汇票。 A.出票人 B.付款人 C.受款人 D.承兑 7.银行审单议付的依据是（ C ）。 A. 合同和信用证 B. 合同和单据 C. 单据和信用证 D. 信用证和委托书 计算题(10分) 1.某商品出口我对外报FOB净价180美元，若国外客户要求改报含佣4%的价格时，我应对外报价多少？ 解：FOBC4%价=净价/（1-佣金率）=180/（1-4%）=187.5（美元）。 2.某批商品的卖方报价为每打60美元CIF香港，若该批商品的运费是CIF价的2％，保险费是CIF价的1％，现外商要求将价格改报为FOBC3%.问FOBC3%应报多少？ 解:FOB价=CIF价—运费—保险费=60—60×2%—60×1%=58.2美元 FOBc3%=FOB价/（1—佣金率）=58.2/（1-3%）=60美元 3.一批出口货物做CFR价为250000美元，现客户要求改报CIF价加20%投保海运一切险，我方同意照办，如保险费率为0.6%时，我方应向客户报价多少？ 解:CIF=CFR/(1-投保加成*保险费率)=CFR÷（1-120%×0.6%） =250000÷0.9928 =251813.05美元 案例分析（30分） 1.某口岸出口公司按CIF London向英商出售一批核桃仁，由于该商品季节性较强，双方在 合同中规定：买方须于9月底前将信用证开到，卖方保证运货船只不得迟于12月2日驶抵目的港。如货轮迟于12月2日抵达目的港，买方有权取消合同。如货款已收，卖方须将货款退还买方。问这一合同的性质是否属于CIF合同？ 按CIF条件签订的合同属于装运合同，其特点是“凭单据履行交货义务，并凭单据付款”。只要卖方按合同的规定将货物装船并提供齐全的、正确的单据，即使货物在运输途中已遭灭失，买方也不能拒收单据和拒付货款。所以，本案例的合同不属于CIF合同。
《国际贸易实务》实训大纲 适用对象：经济学专业 一、课程性质、目的与任务： 国际贸易实务实训是市场营销本科专业重要的综合性实践教学内容之一。主要是对国际贸易的整个流程进行模拟训练，包括、交易磋商、合同的签订、合同的履行等，涉及到银行、保险、海关、运输等各个部门，需要填制各种单据，包括信用证申请书、报验单、报关单、出口结汇单据等。 二、教学基本要求： 国际贸易实务实训覆盖了国际贸易市场营销、国际贸易商法、国际贸易实务、电子商务等课程教学的主要内容，其操作性很强。通过实验可以使学生全面掌握进出口业务的整个流程及具体内容，主要包括： 1．进出口贸易合同的磋商与签订。 2．进出口贸易合同履行的整个流程。 3．进出口业务中各种单据的制作。 实验方式：本课程实验内容进行上机操作。 基本要求： 1．认真阅读实验指导书，以便顺利完成实验要求。 2．每人至少完成一笔进口业务和一笔出口业务。进口业务与出口业务可以同时进行。 3．写出实验日记。 4．实验完毕后应编写实验报告，实验报告为按实验指导书要求编写的实验结果，包括进口业务和出口业务所涉及的各项内容，交打印版和电子版各一份。 三、课程内容与学时分配：
四、考核方法与规定 本课程实验教学的成绩评定采用考查方法进行，根据实验态度、出勤率、实验质量、实验日记、实验总结、实验报告等综合评定。成绩分为优、良、中、及格、不及格五等。 五、综合训练其它有关问题的说明与建议： 1．本课程与其相关课程的联系与分工： 本课程的先修课程是《国际贸易》、《国际贸易实务》等。 2．课外练习方面的要求： 要求学生课外多阅读贸易谈判方面的参考书籍；查找外贸业务的相关案例。 \大纲制定人：田小伟大纲审定人 制定时间：2014.08.27
高考数学模拟试题 （第一卷） 一、选择题：（每小题5分，满分60分） 1、已知集合A={x|x 2+2ax+1=0}的真子集只有一个，则a 值的集合是 A ．（﹣1，1）； B ．(﹣∞,﹣1)∪[1，+∞]； C ．{﹣1，1}； D ．{0} 2、若函数y=f(x)的反函数y=f －1(x)满足f －1(3)=0，则函数y=f(x+1)的图象必过点： A ．（0，3）； B ．（－1，3）； C ．（3，－1）； D ．（1，3） 3、已知复数z 1,z 2分别满足| z 1+i|=2，|z 2－3－3i|=3则| z 1－z 2|的最大值为： A ．5； B ．10； C ．5+13； D ．13 4、数列 ,4 3211,3211,211++++++ ……的前n 项和为： A ．12+n n ； B ．1+n n ； C ．222++n n ； D ．2+n n ； 5、极坐标方程ρsin θ=sin2θ表示的曲线是： A ．圆； B ．直线； C ．两线直线 D ．一条直线和一个圆。 6、已知一个复数的立方恰好等于它的共轭复数，则这样的复数共有： A ．3个； B ．4个； C ．5个； D ．6个。 7、如图，在正方体ABCD —A 1B 1C 1D 1中，E 、F 是异面直 线AC ，A 1D 的公垂线，则EF 和ED 1的关系是： A ． 异面； B ．平行； C ．垂直； D ．相交。 8、设(2－X)5=a 0+a 1x+a 2x+…+a 5x 5, 则a 1+a 3+a 5的值为： A ．－120； B ．－121； C ．－122； D ．－243。 9、要从一块斜边长为定值a 的直角三角形纸片剪出一块圆形纸片，圆形纸片的最大面积为： A ．2 πa 2； B ．24223a π-； C ．2πa 2； D ．2)223(a π- 10、过点（1，4）的直线在x,y 轴上的截距分别为a 和b(a,b ∈R +)，则a+b 的最小值是： A ．9； B ．8； C ．7； D ．6； 11、三人互相传球，由甲开始发球并作为第一次传球。经过5次传球后，球仍回到甲手中，则不同的传球方式共有： A ．6种； B ．8种； C ．10种； D ．16种。 12、定义在R 上的偶函数f(x)满足f(x+2)=f(x －2)，若f(x)在[﹣2，0]上递增，则 A ．f(1)>f(5.5) ; B ．f(1) 一单项选择题 1、我方出口大宗商品，按CIF Singapore 成交，运输方式为Voyage Charter,，我方不愿承担卸货费用，则我方应选择的贸易术语的变形是 （ C ）。 A、CIF Liner Terms Singapore B、CIF Landed Singapore C、CIF E x Ship’s Hold Singapore D、CIF Ex Tackle Singapore 2、按照《INCOTERMS2000》的解释，以FOBST成交，则买卖双方风险的划分界限是（B以船舷为界）。 4、在CIF条件下，Bill of Lading对运费的表示应为( A )。 A．Freight Prepaid B．Freight Collect C．Freight Pre-payable D．Freight Unpaid 5、在进出口业务中，能够作为物权凭证的运输单据有( B )。 A．Rail Waybill B．Bill of Lading C．Air Waybill D．Parcel Post Receipt 6、预约保险以（ B ）代替投保单，说明投保的一方已办理了投保手 续。 A、B/L B、Shipping advise from abroad C、Mate，s receipt D、Sales contract 7、我某公司与外商签订一份CIF出口合同，以L/C为支付方式。国外 银行开来的信用证中规定：“Latest shipment 31st, May, L/C validity till 10th, June.”我方加紧备货出运，于5月21日取得大副收据，并换回正本已装船清洁提单，我方应不迟于（ C ）向银行提交单据。 A．5月21日 B．5月31日 C．6月10日 D．6月11日 8、某批出口货物投保了CIC 的WPA，在运输过程中由于雨淋致使货物遭受部分损失，这样的损失保险公司将（ C ）。 A、负责赔偿整批货物 B、负责赔偿被雨淋湿的部分 C、不给于赔偿 D、在被保险人同意的情况下，保险公司负责赔偿被雨淋湿的部分 9．在短卸情况下，通常向( B )提出索赔。 A. the seller B. the carrier 湖南女子学院 外贸单证实训报告 （2014年下学期） 院系经济与管理系专业国际经济与贸易班级11级国贸一班姓名王珏 学号2011111129 指导教师袁学军 成绩 2014年12 月 一、引言 国际贸易是跨国的商品买卖，不能用简单的货物和货款交换来形容这种特殊性的跨国交易，跨国的商品买卖以单证作为交换的媒介手段，故外贸单证是国际贸易中最重要的环节，买卖双方处理的只是与货物相符的单据。单证工作是国际贸易业务中最重要的环节，贯穿于进出口合同履行的全过程。 二、实训目的 外贸单证制作实训是在《外贸单证实务》课程的基础上开设的，通过综合业务模拟制单，使学生能够将课程中比较零散的制单练习贯穿起来，从而系统地了解外贸企业单证工作流转程序和具体的制单要求，加强对所学专业知识的理解，明确掌握各种进出口单证的制单技巧，以培养学生的实际操作能力，提高自身的制单水平，同时也培养了学生耐心、细致的工作作风。 三、实训时间：2014年9月-12月 四、实训地点：实训楼504 五、实训内容 本实训要求学生根据信用证、合同、订单等各种材料及相关信息，进行综合制单训练。由于信用证项下制单对单证的要求最为严格，所以本实训内容也主要以信用证制单为主，结合托收和汇付方式的制单，材料涉及到信用证、合同、订单等各种外贸文件，实习素材也基本上来自于外贸公司的真实业务，模拟了不同的贸易术语、分批交货、选择港的确定等各种贸易情形，使学生能够熟练掌握各种外贸单证的制单技巧，逐步学会独立制作各种外贸单证，丰富制单经验。 具体包括： (一) 审核信用证 1、目的与要求 信用证的开立是以合同为基础的，而其下的制单要求是:单证一致，单单一致。信用证受益人只有提交的单据合格，才能获得银行的付款保证。因而认真审核国外开来的信用证，关系到受益人能否收到货款。通过实训操作，使学生进一步掌握审证的基本规律和方法，了解“UCP600”和国际标准银行实务的规定的有关规定，同时会及时联系进口商通过开证行对信用证进行修改。 2、实训内容 (1)审核信用证主要是信用证内容的审核，是否与合同一致，以及一些特别条款的审核。 (2)修改信用证撰写一封完整的改证函 (二) 出口托运 1、目的与要求 出口方在合同的履行过程中，如需要订舱，则出口方必须负责与承运人订立运输合同、预订船只或舱位。通过实训操作，要求了解出口货物托运的程序，会托运单、订舱委托书的填写。 2、实训内容 (1)出口订舱流程会查阅各班轮公司的船舶、船期、挂靠港及船舱箱位数等具体情况，然后选择合适的船只订舱。(2)会缮制有关单据，如订舱委托书、托运单 (三) 出口货物报检 1、目的与要求 商品检验检疫是商品出口过程中的一个重要环节。通过实训操作，使学生掌握报验流程， ( 实习报告 ) 单位：_________________________姓名：_________________________日期：_________________________ 精品文档 / Word文档 / 文字可改 国际贸易实务实训总结Summary of international trade practice training 国际贸易实务实训总结 为期一周半的国际贸易与实务实训已经结束了，不能说完成得很圆满，但是有一点可以肯定的是，通过这次实训，我了解了国际贸易的基本流程，并且巩固了所学的理论知识，切身体会到了商品进出口贸易的全过程。 其实，说真的，还没实训之前心里总是有点忐忑不安，怕自己不能顺利完成这次实训任务。我们实训的第一步就是拟写建交函，由于我们之前并没有写过这种信函，对它的格式不是很清楚。所以，我就先在网上搜索了建交函的范文，知道了基本格式以后，然后就根据操作的要求写好建交函。这一步实际上并不难，所以所花的时间也不多，但这仅仅是第一步工作，接下来还有一连串的工作要做。 整个过程下来，对我来说最难也是我最欠缺的就是那一系列的核算。我们要做的有三个核算，出口报价核算、出口还盘核算和成 交核算。要进行核算首先要知道计算公式以及它们的转化公式。刚开始算的时候，可能是因为自己太过粗心，老是算错，算出来的结果总是对不上。后来还是在老师的帮助下，才找到了问题的症结所在，原来我小数点后面少加了一个零。这次教训让我知道了细心仔细的重要性。在进行核算的过程中，还应该引起注意的就是不同币制的转换，有的要的是美元，如进行对外报价时。而在计算利润率时则需要的是人民币。在做这一步时，最重要的就是要细心，还要有耐心，算错了不能心急，要耐心地找出错误的原因。 完成成交核算之后，接下来就是合同的签订。我们要根据合同基本条款的要求和双方在信函中确定的条件制作售货确认书，另外还要给对方寄出成交签约函。在这一过程中，合同的条款要全面、内容要完整；合同没有会签之前，买方是不可能签署的，这一点尤其值得注意。接下来就是审核信用证和写改证函，根据审核信用证的一般原则和方法对收到的信用证认真的审核，列明信用证存在的问题并陈述改证的理由。这个过程需要根据合同，把信用证和合同相比较，仔细认真地进行审核。收到对方的改证函后，接下来就要 《国际贸易实务》模拟题 一单选题 1.A公司5月18日向B公司发盘,限5月25日复到有效,A公司向B公司发盘的第二天,A公司收到B公司5月17日发出的,内容与A公司发盘内容完全相同的交叉发盘,此时(). A.合同即告成立 B.合同无效 C.A公司向B公司或B公司向A公司表示接受,当接受通知送达对方时,合同成立 D.必须是A公司向B公司表示接受,当接受通知送达对方时,合同成立 [答案]:C 2.CFR术语有多种变形,其目的是明确() A.装货费用由谁负担 B.卸货费用由谁负担 C.风险划分的界线 D.运费由谁负担 [答案]:B 3.CPT和CFR相同的是(). A.属装运合同 B.交货地点 C.费用划分界限 D.提交的单据 [答案]:A 4.CPT贸易术语条件下,卖方将合同中规定的货物(),完成交货. A.交到装运港船上 B.置于买方处置之下 C.交给买方自己指定的承运人 D.交给卖方自己指定的承运人或第一承运人 [答案]:D 5.FOB,CFR和CIF贸易术语,最宜采用()检验方法 A.出口国检验,进口国复验 B.在进口国检验 C.在出口国检验 D.装运港()检验重量,目的港()检验品质 [答案]:A 6.FOB条件下,风险划分的界线是() A.装运港船舷 B.装运港船舱 C.装运港船上 D.装运港码头 [答案]:C 7.SWIFT采用0-9的数字区别电文业务性质,7代表跟单信用证和保函.修改信用证的代码是(). A.MT700 B.MT707 C.MT720 D.MT705 [答案]:B 8.按CIF术语成交的贸易合同,货物在运输途中因火灾被焚,应由(). A.卖方承担货物损失 B.卖方负责向保险公司索赔 C.买方负责向保险公司索赔 D.买方负责向承运人索赔 [答案]:C 9.按照《2000通则》的解释,按DEQ成交,买卖双方的风险划分界限在(). A.装运港船上 B.目的地 C.目的港船上 D.目的地码头 [答案]:D 10.按照货物重量,体积或价值三者中较高的一种计收运费,运价表内以()表示. A.M/W B.W/MorAd.Val C.AdVal D.Open [答案]:B 11.包销业务中包销商与出口商之间是一种(). A.买卖关系 B.委托代理关系 C.互购关系 D.代销关系 [答案]:A 12.保险公司承担保险责任的期间通常是() A.钩至钩期间 B.舷至舷期间 C.仓至仓期间 D.水面责任期间 [答案]:C 国际贸易实务模拟实训报告 随着中国在国际贸易的地位的不断上升，我们学习国际贸易专业的学生们要掌握有关于国际贸易方面的知识也要不断增加，这次学校给了我们一个很好的实习锻炼机会，就是让我们模拟国际贸易实务操作，从而从中掌握国际贸易流程。 通过simtrade上机实习，可以使我们熟悉外贸实务的具体操作流程，增强感性认识，并可从中进一步了解、巩固与深化已经学过的理fg的运作方式；切身体会到国际贸易中不同当事人面临的具体工作与他们之间的互动关系；学会外贸公司利用各种方式控制成本以达到利润最大化的思路；认识供求平衡、竞争等宏观经济现象，并且能够合理地加以利用。老师通过在网站发布新闻、调整商品成本与价格、调整汇率及各项费率等方式对国际贸易环境实施宏观调控，使我们在实习中充分发挥主观能动性，真正理解并吸收课堂中所学到的知识，为将来走上工作岗位打下良好基础。 上机模拟操作 simtrade软件 **年5月16日——**年6月13日 经过一个多月的simtrade模拟训练，我们对国际贸易的业务流程及操作有了更进一步的了解和感触，现在我们对贸易的理解已经不在停留在单纯的理论层面。 在头一两个星期里，我们处理起业务是不知从何做起，填写单据那是相当的慢，算一笔进出口预算表都要算上一个多小时。经过两个星期的不间断联系，早后来的操作练习中我们处理的是得心应手，可谓从容自如。 在我国继续扩大开放、深化改革和加入世界贸易组织以来的新形势下，作为未来从事国际贸易方面业务的我们必须熟练掌握国际贸易的sdf这两年学习的一个大总结。从国际贸易理论，到国际贸易实务，再到上学期的外贸函电及本学期外贸合同的制定、国际货物运输风险和保险，在本次模拟训练中都一一体现，通过simtrade模拟训练我们对以前所学过的知识有了一次系统的回顾，又在训练中对国际贸易的流程及操作有了更加深刻的体会，这对我们未来的工作在思想上做了充分的准备。 通过本次的模拟实习，我们可以发现以前学习中薄弱环节，为今后的学习指明了方向，也会实际操作打下一个良好的基础。本次模拟训练给我最大的体会就是操作细节的细腻及流程的缜密，各个流程相互衔接，此流程的疏忽将会导致彼流程无法完成，某一细节的不慎错误或纰漏将会导致整个流程操作前功尽弃，这为未来的实际工作敲响了警钟：做贸易一定要仔细谨慎。 在本次实习中，我们充分利用了simtrade提供的各项资源。我们充分使用邮件系统进行业务磋商，这是我们未来 2019年高考数学仿真模拟试题 本试卷共6页。考试结束后，将本试卷和答题卡一并交回。 注意事项： 1．答题前，考生先将自己的姓名、准考证号码填写清楚，将条形码准 确粘贴在考生信息条形码粘贴区。 2．选择题必须使用2B 铅笔填涂；非选择题必须使用0.5毫米黑色字迹的 签字笔书写，字体工整、笔迹清楚。 3．请按照题号顺序在答题卡各题目的答题区域内作答，超出答题区域 书写的答案无效；在草稿纸、试卷上答题无效。 4．作图可先使用铅笔画出，确定后必须用黑色字迹的签字笔描黑。 5．保持卡面清洁，不要折叠，不要弄破、弄皱。不准使用涂改液、修正带、 刮纸刀。 一、选择题：本题共12小题,每小题5分,共60分。在每小题给出的四个选 项中,只有一项是符合题目要求的。 1.已知集合{}3,2,1=A ，{} Z x x x x B ∈<--= ,0322 ,则=B A Y A ．{}2,1 B ．{}3,2,1,0 C ．[]2,1 D ．[]3,0 2.复数 i i 212-+的共轭复数的虚部是 A ．53- B ．53 C ．1- D ．1 3.下列结论正确的是 A ．若直线⊥l 平面α，直线⊥l 平面β，且βα,不共面，则βα// B ．若直线//l 平面α，直线//l 平面β，则βα// C ．若两直线21l l 、与平面α所成的角相等，则21//l l D ．若直线l 上两个不同的点B A 、到平面α的距离相等，则α//l 4.已知34cos sin = -αα，则=?? ? ??-απ4cos 2 A. 91 B. 92 C. 94 D. 9 5 5.设直线l 过双曲线C 的一个焦点，且与C 的一条对称轴垂直，l 与C 交于B A 、两点， 一、把以下英文术语翻译成中文，是英文简称的需先写出其全称再翻译（本大题共5小题，每小题1分，共5分） 1、Neutral Packing 2、Insurance Policy 3、Order B/L 4、OCP 5、O/A 二、单项选择题（本大题共20小题，每小题1分，共20分） 1、我方出口大宗商品，按CIF Singapore 成交，运输方式为Voyage Charter,，我 方不愿承担卸货费用，则我方应选择的贸易术语的变形是（）。 A、CIF Liner Terms Singapore B、CIF Landed Singapore C、CIF E x Ship’s Hold Singapore D、CIF Ex Tackle Singapore 2、按照《INCOTERMS2000》的解释，以FOBST成交，则买卖双方风险的划分界限是（）。 A、货交承运人 B、货物越过装运港船舷 C、货物在目的港卸货后 D、装运港码头 3、山东渤海公司与日本东洋株式会社在万国博览会上签订了一份由日方向中方提供BX2-Q船用设备的买卖合同，采用的贸易术语是DES。运输途中由于不可抗力导致船舶起火，虽经及时抢救，仍有部分设备烧坏，则（）应来承担烧坏设备的损失。 A.东洋株式会社 B.山东渤海公司 C.船公司 D.保险公司 4、在CIF条件下，Bill of Lading对运费的表示应为( )。 A．Freight Prepaid B．Freight Collect C．Freight Pre-payable D．Freight Unpaid 5、在进出口业务中，能够作为物权凭证的运输单据有( )。 A．Rail Waybill B．Bill of Lading C．Air Waybill D．Parcel Post Receipt 6、预约保险以（）代替投保单，说明投保的一方已办理了投保手续。 A、B/L B、Shipping advise from abroad C、Mate，s receipt D、Sales contract 7、我某公司与外商签订一份CIF出口合同，以L/C为支付方式。国外银行开来的信 F D C B A 2019年高考数学模拟试题（理科） 注意事项： 1．本试卷分第Ⅰ卷（选择题）和第Ⅱ卷（非选择题）两部分。答卷前，考生务必将自己的姓名、准考证号填写在答题卡上。 2．回答第Ⅰ卷时，选出每小题答案后，用铅笔把答题卡上对应题目的答案标号涂黑。如需改动，用橡皮擦干净后，再选涂其他答案标号。写在本试卷上无效。 3．回答第Ⅱ卷时，将答案写在答题卡上。写在本试卷上无效。 4．考试结束后，将本试卷和答题卡一并收回。 一．选择题：本大题共12个小题，每小题5分，共60分。在每小题给出的四个选项中只有一项是符合题目要求的 1．已知集合}032{2>--=x x x A ，}4,3,2{=B ，则B A C R ?)(= A ．}3,2{ B ．}4,3,2{ C ．}2{ D ．φ 2．已知i 是虚数单位，i z += 31 ，则z z ?= A ．5 B ．10 C ． 10 1 D ． 5 1 3．执行如图所示的程序框图，若输入的点为(1,1)P ，则输出的n 值为 A ．3 B ．4 C ．5 D ．6 （第3题） （第4题） 4．如图，ABCD 是边长为8的正方形，若1 3 DE EC =，且F 为BC 的中点，则EA EF ?= A ．10 B ．12 C ．16 D ．20 5．若实数y x ,满足?? ???≥≤-≤+012y x y y x ，则y x z 82?=的最大值是 A ．4 B ．8 C ．16 D ．32 6.一个棱锥的三视图如右图，则该棱锥的表面积为 A ．3228516++ B ．32532+ C ．32216+ D ．32216516++ 7. 5张卡片上分别写有0，1，2，3，4，若从这5张卡片中随机取出2张，则取出的2张卡片上的数字之和大于5的概率是 A ． 101 B ．51 C ．103 D ．5 4 8．设n S 是数列}{n a 的前n 项和，且11-=a ，11++?=n n n S S a ，则5a = A ． 301 B ．031- C ．021 D ．20 1 - 9. 函数()1ln 1x f x x -=+的大致图像为 10. 底面为矩形的四棱锥ABCD P -的体积为8，若⊥PA 平面ABCD ,且3=PA ，则四棱锥 ABCD P -的外接球体积最小值是 篇一:《国际贸易实务模拟实验实训总结》 国际贸易实务模拟实验实训总结 经过两周的模拟实验实训，我们对国际贸易的业务流程及操作有了更进一步的了解和感触。现在我们对贸易的理解已经不再停留在单纯的理论层面，而是上升到了一定的高度。 在这次实训中，我们充分利用了世格外贸单证教学系统提供的各项资源进行练习。通过老师的悉心指导和查阅相关资料，我们对知识有了更深入的理解。 这次的模拟实验操作，大致上可以分为三个方面的内容，分别为出口磋商谈判、合同的签订、信用证的审核等。出口磋商谈判又包括建立业务关系、询盘、发盘、还盘、接受等内容。出口磋商谈判的各个环节是相互联系的，形成一个有机的整体。 实训第一天的时候，为了之后的练习能顺利进行，老师让我们在网上查找资料，在相关网站上了解一些与国际贸易相关的知识。开始做练习的时候，我们要建立业务关系、写贸易函电，由于这是在实践中第一次接触，所以就比较迷茫，不知从何做起，完全找不到头绪。后来在老师的指导下，结合上网查找相关资料， 我们慢慢找到了做题的方法。经过两个星期的不间断练习，在后来的操作练习中，我们处理起来就比较轻松，比较得心应手了。 实训过程中，信用证的审核相对来说比较难，但同时这部分也是重点，在进出口贸易中是比较重要的一部分。面对密密麻麻的文字，并且还是英文的，先不审核，自己就先晕了。所以，在做信用证审核的练习中，细心和耐心是必不可少的。刚开始时，面对陌生的合同和信用证，里边好多术语都不明白是什么意思。然后，老师就带着大家一起分析销售合同和信用证，逐句翻译。后来，题做得多了，慢慢就掌握了分析的方法。实训结束时，自己差不多可以独立阅读信用证了，上边的英文看着也不再那么陌生了。 这两周，我们一直坐在电脑前做各种国际贸易实务模拟操作的练习，每天盯着电脑很忙很累，但也收获了很多。在练习中，我了解和掌握了进出口贸易的基本操作程序和主要操作技能，使自己在模拟操作中进步了；同时也认识到了自己身上存在的很多不足点，发现对于国际贸易中的很多东西，我们都没有搞懂,尤其是里面的规则等等。 通过这次实训，我感觉在国际贸易中，出口商是最为重要的角色。在出口过 程中，出口商为了找到客户并顺利完成交易过程，需要经过准备、磋商、签约、履约、善后几个流程。在准备阶段，出口商需要及时了解市场行情，并同工厂和进口商建立广泛而牢固的业务关系，这是非常重要的。 国际贸易实务模拟试卷及参考答案 注意事项：所有的答案都必须写在答题纸上，答在试卷上一律无效 一、把以下英文术语翻译成中文，是英文简称的需先写出其全称再翻译（本大题共5小题，每小题1分，共5分） 1、Neutral Packing 中性包装 2、Insurance Policy 保险单 3、Order B/L 指示提单 4、OCP Overland Common Points 内陆地区（或陆路共通点） 5、O/A Documents against Payment, Trust Receipt 付款交单凭信托收据借单 二、单项选择题（本大题共20小题，每小题1分，共20分） 1、我方出口大宗商品，按CIF Singapore 成交，运输方式为Voyage Charter,， 我方不愿承担卸货费用，则我方应选择的贸易术语的变形是（ C ）。 A、CIF Liner Terms Singapore B、CIF Landed Singapore C、CIF E x Ship’s Hold Singapore D、CIF Ex Tackle Singapore 2、按照《INCOTERMS2000》的解释，以FOBST成交，则买卖双方风险的划分界限是（ B ）。 A、货交承运人 B、货物越过装运港船舷 C、货物在目的港卸货后 D、装运港码头 3、山东渤海公司与日本东洋株式会社在万国博览会上签订了一份由日方向中方提供BX2-Q船用设备的买卖合同，采用的贸易术语是DES。运输途中由于不可抗力导致船舶起火，虽经及时抢救，仍有部分设备烧坏，则（ A ）应来承担烧坏设备的损失。 A.东洋株式会社 B.山东渤海公司 C.船公司 D.保险公司 4、在CIF条件下，Bill of Lading对运费的表示应为( A )。 A．Freight Prepaid B．Freight Collect - 1 - （共7页） ---------------------------------------------------------------范文最新推荐------------------------------------------------------ 2018年国际贸易实务模拟实训报告 这两周一直在进行tmt on line 国际贸易实务模拟操作，每天盯着电脑很忙很累，但真的感觉很好，在以出口商完成整个出口流程的过程中我了解和掌握了出口贸易的基本操作程序和主要操作技能，使自己在模拟操作中进步了，同时也认识到了自己身上存在的很多不足点，发现对于国际贸易的很多东西我们都没有搞懂,尤其是里面的规则等等.。 在这次模拟操作中，一共有十五个步骤，具体为：建立业务关系、出口报价核算、出口发盘出口还价核算、出口还盘、出****易磋商、出口成交、出口成交核算、出口合同签订、信用证审核、修改信用证、出口托运订舱、出口货物投保、出口货物报验报关、出口制单结汇、出口业务善后。 在操作中我被上海安德国际公司聘为销售部经理助理，公司出口的主要是不锈钢茶具厨具以及一些高级精密仪器等等，哈哈，很高兴! 在与埃及客户建立业务关系时，由于刚刚学习了函电，加上老师的指导，写起来还算轻松。但是在出口报价核算时就感觉很吃力了，个人觉得远洋运费的计算有些难，还有银行手续费和银行贷款费用的计算到底使用采购成本还是报价或者发票金额作为基数，总是容易混淆，老师大概花了两个课时详细讲解了这几个问题，总算明白了。我认为出口商是最为重要的角色，在扮演出口商的角色的过程中，要经 1 / 6 过准备、磋商、签约、履约、善后几个流程。在准备阶段，需及时了解市场行情，并同工厂和进口商建立广泛而牢固的业务关系是非常重要的交易过程中市场是变化的，作为出口商需不断核算成本、费用和利润，才能获取最佳交易条件和价格，核算过程本身是复杂的，这需要足够耐心、细心。 在国际贸易中，由于交易双方的成交量通常都比较大，而且交易的商品在运输过程中可能遭到各种自然灾害、意外事故和其它外来风险。所以通常还需要办理各种保险，以避免或减少经济损失。保险费的核算很关键，不同的贸易术语下，保险费的承担者有所不同，二者的紧密关系众所周知，在贸易术语上，我们分别采用了cif、 fob、cfr的术语，在十三种贸易术语中这三种是最常用的。 出口单证的审核也是一大难点，密密麻麻的英文表格让你先去缮制然后再审核真的不是一件轻松的事情，不说细看那些英文，就是看见那表格就头疼。静下心是很有必要的，慢慢看就习惯了就会了。在电脑里审核单据有些麻烦，只能把两张表格缩小到同一个界面再来对比。由于老师在发下一步操作时前一步的参考答案系统会自动给出，所以我们在训练时必须克服想看答案的心理。 结汇可选择t/t l/c d/a d/p等方式，信用证结汇可以保证出口商及时得到货款但是费用高，多笔业务的开展，不同术语的运用可以加强我们对知识掌握的熟练程度，在费用上的不同核算和支付更是对我们关于知识掌握程度的考验。签订合同进一步明确双方的权利和义务，标志着完成了一半的业务，通过询盘、发盘、还盘、接受四个环 国际贸易实务实训 项目名称：发盘的书写、英文合同的填制以及L/C的审核。 实训目的：学生通过实训熟练掌握如何书写发盘、填制销售合同和审核信用证。组织：一人一组。 内容： 1.书写发盘 （2）填制合同 （3）审核信用证 售 货 确 认 书 SALES CONFIRMA TION 卖方（Sellers ）： Contract No.: 09TG28711 NANJING LANXING CO.,LTD Date ： JULY ,22,2009 ROOM 2501,JIAFA MANSTION, BEIJING WEST ROAD , NANJING Signed at: NANJING 买方（Buyers ）： EAST AGENT COMPANY 3-72,OHTAMACHI,NAKA-KU,YOKOHAMA,JAPAN231 This Sales Contract is made by and between the Sellers and Buyers, whereby the sellers agree to sell and the buyers agree to buy the Packing: CARTON Delivery : From NANJING to AKITA Shipping Marks: V .H LAS PLAMS C/NO. Time of Shipment: Within 30 days after receipt of L/C. allowing transshipment and partial shipment. Term of Payment: By 100% Confirmed Irrevocable Letter of Credit on favor of the Sellers to be available. By sight draft to be opened and to reach China before JULY 30, 2009 and to remain valid for negotiation in China until the 15th days after the foresaid Time of Shipment. L/C must mention this contract number L/C advised by BANK OF CHINA NANJING BRANCH. TLX: 44U4K NJBC, CN. ALL banking Charges outside China (the mainland of China) are for account of the Drawee. Insurance: To be effected by Sellers for 110% of full invoice value covering F.P.A up to AKITA To be effected by the Buyers. Arbitration All dispute arising from the execution of or in connection with this contract shall be settled amicable by negotiation. In case of settlement can be reached through negotiation the case shall then be submitted to China International Economic & Trade Arbitration Commission. In Nanjing for arbitration in act with its sure of procedures. The arbitral award is final and binding upon both parties for setting the Dispute. The fee, for arbitration shall be borne by the losing party unless otherwise awarded. THE SELLER: THE BUYER: ISSUE OF DOCUMENTARY CREDIT国际贸易实务—模拟试题及答案
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