The effect of two realistic Radio Propagation Models for Mobile Ad hoc NETworks in Urban Area Environment Supported with stations

Transcription

1 International Journal of Scientific & Engineering Research Volume 2, Issue 1, Oct The effect of two realistic Raio Propagation Moels for Mobile A hoc NETworks in Urban Area Environment Supporte with stations Dr.Ibrahim khier, Prof.Wang Furong,Amna Saa Abstract In the fiel of Mobile A Hoc Networking, most current results have been achieve using simulators. Network simulation tools are frequently use to analyze performance of MANET protocols an applications. The nee for reproucible results an easy to observe s limits the use of real worl measurements for those kin of networks. They commonly offer only simple raio propagation moels that neglect obstacles of a propagation.the raio wave propagation moel has a strong impact on the results of the simulation run. It is state here that the two more realistic raio propagation moels has a strong impact on the results of the simulation run. The moel is base on ata of the simulation area in urban area. Consequently, we obtain ifferent performance evaluation results. This paper gives insights on the effect of these propagation moels for MANETs in inoor an outoor s an presents the parameters an the results of simulating Inex Terms Mobile Ahoc Network, Propagation moels, Mobility Moels, base stations, Simulation M 1 INTRODUCTION obile a-hoc networks (MANETs) are create spontaneously by wireless communication peers, without relying on a fixe infrastructure. The evices communicate irectly with each other when they are in transmission range. Network simulation tools [1], [2] are frequently use to analyze the performance of MANET protocols an applications. These tools moel the applications running on mobile evices, the wireless network protocol stack, raio signal propagation, an the mobility of the network users. The raio propagation moels use in common MANET simulators assume an obstacle-free area an a free line-of sight between all communicating partners. As a consequence, the communication range is moele by a simple circle aroun the mobile evice. However, this poorly reflects raio wave propagation in a typical outoor scenario, like a city center, in which builings significantly affect the communication between noes. Nevertheless, the vast majority of publications that investigate MANET protocol an Ibrahim khier is assistant professor,suan University of science an technology, Suan, ibrahim_khier@hotmail.com Wang Furong is professor at huazhong university,china. wangfurong@hust.eu.cn Amna saa, suan university,engineer,computer center,suan, ahabsaa@hotmail.com application behavior still rely on such simple moels. Due to the nature of self-organization, the ynamic topology cause by mobility an transmission power control, an the multiple-hop routing in MANETs, it is ifficult to buil a complete analytical moel to stuy the network performance. On the other han, a real testbe is expensive. Therefore, the simulation stuy of MANETs is important. In this paper, we stuy ifferent raio propagation moels using ns-2 [2] because it is open source an is wiely use in both acaemia an inustry. In ns-2 the raio propagation moels have the following features: the Friss-space moel is use for short istances an the approximate two-ray-groun moel is use for long istances. The shaowing moel is employe to characterize the probabilistic multiple path faing uring raio propagation. These moels are consiers ata of the simulation area, which are available from urban. Raio propagation waves are necessary propagation characteristics for any configuration. The s systems are intene to be installe are ranging from inoor up to outoor.hence wave propagation moels are require covering whole range incluing inoor an outoor scenarios. The phenomena which effect raio wave propagation can generally be escribe by five mechanisms as following; Reflection: is the abrupt change in irection of a wave front at an interface between two issimilar meia so that the wave front returns into the meium from which it originate. Reflecting object is large compare to

2 International Journal of Scientific & Engineering Research Volume 2, Issue 1, Oct wavelength. Scattering: is a phenomenon in which the irection (or polarization) of the wave is change when the wave encounters propagation meium iscontinuities smaller than the wavelength results in a isorere or ranom change in the energy istribution. Diffraction: is the mechanism that the waves sprea as they pass barriers in obstructe raio path (through openings or aroun barriers).diffraction is an important when evaluating potential interference between terrestrial an stations sharing the same frequency. Absorption is the conversion of the transmitte EM energy into another form, usually thermal. The conversion takes place as a result of interaction between the incient energy an the material meium, at the molecular or atomic level. One cause of signal attenuation ue to walls, precipitations an atmospheric gases. Refraction: is reirection of a wave front passing through a meium having a refractive inex that is a continuous function of position or through a bounary between two issimilar meia. For two meia of ifferent refractive inices, the angle of refraction is approximate by Snell's Law known from optics penetration. Figure.1 shows these mechanisms. We use an existing implementation of the propagation moel from a specialize tool. We prove that the usage of raio propagation moels change simulation results consierably. The remainer of this paper is structure as follows. In Section II, we present mobility moels. Section III gives an overview of shaowing an ricean moels. Section IV escribes the scenarios in urban area. Section V illustrates the results.section VIconclues this paper. Scattering Reflection Diffraction Fig. 1, the phenomena effect raio wave propagation 2 MOBILITY MODELS A mobility moel is a representation of a certain real or abstract worl that contains moving entities. A mobility moel is usually use to escribe the mobility of an iniviual subscriber. Sometimes it is use to escribe the aggregate pattern of all subscribers. The following iscussion attempts a brief overview of the two commonly use mobility moels to analyze esign systems in wireless a hoc networks, each with a specific goal an suitable for a specific scenario. Ranom Way Point mobility moel (RWP) [3] [4] [5] [6] is a simple, wiely use, moel in the many simulation stuies of a hoc routing protocols. In this moel each noe is assigne an initial position uniformly istribute within a region (rectangular region). Then, each noe chooses a estination uniformly insie the region, an selects a spee uniformly from [minspee, maxspee] inepenently of the chosen estination. That means the istributions of noes spees an locations are stationary. To avoi the transient perio from the beginning, one solution is to choose the noes initial locations an spees accoring to the stationary istribution; another one is to iscar the initial time perio of simulation to reuce the effect of such transient perio on simulation results. The noe then moves towar the chosen estination with the selecte spee along a straight line starting from current waypoint. After reaching the estination, the noe stops for uration calle pause time, an then repeats the proceure. All noes move inepenently of each other at all times. Manhattan moel is use to emulate the noes movement on streets efine by maps [4] [5]. The map is compose of a number of horizontal an vertical streets. Each street has two lanes, one in each irection (North an South for vertical streets, an East an West for horizontal ones). Each noe is only allowe to move along the gri of horizontal an vertical streets. At an intersection of horizontal an vertical streets, a mobile noe can turn left, or right, or go straight with probabilities.25,.25, an.5, respectively. The spee of a mobile noe is temporarily epenent on its previous spee If two mobile noes on the same freeway lane are within the Safety Distance (SD), the velocity of the following noe cannot excee the velocity of preceing noe Mobility moels capture the geographic restrictions. 3 RADIO PROPAGATION MODELS Raio channels are much more complicate to analyze than wire channels. Their characteristics may change rapily an ranomly. There are large ifferences between simple paths with line of sight (LOS) an those which have obstacles like builings or elevations between the sener an the receiver (Non Line of Sight (NLOS)). To implement a channel moel generally two cases are consiere: large-scale an small-scale propagation moels. Large scale propagation moels account for the fact that a raio wave has to cover a growing area when the istance to the sener is increasing. Small scale moels (faing moels) calculate the signal strength epening on small movements or small time frames. Due to multipath propagation of raio waves, small movements of the receiver can have large effects on the receive signal strength. In the following, frequently use propagation raio moels are escribe in more etail. -Shaowing moel: The shaowing moel realizes the log-normal shaowing moel. It is assume that the average receive signal power ecreases logarithmically with istance. A Gaussian ranom variable is ae to this path loss to account for al influences at the sener an the receiver. The shaowing moel consists of two parts. The first one is known as path loss moel, which also preicts the mean receive power at istance, enote by P r It uses a close-in istance as a

3 International Journal of Scientific & Engineering Research Volume 2, Issue 1, Oct reference. follows. P r P r P r is compute relative to P r as is calle the path loss exponent, an is usually empirically etermine by fiel measurement. From Eq. (1) we know that = 2 for free space propagation. Table.1 gives some typical values of larger values correspon to more obstructions an hence faster ecrease in average P receive power as istance becomes larger. r can be compute from Eq. (1). The path loss is usually measure in. So from Eq. (1) we have Pr Pr 1 log (2) The secon part of the shaowing moel reflects the variation of the receive power at certain istance. It is a log-normal ranom variable that is; it is of Gaussian istribution if measure in. The overall shaowing moel is represente by Pr Pr 1 log X (1). (3) Where X is a Gaussian ranom variable with zero mean an stanar eviation. is calle the shaowing eviation, an is also obtaine by measurement. Table.2 shows some typical values of (). Eq. (3) is also known as a log-normal shaowing moel. The shaowing moel extens the ieal circle moel to a richer statistic moel: noes can only probabilistically communicate when near the ege of the communication range [7] [8] [9] [1]. Table.1 Some Typical values of path loss Environment Outoor Free space 2 In builing Shaowe urban 2.7 to 5 area Line-of-sight 1.6 to 1.8 Obstructe 4 to 6 Table.2 Some Typical values of shaowing eviation Environment Outoor 4 to 12 Office, har partition 7 Office, soft partition 9.6 Factory, line-of-sight 3 to 6 Factory, obstructe 6.8 () -Ricean faing moel: This moel is faing moel, meaning that it escribes the time-correlation of the receive signal power. Faing is mostly cause by multipath propagation of the raio waves that means faing is the result of variation (with time) of the amplitue or relative phase, or both, of one or more of the frequency components of the signal because of changes in the characteristics of the propagation path with time.the factors that affect faing inclue motion, transmission banwith of signal compare to banwith of channel an multipath propagation.. If there is one ominant (line of sight) path an multiple inirect signals, Ricean faing occurs [1]. The PDF of the Ricean istribution is given by: 2 2 r r exp A Ar p r r A,r (4) Where A is peak amplitue of the ominant signal,i() represents a moifie Bessel function of the first kin an r is the mean value of the ricean istribution. DESCRPTION OF URBAN area SCENARIOS To evaluate the impact of the raio wave propagation moel on the performance of a Mobile A Hoc Network the throughput an elay of multiple constant bit rate (CBR) streams is taken as an inicator. Measurements conucte by several researchers show that most simulators give too goo values for these metrics. So any preiction erive from this simulation that concerns real networks is base on false assumptions. In this work, two scenarios are simulate in etail. They represent very ifferent working s. One is an inoor scenario with low mobility. The secon one is an outoor scenario simulating peestrian walking through a city. This scenario is characterize by hostile for raio waves. Both scenarios share some similarities: Network traffic is create by starting CBR connections between ranomly selecte noes. The simulation uration is 9 sec. We have implemente a shaowing moel as raio propagation moel with values of the path loss exponent 5 an the shaowing eviation 4.For ricean faing moel we use k factor 6 an value of maximum spee 2.5 m/sec. We ran our simulations with movement patterns generate for 6 ifferent maximum spees, 1, 2, 3, 4, 5, 6 m/s with

4 International Journal of Scientific & Engineering Research Volume 2, Issue 1, Oct environme nt constant pause time 2. sec an 7 ifferent pause times,, 5, 1, 2,3,4,5 secons with constant spee 5m/sec. This part introuces scenarios of urban area which is ivie in two parts as following: - scenario:the inoor scenario is conucte on a simulation area whose layout shown in fig.1. For this layout a map with 2D an some measurements of the raio signal strength exists on an area of 1m 1m. The movement for the noes is create using ranom waypoint moel. Noes moving insie builing have a very low mobility. Their pause time is equally istribute. The movement spee is istribute uniformly. The number of noes in a scenario is ten. The maximum number of CBR connections is set to ten; the offere loa per connection is 512Byte/s. Outoor scenario:the outoor scenario is base on the street map of city, when the noes are on the street, they move as Manhattan mobility moel movement pattern. The Builings act as obstacles for the raio waves an narrow streets may act as wave guies. Builings have high attenuation but o not completely block the signal. The movement noes are ivie in two groups epening on their spee a peestrian group with a low spee an a vehicular group with a higher spee. The peestrian group of users is moving with a normal istribute spee with a mean of 3 km/h an a stanar eviation of.3 km/h [4]. The vehicular group of users has also a normal istribute spee but with a mean of 5 km/h an a stanar eviation of 2.5 km/h. At each cross-roa, users of both groups have can either continue straight with the probability Pr (straight) =.5 or turn left/right with the probability Pr (right) = Pr (right) =.25. In this paper the area is wrappe aroun North-South an West-East an the gri is compose of 3 by 3 builings. The builings are 3x3 m an the street has two opposite lane, the istance between lane 1 m an the with of lane 6 meter. The movements of a noe switch from one mobility moel to another base on its location in urban.fig.2 shows the movement of noes in simulation area. Outoor Fig. 3, movement of noes in simulation fiel With 9 base stations 4 SIMULATION RESULTS The analysis of simulation results is performe base on the stanar metrics of number of sent packets, throughput, number of roppe packets, packet elivery ratio an packet routing overhea between ifferent raio propagation moels. We conucte our simulations on changing the parameters for mobile noes' movement scenarios an their connection pattern files. We suppose ifferent spee an pause time for movement scenarios files.figure.4 inicates that shaowing moel sens very few packets; ricean faing sen high packets. Figure.5; shows that ricean is better performance than shaowing moel when throughput is consiere as metric.in contrast, shaowing raio propagation moel rops few packets as shown in figure.6, although the results inicate that its throughput is lower than ricean faing moel. Figure.7 evaluates the reliability of packet elivery ratio. In comparison to ricean faing moel, the results in Figure.7 inicate that shaowing raio propagation moel is low with respect to the measure elivery rate. Our results in Figure.8 show that ricean faing an shaowing propagation moels perform consistently well with respect to routing overhea (routing overhea equal zero). environmen t Outoor fig. 2, Layout of MANET 3X3 urban

5 International Journal of Scientific & Engineering Research Volume 2, Issue 1, Oct Fig. 5, Throughput Vs Max Spee, Pause Time Fig. 4, packet sent Vs Max Spee, Pause Time Fig. 6, Packet Droppe Vs Max Spee, Pause Time

6 International Journal of Scientific & Engineering Research Volume 2, Issue 1, Oct Fig. 8, Routing Overhea Vs Max Spee, Pause Time 5 CONCLUSION Fig. 7, Packet Delivery ratio Vs Max Spee, Pause Time The area of a hoc networking has been receiving increasing attention among researchers in recent years, as the available wireless networking an mobile computing harware bases are now capable of supporting the promise of this technology. In this paper, we have use pattern compoun of more sophisticate mechanisms to moel mobility that contribute to make the simulation realistic. We introuce urban which inclue inoor an outoor using integrate mobility moels. We use our simulation moel to stuy some general characteristics of urban s an their impact on MANET performance. We investigate some important issues relate to the simulation an use of MANETs in urban s supporte with base stations. We have presente a raio wave propagation moels showe how these moels affect the performance of Mobile A Hoc Networks in urban area. We present the options available an provie the parameters use in the creation of scenarios for inoor an outoor s in an urban. We showe the effect of raio propagation moels for wave propagation. We emonstrate that the usage of more accurate raio propagation moels change simulate topologies consierably between commonly use propagation moels. Consequently, we obtain ifferent performance evaluation results. We compare raio propagation moels performance variety of metrics, Packets sent, throughput, roppe packets, Packet Delivery Ratio, an packet routing overhea. For movement scenarios case, we suppose maximum spee an pause time. Researchers must be aware of significant ifference between the real connection topologies an the topologies obtaine with simple moels offere by MANET simulation tools. For obtaining quantitative performance evaluation results in the

7 International Journal of Scientific & Engineering Research Volume 2, Issue 1, Oct target area, more accurate raio propagation moels nee to be use. REFERENCES [1]Xiang Zeng, Rajive Bagroia, Mario Gerla, Library for Parallel Simulation of Large-scale Wireless Networks", [2] Jae Chung,Mark Claypool, ns by example [3] J. Yoon, M. Liu, an B. Noble, Soun Mobility Moels, in Proc. ACM/IEEE Int l Conf. Mobile Computing an Networking (MOBICOM 3), pp , September23. [4] F. Bai, N. Saagopan, an A. Helmy, IMPORTANT: A framework to systematically analyze the Impact of Mobility on Performance of RouTing protocols for Ahoc NeTworks, in IEEE INFOCOM 3, San Francisco, March/April, 23. [5] F. Bai an A. Helmy, A Survey of Mobility Moeling an Analysis in Wireless Ahoc Networks,chapter 1,University of southern California,USA. [6]W. Navii an T. Camp, Stationary Distributions for the Ranom Waypoint Mobility Moel, IEEE Transactions on Mobile Computing ITMMC-3 (24), pp [7]Ingo Gruber, Oliver Knauf an Hui Li, Performance of A Hoc Routing Protocols in Urban Environments, In Proceeings of European Wireless 24 (EW'24, Barcelona, Spain,February24-27,24. [8] kavein fall,kannan varahan, ns-manual S2/noe196.html [9]WeiYe, raio propagation moels [1]Arne Schmitz, Martin Wenig, The Effect of the Raio Wave Propagation Moel in Mobile A Hoc Networks, Torremolinos, Malaga, Spain,MSWiM 6, October 2 6, 26.