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Statistical performance analysis of wireless communication in public transports


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  • 1. International Journal of Computer Engineering and Technology (IJCET), ISSN 0976-6367(Print), ISSN 0976 – 6375(Online) Volume 4, Issue 2, March – April (2013), © IAEME290STATISTICAL PERFORMANCE ANALYSIS OF WIRELESSCOMMUNICATION IN PUBLIC TRANSPORTS & IMPROVINGPERFORMANCE THROUGHINTEGRATED HETEROGENEOUS NETWORKArindam Banerjee1, Prof. Siladitya Sen21(Electronics & Communication Engineering Department, Heritage Institute of Technology,Kolkata, West Bengal, India)2(Electronics & Communication Engineering Department, Heritage Institute of Technology,Kolkata, West Bengal, India)ABSTRACTThere are many mobile subscribers in metropolition areas travelling in local trains.Subscribers face lot of problems to make a call while in motion. In metro (underground)railways, sometime there is no network coverage & inside local trains the voice quality is notclear along with network problems. This paper focusses on causes behind these problems.This also analyzes the performance after implementing heterogeneous network in high speedpublic transports.Using heterogeneous network, the problems of network coverage, networkconjunctions etc will reduced enrormously. In this case there is intelligent integrator networkso call establishment time will reduced and the End to End delay will reduce. Cunulativelythe QoS of Wireless network is increased. Therefore a performance comparision is alsocarried out in this paper. Such networks not only improve the performance of voice & datacommunication but also improves network security.Keywords : End to End Delay, high speed, Integrated Heterogeneous Network, MobileUsers, Voice Quality.1. INTRODUCTIONIn past decade the telecom industry has been revolutionized by advancingtechnologies. Advancing in technology simultaneously improve network capacity & networkperformance. There are several wireless systems are in practice, like cellular [1], Wi-Fi [2],INTERNATIONAL JOURNAL OF COMPUTER ENGINEERING& TECHNOLOGY (IJCET)ISSN 0976 – 6367(Print)ISSN 0976 – 6375(Online)Volume 4, Issue 2, March – April (2013), pp. 290-299© IAEME: Impact Factor (2013): 6.1302 (Calculated by GISI)www.jifactor.comIJCET© I A E M E
  • 2. International Journal of Computer Engineering and Technology (IJCET), ISSN 0976-6367(Print), ISSN 0976 – 6375(Online) Volume 4, Issue 2, March – April (2013), © IAEME291and WiMAX [3,4] etc. Each system uses its own spectrum as prescribed by law ofinternational body to avoid interference & other technical problems. Also, these wirelesscommunication systems operate independently, because the mechanisms of these systems arefundamentally different. Therefore there is a manual switching systems among them. But inmanual shift may cause call drops & interruption in communication. To avoid thisinconvenience, an integrated network [5, 6], within which these systems can interwork, hasbeen designed for next generation wireless communication system. In such an integratednetwork, mobile users can have seamless, continuous communication via the best availableservice providing system with optimum uses of radio resources. Although the amount ofavailable radio spectrum for a particular form of wireless communication is decreasingbecause of the increasing diversity of wireless networks, the traffic demand for wirelessnetworks is increasing with the increasing variety of broadband applications [7,8]. In thisscenario quality of service in high speed public transports like bus trains are still belowaverage for mobile voice & data communication network. Call drops, jitter, delay are high forexisting network.An integrated network is designed to solve the problem for trains & statistical analysis ofthe system also present in this paper.2. NETWORK INTEGRATIONIn this proposed network architecture two types of internetworking exists. Wi-Fi/WiMAX internetworking & WiMAX/GSM inter networking. A call will route Wi-Fi toGSM network via WiMAX network in case of trains or directly in case of buses. Two typesof interworking architecture approaches exist. They are tight couple loose couple and [9] and[10] architecture.2.1.Tight couple schemeThis scheme integrates two networks at the radio access network- core network level,making the two different access technologies to work in unity with a single core network.Considering the GSM and mobile WiMAX networks, in tight couple mode, the data streamsof WiMAX must traverse the in Network Coupler and the core network of GSM. This meansthat each of these networks will have to modify their interfaces, protocols, and services inorder to meet the interworking requirements. This mode reduces latency in handover andensures seamless handover [11, 12].2.2.Loose couple schemeThe loose couple interworking scheme offers a shared or joint interface for informationexchanges between the two networks. WiMAX uses the AAA (Authentication,Authorization, Accounting) server of UMTS network, and unlike the tight couple, datastreams do not traverse the UMTS core network. This mode guarantees WiMAX networkindependence but has high latency during handover [11, 13]. This makes it unsuitable forreal-time services following researches of handover between WLAN and UMTS [13].
  • 3. International Journal of Computer Engineering and Technology (IJCET), ISSN 0976-6367(Print), ISSN 0976 – 6375(Online) Volume 4, Issue 2, March – April (2013), © IAEME2923. NETWORK MANAGEMENTThere are many steps involved in network management. Spectrum assignment is thefirst step of it. As in public transport like train or bus numbers of passengers are variable thenrequirement of radio resources is a time varying function. While we incorporate manynetworks so maintaining proper throughput for overall network is one of the major criteria.At a particular time system calculate instantaneous load i(t) or i in a sub-network(a networkdominate by a Wi-Fi access point). Let there are n number of sub-network (s) then totalinstantaneous load of the system:I(t)= ( )1nsi ts=∑ … (1).Network conjunction occurred after a threshold value l for sub network & L for totalnetwork. so after l’ (l’<l) & L’ (L’<L) system ask for extra channel so that network can workproperly when threshold value become la (la<l’) & La (La<L’) extra assigned channels willreturn.THROUGHPUTWi-Fi= ……….. (2)n is number of Wi-Fi stations, Us is the used capacity of Wi-Fi system & Cs is the totalcapacity of the Wi-Fi system. Combine throughput for WiFi & WiMAX system will beTHROUGHPUT WiFi/WiMAX= 11( )1( )nssnssssI t uCUI t ucu==     ×   ∑∑….. (3)C’ & U’ are ideally total capacity & used capacity of a WiMAX system. But this through putwill degraded due to different kind of losses like velocity, different geographical scenario etc& which will be denoted by DL. Therefore available throughput will be,THROUGHPUT WiFi/WiMAX= 11( )1( )nssn LssssI t uCDUI t ucu==     − ×   ∑∑……. (4)( ) ( )L L L LD P V t E t= + + ….. (5)11( )1( )nssnssssI t uI t ucu==×∑∑
  • 4. International Journal of Computer Engineering and Technology (IJCET), ISSN 0976-6367(Print), ISSN 0976 – 6375(Online) Volume 4, Issue 2, March – April (2013), © IAEME293PL stands for propagation loss which is a constant & unavoidable factor which includes lossesdue to Transmitters & Receivers designing. VL is velocity losses. EL is extra environmentallosses depends on different kind of fading, obstacles, propagation model. Both VL & EL aretime varying so DL can also represented as a time varying factor DL(t). In wirelesscommunication channels there are two types of fading effects those areI. Large Scale FadingII. Small Scale FadingLarge-scale fading which depends on distance, is the slow variation of the meansignal power over time. Also this depends on the presence of obstacles in the signal path andon the position of the mobile unit. The large-scale fading is assumed to be a slow process andis commonly modeled as having lognormal statistics [14, 15].Small-scale fading is also called Rayleigh or Rician fading because if a large numberof reflective paths is encountered the received signal envelope is described by a Rayleigh or aRician probability density function (PDF) [16]. The small-scale fading under consideration isassumed to be a flat fading where there is no inter-symbol interference. It is also assumed thatthe fading level remains approximately constant for (at least) one signaling interval. With thismodel of fading channel the main difference with respect to an AWGN channel resides in thefact that fading amplitudes are now Rayleigh or Rician distributed random variables, whosevalues affect the signal amplitude (and, hence, the power) of the received signal. The fadingamplitudes can be modeled by a Rician or a Rayleigh distribution, depending on the presenceor absence of specular signal component. Fading is Rayleigh if the multiple reflective pathsare large in number and there is no dominant line-of-sight (LOS) propagation path. If there isalso a dominant LOS path, then the fading is Rician distributed The fading amplitude ri at theithtime instant can be represented as( )2 2r x yii iβ= + + ………… (6)where β is the amplitude of the specular component and xi, yi are samples of zero-meanstationary Gaussian random processes each with variance σ02. The ratio of specular to defuseenergy defines the so-called Rician K-factor, which is given by2202Kβσ= …………. (7)The best- and worst-case Rician fading channels associated with K-factors of K = ∞ and K =0 are the Gaussian and Rayleigh channels with strong LOS and no LOS path, respectively.So, the Rayleigh fading channel can be considered as a special case of a Rician fadingchannel with K = 0. The Rician PDF is given by [16]( ) ( )22 20 02 200exp / 2Ricer rf r r Iββ σσ σ  = − +    …. (8) 0r ≥
  • 5. International Journal of Computer Engineering and Technology (IJCET), ISSN 0976-6367(Print), ISSN 0976 – 6375(Online) Volume 4, Issue 2, March – April (2013), © IAEME294Where I0 is the zero-order modified Bessel function of the first kind. Now, if there is nodominant propagation path, K = 0 and I0 = 1 yielding the worst-case Rayleigh PDF( )22 20 0exp2Rayleighr rf rσ σ− =   ……. ..(9) 0r ≥The Rician Cumulative Distribution Function (CDF) takes the shape of [16]( ) ( ) 20 01 exp ImRicemmrC rrβ βγσ∞=   = − −       ∑ …… (10)Where γ = (K + r2/ 2σ02). Clearly, this formula is more difficult to evaluate than the PDF of(8) due to the summation of an infinite number of terms. However, in practical terms it issufficient to increase m to the value, where the last terms contribution becomes less than 0.1percent. Having described the main fading statistics let us consider the effects of the Dopplerfrequency shift. Doppler shift from the carrier frequency fc occurs when the distance betweenthe mobile receiver and the transmitter is changing. The magnitude of the Doppler frequencyshift fm is determined bycvffm C= …… (11)where ν is the mobile station velocity and c = 3⋅108 m/s is the speed of light. The Dopplerfrequency fm is often called fading bandwidth or fading fate of the channel. The relationshipbetween Fm and the coherence time Tm of the channel (i.e., the time over which thechannel’s response to a sinusoid is essentially invariant) is given by [17]0.5Tmfm≈ ……… (12)The Doppler power spectral density S(f) of the mobile channel is often expressed as( )( )211 /S ff f fmmπ=−……. (13)The above equality holds for frequency shifts of f in the range ±fm about the carrierfrequency fc. Some important notes are in order here. First, the primary factor, which affectsthe performance of digital communication systems in a mobile environment, is the small-scale fading. So, we will consider Rayleigh and Rician fading channels from now on[18, 19].There is also scattering effects but which can be neglected if the scattered wave power isknown.There is also scattering effects which can be neglected if the scattered wave power is known.Standered deviation of fading is given by
  • 6. International Journal of Computer Engineering and Technology (IJCET), ISSN 0976-6367(Print), ISSN 0976 – 6375(Online) Volume 4, Issue 2, March – April (2013), © IAEME295[ ]211( ) ( )ne i d iiM d M dnσ== −∑…….(14)( )e iM d is the path loss value at a distance id & Md(di) is a veriable which is given by010( ) logddd iM d k   = − ……… (15)3.1. Hand off ManagementIn this network both horizontal & vertical hand offs are to be managed. When themobile terminal switching between the networks with the same technology (WiMAX toWiMax) this process called horizontal hand-off (HHO). When the mobile users switching indifferent networks which have different technology (GSM to WiFi) the vertical hand-off(VHO) occur. As the there is fixed path in railway so horizontal hand offs can be managedpre calculated manner. But then also unpredictability of microwave radiation may createproblem in network coverage as shown in fig 1. Where pre-calculation predict a normal handoff between A to C. But due to the radiation pattern, at hand-off point there is no networkcoverage by C. Therefore mobile system itself find available network and register in it.Figure 1: Schamatic Diagram of Radiation PatternSo there must be an inbuilt network scanning algorithm in mobile system employing throughWiMAX.
  • 7. International Journal of Computer Engineering and Technology (IJCET), ISSN 0976-6367(Print), ISSN 0976 – 6375(Online) Volume 4, Issue 2, March – April (2013), © IAEME2963.1.1. Proposed Mixed Algorithm for Horizontal Hand offsIf T Ts≥ // actual time is greater than or equal to the schedule time for hand offIf RC< Rmin // Radiation coverage provided by C is less than min requirementIf N SS S∈ // services required for mobile network is belongs to the service setMS send the request to hand off(CHECK THE BANDWIDTH AVAILABILITY/ NETWORK CAPACITY)CASE 1:11 N nn n b nnmnm b B A m b AvailableBandwidth+==+ + ≤∑∑Accept in NetworkCASE 2:1Nn n bnm b B A AvailableBandwidth=+ + ≤∑Accept in NetworkElse Reject the requestElse Continue ScanningElse Hand off in CElse Wait for time3.1.2. Proposed Algorithm for Virtical Hand offThis network will follow a location and power based hand off algorithm between GSM & WiFinetworkCHECK THE LOCATIONIF PL =DLN // Subscriber location is near to Wi-Fi zone or max power form other WiFiIf Active Call=0!Hand off: Start Hand Off sequencingElse wait (either PL=DL or Active Call=0)Goto Hand off;End3.2. Intelligent Searching of Receiver NumberFig 2: Schematic Diagram of Network
  • 8. International Journal of Computer Engineering and Technology (IJCET), ISSN 0976-6367(Print), ISSN 0976 – 6375(Online) Volume 4, Issue 2, March – April (2013), © IAEME297In every compartment of a train there will be two three access points which will beconnected with a Wi-Fi service providing network. There will be one such network in each coachthose are connected with WiFi/WiMAX integrator or the main service provider in train. Thisintegrator also maintain connection with WiMAX Base Stations. In this scenario a MS wants tomake a call. There are three probabilities-I. Both the user are in same compartmentII. Both the users are in same trainIII. Both the users are in different locationsTraditional systems use same mechanism to find called party it may consume unnecessaryfew seconds for first two cases. For a compartment there maximum capacity of passengers will be100~120 or 150. Let assume there are 12 coaches. Maximum number of load will be 1200~1440or 1500 users. Therefore in network there will be two extra VLR. One with WiFi networkprovider in compartment other with the network integrator. This are special type VLR where theother information like call rate, plans, other call management issues etc can be stored. Incompartment the memory stack is divided with respect to the number of access points. Thememory of VLR with integrator is divided with respect to the number of coaches. Therefore inintelligent searching mechanism while a call request is forwarding then the call request beforeproceeding to regular MSC it activated two pointers for two VLR simultaniously. A parallelsearching mechanism is carried out in memories. But in integrator VLR searching will be omittedfor the memory from which the call is forwarded. If any one among two pointer is successful totrace the user the call will established. As there is processors in GHz frequency so searching 150or (150x11) stack take much less time than traditional system. Which will decreases end to enddelay & increase throughput.4. PERFORMANCE ANALYSISIn traditional wireless network the jitter will vary due to surrounding cercumstances,velocity of train, wind, number of subscribers, geographical conditions etc. So the Jitter is quitehigh for traditional network in fig 3 represented in red line. Same thing occur in the case ofthroughput. Throughput is fluctuating for traditional network. For the integrated networkapproximation of 0.12% is taken and the throughput remain constant. In integrated network thethroughput is constantly high because it use Wi-Fi throughput which is high. Flat & low jitter,with low end to end delay helps to achieve this performance.Figure 3: Jitter Comparision Figure 4: Average Throughput Comparision
  • 9. International Journal of Computer Engineering and Technology (IJCET), ISSN 0976-6367(Print), ISSN 0976 – 6375(Online) Volume 4, Issue 2, March – April (2013), © IAEME298Figure 5: Reduction Of Average End To End DelayIn case of end to end delay 100 calls taking randomly in same train for 1500 users it showsbetter reduced performance. This reduction directly impact on throughput.5. CONCLUSIONUsing heterogeneous network is the best solution for handling the increasing load ofsubscribers. This proposed network shows better performance in terms of low & flat jitter,high & constant throughput, low end to end delay. Therefore the quality of service is alsoincreased. Such network can be applied for security like explosive detection, & other securitymeasure by just adding distributed sensor array with this network. This is conclude that thisheterogeneous network can able to solve the voice clearity problem for the subscriberstravelling in train. For Indian scenario this is very important as many people travelling trainsin Mumbai, Kolkata, etc metropolition cities.REFERENCES[1] 3GPP,[2] WiFi Forum,[3] “Air Interface for Fixed Broadband Wireless Access Systems,” IEEE STD 802.16–2004.,(Oct. 2004).[4] “Air Interface for Fixed and Mobile Broadband Wireless Access Systems,” IEEEP802.16e/D12., (Feb. 2005).[5] S. Ohmori, Y. Yamao and N. Nakajima, “The Future Generations of MobileCommunications Based on Broadband Access Technologies,” IEEE CommunicationsMagazine, vol. 38, no. 12, pp. 134–142, (Dec. 2000).[6] M. Buddhikot, G. Chandranmenon, S. Han, Y.W. Lee, S. Miller and L. Salgarelli,“Integration of 802.11 and Third-Generation Wireless Data Networks,” IEEE INFOCOM’03,vol. 1, pp. 503–512, (Apr. 2003).
  • 10. International Journal of Computer Engineering and Technology (IJCET), ISSN 0976-6367(Print), ISSN 0976 – 6375(Online) Volume 4, Issue 2, March – April (2013), © IAEME299[7] J. Mitola III and G. Q. Maguire, “Cognitive Radio: Making Software Radios MorePersonal,” IEEE Personal Communications, vol. 6, no. 4, pp. 13–14, (Aug. 1999).[8] I.F. Akyildiz, et al., “Next generation/dynamic spectrum access/ cognitive radio wirelessnetworks: A survey,” Computer Networks Journal, vol. 50, pp. 2127–2159, (Sept. 2006).[9] T. Shiao-Li and L. Chia-Ching, "Design and Evaluation of UMTS-WLAN InterworkingStrategies," in Vehicular Technology Conference, 2002. Proceedings. VTC 2002-Fall.2002 IEEE 56th, 2002, pp. 777-781 vol.2.[10] M. Jaseemuddin, "An Architecture for Integrating UMTS and 802.11 WLANNetworks," in Computers and Communication, 2003. (ISCC 2003). Proceedings. EighthIEEE International Symposium on, 2003, pp. 716-723 vol.2.[11] N.-V. Quoc-Thinh, et al., "An Architecture for UMTS-WIMAX Interworking," inBroadband Convergence Networks, 2006. BcN 2006. The 1st International Workshop on,2006, pp. 1-10.[12] X. Fangmin, et al., "Interworking of Wimax and 3GPP Networks Based on IMS [IPMultimedia Systems (IMS) Infrastructure and Services]," Communications Magazine, IEEE,vol. 45, pp. 144-150, 2007.[13] S. Jee-young, et al., "Hybrid Coupling Scheme for UMTS and Wireless LANInterworking," in Vehicular Technology Conference, 2003. VTC 2003-Fall. 2003 IEEE 58th,2003, pp. 2247- 2251 Vol.4.[14] SKLAR, B. Rayleigh fading channels in mobile digital communication systems, Part I:Characterization. IEEE Communications Maga-zine, 1997, vol. 35, no. 7, p. 90 - 100.[15] SUZUKI, H. A statistical model for urban radio propagation. IEEE Transactions onCommunications, 1977, vol. COM-25, no. 7, p. 673 to 680.[16] PROAKIS, J. G. Digital communications. 2nd ed. New York: McGraw-Hill, 1989.[17] SKLAR, B. Rayleigh fading channels in mobile digital communica-tion systems, Part I:Characterization. IEEE Communications Maga-zine, 1997, vol. 35, no. 7, p. 90 - 100.[18] JAKES, W. C. Microwave mobile communications. New York: Wiley, 1974.[19] ZHENG, Y., R., XIAO, C. Improved models for the generation of multiple uncorrelatedRayleigh fading waveforms. IEEE Communi-cations Letters, 2002, vol. 6, no. 6, p. 256 - 258.[20] T.Regu and Dr.G.Kalivarathan, “Prediction of Wireless Communication Systems in theContext of Modeling” International journal of Electronics and Communication Engineering&Technology (IJECET), Volume 4, Issue 1, 2013, pp. 11 - 17, ISSN Print: 0976-6464, ISSNOnline: 0976-6472.[21] Kamatham Harikrishna and T. Rama Rao, “An Efficient Radix-22 FFT for Fixed &Mobile Wimax Communication Systems”, International journal of Electronics andCommunication Engineering &Technology (IJECET), Volume 3, Issue 3, 2012,pp. 265 - 279, ISSN Print: 0976-6464, ISSN Online: 0976-6472.[22] S. B. Patil, S. M. Deshmukh, Dr. Preeti Patil and Bhargava Shuchita, “InformationSystem Through a Heterogeneous Wireless Technologies and Services: Detect UnwantedAttempts at Accessing, Manipulating and Disabling by Enforcement of Security”International Journal of Information Technology and Management Information Systems(IJITMIS), Volume 3, Issue 1, 2012, pp. 8 - 14, ISSN Print: 0976 – 6405, ISSN Online: 0976– 6413.[23] Sonia and Satinder Pal, “An Effective Approach to Contention Based BandwidthRequest Mechanism in Wimax Networks”, International journal of Computer Engineering &Technology (IJCET), Volume 3, Issue 2, 2012, pp. 603 - 620, ISSN Print: 0976 – 6367,ISSN Online: 0976 – 6375.