An Optimized Algorithm to Adjust the Channel Quality in HSDPA Network

2013, I J ARCSSE All Rights ReservedPage | 184 Volume 3, Issue 2, February 2013ISSN: 2277 128X International Journal of Advanced Research in Computer Science and Software Engineering Research Paper Available online at: www.ijarcsse.com An optimized Algorithm to adjust the Channel Quality in HSDPA Network Nagendar Yamsani1, Govindavaram Madhu Sri2, Sathish Kumar Konga3 and Sangameswar Kanugula4 1Assistant Professor, SR Engineering College, Warangal, AP, INDIA 2Assistant Professor, University Post Graduate College, Kakatiya University, Warangal, AP, INDIA 3Dept. of Comp. Science (School of Computing), Debre Birhan University, ETHIOPIA 4SR Engineering College, Warangal, AP, INDIA Abstract We investigate single user throughput optimization in High Speed Downlink Packet Access (HSDPA). Specifically, we propose offline and online optimization algorithms which adjust the Channel Quality I ndicator (CQI ) used by the network for scheduling of data transmission. I n the offline algorithm, a given target block error rate (BLER) is achieved by adjusting CQIbased on ACK/NAK history. By sweeping through different target BLERs, we can find the throughput optimal BLER offline. This algorithm could be used not only to optimize throughput but also to enable fair resource allocation among multiple users in HSDPA. I n the online algorithm, the CQIoffset is adapted usinganestimatedshorttermthroughputgradientwithouttheneedforatargetBLER.Anadaptivestepsize mechanism is proposed to track temporal variation of the environment. Convergence behaviour of both algorithms is analyzed.Thepartoftheanalysisthatdealswithconstantstepsizegradientalgorithmmaybeappliedtoother stochastic optimization techniques. The convergence analysis is confirmed by our simulations. Simulation results also yield valuable insights on the value of optimal BLER target. Both offline and online algorithms are shown to yield up to 25% of throughput improvement over the conventional approach of targeting 10% BLER. Keywords Data transmission, Packet, Optimization, Wireless Network. I. Introduction Thesuccessof3rdgenerationwirelesscellularnetworksismainlybasedonefficientprovisioningoftheexpected wide variety of services requiring different Quality of Service with respect to data rate, delay and error rate. In order to improvesupportforhighdataratepacketswitchedservices,3GPPhasdevelopedanevolutionofUMTSbasedon WCDMA known as High Speed Downlink Packet Access (HSDPA) which was included in the Release 5 specifications. HSDPAtargetsincreasedcapacity,reducedroundtripdelay,andhigherpeakdownlink(DL)datarates.Evolutionsof HSDPA featuring data rates up to 84 Mbps are under development. InHSDPA,theuserequipment(UE)(alsoknownasmobilestation)monitorsthequalityofthedownlinkwireless channelandperiodicallyreportsthisinformationtothebasestation(referredtohereasNodeB)ontheuplink.This feedback, called Channel Quality Indicator (CQI), is an indication of the highest data rate that the UE can reliably receive intheexistingconditionsonthedownlinkwirelesschannel.ThefrequencyofreportingCQIisconfiguredbythe network, and is typicallysetto once everyfewmilliseconds. Using thechannelquality reports, theNodeB accordingly schedulesdataontheHighSpeedPhysicalDownlinkSharedChannel(HS-PDSCH).TheNodeBsselectionofthe transport block size(numberof information bits per packet), number of channelization codes,modulation and resource allocation choices such as HS-PDSCH transmit power allocation are guided by the NodeBs interpretation of the reported CQI.CQI reports areintended to accurately reflecttheHSPDSCHperformance thattheUE can support in theexisting wirelesschannelconditions.Itisrecommendedinthat,instaticchannelconditions,theUEreportCQIsuchthatit achievesablockerrorrate(BLER)closeto10%whenscheduleddatacorrespondingtothemedianreportedCQI.In practice,theaccuracyofCQIreportsinreflectingHS-PDSCHperformanceisinfluencedbythewirelesschannel conditions such as the speed of the mobile user and the dispersive nature of the channel. Achieving a certain target BLER atagivenscheduleddataraterequiresdifferentaverageHS-DSCHSNRunderdifferentchannelconditions.Also,the NodeBoftenusesdifferenttransportblocksizes,numberofcodesandmodulation,collectivelyreferredtoasthe transport format resource combination (TFRC), to achieve similar data rates. The exact choice of TFRC that the NodeB usesaffectstherequiredHS-PDSCHSNRtoachieveacertaintargetBLER.Thisvariabilitysmaycausetheactual BLERtodeviatefromthe10%target.Moreover,the10%targetBLERmaynotyieldmaximumthroughputunderall conditions of the wireless channel. The cell throughput optimization in HSDPA can be considered a two part problem: one is code and power allocation across users and the other is maximizing the link throughput for each user for a given resource allocation. In this paper, wefocusonthelinkthroughputoptimizationandconsiderthroughputoptimizationthroughsimpleadjustmentstothe reported CQI. We propose offline and online algorithms for adjusting the CQI. In the offline algorithm, we first propose Nagendaret al., I nternational J ournal of Advanced Research in Computer Science and Software Engineering 3(2), February- 2013, pp. 184-194 2013, I J ARCSSE All Rights ReservedPage | 185 anadaptivealgorithmtoachieveagiventargetBLERusingthestochasticgradientdescentmethod,whichadjuststhe CQIoffsetadaptivelybasedontheshorttermBLERobtainedfromtheACK/NACKhistory.Bysearchingthrough different target BLERs, we can find the throughput optimal BLER offline. The proposed algorithm can be implemented attheUE aswell as at theNodeB. When applied attheNodeB, in addition to achieving thetargetBLER, it can also savetransmitpower.ThisalgorithmcouldbeusednotonlytorefineCQI-BLERalignmentbutalsotoenablefair resource allocation among mobile users in HSDPA. Standard stochastic approximation (SA) algorithms typically require a decreasing step size. We show the convergence of the offline algorithm with a constant step size. In the online algorithm, we use a variation of the Kiefer-Wolfowitz algorithm in SA, which does not need to specify a target BLER. The CQI offset is adapted gradually using an estimated short term throughput gradient. Unlike, the stepsize intheproposedalgorithmdoesnotdecreasetozero.Inaddition,anadaptivestepsizemechanismisproposedtotrack temporal variation of the environment. With a constant step size, we show that the proposed online algorithm converges toasmallneighborhoodofthelocaloptimalsolution.Oursimulationresultsshowthattheproposedofflinealgorithm can achieve the given target BLER with good accuracy. Both throughput optimization algorithms are shown to improve the throughput by up to 30% in simulation. The throughput optimal BLER is calculated for popular channel path profiles. Ingeneral,thethroughputoptimalBLERisnotalways10%anddependsonthechannelpathprofile.ForAWGN channels,itisabout10%,asisimpliedin.ConsideringthattheUEimplementationinthesimulationcloselymirrors commercially shipping devices and already includes several receiver optimizations, the additional gain obtained through the algorithm is indicative of potential HSDPA throughput enhancement realizable in practice. II. Related Work Literaturesurveyisthemostimportantstepinsoftwaredevelopmentprocess.Beforedevelopingthetoolitis necessary to determine the time factor, economy n company strength. Once these things are satisfied, then next steps is to determinewhichoperatingsystemandlanguagecanbeusedfordevelopingthetool.Oncetheprogrammersstart building the tool the programmers need lot of external support. This support can be obtained from senior programmers, from book or from websites. Before building the system the above consideration r taken into account for developing the proposed system. WehavetoanalysistheNetworking:Intheworldofcomputers,networkingisthepracticeoflinkingtwoormore computingdevicestogetherforthepurposeofsharingdata.Networksarebuiltwithamixofcomputerhardwareand computer software. Networksconsistofthecomputers,wiring,andotherdevices,suchashubs,switchesandroutersthatmakeupthe networkinfrastructure.Somedevices,suchasnetworkinterfacecards,serveasthecomputersconnectiontothe network.Devicessuchasswitchesandroutersprovidetraffic-controlstrategiesforthenetwork.Allsortsofdifferent technologies can actually be employed to move datafrom one place to another, including wires, radio waves, and even microwave technology. Fig.1 Network architecture Asynchronous Transfer Mode: Asynchronous Transfer Mode (ATM) is a switching technique for telecommunication networks. It uses asynchronous time-divisionmultiplexingandencodesdataintosmall,fixed-sizedcells.Thisdiffersfromotherprotocolssuchasthe InternetProtocolSuiteorEthernetthatusevariablesizedpacketsorframes.ATMhassimilaritywithbothcircuitand packet switched networking. This makes it a good choice for a network that must handle both traditional high-throughput data traffic, and real-time, low-latency content such as voice and video. ATM uses a connection-oriented model in which a virtual circuit must be established between two endpoints before the actual data exchange begins. Network topology-Common layouts A network topology is the layout of the interconnections of the nodes of a computer network. Common layouts are: A bus network: allnodes areconnected to a commonmedium alongthismedium. Thiswas thelayoutused inthe original Ethernet, called 10BASE5 and 10BASE2. A star network: all nodes are connected to a special central node. This is the typical layout found in a Wireless LAN, where each wireless client connects to the central Wireless access point. A ring network: each node is connected to its left and right neighbor node, such that all nodes are connected and that eachnodecanreacheachothernodebytraversingnodesleft-orrightwards.TheFiberDistributedDataInterface (FDDI) made use of such a topology. Nagendaret al., I nternational J ournal of Advanced Research in Computer Science and Software Engineering 3(2), February- 2013, pp. 184-194 2013, I J ARCSSE All Rights ReservedPage | 186 A mesh network: each node is connected to an arbitrary number of neighbors in such a way that there is at least one traversal from any node to any other. A fully connected network: each node is connected to every other node in the network. Notethatthephysicallayoutofthenodesinanetworkmaynotnecessarilyreflectthenetworktopology.Asan example, with FDDI, the networktopology is a ring (actually two counter-rotating rings), but the physical topology is a star, because all neighboring connections are routed via a central physical location. Overlay network: An overlay network isavirtualcomputernetworkthatisbuiltontopofanothernetwork.Nodesintheoverlayareconnectedbyvirtualor logical links, each of which corresponds to a path, perhaps through many physical links, in the underlying network. The topology of the overlay network may (and often does) differ from that of the underlying one. Fig.2 A sample overlay network: IP over SONET over Optical Forexample,manypeer-to-peernetworksareoverlaynetworksbecausetheyareorganizedasnodesofavirtual system of links run on top of the Internet. The Internet was initially built as an overlay on the telephone network. The most striking example of an overlay network, however, is the Internet itself: At the IP layer, each node can reach anyotherbyadirectconnectiontothedesiredIPaddress,therebycreatingafullyconnectednetwork;theunderlying network,however,iscomposedofamesh-likeinterconnectofsub-networksofvaryingtopologies(and,infact, technologies). Address resolution and routing are the means which allows the mapping of the fully-connected IP overlay network to theunderlying ones.Overlaynetworks havebeen around since theinvention of networkingwhen computer systems were connected over telephone lines using modems, before any data network existed. Another example of an overlay network is a distributed hash table, which maps keys to nodes in the network. In this case, the underlying network is an IP network, and the overlay network is a table (actually map) indexed by keys. OverlaynetworkshavealsobeenproposedasawaytoimproveInternetrouting,suchasthroughqualityofservice guaranteestoachievehigher-qualitystreamingmedia.PreviousproposalssuchasIntServ,DiffServ,andIPMulticast have not seen wide acceptance largely because they require modification of all routers in the network. On the other hand, anoverlaynetworkcanbeincrementallydeployedonend-hostsrunningtheoverlayprotocolsoftware,without cooperationfromInternetserviceproviders.Theoverlayhasnocontroloverhowpacketsareroutedintheunderlying network between two overlay nodes, but it can control, for example, the sequence of overlay nodes a message traverses beforereachingitsdestination.Routers:Arouterisaninternetworkingdevicethatforwardspacketsbetweennetworks byprocessinginformationfoundinthedatagramorpacket(InternetprotocolinformationfromLayer3oftheOSI Model). In many situations, this information is processed in conjunction with the routing table (also known as forwarding table). Routers use routing tables to determine what interface to forward packets (this can include the "null" also known as the "black hole" interface because data can go into it, however, no further processing is done for said data). Networksecurity:Inthefieldofnetworking,theareaofnetworksecurityconsistsoftheprovisionsandpolicies adopted by the network administrator to prevent and monitor unauthorized access, misuse, modification, or denial of the computernetworkandnetwork-accessibleresources.NetworkSecurityistheauthorizationofaccesstodataina network,whichiscontrolledbythenetworkadministrator.UsersareassignedanIDandpasswordthatallowsthem access to information and programs within their authority. Network Security covers a variety of computer networks, both publicandprivatethatareusedineverydayjobsconductingtransactionsandcommunicationsamongbusinesses, governmentagenciesandindividuals.Networkscanbeprivate,suchaswithinacompany,andotherswhichmightbe open to public access. Network Security is involved in organization, enterprises, and all other type of institutions. It does as its titles explains, secures the network. Protects and oversees operations being done. III. Definition of Loss Characteristics CQIreportsareintendedtoaccuratelyreflecttheHS-PDSCHperformancethattheUEcansupportintheexisting wirelesschannelconditions.Itisrecommendedinthat,instaticchannelconditions,theUEreportCQIsuchthatit achievesablockerrorrate(BLER)closeto10%whenscheduleddatacorrespondingtothemedianreportedCQI.In practice,theaccuracyofCQIreportsinreflectingHS-PDSCHperformanceisinfluencedbythewirelesschannel conditions. Disadvantages: 1.The code and power allocation across users. 2.To maximizing the link throughput for each user for a given resource allocation. 3.Higher round trip delay. IV. System Design Nagendaret al., I nternational J ournal of Advanced Research in Computer Science and Software Engineering 3(2), February- 2013, pp. 184-194 2013, I J ARCSSE All Rights ReservedPage | 187 Data Flow Diagram / Use Case Diagram / Flow Diagram TheDFD is also called as bubblechart.It is asimplegraphicalformalism thatcan beused to represent asystemin terms of the input data to the system, various processing carried out on these data, and the output data is generated by the system. Dataflow Diagram: SERVER CLIENTIP AddressBrowse aFileVia HiddenLinkyesConnecting..noROUTERFIle TransferIP AddressConnecting..Flle ReceiveSelect NodeyesnoConnecting..Detect Hidden LinkInside a SegmentVia HiddenLinkDetect Hidden LinkOutside a SegmentService TimeBrowse areceived pathEndFile Request Fig.3 Dataflow Diagram Activity Diagram: CLIENT ROUTERConnecting..BrowseFILE RECEIVEIP AddressVia HiddenLinkBrowse aFileNOYesFILE TRANSFERIP AddressSelect a NodeVia HiddenLinkYesNoDetect Hidden LinkInside a SegmentDetect Hidden LinkOutside a SegmentSERVICE TIMEConnecting..Connecting..SERVERSelect aReceiving Path Nagendaret al., I nternational J ournal of Advanced Research in Computer Science and Software Engineering 3(2), February- 2013, pp. 184-194 2013, I J ARCSSE All Rights ReservedPage | 188 Fig.4 Activity Diagram Sequence Diagram: SERVERCLIENTROUTERSocket ConnectionSocket ConnectionClick TransferHidden LinkSet transaction PathSplit to PacketFile TransferAcknowledgementFile Received Fig.5 Sequence Diagram Use Case Diagram: SERVERCLIENTReceivi ngPathsocket connectionROUTERDownload RequestIP AddressPath SelectionBrowse a Fi leReceive a FilePacket Spl iting Fig.6 Use-case Diagram INPUT DESIGN Nagendaret al., I nternational J ournal of Advanced Research in Computer Science and Software Engineering 3(2), February- 2013, pp. 184-194 2013, I J ARCSSE All Rights ReservedPage | 189 Theinput designis thelinkbetween theinformation system andtheuser. It comprises thedeveloping specification andproceduresfordatapreparationandthosestepsarenecessarytoputtransactiondataintoausableformfor processing can be achieved by inspecting the computer to read data from a written or printed document or it can occur by havingpeoplekeyingthedatadirectlyintothesystem.Thedesignofinputfocusesoncontrollingtheamountofinput required,controllingtheerrors,avoidingdelay,avoidingextrastepsandkeepingtheprocesssimple.Theinputis designed in such a way so that it provides security and ease of use with retaining the privacy. Input Design considered the following things: What data should be given as input? How the data should be arranged or coded? The dialog to guide the operating personnel in providing input. Methods for preparing input validations and steps to follow when error occur. OBJECTIVES 1.InputDesignistheprocessofconvertingauser-orienteddescriptionoftheinputintoacomputer-basedsystem. This design is important to avoid errors in the data input process and show the correct direction to themanagement for getting correct information from the computerized system. 2.Itisachievedbycreatinguser-friendlyscreensforthedataentrytohandlelargevolumeofdata.Thegoalof designing input is to make data entry easier and to be free from errors. The data entry screen is designed in such away that all the data manipulates can be performed. It also provides record viewing facilities. 3.Whenthedataisentereditwillcheckforitsvalidity.Datacanbeenteredwiththehelpofscreens.Appropriate messages are provided as when needed so that the user will not be in maize of instant. Thus the objective of input design is to create an input layout that is easy to follow OUTPUT DESIGN Aqualityoutputisone,whichmeetstherequirementsoftheenduserandpresentstheinformationclearly.Inany systemresultsofprocessingarecommunicatedtotheusersandtoothersystemthroughoutputs.Inoutputdesignitis determinedhowtheinformationistobedisplacedforimmediateneedandalsothehardcopyoutput.Itisthemost importantanddirectsourceinformationtotheuser.Efficientandintelligentoutputdesignimprovesthesystems relationship to help user decision-making. 1.Designingcomputeroutputshouldproceedinanorganized,wellthoughtoutmanner;therightoutputmustbe developedwhileensuringthateachoutputelementisdesignedsothatpeoplewillfindthesystemcanuseeasilyand effectively.Whenanalysisdesigncomputeroutput,theyshouldIdentifythespecificoutputthatisneededtomeetthe requirements. 2. Select methods for presenting information. 3. Create document, report, or other formats that contain information produced by the system. The output form of an information system should accomplish one or more of the following objectives. Convey information about past activities, current status or projections of the Future. Signal important events, opportunities, problems, or warnings. Trigger an action. Confirm an action. V. Implementation Implementation is the stage of the project when the theoretical design is turned out into a working system. Thus it can be considered to be themost critical stage in achieving a successful new system and in giving theuser, confidence that the new system will work and be effective. Theimplementationstageinvolvescarefulplanning,investigationoftheexistingsystemanditsconstraintson implementation, designing of methods to achieve changeover and evaluation of change over methods. MODULES: 1.Server Module. 2.Path Set Module. 3.Packet Transaction Module. 4.Client Module. ServerModule:Servermoduleisusedtouploadthefiletotheuserandviewtotheuserfilerequest.Iftheserverto accepttheuserfilerequestthecontrolispassingtotherouterotherwisetheservertorejecttheuserrequest, automatically the request is deleted and user download option is canceled. Path Set Module: The Path set module is used to set the path to transact the files based on this path selection. The server to provide the ten possibilities based on the shortest path. Normally, twelve towers are used for this transaction process. For each transaction, the transaction path takes minimum four towers or five towers. Packet Transaction Module: A Packet transaction module is used to split the file into eight packets in same size and then the router send the packets server to client, the client returns the acknowledgement to the server. The server once gets the Nagendaret al., I nternational J ournal of Advanced Research in Computer Science and Software Engineering 3(2), February- 2013, pp. 184-194 2013, I J ARCSSE All Rights ReservedPage | 190 acknowledgement; send another packet to the client. If tower size is less than the packet size, the server cant send via the tower.Client Module:TheClientmodulecan view theserver uploaded files and send thedownload request to theserver. For downloadingfilestheclientregisterstheirpersonaldetails.Afterlogin,theclientcanchangetheirpasswordand download the server accepted files. VI. Test case and Sample Screens Here are some screens captured from test cases: Nagendaret al., I nternational J ournal of Advanced Research in Computer Science and Software Engineering 3(2), February- 2013, pp. 184-194 2013, I J ARCSSE All Rights ReservedPage | 191 Nagendaret al., I nternational J ournal of Advanced Research in Computer Science and Software Engineering 3(2), February- 2013, pp. 184-194 2013, I J ARCSSE All Rights ReservedPage | 192 Nagendaret al., I nternational J ournal of Advanced Research in Computer Science and Software Engineering 3(2), February- 2013, pp. 184-194 2013, I J ARCSSE All Rights ReservedPage | 193 VII. Conclusion WehaveinvestigatedthroughputoptimizationinHSDPAusingtwoadaptiveouterloopalgorithms.Bothofthem adjust theCQI offsettomaximizethethroughput.Theofflinealgorithmused an adaptivealgorithmto achieveagiven targetBLERusingthestochasticgradientdescentmethodbasedonthehistoryofACK/NACK.Bysearchingthrough different target BLERs, the throughput optimal BLER can be found offline. The online algorithm used a variation of the Kiefer-WolfowitzalgorithmwithoutspecifyingatargetBLER.Anadaptivestepsizemechanismwasalsoproposedto makethealgorithmrobusttonon-stationarycondition.Wehaveshowntheconvergenceofbothalgorithmswitha constant step size. Simulation results show that the proposed algorithms can achieve up to 30% throughput improvement over that with 10% target BLER. Interplay between the algorithms proposed here and other system level optimizations. VIII. References 1.H. J. Kushner and G. G.Yin,Stochastic Approximation and Recursive Algorithms and Applications, 2nd ed. Springer-Verlag, 2003. 2. 3GPP, TR 25.858 version 5.0.0, Physical Layer Aspects of UTRA High Speed Downlink Packet Access Mar. 29, 2002. 3. J. Derksen, R. Jansen, M. Maijala, and E. Westerberg, HSDPA performance and evolution Ericsson Review, vol. 3, pp. 117120, 2006. 4.H. J. Kushner and J. Yang, Analysis of adaptive step size SA algorithms for parameter tracking IEEE Trans. Automat. Contr., vol. 40, no. 8, pp. 14031410, Aug. 1995.