End-to-end QoS Management Across LTE Networks.pdf

End-to-end QoS Management Across LTE Networks.pdfFigure 3. ) an execution phase(steps 7-9)and a completion support this, common interfaces should be provided On Sl, s5phase(step 9-)and X2 interfaces it can be matched easily to IP network layernehr. In order to provide end-to-end Qos in a multi-vendor LTE with the help of GISt signaling transport. The challenging partnetwork, we propose to apply a signaling protocol for resource is to adopt LQsig to rrc on radio interface. LQSIG proposesreservation. One of the key features of such a QoS singaling a hybrid method for interworking with rrc between UE andprotocol is to be mobility-aware since LtE access network caneNodeB. The protocols behavior is presented through the mostbe one of the bottlenecks which have huge effect on end-to-endsignificant use cases of lte. the bearer establishment andQoS. In the next section it is described how an NSIS-based handover procedure on X2 interfaceNext Step in Signaling) Qos signaling protocol can be appliedin LtE environment. We demonstrate the interworking duringa bearer establishment can be triggered in sevbearer establishment and X2 handover procedures to coversuch as initial attach to the network, ue request, network-sidemost of the significant use-cases in LTE [8request. From resource reservation point of view these all arethe same procedure, so keeping simplicity we only concentrateII. RESOURCE RESERVATION IN LTE WITH LQSIGon the attach procedure. GTP Create Session Request fromNext Step in Signaling (NSIS), designed by IEtF, isMME to sGw is triggered by the Update Location Requeststandardized signaling protocol suite with Qos signaling asAnswer received by the MMe, right after the random Accessprimary use case. The framework consists of two layers. The Procedure and RRC Connection Establishment phase. At thilower layer, NSIS Transport Layer Protocol (NTLP), ipoint sgw knows about the Qos parameters(ARP, QCD) ofresponsible for providing general transport service for thethe new bearer since these are embedded into the gtPsignaling messages. The General Internet Signaling Transport message received from MME. As S5 bearer is the first part of(GIST) protocol is used in this layer. The signaling messages the Eps bearer to be established, SGW has to initiate resourceare originated from the upper layer, NSIS Signaling Layer reservation on the S5 interface. LtE does not have a solutionProtocol (NSLP). As the protocol suit was originally designed to complete such reservation, but LQsiG based on QoS-NSLPto be generic, there is a specified NsLP for ensuring Qos, is able to do so. Our concept for the reservation is based on thealled QoS NSLP. One of the urgent needs of Nsis is to three parts of an EPS bearer(RB(Data Radio Bearer), SIprovide mobility support. In mobile environments frequent and S5 bearers)and not making reservation for the whole pathhandover events may result in degradation of Qos performance in one phase. As IP is the network layer protocol on S1 and S5interfaces CP layer, it is easy to use an NSIS GIST-basedA. Resource reservation during the attach proceduresignaling transport protocol for LQSIG messagesThe lte Qos Signaling Protocol (LQsiG) proposesimmediate interaction with the LtE CP protocol stack. ToTABLE ILTE QCI TO LQSIG QSPEC MAPPINGLTE QoS ClassesLOSIG OSPEC ObjectExample serviceConversational voicel00l00Conversational video (live streaming)415C1015004Real time gaming≤050Non-conversational video(buffered streaming)3003005IMS Signaler100Video(buffered streaming)TCP-based105(e.g. www, e-mail, chat, ftp. p2p, file sharing300progressive video etcVoice, video (live streaming), InleracLive garning10010102Video(buffered streaming TCP-hased10(e.g. www, e-mail, chat, ftp. p2p, file sharing,300progressive video, etc.91061039QoS-nSLP defines an RSVP-like RESERvE-RESPONse classes and Qspec object identifiers. Four main parametersrequest-acknowledgement pair. RESERVE is the only are assigned to each QCI value: resource type(gbr or nonmessage that manipulates QoS-NSLP reservation state. GBR) priority, packet delay budget and packet loss rate(PLr)RESErVE always contains information about the previousTo provide guarantees for bitrates operator has to allocateQoS-NSLP message. It can be an explicit confirmation forbandwidth on a specific data path. For bandwidth definition inRESERVE, response to a QUERY or an error code. With aa Qspec object there is a recommended setting r=p to theQUERY the initiator can request information about the path peak rate, b and m to some large value. as r and parewithout making any reservation. to be accurate, themeasured in bytes/sec (including IP header)and maximumhandshake has to start with a QUERY initiated by the SGwvalue is 40 terabytes, this method fits to any LtE networkit does not have any information about the availablePacket delay budget can be converted easily to path latency. Itresources on the pdn-Gw side. With such a three-wayis a 32 bit unsigned integer, measured in msec. This parameterhandshake between sgw and pdn-Gw resource are reservegives the application knowledge on both the minimum anmaximum packet delivery delay. Path packet loss rate is alsofor the s5 bearer, attach continues with Create bearer requestsimple to use as Pl is assigned to some Qci value. It is a 32sent from sgw to pdn-gwunits. It fits properly forsI bearer resource reservation is very similar to s5. It isthe values between 10 and 10 used in LtE Qos modeltriggered by Create Bearer Request message initiated by SGwPriority assigned to QCI values is considered as schedulingtransferred to the eNodeB through MME. In this case also weight factor for admitted flows. Among QSPEC parametersSGW sends the QUERY message to obtain QoS knowledge on preemption and defending priority is a good candidate to deathe path towards the serving eNodeB. That sends back the with scheduling. Once a flow is admitted, the preemptionavailable Qos model description in QSPEC; finally SGw priority becomes irrelevant. Instead, its defending priority iaccepts it in case of agreementused to compare with the preemption priority of the flowsWith the help of such mapping operators can define severalResource reservation for the DRB needs the most effort Qos classes in addition to standardized ones. If not thesince IP is not used on CP of the radio interface. We have only standard QCT values are applied, Y 1541 QoS Class parameterRRC to operate with therefore clear interface has to be defined could be considered as well [91between RRC and Gist protocol layer. A hybrid solution isthe extended asn. 1 definition of rrc connection是N"器FMME′sGMReconfiguration and Connection Reconfiguration Completemessages. Both have the possibility to provide this extra1. Provision cfaea restricti 2scontent. The extension field allows addition of new fields to2. Measurement controthe structure without modification of the asn. 1 definition. A3 Handover decisionon-critical extension may be ignored if it is not recognized,4. HandoverFeques.but must be processed if it is recognized. This property givesthe opportunity for terminals without LQSIG-capability toPEC. apping濺operate according to legacy lte Qos modelB. OSPEC object mapping to LTE QoS classes3. Res ource setupEvery QUeRY and reserve message of the LQSIg5 Han 1ARcontains the description of the actual Qos model being usedImporting from QoS-NSLP, a so called QSPEC object is sentEx2 transporl bearer reservawithin the messages. It describes the current resources that areData forwading over X2 nterface to avod data 5ssrequired and depends on the qos model being used. To be7. landauer Commandable to transfer LtE Qos model parameters and reserveR对 Transferresources on the path based on QCi values, we define aI wow ay hondahaAcmapping between QSPEC object and LTE Qos classes as:: DRB reserved 0 ::n e: ifolleOWSQSPEC objects have several parameters to1.ath≌ wIich Requestscribedifferent Qos models. TMOD-I is an obligatory parameter,quest ACKconsists of the rate(r), bucket size(b), peak rate (p), minimum1 Release Resourcespoliced unit (m) and maximum packet size(MPS) fields. AQSPEC object can have several optional parameters as wellincluding path latency, path jitter, path packer error and lossrate, preemption and defending priority. Bandwidth was lig. 4. X2-based handover procedure with LQsIGeliminated recently as it can be derived from TMOD-1 fieldvalues.C. Resource reservation during x2 handover procedureIn addition to initial bearer establishment mobility eventsOne of the key questions to be-answered how to definemapping between QSPEC object fields and L,TE Qos modelalso have to be considered to realize the properties of lQsigTable 1 presents our proposal for this mapping between QCI An X2 handover is a challenging procedure since one part ofthe eps bearer must be kept(S5 bearer), other parts need to be a good candidate to be the bottleneck in LtE networks and itsreleased and rebuilt on a new location(DRb and SI bearer). optimum utilization is highly economicalAs an intermediate step, during this kind of handover we alsoOur analytical model is a cluster based hierarchicalhave X2 transport bearer; resource reservation is alsoapproach. Several bearer requests are coming into a cellnecessary on this section to keep end-to-end Qos forming level 0 clusters. Level 1 is the geographical area of anrequirementseNodeB. consists of several level 0 clusters. All clusters on theFrom resource reservation point of view X2 handover same level are considered statisticallly identical because ofprocedure starts with an X2AP Handover Request sent fromanalytical reasons. Hierarchical model can be continued tothe source enodeb to the target one through x2 interface asSGW and PDN-GW level in order to analyze any bottleneckshown in Figure 4. This message can contain several E-RABs point of LtE networks [61to be set up, each described with QCI and ArP parametersBased on the Erlang-B formula, the blocking probability atBased on these target eNodeB can generate the appropriate level i=0 is given asQSPEC objects. Network Notification command from GISTinitiates this step Target eNodeb starts the three-wayhandshake procedure with the QUERY message towardsSGW. It is important to emphasize that handover process has where the offered traffic Ao consists of the traffic due to newto be as quick as possible since active data connections can be arrivals, the traffic due to handoffs and the traffic that createin progress. LQSIG provides QoS-NSLPs feature, the stale connectionaggregated RESERVATION for that purpose. Note that this(0+Ah.D)sI bearer is UL only, so the other direction must be reserved+ahndlaterall parameters in the above equations are listed belowX2 bearer establishment is triggered by X2AP HandoverAi is the aggregate traffic at leRequest Ack message is sent from target eNodeb to the sourceci is the number of shared channels at each node ofone. Before bearer is established. resources must be reservedlevel iwith the well-known three-way handshake procedure initiatedu is call durationy the source eNodeB. It is important particularly at this stageNiis the number of clusters at level ito make the reservation quick and simple because UE cannot2i is the arrival rate at level ireceive any packages hetween the HandoverAh, i is the generation rate of handoffs at level iCommand and Handover Confirm; target eNodeb buffers thedownlink packages. So extending RRC ConnectionPs, i is the blocking probability at the nodes of level iReconfiguration and Connection Reconfiguration Completed is the flow reservation maintenance time withoutmessages with LQSIG ReserVe and ResPonse isrefreshespecially effective in this case. After completing this twoThe call durations are modeled as independentway handshake, DrB bearer can be established using therandom variables following the exponentialreserved resources. Downlink traffic is now tunneled throughdistribution with parameter /uX2 transport bearer; uplink traffic uses the new sI bearer onlyMobile stations' cluster dwell times are modelled asexponentially distributed random variables withWith Modify Bearer Request dl sI bearer establishmentparameter ni, where i is the cluster levelAt the next level, new traffic is arriving to the enodeb withis triggered, resources must be reserved with three-way A,=Nodo1-Pb, and the handoff rate is Ah, /=Ph, (y+ln,iN(handshake initiated from the other side. SGw. now that allthe bearers of the new path are established, traffic has to beterminated on the old one. sgw sends end marker to sourceBased on [11, blocking probability on the second level isand target eNode bs to switch the path to the newly established given asone. Following this a reFRESH message is sent by LQSIG,where tear flag is set. all the reserved resources areP,1=acombined within a session ID list. included also into the1204/lsent REFRESH message. After this step both UL and DL wheretraffic uses the rerouted eps bearerN0入0(1-Pt Noah.odIV. PERFORMANCE EVALUATIONUSing LQsiG, the aggregate traffic on the s1 interfaceA. Analytical modeltowards sgw isIn terms of end-to-end Qos provided via resourceNoλ0(1-Pb0)reservation, one of the practical measures is to calculateQsiG(1- 1)+Noanod(5)blocking probability. This means the probability that a newrequest for a bearer cannot been served. We focus our study onSI interface(between eNode B and SGw) since we believe it isRestricting the number of eNodeBs to one, PhI=0, an2009..Clerk Maxwell, A Treatise on Electricity and Magnetism, 3rdtherefore h 1=0 and nI =0. Therefore equation (5) can becd. vol. 2. Oxford Clarendon. 1 89simplified as follows[2] Mario Marchese,"QoS over Hetergenous Networks,John WileySons Lid. 2007ALQSIGNo20(1-Pb8(1-Pb,1)+NoAh,od3 Ronit Nossensonl, "Lony TerIn Evolulion Network Architecture, IEEECOMC AS November 2009The blocking probability on SI interface is[4]Li Li, Subin Shen and Charlie Chen-Yui Yang,""LTE CoS/QosHarmonization Emulator", IEEE CyberC, pages 154-161. October 20115 Stefania Sesia, Issam Toufik and Matthew Baker, "LTE - The UMTSP3=2aLong Term Evolution From Theory to Practice, John wiley sonsV. CONCLUSiON[6 Sung-Hyuck Lee, Suwon Lee, B young-Joon Lee and Jongho BangNext Generation Qos Signaling Protocol for IP-based Wireless/MobileQos is a critical issue in the operation of todays telecomNetworks.Samsung Tech Conference 2005networks. In this paper we identified the need for providing [7] Roland Blcss and Martin Rohricht, "QoS Support for Mobilc Uscrsend-to-end Qos in LtE networks. Based on the findings weusing NSIS, Networking 2009, Lecture Notes in Computer Science,proposed a LtEmobility-aware Qos signaling protocolVol.5550,pp.169-181,209LQSIG with key features such as QSPeC to Lte Qos class[8] J Manner, G. Karagiannis and A McDonald, "NSIS Signaling Layerntocol (NSI P) for Quality-of-Service Signaling, RFC5974, IETF,mapping, interworking with LtE CP protocol stack,October 2010emphasizing the hybrid solution with RRC extension. The [9] G. Ash, A. Bader, C. Kappler and D. Oran, "QSPEC Template for theproposed analytical model is used to determine the blockinQualily-of-Service NSIS Signaling Layer Protocol NSLP)", RFC 5975probability on SI interfaceIETF, October 2010[10] 3GPP Tech. Spec. 25.331, Radio Resource Control (RRC); ProtocolREFERENCESSpecification, V. 11.5.0[1 Hannes ekstrom, " QoS Contrul in the 3GPP Evolved Picket Syslelll[Il]s. Paskalis, A. Kaloxylos, E. Zervas and L. Merakos, An EfficientRSVP Mobile IP Interworking Scheme", Mobile Networks andIEEE Communications Magazine, Vol 47, Issue 2. pp. 76-83, FebruarApplications 8, pages 197-207, 2003