Telecommunication Services Exchange Architecture for 3G and Beyond MobileCommunication SystemsDonna Griffin & Dirk Pesch

Centre for Adaptive Wireless Systems, Cork Institute of Technology, Irelanddy-iff'(,it.ie. di)esch(&cit.ie

Abstract- In the current communications services, wired andwireless, subscribers are more or less tied to their serviceproviders by means of long-term contracts. This business model isrigid in that customers do not have the means ofsimply availing ofspecial offers or additional services that an alternative serviceprovider might offer. This scenario is unique to the communicationmarket, and can restrict competition within the communicationsector with regard to tariffs and services. In the ideal scenario,users should be free to buy telecommunication servicesjust as theyare able to buy products in a supermarket, without beingcompelled to buy a productfrom a particular producer. This paperwill outline the designed Telecommunication Service Exchange(TSE) Architecture, which aims to address this issue and alsodetails how this architecture can be integrated into the currentUMTS architecture based on SIP signalling.

Keywords- Agents, Auctions, SIP, B3G, MVNO, UMTS,Telecommunication Service Exchange (TSE), QoS

I) INTRODUCTIONTelecom network operators in the future will be faced withtough competition through emerging wireless accessproviders and MVNOs. In the face of this new competitioncurrent network operators need to face the inevitablederegulation of their access network, and must provide newand innovative ways of conducting their business, tomaintain and improve their market presence. However inthe current communication services, wired and wireless,subscribers are more or less tied to their service providersby means of long term contracts. This business model isinflexible but can be improved with the TelecommunicationService Exchange (TSE) architecture, allowing customers tobuy telecommunication and wireless services on a per callbasis [1]. This approach has a number of advantages overthe current method:* It will introduce more competition into the

communications market, thus forcing the serviceproviders to better serve the interests of users.

* The success of the service provider will be based purelyon the merit in being able to provide good value formoney services

* There will be an opportunity for service providers todynamically price their service depending upon thedemand and supply, presenting them with theopportunity to increase their network utilisation

* The potential exists to decouple service providers andnetwork operators allowing operators to dynamicallysell their capacity to service providers, thus potentiallyincreasing their revenues.

In this paper, Section (II) will examine e-commerce and thevarious types of e-commerce that currently exist. E-

commerce importance is represented in the fact that themain transactions of e-commerce are modelled in the TSE.Agents are then outlined to provide a greater degree ofautomation within the e-commerce environments, while theauction protocol, First Price-Sealed Bid is provided as thenegotiation model between these agents. Section (III) ofthis paper presents Session Initiation Protocol, its rationalfor its use and the main SIP requests used in the TSE.Universal Mobile Telecommunication Service (UMTS) andPolicy Based Admission Control are outlined in Section(IV), as UMTS is used as the backdrop in our evaluationwith Policy Based Admission Control employed in UMTS.Next, in Section (V) the paper will present the General TSEarchitecture, while Section (VI) will look at the B2B marketwithin the TSE in detail. Once presented B2B market and itsoperation and potential integration into UMTS is providedin Section (VII).

II) E-COMMERCE, AGENTS & AUCTIONSThe TSE will be represented as an electronic

marketplace where shifts in the supply-demand chain willessentially affect the price of the good or service sought.Electronic Marketplaces are e-commerce environments,which offer new channels and business models for buyersand sellers to efficiency trade goods and services over theInternet [2]. According to the nature of the transactions themain types of e-commerce are distinguished: Business-to-Business (B2B) and Business-to-Customer (B2C) which aremodelled in the TSE architecture.

E-commerce in the future will be characterised bybuyers and sellers having a greater degree of automation. Inorder to provide this level of automation, agents must beintroduced into e-commerce applications, marketplaces andresearch [3]. An agent is a software program that acts onbehalf of its owner to meet a particular objective and isdescribed as being autonomous, proactive and social [4].Automating these activities through the use of agents cansave time, and in complex settings it has been shown byresearch by Das et al [5] that when agents and humansparticipate simultaneously in a realistic auction, the softwareagents consistency produce greater gains compared to theirhuman counterparts.

Over the past few years, auctions have gained a newlease of life, with the advent of third-party online auctionweb sites and forums. There exists a wide variety of auctionlogics used to set the rules for auction events. These typesinclude English, Dutch, Vickrey and First Price - SealedBid. Because the TSE is involved in a particular class ofnegotiations - namely where there is one buyer, and

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numerous sellers, it was necessary to devise a negotiationmodel that is fast and efficient and can be easilyimplemented in a computation system. The TSE is going touse a variation of First Price, Sealed bid, where theoperation of this bidding strategy involves the buyer statingthe service it wishes to purchase, at a level of QoSdetermined by the buyer. The seller then examines if it cansupport the media characteristics of the call, at the specifiedQoS, and returns a sealed bid to an intermediary agent. Theintermediary agent then determines the winner of thebidding session by choosing the lowest bid at the specifiedQoS. This type of auction can be described as, Lowest Price- Sealed Bid.

III) SESSION INITIATION PROTOCOL (SIP)Session Initiation Protocol (SIP) is an Internet

Engineering Task force (IETF) standard. SIP is a signallingprotocol used for establishing, terminating and modifyingcommunication sessions in a network. [6]. Due to the factthat SIP is an access-independent, application-layer protocoland also because 3GPP has chosen SIP as the signalingprotocol in the IP Multimedia Subsystem (IMS) of UMTSnetworks, it was the natural choice for the signaling andcommunication protocol between the external buyer agentand seller agents. Some important SIP requests used in theTSE architecture include:* Invite, used to establish communication sessions* Register, informs a server about a users current location* Bye, used to terminate an open communication session* Refer, provides call transfer capabilities

IV) UMTS & END-To-END QoSUniversal Mobile Telecommunication Service (UMTS)

is the dominant network standard for 3rd generationwireless systems. UMTS Rel5/6 provided an evolution withregards to business opportunities and maturing enablingtechnologies, the most important evolutions being the corenetwork consolidation towards a general purpose multi-service connectivity network, legacy GSM/UMTS voiceservice migration to the consolidated packet based UMTScore network domain, and introducing a wide range ofoptimized multimedia communication and informationservices, based SIP. In order to provide End-to-End Qualityof Service in UMTS, 3GPP has devised an architecture,which provides this shown in Figure 1.

Within this architecture, the GGSN acts as the IP PolicyEnforcement Point (PEP). Policy based [7] admissioncontrol ensures that the resources that can be used by aparticular set of IP flows are within the "authorizedresources" specified in the Go interface. The two mainarchitectural elements for this policy control are the PolicyEnforcement Point (PEP) and the Policy Decision Point(PDP). In UMTS, the PDF makes decisions in regard toService Based Local Policy (SBLP) using policy rules andcommunicates these decisions to the IP BS Manager in theGGSN, which is the IP Policy Enforcement Point (PEP).The PDF in UMTS makes policy decisions based on

information located in the Application Function (AF). TheAF offers services that require the control of IP bearerresources and maps QoS application level parameters (SDP)into policy set-up information, and sends this information tothe PDF via the Gq interface. In UMTS the AF and the PDFis the P-CSCF, which is in the same domain as the GGSN.

For each authorized use of resource the PDF generatesan authorization token upon request from the AF. Theauthorization token generated conforms to IETF RFC 3313[8]. The PDF also enables coordination between events inthe SIP session level and resource management in the bearerlevel. The binding mechanism associates the PDP contextbearer to the IP flow to support SBLP policy enforcement inthe GGSN and can be used in context activation andmodification procedures.

- - -_

Figure 1 End-to-End QoS Architecture in UMTS

V) TSE ARCHITECTUREThe TSE architecture, in Figure 2, provides a multi-agentmarket architecture that can provide explicit and integratedsupport for complex agent interactions, such as automatedcontracting and auctions.

Figure 2 General TSE Architecture

The TSE also provides a framework for secure and reliablee-commerce using intelligent agents [9]. Because the TSE isan e-commerce environment, it must facilitate B2B andB2C transactions. To provide this we need an exchangewithin the architecture [10], which is a collection of domainspecific markets in which goods and services are traded,along with some generic services required by all markets,such as the Agent Management System and the Directoryfacilitator (DF), provided by JADE [11]. The DF [12]provides a list of services, which can be provided, the agentsthat can provide them and what languages, interactionprotocols and ontologies that the services provide. The TSEcontains two markets allowing for both B2B and B2Ctransactions. The B2C market within the exchange createsthe e-commerce market environment where buyers canactually purchase their calls on a per call basis. MNVOs andnetwork operators can provide a Service Provider Agent in

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the B2C market representing the seller, while customers canconnect to the B2C market looking for sellers that cansupport their call.

VI) B2C MARKET ARCHITECTUREThe focus of our research will be based on the B2C

market, as shown in Figure 3 and as a result, we will outlinethis architecture and operation in detail. In the B2C market,elements are represented as agents, and are detailed below:

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Figure 3 B2C Market in TSE

Buyer User Agent (BUA)- software installed on the Buyerdevice. The BUA will incorporate a GUI to allow the user toselect the media it wishes to incorporate into the call, aswell as a basic QoS/Price editor.Market Interface Agent (MIA)-the interface between theBuyer User Agent (BUA) and the B2C market within theTSE exchange and represents the entry point into the B2Cmarket. Its main function is to maintain and accept presenceinformation from the BUA, and assign the BUA a TrustedIntermediary Agent.Trusted Intermediary Agent (TIA)- the agent that tradeson behalf of the buyer and its main function is to send a Callfor Proposal the various Service Provider Agents asking fortheir participation in the auction.Service Provider Agent (SPA)- determines participation inthe auction when it receives a Call for Proposal. If the SPAsubmits a bid it will be penalised if later it decides it cannotsupport it.Network Operator Agent (NOA)- acts on behalf of thenetwork operator in the market. In the case where thenetwork operator is a telecom network operator then theNOA interacts with the Policy Decision Function (PDF) andthe UMTS Call Admission Control function to see if theycan support the call.Better Business Bureau Agent (BBBA)- maintains adatabase of essentially a Service Provider rating in themarket. When a TIA receives bids back from SPAs then theTIA uses the BBBA rating in its evaluation of who is thebest SPA for the current bidding session. When the call hasbeen completed, the SPA has to return the achieved QoS forthe call.Mapping Agent (MA)- Different bearer attributes areassociated with UMTS and IP networks and as a result amapping function is required to correctly describe thesubjective QoS/Price request of the BUA into specificattributes as required by the access technology.

VII)B2C MARKET OPERATIONThe Operation ofthe B2C market using the agents describedin Section (VI) is further described based on the SIPSignalling and the Foundation for Intelligent PhysicalAgents, Agent Communication Language - FIPA ACL [13].

A) Registration with TSE:Registration with the MIA in the B2C is achieved using theSIP Register request and is required for the BUA to avail ofthe goods and services located within the B2C market.

B) Assignment ofTIAOnce registered with the market the BUA can now avail ofthe services available. Session establishment between theBUA and the best service provider is initiated with thesending of an Invite. This procedure is shown in Figure 2.

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1. The BUA determines if it wants to make a call throughthe B2C market within the TSE exchange and as aresult uses the QoS editor to determine the media andQoS to be set in the call. This information is then usedto generate an Invite and associated SDP, which is sentto the MIA.

2. The MIA then searches the Directory Facilitator (DF)for agents that support the TSE ontology. The DFreturns a list of agents.

3. The MIA uses FIPAs ACL to formulate a message toall agents in the returned list. The message is set asPropose [13], and the content will be represented usinga predicate expression in the TSE ontology, asking allagents can they accept assignment of the BUA. ACLsPropose act is a general-purpose act to make a proposalsubject to certain conditions being true. Predicates areexpressions that say something about the status of theworld and can be true or false.

4. Any TIA can answer true the predicate expression willstate this in the content of the returned Accept-Proposalact to the MIA. The first TIA that states thisinformation in the Accept-Proposal will be assigned tothe BUA in the market.

C) Callfor ProposalThe Call for Proposal procedure is outlined below and isshown in Figure 5.1. The DF is queried for all SPAs. The TIA formulates a

Inform message, which used to notify all SPAs at thebeginning of an auction, and the content contains therelative time by which all bids must be retumed.

2. Once sent, the TIA sends another message, Call forProposal, and the content will include the BUA's SDP

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required for the SPA and NOA to determine if they cansupport the call.

3. The SPA now needs to check if it will submit a bid andforwards the message to their NOA to see if the mediain the SDP is within operator policy rules and also if thenetwork has the capacity to support the call.

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D) Calculate and Return BidIn order to determine if it can support the call, the NOAneeds to contact its network. The following procedurepresumes the NOA is a UMTS network with SBLPemployed on the network and backbone IP network isDiffServ enabled. The outlined procedure makes referenceto Figure 1, and is shown in Figure 6.MMCh ULSNCk

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The Invite along with its SDP is sent from the NOA tothe P-CSCF located in the IMS of the UMTS network,to decide if the media characteristics of the call arewithin the SBLP

2. Because SBLP is used, the Proxy Call State ControlFunction (P-CSCF) will forward the SDP to theApplication Function (AF). Upon receipt of this requestthe AF maps QoS-related application level parametersinto policy setup information, and sends thisinformation to the Policy Decision Point (PDF) via theGq interface.

3. If the IP QoS resources are consistent with operatorpolicy rules defined in the PDF, the PDF sends anauthorization token in the authorizationacknowledgment message to the AF. The authorizationtoken is then forwarded to the NOA.

4. The NOA now needs to determine if the multiplexingelements in the UMTS network call accept the call [14].The NOA will as a result have to send a service requestto the SGSN with the authorization token. The SGSN isresponsible for mapping the UMTS bearer attributes asdefined by the UE in the Invite SDP into RABattributes and sends a Call Admission Control (CAC)request to the GERAN. The GERAN admission control

function determines if it can accept the call and willmodify the Radio Access Bearer (RAB) attributes ifnecessary. The SGSN will also send a CAC request tothe GGSN. Once again the GGSN determines it canaccept the call. If accepted it will send the appropriateresponse back to the SGSN. The SGSN then informsthe NOA of whether the call can be accepted and thelevel of QoS that can be provided [14].

5. The NOA now temporary reserves this level of QoS forthe BUA, and then returns this QoS along with theauthorization token generated by the network to theSPA

6. The SPA now calculates a price for the returned QoS.The price presented will be determined by theauctioning protocol Lowest Price - Sealed bid as wellas the SPA own true valuation, on its attitude towardsrisk as well as prior beliefs about the valuation of otherbidders. Game theory is going to be used to addressthese complex economic issues. The SPA forwards itsprice and level ofQoS to the TIA for review.

E) Determine WinnerAt the end of relative time t, bids submitted by the variousSPA need to be evaluated to determine the winner. Thisprocess is shown in Figure 7.L -¶4 ~~~~~~~1)gn*3(r%9Am F-m~~~~~~~~i t)llSOr

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1. Using the DF, the TIA sends a Request to the BBBA onall SPAs that submitted a bid, to determine the SPApast performance or rating in the TSE. The BBBAreturns this information in the content ofan Inform.

2. The SPAs bid and its performance is now inputted intoa cost function, and the output is the winning SPA. Thewinner is notified in an Accept-Proposal message.

3. The winning SPA now needs to reserve the agreed QoSfor the BUA, and as a result it forwards the BUAInternational Mobile Subscribers Identity (IMSI) to theNOA, who forwards this into the networks HomeLocation Register (HLR), enabling the BUA to attachduring Data Connection Setup. The BUA can also atthis stage be assigned a QoS profile.

4. The SPA also forwards the authorization token and thenetworks Network IDentification/System IDentification(NID/SID) to the TIA in the content of an Inform. Theauthorization can be used by the BUA whenestablishing a PDP context with the network.

5. The TIA also informs the BBBA which SPA was thewinner, along with the agreed QoS between the parties.

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F) Connection EstablishmentThe TIA forwards the authorization token and the NID/SIDof the network that the BUA needs to connect to in anAccept Proposal message. A possible procedure forconnection establishment is outlined below and is shown inFigure 8.

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1. An OK, to the original Invite request is sent from theMIA to the BUA. The MIA now constructs a SIP Referrequest, the originator set to the MIA and the finalrecipient identified by the NID/SID parameters of thenetwork. Using this information the BUA can nowconnect to the new network

2. Once the network system has been acquired, the nextstep is to establish the data connection to the SIPservices. The BUA sends an attach message to theSGSN, which includes the BUA IMSI. The SGSN usesthe BUA IMSI to send a request the networks HLR tohelp authenticate the user. Once authenticated theSGSN sends an Attach Complete message to the UE.The BUA now needs to activate its PDP address toestablish a path to the Internet.

3. The BUA now activates a primary PDP address, whichenables the BUA to send the original Invite request tothe P-CSCF, which includes the authorization token inthe field header. The network responds Sessionprogress response back to the BUA. The primary PDPis now insufficient to ensure QoS, as this PDP contextwas related to SIP signaling only.

4. BUA now sends an Activate PDP context message tothe SGSN, and once again includes the authorizationtoken in its request [15]. As the resources are alreadyreserved for the SGSN makes reference to thisreservation by looking at the authorization token in thePDP context request. The SGSN sends back an Acceptresponse to the BUA. End-to-End QoS can as a resultbe achieved through the BUA Secondary PDP contexts.

5. Once the network responds with an OK response, theBUA sends a Notify message back to the MIA,informing it of it successful connection to the UMTSnetwork. The call is now established between the BUAand the end recipient at the specified QoS through theUMTS network.

VIII) CONCLUSIONS AND FUTURE WORKThe TSE architecture provides for B2B and B2C e-commerce transactions while the elements devised arerepresented as agents. Our aim is to provide a testbed forthis architecture using SIP as the communication protocolbetween the external and interface agent and using JADEsplatform to create and deploy the devised architecturalelements. We aim to test the variety of auction protocolsand in particular Lowest Price-Sealed Bid. The effect ofcounterspeculation is going to be examined, while gametheory will be used to address the economic associated withbidding.

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[8] Marshall, Ed., Network Working Group, Requestfor Comments:3313,Retrieved from: http://www.faos.ore./rfcs/rfc3313.html. Jan 04

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[10] Collins, J., Jamison, S., Mobasher, B., Gini, M., A MarketArchitecture for Multi-Agent Contracting, In Proceedings of the 2ndInternational Conference on Autonomous Agents Minneapolis/St.Paul, May 9-13, 1998

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[13] Foundation for Intelligent Physical Agents, FIPA Communicative ActLibrary Specification, Retrieved from:htto://www.fina.org/repositorv/cas.php3 Mar '05

[14] Laiho, J., Wacker, A., Novosad, T., Radio Network Planning andOptimisationfor UMTS, John Wiley & Sons, 2002, New York

[15] 3GPP TS 23.207 V6.4.0, , 3' Generation Partnership Project TechnicalSpecification Group Services and System Aspects End-to-End Quality ofService (QoS) concept and architecture, Release 6, Retrieved From:http://www.3ugnp.oru/ftp/Soecs/html-info/23207.htm December 2004

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