ABSTRACT
Preface................................................................................................................... 473 Introduction.......................................................................................................... 474 Offline.Charging.................................................................................................. 475
Offline.Architecture................................................................................... 475 Online.Charging.................................................................................................. 476
Online.Architecture................................................................................... 476 Immediate.Event.Charging.Example..........................................477 Event.Charging.with.Unit.Reservation.Example.......................477 Session.Charging.with.Unit.Reservation.................................... 478
SIP-Based.Prepaid.AS.Implementation............................................................ 479 Observed.Shortcomings..................................................................................... 481
Dependency.on.End-User.Terminals...................................................... 481 B2BUA.Architecture................................................................................... 482 Failure.Issues...............................................................................................483 Keep-Alive.Mechanism.............................................................................486 SIP.Stack.Implementation.........................................................................486 Service.State.Machine................................................................................ 487 Charging.for.Usage.of.Supplementary.Services.................................... 489
Conclusions.......................................................................................................... 491 References............................................................................................................. 492
As.traditional.communication.networks.move.to.IP-based.protocols,.session. initiation. protocol. (SIP)-based. applications. have. been. rapidly. introduced,. bringing.evolution.to.telecommunication.services.but.also.some.new.challenges..SIP.is.accepted.by.the.3rd.Generation.Partnership.Project.(3GPP).as.a. signaling.protocol.in.the.IP.multimedia.subsystem.(IMS),.an.IP-based.architecture.that.is.expected.to.take.over.a.main.role.from.legacy.signaling.system.
7. (SS7).networks.. Services. in. the. IMS.are. provided. by.application. servers. and.while.the.number.of.services.grows,.it.is.essential.to.provide.consistent. and.reliable.charging.mechanisms..This.chapter.aims.to.show.challenges.in. implementing.a.SIP-based.application.server.based.on.experiences.collected. while. working. on. solutions. for. application. servers. that. provide. prepaid. front-end.functions,.providing.call.control.of.prepaid.sessions,.allowing.session-based.charging.with.unit.reservation.as.well.as.event-based.charging,. and.other.supporting.prepaid. functionalities.such.as.self-care.services. for. end.users..Application.servers.(ASs).can.be.used.to.charge.various.prepaid. services,.but.in.this.chapter.we.primarily.analyze.aspects.of.charging.voice. calls. and. usage. of. voice. supplementary. services.. Several. issues. observed. during. the. implementation. and. possible. solutions. are. discussed.. We. will. provide.basic.principles.of.offline.and.online.charging.as.a.background.for. examples.shown.in.this.chapter.
