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Wireless and Mobile Network Architectures VoIP Service for Mobile Networks Chapter 16 03, 05,06 [email protected] Network Computing LAB 김응도 http://netcom.kw.ac.kr Kwangwoon Univ. Wireless and Mobile Network Architectures VoIP is considered as a promising trend in telecommunication. Integrating mobile phone services with VoIP in particular has become an important issue. Telecommunications and Internet Protocol Harmonization over Network (TIPHON) specifies the mechanism (i.e. a mediation gatekeeper) to provide the service control functions for convergence of IP networks, mobile networks, fixed wireless networks, and PSTN. Several scenario are defined in TIPHON to illustrate different ways of integrating IP and mobile networks. We use GSM as an example of mobile networks to describe mobile/IP integration, where the mobile signaling protocol is GSM MAP http://netcom.kw.ac.kr Kwangwoon Univ. Wireless and Mobile Network Architectures TIPHON IP and mobile integration scenario. IP Network Mobile Network (VLR) Mediation Gatekeeper VLR BSC/BTS MSC HLR http://netcom.kw.ac.kr Gateway Signaling Gateway BSC/BTS Kwangwoon Univ. Wireless and Mobile Network Architectures contents GSM on the Net The iGSM Wireless VoIP Solution The H.323 Network The iGSM Architecture iGSM Procedure and Message Flows Registration Deregistration Call Delivery to the IP network Implementation Issues Reducing GSM Tromboning Effect Misrouting Due to User Mobility http://netcom.kw.ac.kr Kwangwoon Univ. Wireless and Mobile Network Architectures GSM on the Net Based on a concept similar to TIPHON, Ericsson’s GSM on the Net utilizes a corporate intranet to integrate an enterprise communication network with the public GSM network This system supports both terminal mobility and user mobility. Terminal mobility : whereby a terminal can be moved around the service area without losing contact with the system User mobility : whereby, using various types of terminals, a user can move around the service area without losing contact with the system Each of the elements in the corporate network is connected to a switched Ethernet with 10Mbps bandwidth. They communicate with each other using the H.323 family of protocols. http://netcom.kw.ac.kr Kwangwoon Univ. Wireless and Mobile Network Architectures GSM on the Net Corporate offices GSM Network IP Phone/PC Access node VLR BSC/BTS MSC HLR http://netcom.kw.ac.kr Intranet Gateway Service node GSM/BTS Kwangwoon Univ. Wireless and Mobile Network Architectures GSM on the Net Service node Enables user mobility. Controls calls among different types of terminals. Translates addresses between PSTN and GSM on the Net. Provides authentication, resource management, least-cost routing, and administration for user identity and service profile. Access node Resembles the MSC, VLR, and BSC to manage connection, mobility, and radio resources. Does not provide trunks; instead, controls only the communication between the endpoints. Consist of network access controller (NAC), and the radio network server (RNS) http://netcom.kw.ac.kr Kwangwoon Univ. Wireless and Mobile Network Architectures GSM/BTS Provides wireless access for a GSM MS in the IP network Gateway Provides interfaces between GSM on the Net and other networks (particularly the GSM network) Consists of both voice and SS7 gateway functionality Terminal equipment Can be an IP phone, PC, DECT phone, or GSM mobile station. http://netcom.kw.ac.kr Kwangwoon Univ. Wireless and Mobile Network Architectures The iGSM Wireless VoIP soultion We proposes the iGSM service that realizes another TIPHON scenario supporting user mobility for GSM subscribers to access VoIP service. GSM Network에서 GSM 서비스를 받던 사용자가 GSM MS없이 IP Network으로 이동하여 자신의 MSISDN 으로 수신되는 전화를 받기 위해서 H.323 terminal을 사용할 수 있다. iGSM solution is different from GSM on the Net Unlike GSM on the Net, iGSM is a value-added service to the public GSM Networks. iGSM network does not introduce wireless access equipment in the IP network; rather, iGSM service is implemented using standard platforms(general IP gateway / gatekeeper) http://netcom.kw.ac.kr Kwangwoon Univ. Wireless and Mobile Network Architectures The iGSM Wireless VoIP soultion We describe the iGSM architecture and the protocols for location update and call delivery. We discuss how the tromboning effect in standard GSM systems can be avoided when accessing the IP Network. We investigate the problem of misrouting a call caused by user mobility. http://netcom.kw.ac.kr Kwangwoon Univ. Wireless and Mobile Network Architectures H.323 Network The iGSM system consists of the GSM and H.323 (IP) networks. ITU-T H.323 covers the technical requirements for multimedia communications Over packet-based networks that may not provide a guaranteed quality of service MP MP MC H.323 Gatekeeper MC MC ISDN H.323 Gateway LAN PSTN MC H.323 Multipoint Control Unit MP H.323 Terminal (phone or PC) http://netcom.kw.ac.kr <H.323 Architecture> Kwangwoon Univ. Wireless and Mobile Network Architectures H.323 architecture Terminal Customer premises equipment (CPE) that provides audio, video, and data communications capability for point to point or multipoint conferences in the H.323 network Gateway Perform call control function and the communication protocol translation mechanism between an H.323 endpoint and endpoint of a circuit-switched network, such as ISDN,PSTN Gatekeeper Optional in an H.323 network May be colocated with a terminal, gateway, or multipoint control unit Provide these functions that address translation, admissions control, bandwidth control, and zone management. http://netcom.kw.ac.kr Kwangwoon Univ. Wireless and Mobile Network Architectures H.323 architecture Multipoint control unit (MCU) Utilizes multipoint controllers to support multipoint conferences Multipoint controller Provides control functions to support conferences between three or more endpoints in a multipoint conference. Every MCU contains an MC. Multipoint process (MP) Receives audio, video, and data streams from the endpoints involved in a multipoint conference. An MP is optionally included in a gateway, gatekeeper, or MCU http://netcom.kw.ac.kr Kwangwoon Univ. Wireless and Mobile Network Architectures The iGSM Architecture iGSM gateway is implemented to perform two major functions besides the standard H.323 mechanisms GSM MAP and H.225 RAS (registration, admission, status) protocol translation. GSM/PSTN/IP call setup and release An iGSM gatekeeper is implemented to serve as the VLR for iGSM subscribers who visit the IP network. Every iGSM gatekeeper is assigned an ISDN number that can be recognized by the HLR. The iGSM gatekeeper maintains a list of all iGSM subscribers. Based on this list, the gatekeeper performs MSISDN-totransport address translation and GSM roaming management procedures for the iGSM subscribers. http://netcom.kw.ac.kr Kwangwoon Univ. Wireless and Mobile Network Architectures iGSM architecture MS BTS/BSC H.323 Terminal VLR IP network MSC iGSM Gateway GSM HLR Gatekeeper iGSM VLR http://netcom.kw.ac.kr Kwangwoon Univ. Wireless and Mobile Network Architectures iGSM procedures and Message Flows Every iGSM subscriber has a record in the datebase. MSISDN of the MS Transport address of the H.323 terminal for the subscriber in the IP network. Password of the iGSM subscriber HLR address of the iGSM subscriber IMSI of the MS User profile which indicates the service features and restrictions the iGSM subscriber Presence indication of the iGSM subscriber in the IP network. http://netcom.kw.ac.kr Kwangwoon Univ. Wireless and Mobile Network Architectures H.323 수신된 iGSM HLR은 terminal registration deregistration을 IMSI를 Pass를 통해 turn 통해 과정을 HLR은 on user validate oldVLR에 profile을 끝낸다 user검사 profile 알린다 기록 수정 iGSM gatekeeper는 user moves MSISDN password 입력 MAP_INSERT_SUBSCRIBER_DATA IRQ(InsSubDataAck) MAP_UPDATE_LOCATION_ack MAP_CANCEL_LOCATION fromIRQ(UpdateLoc, theand GSM network IMSI, VLR, MSC (user num) profile) 을 iGSM 을 전달 iGSM 전달 전달, passwd) Gatekeeper로 to oldVLR로 the IPgateway로 network RASgateway로 RRQ(MSISDN 전 송 iGSM oldVLR은 Gateway Gateway는 iGSMGSM IRR(InsSubsData, MS의 ACK를 RFC(Registration MAP으로 기록을 HLR로 지운다 변환 전송 user HLR로 Comfirm) profile) MAP_UPDATE_LOCATION(IMSI, 을 gatekeeper로 전달 를 전송 VLR, MSC num) 전송 Registration MS BTS/BSC 1 H.323 terminal VLR MSC 7,8 IP network 3 4 GSM HLR 5 2 3 4 6 http://netcom.kw.ac.kr iGSM Gateway 6 5 Gatekeeper iGSM VLR Kwangwoon Univ. Wireless and Mobile Network Architectures Message flow for iGSM registration H.323 Gatekeeper terminal (new VLR) PRQ(MSISDN) 2 IRQ 3 4 5 IRR Gateway 3 4 6 RCF IRR http://netcom.kw.ac.kr 6 Old VLR MAP_UPDATE_LOCATION MAP_INSERT_SUBSCRIBERDATA 7 IRQ 5 6 HLR MAP_CANCEL_LOCATION MAP_CANCEL_LOCATION_ack 8 MAP_INSERT_SUBSCRIBER_DATA_ack MAP_UPDATE_LOCATION_ack Kwangwoon Univ. Wireless and Mobile Network Architectures deregistration In this case of the iGSM gatekeeper is the “OLD VLR” iGSM subscriber moves from the IP Network to the GSM Network. Gatekeeper HLR Gateway H.323 terminal (old VLR) MAP_CANCEL_LOCATION(IMSI) 1 1 IRR (CanLoc, IMSI) 1 2 IACK (CanLocAck) URQ(unregister Request) UCF(Unregister Confirmation) 2 MAP_CANCEL_LOCATION_ack 2 http://netcom.kw.ac.kr Kwangwoon Univ. Wireless and Mobile Network Architectures Call delivery to the IP network 12 11 HLR 3 3 2 H.323 terminal 8 2 7 iGSM Gateway GSM Gateway MSC 4 IP network 10 6 9 5 3 Gatekeeper 2 iGSM VLR 1 Originating Switch 1 PSTN http://netcom.kw.ac.kr iGSM가입자의 MSISDN입력(0-936105401) GMSC query the location ofatIAM iGSM subscriber Getekeeper는 Gateway H.323 얻은 iGSM Ringing MSRN을 subscriber의 subscriber가 terminal은 tone sends is 통해 Gateway와terminal의 the generated gatekeeper와 GMSC는 MSRN을 수신하면, H.225(Q.931) 수신한 H.323 the ARQ message를 H.323 Set-up gateway는 주소를 terminal은 and ACF msg 통 0to: HLR special digit , 936 : GMSC MSISDN을 통해 HLR은 가입자가 IP 해 를 RAS terminal MSRN H.323 Connect terminal에 생성 H.225 message RAS Alerting 전달 LCF(Location 를 gateway에 message CallACF Proceeding Confirm) isReject) 전달 sent to message를 통하여 ARQ (Admission Gateway와 교환(이때 Request) trunk ARJ(Admission 설정 and Originating switch send SS7 IAM message to network에 있음을 확인 HLR send 를 (Admissions gateway gateway로 gateway는 Confirm) 전달 originating gateway는 exchange Alerting message를 iGSMreply (충분한 수신 SS7 가능 ANM로 routing 변형되어 정보를 받았다) message switch에 전달 GMSC gateway(MAP_PROVIDE_ROAMING_NUMBER) MAP_PROVIDE_ROAMING_NUMBER_ack gatekeeper로부터 대화 SS7 ACM 시작message로 MSRN을 변형하여 통해 GMSC에 terminal의 with 전달 Gateway LRQ(Location Request)를 MSRN 을 HLR에 전달 transport HLR은 GMSC에 call-signaling channel address 획득 Gatekeeper에 전달. MAP_SEND_ROUTING_INFORMATION_ack Kwangwoon Univ. Wireless and Mobile Network Architectures Message flow for iGSM call setup http://netcom.kw.ac.kr Kwangwoon Univ. Wireless and Mobile Network Architectures Implementation Issues iGSM을 구현함에 있어서 고려해야 할 두가지 이슈 Reducing GSM Tromboning Effect Investigating misrouting of user mobility http://netcom.kw.ac.kr Kwangwoon Univ. Wireless and Mobile Network Architectures Reducing GSM Tromboning Effect Tromboning occurs when the caller and the called MS are in the same city but the GMSC is in another city. Both GSM MSCs and iGSM gateways can serve as GMSCs for iGSM subscribers If an iGSM subscriber is assigned a GSM MSC as his GMSC, call delivery follows the procedure iGSM call delivery and tromboning occurs. If an iGSM subscriber is assigned a iGSM gateway as his GMSC, call delivery tromboning can be avoided http://netcom.kw.ac.kr Kwangwoon Univ. Wireless and Mobile Network Architectures Reducing GSM Tromboning Effect iGSM IP network PSTN iGSM user Switch 2 IP Network iGSM user iGSM 5 Gateway 1 3 caller iGSM IP network iGSM 2 Gateway 4 Gatekeeper iGSM VLR <PSTN-to-IP Cal Setup> 1 caller Gatekeeper iGSM VLR <IP-to-IP Cal Setup> Two kinds of subscribers are anticipated in iGSM The GMSCs of the iGSM subscribers are standard GSM MSCs. In this case, the subscibers typically subscribe to the standard GSM services at the beginning, and determine to include the iGSM service later The GMSC of the subscribers is the iGSM gateway. In this case, the subscribers typically subscribe to the iGSM service from the beginning http://netcom.kw.ac.kr Kwangwoon Univ. Wireless and Mobile Network Architectures Reducing GSM Tromboning Effect The first kind of subscribers call delivery follows the standard GSM procedure A subscriber visits the IP network, tromboning may occur as in traditional GSM networks The GSM operator would prefer this scenario if the iGSM gateway and gatekeeper are owned by other ISPs. The second kind of subscribers Call-delivery tromboning avoided when the subscriber visits the IP network. The GSM operator is likely to own the iGSM gateway and gatekeeper http://netcom.kw.ac.kr Kwangwoon Univ. Wireless and Mobile Network Architectures Misrouting Due to User Mobility To support user mobility, the subscriber needs to explicitly perform registration to inform the system in which location area he resides when the terminal has been changed. Missing call deliveries may be misrouted This problem can be eliminated if the subscriber always turns off the MS when he moves to the H.323 terminal The turn-off action results in a GSM detach message, which deregisters the MS. http://netcom.kw.ac.kr Kwangwoon Univ. Wireless and Mobile Network Architectures Misrouting Due to User Mobility 4 1 GSM MS 2 IP Phone MSC VLR A p GSM VoIP Gateway HLR 3 p B A GSM VLR B p VoIP network step1 step2 step3 http://netcom.kw.ac.kr Kwangwoon Univ. Wireless and Mobile Network Architectures Misrouting Due to User Mobility The misrouting problem is avoided if the subscriber explicitly or implicitly registers with the GSM MS step3. Implicit registration occurs in two cases The subscriber originates a call. In this case, VLR A finds that the VLR record for the subscriber does not exit. VLR A will ask the MS to perform a registration operation, as described in the VLR failure restoration procedure The subscriber moves to another LA in the GSM network. Registration is automatically initiated by the GSM MS. Both case, after the HLR has modified the subscriber’s record, it also cancels the subscriber’s VLR record in VLR B http://netcom.kw.ac.kr Kwangwoon Univ.