Camel Call Flows

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  • Topic: Customised Applications for Mobile networks Enhanced Logic, Global System for Mobile communications, Basic call state model
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  • Published : July 26, 2012
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Research Seminar on Nomadic Computing

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Customised Applications for Mobile Enhanced Logic (CAMEL)
Paulius Meskauskas (paulius.meskauskas@ntc.nokia.com) Research Seminar on Nomadic Computing Department of Computer Science University of Helsinki

1. ABSTRACT Taking the increasing competition of GSM networks into account, a standard was needed to enable competition between operators based on the services offered. ETSI has started in 1994 with the specification of Intelligent Network functionality in GSM, named Customised Applications for Mobile Enhanced Logic (CAMEL). CAMEL will provide the GSM operator with the ability to offer operator specific services based on IN service logic to a GSM subscriber even when roaming outside the HPLMN.

The CAMEL is a network feature and not a supplementary service. It is a tool for the network operator to provide the subscribers with the operator specific services even when roaming in the another network.

CAMEL is divided into several phases to provide GSM operators with CAMEL functionality as soon as possible. The first phase of the standard has been approved in 1997 and is currently implemented by the major GSM vendors. The standardatisation of the second phase has been finalised in 1998 with products to come in 1999. Phase 3 is planned to be finalised in the end of 1999 with products in 2000.

CAMEL makes use of IN SSP-SCP interface. The CAMEL application protocol (CAP) Phase 1 and 2 are based on ETSI Core INAP CS-1R. Howover, limited fraction of the whole operation set is used in order to assure 100% vendor compatibility in face of more than 200 mobile networks looking for mutual roaming agreements.

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2. CAMEL PHASE 1 ARCHITECTURE CAMEL phase 1 architecture is illustrated in figure 1 [1]. Home Network

HLR

MAP

gsmSCF

MAP CAP MAP CAP

gsmSSF

VLR Roaming leg

gsmSSF

GMSC

VMSC

Interrogating Network

Visiting Network

Figure 1. CAMEL phase 1 architecture Continuous lines present a voice connection in the picture. Dotted lines are used for signalling connections between entities. 2.1 Home Network Home network presents the home PLMN of the CAMEL subscriber. Home Location Register and GSM Service Control Function are the network elements or functional entities, which are involved in CAMEL. Home Location Register (HLR) stores subscriber related data, which includes also information whether the subscriber has CAMEL service or not. HLR transfers the CAMEL subscription information to those network elements, which need it to be able to provide CAMEL service. Originating CSI is conveyed to the VLR of visiting network during location update or whenever O-CSI data is modified. HLR passes the originating and

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terminating CSI to the GMSC of the interrogating network while handling terminating CAMEL calls. GSM Service Control Function acts as an entity, where the execution of operator specific services takes place. gsmSCF contains the service logic of OSSs, which is invoked during originating and terminating CAMEL calls. The gsmSSF addresses the gsmSCF based on Global Title. 2.2 Visiting Network The PLMN where the CAMEL subscriber is roaming is called visiting network. It is involved in the handling of originating and forwarded CAMEL calls. Moreover, visiting network may be requested for a location information and a status of the subscriber. The processing of originating CAMEL calls include sMSC, VLR and gsmSSF. Visitor Location Register (VLR) stores the subscriber data received from the HLR of home network. The subscriber data includes the O-CSI, which is passed to the MSC during the originating or forwarded call processing. VLR may also be requested for subscriber’s location and status information at any time by HLR. The purpose of MSC is to setup the calls from and towards the visiting subscriber. While handling the originating calls the MSC...
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