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Contents 1 CAMEL Introduction 3 1.1 What is CAMEL? 4 1.2 CAMEL Services 6 1.3 CAMEL subscription information 10

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1.1 What is CAMEL? As the requirement for additional services grew within the communications industry, a new platform was introduced. This Intelligent Network (IN) is still used today to add these services without the additional cost of developing new software or hardware for the dedicated existing network elements. The IN services were unfortunately vendor specific, meaning that the IN network, along with its services, could be introduced in any existing operators network who uses equipment of that vendor. The IN services became very popular and is used extensively by both the operator and subscriber. The very first usage was for the so called ‘freephone’ or ‘shared-cost’ numbers. Introducing these services in the PSTN networks, it meant that some other party could be charged instead of the calling party. These IN components can however also be added to the mobile networks (GSM, UMTS, or GPRS) to enhance the services available in these networks. One example of such a service, perhaps the mostly used on as well, is the prepaid service. Some problems however did surface, as happens with every new service. The main problem was that these IN subscribers could not roam into other networks and still use their IN services. The reason was quite simple. There was no set standard of assigning the services to the subscribers, nor were there any standard protocols that should be used for transmission of service information between the switching network and the IN. To overcome this problem, an international standard was set up, called CAMEL. It stands for Customized Applications in Mobile Networks Enhanced Logic. It specifically deals with the mobile problem of roaming subscriber and applies to mobile networks only. The emphasis in this course will thus be on mobile networks. As the CAMEL services required were increased, new standards were developed for these new services which lead to CAMEL being introduced in phases: CAMEL phase one, two, three and four. It should be said that CAMEL phase 4 includes all the latest available services as well as all services of CAMEL phases 1, 2 and 3. The specifications for CAMEL can be found in the 3GPP technical specification 23.078 (3GPP TS23.078) and 29.078 (3GPP TS29.078) documents.

TIP It is important to know which versions of these specifications are used in the specific project, since there might be vast differences in the different versions of the specifications. The different CAMEL phases 1 to 4 for instance, are specified in different versions of these documents. Nevertheless, the latest version includes all operations for CAMEL phases 1 to 4.

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What is CAMEL ?

Intelligent network standardOperator specific servicesavailable for roaming sub.Standardized protocolStandardized serviceparameters (CSI)Additional networkcomponents

Customized Application in Mobile Networks, Enhanced Logic

Fig. 1 What is CAMEL?

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1.2 CAMEL Services As already mentioned, IN services are additional services which add to network value, but are not provided by the switching networks. These services are divided into two parts:

a) basic IN services b) subscribed IN services.

1.2.1 Basic IN services The basic IN services provides applications for which the subscribers do not have to have a subscription. Any subscriber can use these IN services as long as they are roaming in that particular network. The standard for basic IN services is only available from CAMEL phase 3. If an operator would like to use basic services but has not implemented CAMEL phase 3 yet, they will have to resort to a proprietary solution. This means they should use a national IN protocol and an own solution to start the IN dialog. Normally, these services are recognized by the dialed digits and many operators or vendors have their own solutions. For instance, routing the call to the PSTN where an IN dialog is triggered or simply using the dialed digits to start an IN dialog if it is defined in the routing database. Examples of basic IN services are the following:

Universal Access Numbers Using a similar idea as cell orientated routing, the subscriber can dial a national number (which may be a short code) to connect to the nearest service center of a specific company. It does not matter where the subscriber is roaming, the dialed number will stay the same and he or she will always be connected to the nearest service center. This may be used for instance for larger taxi companies, airlines, operator service centers and information centers just to name a few.

Premium Rate Calls These numbers are those services that may either provide information or entertainment to the subscriber. Typical examples are weather reports for information and signs of the zodiac for entertainment. These numbers are usually more expensive to phone and should thus be charged accordingly.

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Free phone

Berlin

MünchenDials2525

Dials2525

Routing to 030 XX

Routing to 089 XX

Universal AccessNumber

Please dial7676 1 for Genesis7676 2 for Queens

7676 1

7676 2TelevotingService

+ =

Premium Rate Call

Basic INBasic INServicesServices

Fig. 2 Basic IN Services

Voting Services or Competitions Becoming very popular especially with the reality shows on television, these services are used by subscribers to vote in a certain competition. The services may also allow the subscriber to participate in certain competitions and is usually done by means of an announcement system which also records the subscriber input. A similar service can also be realized using the SMS services. These services are also normally charged at higher rates than normal calls.

Freephone Numbers Freephone numbers can be used in association with universal access numbers. It represents a service where the calling subscriber might not be charged for the call that he is making. This service would typically be used by larger companies for customer support.

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1.2.2 Subscribed IN services Subscribed IN services are services which have to be assigned to a subscriber. Usually the subscriber is then charged a monthly fee (e.g. virtual private network) or a fee every time the service is used (multiparty and call completion to busy subscriber). Sometimes the subscriber might not even be charged for the service itself (e.g. prepaid services). Some examples of subscribed IN services:

Virtual Private Network VPN services allow business clients to reduce costs of communications between their employees. This service allows the company to use the public operator’s resources to establish its own private network. The need for PBX’s is eliminated in this way. Usually the company will also receive their own numbering scheme which will be used for internal calls. Normal outgoing call or incoming calls will use standard destination numbers or MSISDN’s respectfully.

Prepaid subscribers No introduction to the prepaid service is required. This service allows a subscriber to use the network on a pay as you go basis. This can be implemented for the GSM, GPRS or UMTS networks. Usually the subscriber is not charged for the service itself, but is charged for every call made, and in certain networks, if a call is received too.

Family and Friends This service allows the subscriber to assign a specific amount of number to a list. This list is considered friends or family of the subscriber and phone calls to these numbers may be charged at lower rates than normal. This service may be realized by adopting the MCR records for contract subscribers, but may typically use the IN network for prepaid subscribers.

Mobile Access Hunting Also called personal number service, it is mainly used by business people. This service allows the subscriber to be reached by a single number, regardless whether he is in a mobile or fixed network. Along with this function, the subscriber can also administrate which calls must be put through and which calls must be forwarded to the mailbox. It can almost be seen as an enhanced call forwarding service.

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Accountbefore call

after firstcall

after nextcall

Prepaid Call

Friends &Family

Buissnes

special tariff

One number

office

private

mobilemailbox

Personal Number Service

SubscribedSubscribedIN ServicesIN Services

Fig. 3 Subscribed IN services

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1.3 CAMEL subscription information Basic IN services generally do not require the need to assign these services to a particular subscriber. Subscribed IN services however require the operator to assign these services to the subscriber in the HLR. These services are assigned using a special designator called a CAMEL Subscription Information or CSI. These CSI’s are defined by the operator and they contain certain standardized parameters. Different CSI’s are required for different IN services. A limitation however allows us to assign only one CSI of a specific kind to any one subscriber. These CSI’s are stored in the subscriber data in the HLR and some of them are transferred to the VLR or SGN during location update. The CSI contains all the relevant information regarding that specific IN service and is evaluated by the switching network when an IN dialog is triggered.

CSI's parameters These CSI’s contain many different parameters, but the four most important parameters are:

a) Trigger Detection Point (TDP): This tells the switching network precisely when the IN dialog shall be started

b) gsmSCF Address: This address is the E.164 number used to connect to the IN patform. This number is used in the GTT database for conversion to a SPC and Network indicator. It identifies the CAMEL equipment responsible for this IN dialog.

c) Service Key: This parameter identifies the program to be executed by the IN service logic. In other words, it identifies the IN service that is to be used.

d) Default Call Handling: This parameter tells the switch what shall be done of the IN network cannot be contacted. I.e. shall the cal be released or shall the call continue.

CSIs in the different CAMEL phases The CSI’s were developed as a standardized solution to introduce the various services in the existing networks and to assign these services to the subscribers. As the amount of services increased, so did the CSI’s. Not all the CSI’s were available since CAMEL phase 1 and as the different CAMEL phases were introduced, so were new CSI’s. The various CSI’s and their function are listed in the next pages. The table on Fig. 4 shows the characteristics of CSI’s as well as which CAMEL phases they belong to. From this table it can already be seen that CAMEL phase 3 has brought the most changes to the CAMEL environment.

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CSI CAP ph. 1 CAP ph. 2 CAP ph. 3 CAP ph. 4 max. no. of CSIs per MSUB

O-CSI X X X X 1

T-CSI X X X X 1

VT-CSI X X 1

GPRS-CSI X X 1

SS-CSI X X X 1

SMS-CSI X X 1

MTSMS-CSI X 1

D-CSI X X 1

M-CSI X X 1

U-/UG-CSI X X X 1

N-CSI X X ---

TIF-CSI flag in O-CSI X X 1

CSIs, available in the different CAMEL phases

Fig. 4 CSIs, available in the different CAMEL phases

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1.3.1 Mobile Originationg Calls - CSI (O-CSI) The O-CSI is used to start an IN dialog for mobile originating calls. It is transmitted from the HLR to the VLR during location update where it is evaluated when the subscriber starts a mobile originated call. After evaluation of the O-CSI, the signaling address of the CAMEL service equipment is derived by means of global title translation. The gsmSCF address in the CSI is used for this purpose. Call processing is suspended in the switch, or more correct, the SSP (services switching point) and at this point and an IN dialog is started. The connection to between SSP and CSE is pure SS7 and the CAMEL protocol is used. The SSP has to wait for further instructions from the CSE. The CSE may return new call parameters i.e. charging information, new destination address etc. Once the information is received from the CSE, the SSP will continue call processing. If no connection from the CSE is received, the SSP will follow the default call handling procedure as it is described in the CSI.

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VLRVLR gsmSSFgsmSSF

HLR

CSECSE

MOC outgoing leg

MAP V3CAP Home PLMN

Visited PLMN/Home PLMN

2

45

3

6

1

VMSC

INMOC Call flow

Fig. 5 INMOC Call flow

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1.3.2 Mobile terminating Calls CSI (T- and VT-CSI) For mobile terminating calls which should start an IN dialog, the T- or VT-CSI’s are used. The difference between the two is where the IN dialog is started from.

T-CSI The T-CSI is not transmitted to the VLR during location update. It remains in the HLR. When the subscriber received a call, the HLR is interrogated. During the interrogation, the MAP V3 message includes a parameter called ‘Suppress_TCSI’. If this parameter value is equal to 0, it means that this message is the first step of a two step interrogation. In this case, the HLR will return the T-CSI (if it is available i.e. subscriber has a T-CSI assigned and it is allowed to be sent to the MSC) instead of a MSRN. The T-CSI is then evaluated in the interrogating MSC (also called a Gateway MSC or GMSC). Once again, the CSE address can be derived from the T-CSI and this GMSC is responsible for the IN dialog. The IN dialog can only be started for a call attempt. At this point it is not known if the subscriber is busy or will not answer. Call processing is suspended until an answer is received from the CSE. Once call processing is resumed, the GMSC will send a second ‘Send_Routing_Information’ message to the HLR. This time, the ‘Suppress TCSI’ parameter will have the value of 1. This tells the HLR that this is the second step of the interrogation, and that a real MSRN must be requested from the VMSC. The VMSC return a MSRN to the HLR and normal call processing takes place. If the called subscriber does not have a T-CSI assigned, the HLR will immediately request a MSRN from the VMSC. Normal call processing takes place in this case.

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VLRVLR

gsmSSFgsmSSF

CSECSE

MTCincoming leg

Visited PLMN

Home PLMN

InterrogatingPLMN

7 6

5

62

37

1

4

8

VMSC

GMSC

HLR

INMTC Call flow

Fig. 6 INMTC call flow

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VT-CSI The VT-CSI differs from the T-CSI in that it is sent from the HLR to VLR during location update. When the subscriber who is assigned a VT-CSI receives a call, normal call processing takes place. The HLR is interrogated normally; the MSRN is requested by the HLR and returned to the GMSC. This MSRN is used to set up a connection to the VMSC. Once the MSRN is received in the VMSC, one of three things can happen to start an IN dialog:

I) the subscriber may be busy, II) the subscriber might not answer, or III) a terminating attempt is made.

Only if one of these detection points is reached the VLR will send the VT-CSI to the VMSC. Unlike the T-CSI which can only start an IN dialog for a call attempt, the VT-CSI can also start an IN dialog if the subscriber is found busy or not answering. Like before, the VMSC will evaluate the criteria from the VT-CSI and start an IN dialog. Call processing is suspended until an answer from the CSE is received. If a subscriber is roaming in the GMSC and is assigned both the T- and VT-CSI, that GMSC will start two IN dialogs. First for the T-CSI and afterwards when the MSRN is reached, a dialog for the VT-CSI is started.

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ISUP:IAM (MSRN)

MAP:SRI_ACK

MAP:SRI MAP:PRN

MAP:PRN_ACK

B-

MSISDN

GMSC

VMSC

HLR

CSE

Loc.-upd.

(VT-CSI)

VT-CSI

TDP12

TDP13

TDP14

IN-dialog

busy

no answer

gsmSCFgsmSCF

1

2

3 4

56

7

8

9

Evolution of VT-CSI in VMSC

Fig. 7 Evaluation of VT-CSI in VMSC

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1.3.3 Basic IN services CSI (N-CSI) Basic IN services can be used by any subscriber. An IN dialog is started based in the dialed digits received in the VMSC. In CAMEL phase 1 and 2, there was no set standard for these services and a national protocol was used for IN communication as well as a proprietary solution to start the IN dialog. Since CAMEL Phase 3, the N-CSI was introduced in an attempt to standardize the basic IN services. Since these basic services are only available in the HPLMN and they were already in place before CAMEL phase 3, the operators and vendors in general still use the original proprietary solutions.

1.3.4 Dialed IN services CSI (D-CSI) The D-CSI is used as a subscription to dialed IN services. This means that when a subscriber dials a specific number, an IN dialog is started. These services differ from the basic IN services. Basic IN services are usable by any subscriber, whether he or she has an IN subscription or not. The subscribed dialed IN services requires the subscriber to subscribe to this service and then gets assigned a D-CSI. Global companies e.g. airlines or car rentals like to have a universal number which should be valid anywhere in the world. The service might even be used to connect to a voicemail service. The subscriber could then dial the same number, irrespective of where he is roaming to be connected to a service center of that company. The D-CSI contains a list of up to 10 numbers which can be dialed by the subscriber while roaming anywhere in the world. If the subscriber is assigned a D-CSI, the VMSC will compare the dialed digits with the numbers contained in the D-CSI list. If they match, an IN dialog will be started from that VMSC. Call processing is suspended once again, and the IN returns a new destination number used for routing by the VMSC to the required service center.

1.3.5 Supplementary services CSI (SS-CSI) The supplementary service CSI is used to inform the IN if a subscriber activates the CCBS (Call Completion to Busy Subscriber) or multiparty supplementary service. The supplementary service CSI is mainly used for charging the usage of such a service. The SS-CSI is transmitted to the VLR during location update. This CSI does not start an IN dialog, instead it just sends a notification to the CSE that the service has been activated. This is done by means of a MAP message: ‘Supplementary_Service_Invocation_Notification’.

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CSE

HLRVLR

VLR

foreignVPLMN

Ins_Sub_Data(D-CSI:080012345678)

Update_Location

Locationupdate

IN-dialogIN-dialog

HPLMN

080012345678

Update_LocationIns_Sub_Data(D-CSI:

080012345678)

080012345678

1

2

3

4

5

6

7

8

10

Dialed IN services in HPLMN and VPLMN

Fig. 8 Dialed IN services in HPLMN and VPLMN

gsmSCFMAP:Insert_Subscriber_Data[SS-CSI]

HomePLMN

Visited PLMN/HomePLMN

MAP

:SSe

rv_I

nvoc

atio

n_N

otifi

catio

n[SS

V=M

PTY]

Set up conference call

MAP:SServ_Invocation_Notification[SSV=CCBS]Invoke

CCBS

HLR

VMSC

CAMEL services: supplementary servicesinvocation

Fig. 9 CAMEL services: supplimentary services invocation

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1.3.6 ?????? (M-CSI) The M-CSI is transmitted to the VLR during location update. It has to be assigned beforehand to the subscriber in the HLR. This CSI will cause the VLR to send mobility information to the CSE. The information may be sent if the subscriber makes:

a location update in the same or a different VLR

gets attached to the network or

is detached from the network (MS initiated or network initiated). Once again, no IN dialog is started, instead the information is sent from the VLR to the CSE in the form of a MAP message: ‘Note_MM_Event’. This message contains information such as the event which took place, which CAMEL phase is supported in the VLR, the service key, the IMSI and MSISDN of the subscriber and the location information as it is stored in the VLR.

TIP Since CAMEL phase 4, mobility management of GPRS subscribers is available. A different CSI is used however. This MG-CSI is sent from the HLR to the SGSN during location update and is used in the same way as the M-CSI.

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VPLMN

VLR

HLR

You just enteredSUNNYnet. Ourroaming tariffs

are...

CSE

Location update Update_Location

Insert_Sub_Data(M-CSI)

MA

P:N

ote_

MM

_Eve

nt(lo

c-up

d)

„e.g. send SMS“

AC=M

MEV

NTR

SMSC

Mobility management notification

Fig. 10 Mobility management notification (example)

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1.3.7 SMS Originating and SMS terminating CSI ???? (SMSMO- and SMSMT-CSI)

Before CAMEL phase 3 only proprietary solutions were available for IN SMS services. Since CAMEL phase 3, a SMS originating message cold trigger an IN dialog. The delivery of the message could be confirmed up to the SMS center, but not to the final subscriber. Since CAMEL phase 4, the SMSMT-CSI is available which starts an IN dialog as soon as the MS receives a SMS.

SMSMO-CSI Administrated and assigned to the subscriber in the HLR, the SMSMO-CSI is available from CAMEL phase 3 an up. It is transmitted to the VLR during location update in is evaluated if the subscriber send a SMS. Consequently, an IN dialog is started using the parameters available from this CSI. If he IN dialog is successful, the SMS is forwarded to the SMS center. The acknowledge message from the SMS center can be used to inform the IN of a successful or unsuccessful delivery.

SMSMT-CSI Administrated and assigned to the subscriber in the HLR, the SMSMT-CSI is available from CAMEL phase 4. It is transmitted to the VLR during location update in is evaluated if the subscriber receives a SMS. According to the standardized solution, the IN dialog is performed and then only is the mobile station paged. Certain vendors however deviate from this by paging the mobile stations before starting an IN dialog. This CSI can typically be used in services where sport scores are sent to the subscriber after a weekend of important sporting event. To prevent charging of not received SMS’s, the SMSMT-CSI can determine if the SMS was delivered to the MS successfully or not. Acknowledgement from the MS may be used to inform the CSE of the delivery status if such a SMS.

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CSE

MSC/VLR

OP:

IDP_

SMS

(des

tinat

ionS

ubN

o,SM

SCad

r...)

PPSC:tariff information

and prepaid account

SMSoriginating

SMS-Servicecenter MSISDN+called Party address(e.g. VPN short number ornormal MSISDN)

CA

P Ph

3

OP:

CO

N_S

MS

(des

tinat

ionR

outin

gAdd

r...)

MAP:Forward_SM

MAP:Insert_Sub_Data

HLR

SMS-CSI 1

2

3 4

5

SMSC

IN trigger for SMSMO

Fig. 11 IN triger for SMSMO

CSE

MSC/VLR

OP

:IDP

_SM

S(d

estin

atio

nSub

No,

SM

SC

adr..

.)

PPSC:tariff information

and prepaid account

OP

:CO

N_S

MS

(des

tinat

ionR

outin

gAdd

r...)

MAP:Forward_SM

MAP:Insert_Sub_Data

HLR

TSMS-CSI1

2

3

4

5

67

8

9

10

Paging

Paging Response

Forward SM and Forward SM_ack

MA

P:S

RI a

nd M

AP:

SR

I_ac

k

Forward SM_ack

Forward SM_ack

SMSMT with IN dialog

SMSTerminating

SMSC

Fig. 12 SMSMT with IN dialog

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1.3.8 USSD CSI (U- and UG-CSI) In certain instances, a subscriber is allowed to send a USSD code to his home network to activate a certain service. These USSD codes may start an IN dialog if the relevant U-CSI exists. The U-CSI can be split into 2 types:

a) General services (UG-CSI) which can be used by any subscriber b) Subscribed services (U-CSI) to which a subscriber must subscribe and is

assigned a specific U-CSI. In GSM specification 02.90, ot is determined that all USSD codes 100-149 shall be transmitted to the HLR of the subscriber and all codes 150 to 199 shall be evaluated in the VMSC. If the subscriber send a USSD code corresponding to the first list (100 to 149) the VMSC forwards this string to the HLR of that subscriber. In the HLR it is determined if the code belongs to a certain IN service by evaluating the USSD string code to those in the U/UG-CSI’s. If this service is an IN service, the HLR will use the information in the corresponding U- or UG-CSI to relay the service information to the CSE by means of a MAP message.

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MAP_PROCESS_USSD_REQ( ..., USSD String IA#5,....)Y

MAP_PROCESS_USSD_REQ

( ..., U

SSD String IA

#5,....)

global titletranslation

global titletranslation

MAP_PROCESS_USSD_REQ ( ..., USSD String IA#5,....) MAP_PROCESS_USSD_REQ Response

( ..., USSD String IA#5,....)

MAP_PROCESS_USSD_REQ Response( ..., USSD String IA#5,....) MAP__PROCESS_USSD_REQ Respon

se

( ..., U

SSD String IA

#5,....)

U-CSI and/or UG-CSIwith gsmSCF address

U-CSI and/or UG-CSIwith gsmSCF address

HLR relay function for USSD

CSE

HLR

MSC/VLR

HPLMNservice code

?

Fig. 13 HLR relay function for USSD

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1.3.9 CPRS-CSI The IN services for GPRS is mainly limited to prepaid charging of the subscribers. For GPRS it is important to differentiate between to terms:

GPRS session

PDP context establishment. A GPRS session is based on time and specifies the time that the subscriber is booked into the GPRS network, regardless whether he is sending or receiving any data. A PDP context establishment defines the situation where the subscriber establishes a data connection. In either case, the GPRS-CSI is sent to the SGSN as soon as the subscriber makes a location update in the GPRS network. An IN dialog can be started for any of the following reasons:

a) The subscriber is attached to the GPRS network or changes position while attached without an active connection. Note that the CSE may be informed if the subscriber detaches from the GPRS network.

b) The subscriber starts a PDP context. As soon as the request is received from the mobile station, an IN dialog is started.

c) After the PDP context is established. When the GGSN replies after a PDP context establishment request, the SGSN may start an IN dialog.

d) If the subscriber changes position during an active PDP context an IN dialog may also be started.

TIP GPRS IN services have only been available from CAMEL phase 3.

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gprsSSFgprsSSF

gprsSSFgprsSSF

CSEgsmSCF

CSEgsmSCFCAP3

End of 1st IN dialog(OP:ACRgprs)

2nd IN dialog (OP:IDPgprs)

SGSN

Con

tex t

Update PDP Context

Update_Location/

Insert_subscriber_data

(GPRS-CSI)

Cancel Location

Routing Area UpdateRequest

Routing Area UpdateAccept

GGSN

DN

S Q

uery

(OP:ACgprs)

Cancel Location_ack

GPRS: PDP context change of position with

IN dialog

HLR

TDP 14

newSGSN

oldSGSN

DNS

Fig. 14 GPRS: PDP contex change of position with IN dialog

Attach Request

Ide n

tific

atio

nR

eque

st/

Re s

pons

e

Update GPRS Location

Attach Accept

Cancel Location/ackn.

Insert Subscriber Data

newSGSN

CSEIN dialog

gsmSCF

gprsSSF

GPRS attach procedure

oldSGSN

DN

S Q

uery

DNS

TDP 1/2

HLR

Fig. 15 GPRS attach procedure

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