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CAMEL in GPRS prepaid service. Outline. Evolution of IN GPRS overview CAMEL in GPRS Discussion. Plain Old Telephone Service. Service logic were hardwired in switching systems.

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Camel in gprs prepaid service

CAMEL in GPRS prepaid service


  • Evolution of IN

  • GPRS overview


  • Discussion

Plain old telephone service
Plain Old Telephone Service

  • Service logic were hardwired in switching systems.

  • Network operators discuss services customers required with switch vendors. (no standard)

  • Once services were implemented, they were not easily modified.

service logic


Stored program control
Stored Program Control

  • In the mid-1960s, stored program control (SPC) switching systems were introduced.

  • As a result, it was easier to introduce new services.

  • Service logic was not modular.

service logic


Common channel signaling
Common Channel Signaling

  • In the mid-1970s, common channel signaling network (CCSN) was introduced.

  • Signaling system number 7 (SS7) is the protocol that runs over the CCSN.

  • SS7 network separates the call setup information and talk path from the common trunk that runs between switching systems.

Ss7 network components
SS7 network components

  • signal switching points (SSPs)—SSPs are telephone switches equipped with SS7-capable software and terminating signaling links. They generally originate, terminate, or switch calls.

  • signal transfer points (STPs)—STPs are the packet switches of the SS7 network. They receive and route incoming signaling messages to destination.

  • signal control points (SCPs)—SCPs are databases providing information necessary for advanced call-processing capabilities

The introduction of in
The Introduction of IN

  • During the mid-1980s, Telcordia Technologies responded to RBOCs’s request and developed the concept of Intelligent Network 1 (IN/1).

  • Service logic splits from switching system, now resides in service control points (SCP).

service logic

now here

Call model
Call Model

  • PICs represent switching system states that a call goes through from origination to termination.

  • SSPs check TDPs to see if there are any active triggers.

  • If an active trigger is detected, normal switching system call processing is suspended until the SSP and SCP complete communications.

SSP suspended,and ask SCP what to do in next step

Transmission plane in 2 5g
Transmission plane in 2.5G

Multiplexing layer





Frame relay

Multiplexing of network protocols
Multiplexing of network protocols


Transmission plane

Signaling plane

Map cap protocol stack
MAP/CAP protocol stack

  • CAP has the same underlying protocol stack as MAP.

  • Ge interface is first defined in 3G, but didn’t appear in 2.5G.

Detection points dps
Detection Points (DPs)

  • GPRS events maybe made visible to gsmSCF. DPs are points at which these events are detected.

  • DPs can be armed to notify gsmSCF GPRS event was encountered, and to allow gsmSCF to influence subsequent handling of GPRS session/PDP Context.

  • If DP isn’t armed, processing entity continues processing without gsmSCF involvement at the DP.

Detection points dps1
Detection Points (DPs)

  • 3 different types of DP:

    • Trigger Detection Point-Request (TDP-R)

    • Event Detection Point-Request (EDP-R)

    • Event Detection Point-Notification (EDP-N)

Detection points dps2
Detection Points (DPs)

  • TDP-R

    • Statically armed, initiate a CAMEL control relationship

    • When GPRS event is encountered, processing is suspended

  • EDP-R

    • Dynamically armed within CAMEL control relationship

    • When GPRS event is encountered, processing is suspended and gprsSSF waits for inst from gsmSCF

  • EDP-N

    • Dynamically armed within CAMEL control relationship

    • When GPRS event is encountered, processing is not suspended.

Gprs attach detach state model
GPRS Attach/Detach State Model

  • 3 DPs are defined:

    • DP Attach

    • DP Change of Position GPRS session

    • DP Detach

Gprs pdp context state model
GPRS PDP Context State Model

  • 4 DPs are defined:

    • DP PDP Context Establishment

    • DP PDP Context Establishment Ack

    • DP PDP Context Disconnection

    • DP Change of Position Context

Gprs camel scenarios
GPRS CAMEL Scenarios

  • 2 scenarios for CAMEL control of GPRS

    • Scenario 1

      • Allows CAMEL control of GPRS session and of multiple PDP contexts within 1 GPRS dialogue

    • Scenario 2

      • Allows CAMEL control of a single PDP contexts

      • Multiple PDP contexts are controlled via multiple GPRS dialogues.

  • Scenario 1 and scenario 2 are mutually exclusive.

Gprs camel scenario 1
GPRS CAMEL Scenario 1

  • Involves Attach/Detach state model

  • Uses less resource (tcap dialogue)

  • More complicated when implementation

Gprs camel scenario 2
GPRS CAMEL Scenario 2

  • Doesn’t involves Attach/Detach state model

  • Uses more resource (tcap dialogue)

  • Simpler when implementation

Gprs attach
GPRS Attach

  • The message sequence chart is too large to fit in this slide. Please see the supplementary document from 3GPP 23060 spec.

  • Notice the “Insert subscriber data” procedure, GPRS-CSI (CAMEL Subscription Information) is sent from HLR to SGSN.

  • 2.5G HLR does not keep GPRS-CSI, nor does it send GPRS-CSI to SGSN.

  • 3G HLR could keep GPRS-CSI, also it sends GPRS-CSI when doing “Insert subscriber data” procedure.

Gprs csi

  • GPRS-CSI contains following information

    • gsmSCF Address

    • Service Key

    • Default GPRS Handling

    • TDP List

    • CAMEL Capability Handling

    • CSI state

    • Notification flag

    • gsmSCF address list for CSI

Pdp context activation in 2 5g
PDP Context Activation in 2.5G

  • C1 :DP for CAMEL_GPRS_PDP_Context_Establishment

  • C2 :DP for CAMEL_GPRS_PDP_Context_Establishment_Acknowledgement

Pdp context activation in 3g
PDP Context Activation in 3G

  • C1 :DP for CAMEL_GPRS_PDP_Context_Establishment.

  • C2 :DP for CAMEL_GPRS_PDP_Context_Establishment_Acknowledgement