Intelligent Networks and CAMEL

Introduction to Intelligent Networks (INs)
Traditionally, switching equipment (telephone exchanges) would need upgrading
each time a new service was added to the network (Figure 3.42). In some networks,
the presence of hundreds or thousands of telephone exchanges meant that this was
a very long and labor-intensive task.

The concept of Intelligent Networks (INs) allows the service to be provided
within a central computer or service control point (Figures 3.43). Once the telephone
exchanges have been upgraded to include the IN features, no further upgrades are
required except for the updating of the tables that identify the IN triggers, such as
the 1-800- or 0800-digit string to identify the toll-free or freephone service.

These services are generally provided through service control points, which
translate the service-specific dialed numbers (an 800 number perhaps) into standard
numbers for routing to the actual destination (telephone) in the network.
The special number is the initial trigger for the telephone exchange to contact the
service control point, to translate the number, and to carry out special billing, such
as reverse charging or collect calls, or premium rate.

These early services were soon followed by further advanced services based on
the intelligence or control features within the service control point. Extra service
features such as interaction with the user allow further customization of services.
IN separates service intelligence and switching. This means that new services
can be quicker and cheaper to install, and that service creation and switching is
split into two markets, thereby increasing vendor competition.

Most IN, including GSM Phase 2+ networks, use SS7 (Signaling System Number
7) protocols to enable the switches (known as service switching points, or SSPs)
to communicate with databases known as service control points (SCPs). A standardized
set of SS7 messages known as INAP (Intelligent Network Application
Part) is used for interaction between the SSP and SCP.

The intelligent applications that control IN services are defined by the operator,
and are not themselves standardized. This means that IN offers a route to operator
differentiation, but also that in many cases the same services cannot be offered
outside the network of that operator.

Service Control Platforms
Service control platform (SCP) is the name given to a platform that is, in some way,
controlling services on a network, or in some cases, across network boundaries. One
of the main advantages in using an SCP within a network is that it significantly
reduces the upgrade costs within a network whenever a new service is introduced.

Control of supplementary services. These may include services such as conference
calls, advice on billing, and provision of call-back services such as ring
back when free. Supplementary services are seen as key revenue generators for
network operators.

Number translation services. In most modern networks it is possible to dial tollfree,
local or premium rate services. These are, in effect, virtual numbers that
have special tariffs. Number translation services (NTS) minimize the amount
of configuration required on the network when a new service is provided.

CAMEL (Customized Applications for Mobile Networks Enhanced Logic)
INs and Mobile Networks: The Problems
In fixed networks, the IN concept can be implemented in various ways.
In each case, however, the interfaces are confined within a single network, allowing
the defined procedures and information flows to be applied on an interface
with known and defined endpoints, and within hardware belonging to the single
network operator.

Testing is therefore more straightforward as each interface can be tested independently
and, in addition, non-standard procedures and information can be used
to satisfy particular problems (even if this is just a certain way of interpreting an
ambiguous part of the standards). The IN procedures have been specified to interwork
(mainly) with call control, hence a simple relationship exists between the two.
For mobile networks, the situation is more complex because roaming scenarios
require that equipment in more than one network is involved. Considering
all the roaming agreements each network will have in place, and the rapid change of each of these networks as new hardware (switches, etc.) is added, it is
impossible to test each individual interface that will likely be involved in an IN call,
or to interpret specifications in anything other than a single standard way.

The next big complication is that IN procedures need to interwork with call
control, mobility management functions, and the additional features of mobile
networks such as the General Packet Radio Service and the Short Message
Service. Finally, any announcements should be supported by special announcement
machines, the positioning of which needs careful thought. Location in the
home network provides ease of management, but an international call leg would
be needed to play announcements to roaming subscribers. Locating the announcement
machines in serving networks leads to a higher cost of hardware and increased
management costs, but reduced cost per call.