Distance sensitive rating

One of the key concepts used in distance sensitive rating is to model a connection between two subscribers by means of connection points. The connection between subscriber A and B in diagram can be described by a sequence of the points: A party - switch 1 - switch 2 - B party.

Diagram Modelling a connection with points

Connection points are an abstraction for everything that one might consider as point of a connection, such as:

• CGI (Cell Global Identity) that in GSM networks identifies the cell where a mobile station is located.
• Network elements.
• E.164 phone numbers.
• A subscribers home location.
• ...

Each of these entities has an attribute that identifies its assigned connection point. This mapping makes it possible to base all distance sensitive rating on one generic tariff classification system, that uses pairs of connection points as origin and destination to determine the tariff class.

Diagram Responsibilities of tariff classification systems

As shown in diagram specialized mapping TCS identify the connection point of the CDR attributes that should be used as origin and destination for a give usage type and rely on the assigned generic TCS to determine the tariff class.
This construct not only reduces the amount of needed configuration data but also ensures that new objects can be used as rating criteria without changing the core logic.

As an example, consider an outgoing call to a foreign network:

For the A subscriber the usage is rated using its location as origin, while for the PSTN the origin is the gateway switch G. For both ratings, the destination is the B-party number. Because we can assign a connection point to the A-party location and the gateway switch, the same generic tariff classification system may (but need not) be used.

• The mapping TCS that is assigned to the A subscriber does the following:
  

  origin	=	A-party location	=	connection point 4
  destination	=	B-party number	=	connection point 27

• Similar, the TCS valid for the PSTN maps:
  

  origin	=	gateway switch G	=	connection point 4
  destination	=	B-party number	=	connection point 27

• Once the mapping is done, both TCS may use the same generic TCS to determine the tariff class.

Connection points

A connection point is abstraction for everything that can be identified as a point in a network connection. This can be real existing objects, but also conceptual entities, e.g. the voice mail box or the home location of a subscriber.
Connection points have a tree-like structure where, at a given moment in time, each connection point has exactly one parent and multiple children. In order to model Switzerland networks, one might set-up the following hierarchy:

• World
  • Europe
    • Eastern Europe
    • Western Europe
      • Austria
      • France
      • Germany
      • Italy
      • Switzerland
        • Swiss PLMN
          • SwissCom
          • Sunrise
        • Swiss PSTN
          • Bern
          • Geneva
          • Zurich

There is one important requirement, that we need to consider when designing the structure and relationship of connection points: It must be possible to make adjustments to the hierarchy. This mainly means that new points can be inserted into the hierarchy, but whenever possible we should support deletion too.
At the same time we allow for changes, we have to insure that rating is reproducible. This means that the structure of the connection point tree must allow to determine a connection point's parent for a given time. The relevant members of ConnectionPt are shown in diagram

Diagram ConnectionPt members

The most interesting member of ConnectionPt is getParent(DateTime ts): If at ts the status of the connection point is released, the function returns the parent that is released at ts. If the connection point is a root or if it is not released at time ts, an empty connection point id is returned.

Consisteny and allowed modifications

A connection point that is root can always released for production. A non-root connection point must fulfill the following conditions:

• The parent must exist and be in status released throughout the release period of the connection point.

As long the avove condition is fulfilled, connection points can be added to the hierarchy at any time. In order to delete a connection point, its status must be editable. Once a connection point is released to production, its status may be changed to standby (and subsequently to editable) only if the reproduction time has passed.

Mapping of connection points

Diagram Sample classes mapping to a ConnectionPt

The rule(s) and procedure how a CDR attribute is mapped into a connection point is class specific. E.g., a CGI as provided in the CDR consists of four parts (MCC-MNC-LAC-CI); it is matched against the list of configured Cgi's by first checking for an exact match, and then removing part by part until a match is found. For network elements the connection point is simply is corresponding data member²⁾.
The mapping into connection points has a side-effect that should be mentioned here: Connection points define the finest grid where user-defined, symbolic names can be given to real existing objects.

²⁾ Currently OSB does not support hierarchical networks.

Connection point mappers

The mapping of connection points is not hard-coded. Specialized classes -all derived from a common base classs-, are responsible for this. Their only task is to determine the connection point for the CDR attribute they are specialied to; and they can collaborate with other tariff objects to fulfill their job:

Diagram Determination of the connection point for a CGI

In diagram the class Cgi2Cp implements the pure virtual function CpMapper::getCp() by extracting the CGI from the CDR and delegation to CgiList, the list of configured CGIs.

Generic distance sensitive tariff classification system

The generic distance sensitive tariff classification system determines the tariff class for a pair of connection points that represent the origin and the destination of a network connection.

Diagram Structure of GenericDistTcs

GenericDistTcs consists of one or more tariff zones and assigns a tariff class to each of them. The tariff zones support the modularity of tariff systems, in order to understand how the tariff class is identified, we can assume that such a TCS assigns a tariff class to each pair of connection points that is contains. Diagram provides more details on the logical structure.

Determination of the tariff class

For the determination of the tariff class for the pair <mappedOrigin, mappedDestination>, GenericDistTcs gives priority to the destination. From the list of all pairs <origin, destination> that are part of the TCS, the algorithm selects the matched pair that fulfills the following conditions:

The TCS needn't contain the catch-all entry <catch-all, catch-all>, an appropriate error is generated if no valid match could be found.

Example

The following example for the matching rule of a generic distance sensitive TCS does not discuss the validity periods of the tariff zone configurations and the connection point hierarchy. Instead the example emphasizes how the parent-child relationship of the connection points is used to find the nearest destination and origin in its configuration.

The connection point hierarchy is given in table and the configuration entries of the generic TCS are shown in table (tariff zone omitted).

Table Sample connection point hierarchy

Table Sample configuration of a generic TCS

The following matches will be found:

Table Mapped versus matched origins and destinatinons

Discussion of table

Example I
The pair<mappedOrigin, mappedDestination> is found in the configuration of the TCS.

Example II
For the mappedDestination "112" only its parent "11" is configured in the TCS. From the two related origins "1" and "11" the latter is selected because it is the nearer ancestor of the mappedOrigin "111".

Example III
For the mappedDestination "2" the TCS contains 2 pairs. Only one of the two related origins, namely "0", is an ancestor of the mappedOrigin and therefore selected.

Consistency

A generic distance tariff classification system is consistent and can be released for production, if:

• All of its tariff zones exist.
• Each of its tariff zones has a tariff class assigned.
• All its connection points (i.e. origins and destinations) are released.
• It does not contain duplicate <origin, destination> pairs.
  It is important to recognize that this condition must be fulfilled during the whole period for which the TCS is released: The tariff zones must make sure, that adding a new origin-destination pair does not create a conflict in any generic distance TCS they are part of.
• If any previous version of the TCS exists, the set of the tariff classes of the newly released version must be a subset (proper or not) of the existing version(s).

Mapping tariff classification systems

Mapping tariff classification systems are designed to support a flexible and extensible configuration of the usage attributes to be used during rating, i.e., for the determination of the tariff class.

Diagram Configuration of a mapping TCS

The configuration of MappingDistTcs has two parts. On the left side of diagram the class selects for each usage type a CpMapper that will determine the mappedOrigin and a CpMapper that determines the mappedDestination. The right side shows the generic distance sensitive TCS to be used by the MappingDistTcs afterwards.