Number portability Dr. ZOUAKIA Rochdi ANRT

OUTLINE Number portability (NP) definition NP services classification Processing a call to a ported number Different techniques used to implement NP Comparison of those techniques

Number portability (NP) NP refers to the ability of end users to retain their telephone number when they change their network operator/service provider, their location, or their service.

Classification of number portability services There are tree number portability services : Operator portability Location portability Service portability

Operator portability service It refers to the ability of an end user to retain the same telephone number when changing from one operator to another. It is also referred to as ‘service provider number portability’ and is further divided into: · geographic number portability for all fixed public telephone network and integrated services digital network (ISDN) subscribers at a specific location ; · non-geographic number portability or NGNP for fixed numbers at any location ; · mobile number portability or MNP.

Location portability It refers to the ability of an end user to retain the same telephone number when changing from one physical location to another without necessarily changing their operator.

Service portability It refers to the ability of an end user to retain the same telephone number when changing from one type of service to another without necessarily changing their operator. (e.g., from old telephone service to ISDN)

Processing a call to a ported number Two stages are involved : 1. Interception stage It’s the recognition that the call is toward a ported number. It can be performed at : - donor switch (local exchange where the subscriber line was initially attached before being ported), - transit switch, - originating switch (the switch from which the calling party’s call originates). 2. Routeing stage The call is re-routed from the intercepting switch to the new terminating switch.

Intercepting at the donor switch

Intercepting at a transit switch

Intercepting at the originating switch

Implementing Number portability Technical solutions depends on : The time scales required ; The characteristics of the existing network (level of digitalisation, existence of Intelligent Network (IN) platforms, network architecture etc) ; The interconnection structure (number of POIs and level of interconnection, number of transit areas etc); and The scale of implementation of NP (very small number of lines concerned, or generalised use of this service) and the number of operators involved.

Number portability -- Techniques -- Mainly two broad categories of techniques are used to implement NP: On-switch solution. Switches are changing information to look for destination. Off-switch solution. Involves Databases usage to pick portability information.

On-switch solution (1/3) --Technical scheme -- Information is relied on the Donor local exchange . (Original local exchange) The call is forwarding or tromboning to the Recipient Switch. (New local switch)

On-switch solution (2/3) --Two main families-- Solution Category 1 : onward routeing (call forwarding and derivatives): - using a second number, - using a generic routeing number, - using a routeing prefix, - transparent call forwarding (using a routeing prefix). Solution Category 2: translation via routeing tables - using translation into a second number, - using translation into a prefixed number.

On-switch solution (3/3) --Advantages and limitations-- It’s quick to implement, but it Produce « Tromboning », and Require a variable amount of software development in the call processing mechanisms and in the signalling. On-switch solution can be seen as a short term interim solution for Number Portability.

Off-switch solution --Technical scheme-- Portability information is stored into one or several external Databases. Intelligent Network techniques are used. Best routeing of the call to the final destination.

Off-switch solution --Advantages-- No tromboning : The query used to pick up the information portability from databases is a signalling connection, not a traffic connection. More adequate solution than On-switch one.

Carrier Selection

OUTLINE Carrier selection definition Description of carrier selection services Implementing carrier selection Technical and regulatory restrictions of carrier selection

Carrier Selection -- Definition -- It’s a mechanism that permits customers to choose national and/or international long-distance telecommunications carriers Access network Carrier network Caller Generally, the incumbent operator

Carrier Selection -- Generalities -- It’s a context of network interconnection between operators.  Originating interconnection. It refers to the ability of operators who do not have their own directly connected customers to provide services to subscribers who are directly connected to the local loop of another operator.  Indirect access providers. The main local loop operator is generally the incumbent operator.

Carrier Selection services Mainly two services are used : Call-by-call Carrier Selection (CS) Carrier Pre-Selection (CPS)

CS : Generalities The user has possibility to dial for each call the carrier operator that he wants to use. This service enables a fixed subscriber to select a carrier operator different from his local loop operator for the routeing of a specific call. This service requires the selected carrier to be interconnected to the incumbent's network through at least one point of interconnection (POI).

CS : Technical scheme Remarks + In this case, the carrier is a Long Distance operator. + The calling and the called party may belong to the same operator.

CS : Restrictions CS may be excluded from payphones. [it is not possible for operators to bill customers calling from payphones] CS may be excluded for special "low cost" subscribers. [For such subscribers, the incumbent provides a minimum telecommunications service, so he may not generate significant benefits and may not, therefore, wish to provide CS to them in case they select another long distance Operator] Depending on country-specific regulation and interconnection agreements, local calls and special numbers (such as Freephone and mobile numbers) may be excluded. [ No profit]

Implementing CS Assigning prefixes to the carriers The subscriber dials the carrier selection code (prefix) and then the called number. The routeing of calls based on routeing prefix requires that the routeing tables within the network be programmed initially, and the interconnection between the incumbent and the new entrant operator's network be established.

Technical restrictions of implementing CS Restrictions due to the correct provision of the Calling Line Identification (CLI) information at the interconnection (limits of electro-mechanical and analogue switches, and switches based on old digital technology); limits to the number of digits that can be passed through the network (PBXs, switches) : some of them are limited to 18 or 20 digits, whereas a minimum of 23 digits seems necessary; the structure of routeing tables and routeing parameters possibly limits the number of carriers that can be selected; and constraints related to the interconnection between operator networks.

CPS : Generalities This service enables a fixed subscriber to select a carrier different from his local loop operator for the routeing of the relevant outgoing calls.  The selection is done one time for a category of calls. The subscriber can pre-select his carrier beforehand. This service should include the possibility for the subscriber to ignore this pre-selection and to make a different carrier selection for a specific call (“override capability”).

Implementing CPS CPS option(s) of a subscriber have to be stored and memorised in the Line Context of subscriber's local exchange.  This is usually a specific software development. Depending on the choice of possible CPS options, several CPS profiles per subscriber might be necessary. The routeing of calls based on routeing prefix requires to program initially the routeing tables within the network, and to set-up (directly or indirectly via a transit network) the interconnection between the incumbent and the new entrant operator's network.

CPS : Restrictions and possibilities The issues presented for CS may also apply; and In addition, there may be one or several pre-selection possibilities: national calls only, international calls only, national and international calls only, all calls including special numbers, or a combination of several of those options. These options will have an impact on the developments on the switch in terms of call processing mechanism and memory space required for the subscriber context.