Protabilidad numerica

Successfully Implementing Number Portability

Implementing Number Portability requires a "rethinking" of network architecture and the role of the Intelligent Network. While challenging, number portability represents an opportunity to leverage a service provider’s investment in the Intelligent Network to enable future revenue-generating applications and services.

There are three types ofNumber Portability.

1. Location Number Portability
Location number portability allows the subscriber to keep the same phone number when moving from one physical location to another. Today’s implementation of location number portability is limited to enterprises or large corporation relocating the PBX from one location to another and is typically within the same central office switch. In thefuture, location number portability may become a regulatory requirement.

2. Service Portability
Service Portability allows the subscriber to subscribe to selected services from different service providers while maintaining the same phone number. In the future, service number portability may become a regulatory requirement.

3. Service Provider Number Portability
Generally referred toas Local Number Portability (LNP), this allows the subscriber to keep the same phone number when switching from one service provider to another. This paper covers the implementation of Service Provider Number Portability.

Currently in the US, the FCC mandates LNP for fixed networks in most metro cities, meaning that only fixed/ wireline numbers can be ported. The LNP scenario in the US makesfor an interesting case study.

The mobile/wireless NP in the US is planned to be effective in 2002. Although NP is mandated for fixed lines only, calls originated from mobile subscribers to ported fixed numbers must go through LNP queries as well. This prompted both fixed and mobile service providers to deploy NP systems in their networks. The NP databases contain the ported fixed/wireline numbers.

Number portability poses many challenges. Historically, all numbering plans have assumed a fixed relationship between a customer's phone number and a physical switch location. In a "portable" environment, physical switch location is "decoupled" from the customer's number (i.e., the number becomes virtual).

There are four general methods to implement number portability.

1.Call Forwarding
This solution uses the existing call forwarding functions. When a call is made to the ported number, the donor switch (the switch giving up the phone number) forwards the call to the recipient switch (the switch receiving the phone number). This method is considered over taxing and unfair to the donor switch (service provider), as revenue is no longer generated from the portedsubscriber and the donor switch must still handle all calls made to the ported number.

2. Onward Routing

This method requires the donor switch to process the call although the subscriber no longer subscribes to the donor network. This was viewed to be unfair to the donor switch and was not adopted in the US.

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3. Drop Back/ Query on Release

Query on Release resulted ina delay difference of 1.3 seconds between ported and non-ported calls. This was viewed to be degradation in service quality for the ported call by the US regulator and was abandoned.

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4. All Call Query (ACQ)/ Network or Location Routing Number (LRN)

This method required LRN query for all calls to subscribers in the “ported number blocks” and was viewed as fair to all partiesinvolved. In 1997, the US FCC mandated Location Routing Number (LRN) method for NP implementation for fixed networks. In the US, the N-1 switch must perform the LNP queries. The N-1 switch is the switch or transit switch that handles the call right before the terminating switch.

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No matter which method is selected, each network requires new “translation intelligence" to...