Telephonic communications – Plural exchange network or interconnection – With interexchange network routing
Reexamination Certificate
1998-12-11
2004-01-27
Tsang, Fan (Department: 2645)
Telephonic communications
Plural exchange network or interconnection
With interexchange network routing
C379S221050
Reexamination Certificate
active
06683946
ABSTRACT:
BACKGROUND OF THE PRESENT INVENTION
FIELD OF THE INVENTION
The present invention relates generally to telecommunications systems and methods for managing ported calls, and specifically to Service Switching Points (SSPs) selectively performing Local Number Portability (LNP) queries for calls routed to Local Exchange Carriers (LEC).
BACKGROUND AND OBJECTS OF THE INVENTION
In modern telecommunications networks, signaling constitutes the distinct control infrastructure that enables provision of all other services. It can be defined as the system that enables stored program control exchanges, network databases, and other “intelligent” nodes of the network to exchange: (a) messages related to call setup, supervision, and tear-down; (b) information needed for distributed applications processing (inter-process query/response); and (c) network management information.
In addition, the Intelligent Network (IN) and the new Advanced Intelligent Network (AIN) have made possible the transfer of all types of information through the telephone network without special circuits or long installation cycles. In the IN/AIN, everything is controlled or configured by workstations with user-friendly software. Telephone service representatives can, therefore, create new services and tailor a subscribers service from a terminal while talking with the customer. These changes are immediately and inexpensively implemented in the switches, rather than by the more traditional method: expensive programming changes made by certified technicians.
The IN consists of a series of intelligent nodes, each capable of processing at various levels, and each capable of communicating with one another over data links. The basic infrastructure needed is composed of various signaling points, which both perform message discrimination (read the address and determine if the message is for that node), and route messages to other signaling points. The basic three types of signaling points are: (1) Service Switching Points (SSPs); (2) Signal Transfer Points (STPs); and (3) Service Control Points (SCPs), each of which are described in more detail hereinafter.
With reference now to
FIG. 1
of the drawings, the many Service Switching Points (SSPs)
100
serve as the exchanges in a telephone network
90
, a portion of which is shown in FIG.
1
. Across the country, groups of SSPs
100
are divided into separate Local Access Transport Areas (LATA)
130
. Calls placed within a single LATA
130
, intraLATA, are handled by the local exchange carriers (LEC), e.g., GTE, while calls placed interLATA, that is between separate LATAs
130
, are handled by Interexchange Carriers (IXC), e.g., AT&T, which provide long-distance service to customers within a number of LATAs. The LECs and IXCs are separate types of SSPs
100
, which provide either local or long-distance service respectively to subscribers.
The STP
110
serves as a router, and switches messages received from a particular SSP
100
through the network
90
to their appropriate destinations (another SSP
100
). As is also understood in the art, the STP
110
receives messages in packet form from the SSPs
100
. These packets are either related to call connections or database queries. If the packet is a request to connect a call, the message must be forwarded to a destination end office (another SSP
100
), where the call will be terminated.
If, however, the message is a database query seeking additional information, the destination will be a database. Database access is provided through the Service Control Point (SCP)
120
, which does not store the information, but acts as an interface to a computer that houses the requested information.
Presently, a subscriber on one SSP
100
has the ability to move to a different SSP
100
within the same LATA
130
while retaining their public directory number. This is referred to as local number portability. One key advantage of local number portability is that other subscribers can connect to the ported subscriber without any changes to their dialing procedures.
If a subscriber has been ported-out to another SSP
100
, the Initial Address Message (IAM) sent by the originating SSP
100
must be modified to account for the change in the terminating SSP, as is understood in the art. The Local Number Portability (LNP) database is the database that holds the Location Routing Numbers (LRN), which are ten-digit numbers used to uniquely identify the switch that has the ported-out number. Specifically, the LRN is the number for the recipient switch, which is the switch that has ported-in a number from another switch (called a donor switch). This ported-in number was not previously served by the recipient switch.
Typically, the SSP
100
sends a LNP query to the SCP
120
, which accesses the LNP database in order to retrieve the routing information for a ported subscriber. The query response by the SCP
120
provides that SSP
100
with the pertinent LRN, which is populated (that is placed) in the Called Party Number (CPN) parameter in the IAM. The Ported Dialed Number (PDN), e.g., the actual dialed digits for the ported-out subscriber, is placed in the Generic Address Parameter (GAP) in the IAM. The Forward Call Indicator (FCI) M-bit in the IAM is then updated to indicate that the number has been translated. The FCI M-bit is used as a fail-safe mechanism to prevent more than one LNP query from being launched on a call.
If the end-user has not been ported-out, the SCP
120
will return the actual dialed number, not the LRN, to be stored in the CPN parameter. In this case, the GAP is not included in the IAM. It should be noted that the FCI M-bit is always set to “Number Translated” after any LNP query, regardless of whether the end-user has been ported-out or not.
Each subscriber has associated therewith a three-digit Numbering Plan Area (NPA), e.g., area code, and a three-digit Office Code (NXX), e.g., the first three digits of a seven-digit telephone number. Each SSP stores within it a list of LNP triggers, which are the NPANXX digit streams associated with subscribers who have the ability to port, whether or not any subscribers having that NPANXX actually are ported. Every time a call is placed to a subscriber on a different SSP than the calling party's SSP, the originating SSP, which is the SSP responsible for the subscriber placing the call, checks the LNP trigger for the called party to determine if a LNP query should be performed prior to routing the call to the called party's switch. Each LNP trigger has a condition known as a LNP trigger criteria type associated with it. The LNP trigger criteria types are indicators stored in the switch by command or other method, which can be set to either “query” or “do not query”, depending upon different conditions.
Presently, for calls to subscribers having a NPANXX which is a LNP trigger, which are routed to a Local Exchange Carrier (LEC), the LNP trigger criteria type is always set to either “query”, which instructs the originating SSP to perform a LNP query to the SCP before routing the call to the LEC, or “do not query”, which instructs the originating SSP to never perform a LNP query prior to routing the call to the LEC, regardless of the LNP querying capability of the LEC. Therefore, for conventional systems to be implemented successfully, all local exchange carriers (LECs) would need to possess LNP querying capability to deliver calls to ported numbers. Otherwise, the calls would be routed to the donor switches, which results in excessive switching and delays. However, with the deregulation the number of available LECs will increase and it will not be possible for all the LECs to provide LNP querying capability.
Existing systems also present a problem in the case where a single switch acts as both an end office (EO) and a LEC without loop back of calls, which is explained hereinafter. Many EO/LEC switches have a logical boundary between the EO services and the LEC services. Therefore, when a long-distance call is placed, the EO actually routes the call on trunk lines out of the switch back
Frey, Jr. Bert Lee
Rangarajan Kasiviswanathan
Ericsson Inc
Gauthier Gerald
Tsang Fan
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