Local number portability intelligent signaling transfer point

A "Local Number Portability (LNP) intelligent Signal Transfer Point (STP)" which can perform a Local Number Portability (LNP) query towards a Service Control Point (SCP) and modify the incoming Initial Address Message (IAM) with the Location Routing Number (LRN) and the Ported Dialed Number (PDN), and indicate, using the Forward Call Indicator (FCI) (M-bit), whether the number has been translated. This advantageously allows non-Advanced Intelligent Network capable Service Switching Points (SSPs) (but Integrated Services Digital Network User Part, or ISUP, capable SSPs) to support Local Number Portability (LNP) without having to upgrade the SSP's. In addition, the LNP intelligent STP system provides AIN-capable SSPs with an alternative means of LNP, which reduces both the internal switching processes and the cost for the LNP query transactions.

BACKGROUND OF THE PRESENT INVENTION 
1. Field of the Invention 
The present invention relates generally to telecommunications systems and 
methods for routing ported out calls, and specifically to performing Local 
Number Portability (LNP) queries by Signal Transfer Points (STPs). 
2. Backaround and Objects of the Present Invention 
Since the beginning of the telephone in the 1870's, signaling has been an 
integral part of telephone communications. The first telephone devices 
depended on the receiving party standing next to the receiver at the time 
of the call. Later, after the formation of the Bell Telephone Company, 
Alexander Graham Bell's assistant Watson invented the telephone ringer, 
eliminating the foreknowledge requirement. By lifting the receiver and 
allowing DC current to flow through the phone and back through the return 
of the circuit, a lamp would be lit on the exchange operator's switchboard 
to signal the operator that a call was trying to be placed. 
However, early signaling methods were somewhat limited because they used 
the same circuit for both signaling and voice. In addition, they were 
analog and had a limited number of states, or values, that could be 
represented. In the early 1960's, Europe began digitizing the network, 
removing the signaling from the voice network, and placing the phone 
signals on a separate network. With this division of signaling and voice, 
the call setup and tear-down procedures required with every phone call 
were performed faster, while reserving the separate voice and data 
circuits for use when a connection was possible, e.g., no voice connection 
is needed when the called party's number is busy. Common Channel Signaling 
(CCS), which uses a digital facility, but places the signaling information 
in a time slot or channel separate from that of the voice or data it is 
related to, has become the foundation for telecommunications today. 
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, everything is controlled or configured by 
workstations with user-friendly software. Telephone service 
representatives can, therefore, create new services and tailor a 
subscriber's 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 local exchanges in a telephone network 90, 
a portion of which is shown in FIG. 1. The SSPs 100 also provide an 
Integrated Services Digital Network (ISDN) interface for the Signal 
Transfer Points (STPs) 110, as is understood in the art. The ISDN is the 
subscriber interface to the IN. 
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 while retaining their public directory number. This is 
referred to as number portability. One key advantage of number portability 
is that other subscribers can connect to the portable 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. The Local Number Portability (LNP) 
is the database that holds the Location Routing Number (LRN), which is a 
ten-digit number 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 
both the pertinent LRN, which is populated (that is placed) in the Called 
Party Number (CPN) parameter in the IAM, and the Ported Dialed Number 
(PDN), e.g., the actual dialed digits for the ported-out subscriber, which 
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. 
However, with non-AIN capable SSP's, the SSP's are unable to initiate the 
LRN query or receive LRN information from the SCP 120. Therefore, non-AIN 
capable SSPs have to be able to identify whether an incoming call 
terminates to its own switch from the Called Party Number (CPN) without 
the aid of the LRN. After a call is determined to not terminate on its own 
switch, the local SSP 100 routes the call according to its existing number 
analysis database. This involves routing the call to the aforementioned 
donor switch or a tandem (intermediate) switch that has LNP access 
capability. The donor or tandem switch then launches the query to 
determine routing, a process which results in excessive switching and 
delays. 
However, if the first six digits of the CPN point back to the SSPs route 
(indicating that a number has been ported out), the call is typically 
transmitted to an affiliated exchange, over a dedicated route, by 
bilateral agreement, to handle routing for ported out subscribers from the 
non-AIN capable SSP 100. This process is also expensive and 
time-consuming, as is understood in the art. 
It is therefore one object of the invention to allow non-AIN capable SSPs 
access to the LNP database without expensive upgrading. 
It is a further object of the invention to reduce the switching processes 
and the cost associated with LNP queries by AIN-capable SSPs. 
SUMMARY OF THE INVENTION 
The present invention is directed to a "LNP Intelligent STP" which can 
perform a LNP query towards a SCP and modify the incoming IAM with the LRN 
(CPN) and PDN (GAP), and indicate, using the FCI (M-bit), whether the 
number has been translated. This advantageously allows non-AIN capable 
SSP's (but ISDN User Part (ISUP) capable SSPs) to support Local Number 
Portability (LNP) without having to upgrade the SSPs. In addition, the 
present invention provides AIN-capable SSPs with an alternative means of 
LNP, which reduces both the internal switching processes and the cost for 
the LNP query transactions. Furthermore, centralizing LNP in one STP 
benefits all serving SSP's by efficiently handling the LNP queries and 
allowing non-AIN capable SSPs to access the LNP database.

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EXEMPLARY EMBODIMENTS 
The numerous innovative teachings of the present application will be 
described with particular reference to the presently preferred exemplary 
embodiment. However, it should be understood that this class of 
embodiments provides only a few examples of the many advantageous uses of 
the innovative teachings herein. In general, statements made in the 
specification of the present application do not necessarily delimit any of 
the various claimed inventions. Moreover, some statements may apply to 
some inventive features but not to others. 
The Local Number Portability (LNP) intelligent Signal Transfer Points 
(STPs) 110 of a preferred embodiment of the present invention perform 
Location Routing Number (LRN) queries for ported-out numbers. 
Traditionally, the AIN-capable Service Switching Points (SSPs) 100 sent 
the LRN query to the Service Control Point (SCP) 120 and modified the 
Initial Address Message (IAM) accordingly, as described hereinbefore. 
This, however, burdens the SSP's 100 with numerous queries, which is an 
inefficient use of resources. In accordance with the present invention, 
however, by removing the LRN query to the STP 110, the LRN queries for all 
of the serving SSPs 100 (AIN and non-AIN capable) can be more efficiently 
handled. 
With reference now to FIG. 2 of the drawings, in the "LRN intelligent STP" 
system and method of the present invention, after a subscriber has placed 
a call (step 200), the SSP 100 responsible for that subscriber first 
determines if the call terminates on its own switch (step 210). If so, the 
SSP 100 completes the call to the called party (steps 220 and 225). If 
not, the SSP 100 formulates the Initial Address Message (IAM), seizes a 
channel, and sends the IAM to the tandem switch for further routing via an 
STP 110 (step 230). The STP 110 then intercepts the IAM and performs the 
LNP query (step 240). Based on the results of the LNP query, the STP 110 
modifies the IAM (step 250) by inserting the Local Routing Number (LRN) in 
the Called Party Number (CPN) parameter and the Ported Dialed Number (PDN) 
in the Generic Address Parameter (GAP), and setting the Forward Call 
Indicator (FCI) (M-bit) to "Number Translated". The STP 110 then sends the 
modified IAM to the tandem switch for further routing to the recipient 
switch (step 260). 
When the recipient switch receives the contents of the IAM and determines 
that the LRN is its location routing number, the recipient switch performs 
digit analyses on the dialed digits stored in the Generic Address 
Parameter to determine the identity of the subscriber (step 270), and 
completes the call (step 280). 
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. 
The specific process parameters and routing loops are further illustrated 
in FIG. 3. As an example, in FIG. 3, an originating subscriber 300, also 
referred to herein as O-sub, is trying to place a call to a terminating 
subscriber 370, also referred to herein as T-sub, who has been ported out 
from a donor switch SSP-C 350 to a recipient switch SSP-D 360. An 
originating switch SSP-A 310 for subscriber O-sub 300 in this example is 
non-AIN capable, while the tandem switch SSP-B 320 may or may not be AIN 
capable. 
After switch SSP-A 310 determines that the originating call does not 
terminate on its switch, it formulates an original Initial Address Message 
(IAM1) and seizes a physical channel T1 to route the call to SSP-B 320. 
The original IAM (IAM1) in this example contains the following 
information: Called Party Number parameter ="T"; and Forward Call 
Indicator (FCI) (M-bit)="Number not translated". 
The STP 330 intercepts the aforementioned original IAM (IAM1) and performs 
a LNP query towards the SCP 340, as described hereinbefore. Based on the 
results received from the LNP response, also shown in FIG. 3, the STP 330 
modifies the original IAM (IAM1) by placing the Location Routing Number 
(LRN) for the recipient switch SSP-D 360 in the Called Party Number 
parameter and the Ported Dialed Number (PDN) for subscriber T-sub 370 in 
the aforementioned Generic Address Parameter (GAP). The STP 330 also sets 
the FCI (M-bit) to "Number Translated", as discussed. 
The STP 330 then sends out the modified IAM (IAM2) to the tandem switch 
SSP-B 320 for further processing. The tandem switch SSP-B 320 first 
determines if the call terminates at its switch. If so, it terminates the 
call to the end-user. If not, it sends the modified IAM (IAM2) to the STP 
330 for routing of the IAM2 to the designated recipient switch SSP-D 360, 
and seizes a physical channel T1 to route the call to SSP-D 360. The 
recipient switch SSP-D 360 can then terminate the call on its switch to 
subscriber T-sub 370. 
By enabling the STP 330 to perform the LNP query, SSP-A 310 can provide the 
LNP function even without being AIN-capable. In addition, tandem switch 
SSP-B 320 advantageously does not need to perform the LNP query even if 
the preceding switch is not AIN-capable, which reduces the call processing 
for SSP-B 320. 
As will be recognized by those skilled in the art, the innovative concepts 
described in the present application can be modified and varied over a 
tremendous range of applications. Accordingly, the scope of patented 
subject matter should not be limited to any of the specific exemplary 
teachings discussed.