International signaling gateway

Details International signaling gateway International signaling gateway

2000-02-25

2002-03-26

Geckil, Mehmet B. (Department: 2152)

Electrical computers and digital processing systems: multicomput

Multiple network interconnecting

C709S238000

Reexamination Certificate

active

06363431

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to sending messages between multiple devices in separate domains, and particularly, to using a signaling gateway to address the processing, reformatting, and routing of signaling messages between network domains and to resolve incompatibility issues at various network protocol layers.
BACKGROUND OF THE INVENTION
As mobile phone usage has increased, people have become more dependent on the ability to contact others using their mobile phone at any time, any place and anywhere. People use their mobile phones for business and pleasure and have adopted their use not just in a local city or town, but have become accustomed to using them while they are “roaming,” i.e., outside of their local area. Telephone networks have become more adept at sending messages to other networks servicing these roaming mobile phones. National networks have been interlinked so that a person with a mobile phone can now travel all over the country and messages can be sent to the switch servicing the roaming mobile phone. These interlinked networks, however, are each contained within a domain. A domain is defined as a set of addressing and network element identifiers which is independent of other sets of identifiers or domains. An example is the set of ANSI SS7 addressing point codes. These point codes are addresses assigned to SS7 entities located within North America and are independent in format and identity from the addressing point codes used in other regions of the world having their own addressing domains.
A problem occurs when the mobile phone roams into a domain other than its home domain, because domains may use incompatible routing techniques, incompatible signaling protocols, or conflicting messaging parameters or identifiers. The software and equipment of different domains do not generally support direct point code addressing between domains. In addition to the point code addressing issues, there are many times various incompatibilities between device and network element identifiers in different domains, such as System Identification (SID) identifier.
SS7 networks have been in use internationally for signaling between wireline network entities. SS7 is a signaling protocol and is used for signaling functions such as establishing and disconnecting calls, and for enhanced telephony services, and with international gateways it has provided these functions for wireline carriers of different domains. Wireless international roaming is, however, new in some regions of the world and requires use of SS7 signaling for additional functions such as subscriber validation, fraud control, and call delivery to a roaming subscriber. Many wireless carriers utilizing AMPS, TDMA, and CDMA technologies use ANSI-41 messaging over SS7 networks for this purpose. SS7 networks used by wireless carriers in different domains need to get interconnected for exchange of ANSI-41 signaling messages between wireless switches. SS7 protocol however is in use in various variations. The version used in North America is based on the American National Standards Institute (ANSI) standard identified in this document as ANSI SS7. In most other countries, different but similar versions exist based on the International Telecommunication Union (ITU) standard and are known by ITU C7 or by similar names but some countries use ANSI formatted messages.
Signaling between networks of different countries introduces new challenges. With respect to SS7 networks a switch is identified by an address called a “point code.” Within the North American domain, the ANSI standard for SS7 is used and the allocation of point codes has been coordinated so that each switch is identifiable by a unique point code. Yet, there has not been a coordination of point code allocation internationally. Outside North America, where the ITU version of SS7 is used, each country has its own domain of addresses independent of other countries. A specific ITU point code therefore could be in use in multiple domains. If these domains get interconnected without any modification, the same point code would identify multiple switches causing confusion when routing messages. Gateways are needed to perform point code translation between domains.
In addition to the issue of possible duplication of numbers, there is an inherent incompatibility between the ANSI and the ITU networks. An ANSI message is in a different format than an ITU message. Therefore, even if possible duplication of point codes was not a problem, an ANSI network could not be addressed by an ITU point code and vice versa.
The addressing problem has become even more complicated by arbitrary use of the point codes assigned to the North American domain (ANSI point codes) outside North America. Since in the past there has not been any wireless connectivity between countries, in some regions (e.g., in Far Eastern countries), SS7 ANSI point codes have been used for the ANSI-41 networks. This does not pose a problem as long as the North American networks are not connected to other domains. When connected, however, duplication of a North American point code in another country would create routing problems, because more than one switch could have the same point code assigned to it.
A different problem associated with the international connectivity of wireless switches is the limited number of point codes available to carriers. Although presently this may not be an issue, there is a potential for a lack of available point codes in the future. A wireless switch can be identified by more than one point code so that it could be accessed by multiple SS7 networks each having their own addressing domain of point codes. This makes the SS7 network of one domain accessible by another domain. This method, however, would drain the point code resources intended for a specific domain.
Standard organizations (e.g., ITU) have taken steps to solve the aforementioned issues by introducing various standards. The standards have not, however, been completely addressed, and also various countries have not implemented standards. To resolve the international signaling issues, equipment in all countries involved needs to be upgraded with the appropriate software. Partial upgrade of the SS7 nodes will not be of any benefit.
ITU Q.705 has defined international and national domains. The national domains use their own domestic signaling point codes and the international domains use an international signaling point code (ISPC). ITU Q.708 has defined the format of the ISPC, which includes zone and network identifiers. International gateways will translate the national point codes to the international point code and vice versa. The signaling messages are transported domestically to an international gateway using the initiating network local point code. The international signaling gateway in the originating country will translate the domestic point code to the ISPC and using the ISPC, route the messages to the international gateway in the destination country. The destination country international gateway translates the ISPC to the domestic point code of the destination country's domain and delivers the message to a SS7 node in the destination domestic domain. Translation of the domestic point codes to the ISPC and vice versa however requires a capability called Global Title Translation (GTT).
To use the GTT functions, certain standard details need to be defined or modifications to the existing standards need to be made. These include defining national Translator Type (TT) parameters and enhancements to the IS-41 messaging standard. These standards efforts are not fully resolved and what is resolved has not been implemented by the network providers. IS-41 Revisions A, B, and C, do not define the GTT capability for all messaging needed for international signaling. IS-807 standard has defined this capability but requires the roaming partners to implement the standard. Simultaneous upgrade of the equipment software of all parties involved is required for these standards to be beneficial. Therefore, the confl

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