Make an Intelligent Network Connection
By Robert Smith, GTE TSI
(This first article in a series on SS7 signaling discusses the advantages for carriers to use an SS7 networking hub for access to remote network databases.)
The world of wireless is exceedingly complex from all angles, perhaps no more so than within the wireless network itself. The demands of the wireless marketplace require that many types of services offered today and in the future be delivered by an efficient and reliable intelligent network (IN). Even as wireless and Internet providers move toward converged services, IP telephony service providers will look for a bridge between conventional circuit-switched systems and IP-based networks to deliver the best of both worlds.
Today, IN-based services such as number portability, calling name ID, 800 database queries, (see Figure) and line information database (LIDB) queries and responses are table stakes for carriers who want to compete and succeed. As a wireless carrier juggling competition, customer churn, and converging services, you can toss IN over to someone else if you have too many balls in the air. The decision is yours. Should you build IN expertise into your business model and establish your own connections throughout the nationwide network of databases? Or is it best to outsource IN applications so you can focus on building your customer base and new services based on IP? Let's go to SS7 network school, TCAP class 101, so you can make an educated decision.
800 database access call example
What's TCAP Got to Do with It?
The types of IN services just listed are delivered by SS7 TCAP database queries. TCAP stands for Transactional Capabilities Application Part. What does TCAP really mean to the wireless carrier? If you are not interested in staying in business much longer, it means nothing, and you can forget all this terminology and get on with life. But, if you want to remain competitive, you should probably know about the best way to provide the services that TCAP enables.
The Knee Bone is Connected to the Thigh Bone; The Thighbone is Connected to the Hip Bone...
To understand why it makes sense to outsource to an SS7 network hub to provide TCAP-enabled services rather than connecting to each database yourself, it helps to have a basic understanding of SS7 networking.
The SS7 network comprises many acronyms using the letter S, or in more technical parlance, different network components, or nodes, such as STPS, SCPs, SSPs and SPs. These components work together to provide various types of telephony services using SS7 signaling.
Two by Two
The engineers who developed the SS7 protocol tried to make it easy to understand by dividing many things by two. SS7 signaling presents the first duo by dividing a telephone call into two separate parts: the signaling component, which contains address information for call setup and tear-down, and the voice and data component, used for communication between the originator and terminator of a call. These two components are transmitted on two separate facilities. The facility for carrying signaling information is transported across a signaling, or data, link. Voice and data traffic is transported over a voice trunk.
The duet continues. The relationship between the signaling and voice components of a call is called the signaling mode, of which there are two types. There is associated signaling, where the voice and data path take the same route, and the quasi-associated signaling mode, where the voice takes a more direct route and the data path takes another, usually through a switch called a signal transfer point (STP).
Not only can signaling be broken down into two modes, but it also breaks down into two types. First, there is connection-oriented signaling, used in call setup and control, known as integrated services digital network user part (ISUP). The second type is connectionless signaling, used for query response services such as 800 service and alternate billing service, in which the signaling provides access to a database. This second type is TCAP.
What About TCAP?
The North American SS7 network structure is built from a mesh network with mated STPs that are accessed from the various types of switching centers known as signaling hubs, gateways, or service control points (SCPs). Network databases that contain, for example, line billing information, are accessed from multiple locations on the network through a STP, with TCAP providing the application level functions and signaling transport for the database dips. A SCP is needed to supply the translation and routing data necessary to deliver the IN services to your subscribers.
The Value of the Signaling Gateway
Now, how does the wireless carrier efficiently connect to all of these databases? We recommend use of the signaling gateway, or more simply put, the hub.
There are two ways you can connect to the databases described earlier. You can set up STP and SCP connections to each database yourself, or you can connect to a single STP hub, and leave the driving to a hub service provider. With one connection to a hub that in turn connects with all of the major telephone companies in North America, you have access to databases at a much lower cost. One connection provides your local subscribers with North American coverage and saves you a lot of administrative workload and technical headaches.
Consider these issues:
- Routing conflicts—Do you have the technical staff and expertise in place to be sure that your network is selecting the correct circuit path for message transport? TCAP services require routing flexibility to send information over various network paths to avoid congestion and to efficiently use portions of a network that might otherwise be idle.
- Change control procedures—Are you prepared to redirect SS7 traffic due to network expansion or contraction when a new STP or SCP comes on line?
- Monitoring and adjusting links—Do you have the 24 x 7 support to respond to potential capacity or other network problems?
- Global title translation—See below how four digits make a big difference.
- Economics—Connecting to one hub lets you take advantage of the economies of scale derived from serving multiple carriers.
Aside from using a hub to access all of these proprietary databases, one of the most complicated issues that wireless carriers need to consider is the mandate to provide ported number capabilities. With that, global title translation (GTT) rears its ugly head, too.
In a nutshell, GTT essentially provides information on which path in the SS7 network a message needs to take. Pre-LNP, a TCAP query for subscriber information could go its merry way to a database with only six numbers in tow. The six numbers always identified the same single carrier and the location of their database. But because of LNP, many carriers might share a block of ten thousand numbers with the same first six digits, so the query now requires ten numbers to complete the trip. So in addition to STPs and SCPs, you need to have the ability to provide 10-digit global title translation in order to dip into the correct proprietary database to complete the transaction.
The bottom line is simplifying your operations, reducing costs, and adding value to the services you offer to subscribers. That means giving your subscribers the services they have come to know in the wireline world as well as the new services cropping up as wireless, wireline, and IP worlds converge. To focus on what you do best, leave the SS7 and TCAP database issues with a service bureau and focus on your main mission—attracting and retaining subscribers.
About the Author
Robert Smith is GTE TSI's product manager-database services. He can be reached at GTE Telecommunication Services Inc., 201 N. Franklin Street, Suite 700, Tampa, FL 33602. Phone: 813-273-3000; e-mail: rcsmith@ins.gte.com.