Software Breaks Down Cellular Barriers

December 2001
By Henry S. Kenyon

Program allows mobile devices to operate on any network.

Cellular telephone users may be closer to achieving their dream of making telephone calls or accessing messages and services from anywhere in the world. Researchers have developed a software architecture that allows global roaming across all types of wireless systems. The technology offers the potential for upcoming third generation wireless telecommunications systems to operate beyond the current patchwork of regional and national networks.

The ability to use wireless devices any time, anywhere has been a key goal of service providers for many years. However, the current generation of mobile systems uses a mix of different technologies such as wireless application protocol, general packet radio services and code division multiple access (CDMA). Devices designed to operate on these specific systems cannot function on other networks. New technologies like third generation (3G) wireless systems will offer users greater Internet access, video and other high-bandwidth services. But current restrictions on roaming may hamper 3G systems’ economic viability. Only a truly unrestricted wireless environment will allow cellular telephones and other devices to operate everywhere.

A potential solution to this communications conundrum is being developed by researchers at Bell Labs, the research and development arm of Lucent Technologies, Murray Hill, New Jersey. Called Common Operations (COPS), the technology is a software architecture that allows users to access mobile voice and data services, information and e-mail when they are away from their home network.

Consumers, especially business travelers, will see the benefit of COPS. “If you had just one telephone and you went on a trip to Europe and it worked there—all the services that you’d grown accustomed to are there and function the same way they do at home—that would be valuable to a lot of people,” says Kurt Steinert, a company spokesman with Lucent’s Technology Mobility Solutions Group.

COPS provides a generic interface for functions typically performed by a home location register (HLR), explains Thomas LaPorta, director of mobile networking, Bell Labs. An HLR is a database of subscriber information used to identify a mobile user’s location, validate and authenticate that caller’s right to use the service, and conduct profile management and high-level mobility management. These functions are available only to subscribers within their home networks, or rarely, for example, when roaming on networks using similar technology.

The generic interface allows systems engineers to create protocol gateways that allow different network interfaces to operate with each other by translating protocol data into a single common language. This uniformity makes it possible to maintain a single subscriber profile, including authentication, authorization and location data that can be accessed across many different networks.

COPS also allows the control of key HLR functions such as automatically translating user data and signaling technologies from cellular protocols to Internet protocol (IP) and back again. This feature allows carriers to build multiple protocol-specific gateways that permit different types of networks to access HLR data. According to Bell Labs officials, another advantage of building HLRs with COPS is that it creates customer databases that can be automatically updated while supporting both voice and high-speed data services.

Truly global roaming currently is not possible because various wireless network types cannot work together to electronically identify mobile users’ locations, Bell Labs officials say. For example, a subscriber whose network uses CDMA technology cannot access services when roaming on a global system for mobile communications (GSM) network. However, the new program allows for intra-network roaming. If a wireless network operator changes the type of signaling protocols used on its servers, the HLR associated with the old protocol could still communicate with the network via COPS. This feature allows carriers to provide services across multiple systems without interruptions or adding additional HLRs, the officials claim.

COPS is a general-purpose software architecture designed to operate on network servers, LaPorta explains. The program can be written in a variety of object-oriented languages such as C++ and Java. The software is still under development. Bell Labs is evaluating COPS to determine its performance, reliability and ability to interface with other protocols. “We’ve shown that we can do these things very efficiently,” he says.

The software’s scalability and flexibility allow its application in a number of systems. LaPorta notes that if the program is applied to an HLR, it allows network providers to use a database or a single point to admit customers. “You can enter their voice service information, data service information, wireless and wireline information on one database. All the different networks look at that database as if it were their own because they all use their native interfaces. They don’t realize things are being converted to COPS. The program just makes it easier to do this,” he explains.

An advantage to this approach is that when a new service or network is introduced or supported, carriers do not have to re-implement the entire system. The only requirement is the implementation of the protocol gateway, LaPorta says. Bell Labs scientists have studied methods to use protocol gateways and to convert common interfaces for different applications. In the past three years, researchers have done a very good job of understanding how to streamline the software so that it does not create performance penalties, he says.

Although systems that facilitate intra-portal communications exist, they pay a price in reduced performance. COPS does not suffer from this drawback because of its design, which is based on object-oriented techniques and on Bell Labs’ experience with the technology, LaPorta explains. These features also enhance network performance and reliability. “You can make protocol gateways work reliably through COPS. If there are any communications problems, they can be recovered,” he says.

COPS is designed to operate at the network-server level, not on individual mobile handsets and devices themselves, explains Steinert. Multiband or multimode wireless devices will be necessary because the software does not address radio interfaces with protocols such as GSM or CDMA. However, COPS does manage the communication between the networks themselves. “If you had a telephone capable of working on multiple types of networks, this would allow the delivery of services across all those systems,” he says.

The software also is designed to be scalable, although LaPorta cautions that any application has its limitations. Scalability is important to future network growth, and he cites projections of HLR traffic growing from one million to 20 million users. COPS itself will not limit network scalability. Those boundaries are determined by other factors such as database size and call processing software, he explains.

Other organizations have proposed approaches similar to COPS. These technologies operate by having a device serve as a translator between two or more HLRs operating on different protocols. The problem with this approach, according to LaPorta, is that it creates multiple systems in a network instead of a single unit. This brute force approach to connect networks has its flaws because it typically is not as integrated as COPS. “You have more failures and higher delays because you have to talk between these boxes. And there are additional databases to manage and provision,” he says.

Lucent developed COPS with 3G applications in mind, Steinert says. The software will be integrated with a number of products entering the market in the latter half of 2002. That first application will probably resemble a 3G HLR to support voice and data services built into products based on universal mobile telecommunications services (UMTS) technology. Full global roaming capabilities probably will become available in 2003. Steinert adds that the UMTS products will be backward compatible to support global roaming. However, he cautions that this does not mean that full capability will be available immediately.

Although the software’s initial applications are not limited to UMTS, market opportunities exist as telecommunications providers begin deploying the technology in North America and Europe. Steinert notes that company plans call for providing subscriber databases capable of supporting both voice and data services for 3G networks, and UMTS is an obvious candidate for the job, he says. UMTS is a spread-spectrum wireless technology designed for use by GSM carriers. It spreads its signal across the radio spectrum in a manner similar to CDMA, but it is based on codes assigned to each transmission. UMTS is also a more packet-based solution as opposed to GSM and CDMA, which are circuit-type—they assign times to particular calls to create time slots in a given spectrum band.

COPS will provide network operators with the ability to deploy any number of subscriber databases as they add services. This allows various functions to be added in what is essentially one system, as opposed to adding multiple boxes to a system. But carriers will still have to reach roaming agreements with each other to implement these types of 3G services, Steinert says. He adds that COPS will create a more cost-effective way to do this and probably make it easier for network providers to establish these types of agreements.

While the software will create a common technology base for network providers to use, challenges still exist. Steinert notes that firms are already trying to address roaming issues, but these are primarily aimed only at voice services. The challenge will increase incrementally as roaming development work moves to address more complex data service problems. The program will help simplify this process and allow carriers to do this in a more comprehensive and cost-effective manner, he says.

Additional information on COPS is available on the World Wide Web at

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