Integrating Voice And Data On Residential Broadband Networks.

Cable operators, ILECs, and competitive carriers are all investing in and deploying broadband services and the increasingly competitive market for customers has already resulted in downward pricing pressure for DSL, cable, and fixed wireless services. This has forced service providers to re-evaluate their broadband business models and find new ways to leverage their broadband infrastructures to deliver value added services.

While the early build-out of the broadband infrastructure was centered around the support of one customer application--high speed Internet access-this is changing. The ability to overlay toll-quality, packetized voice services onto the broadband network is revolutionizing the way service providers view their broadband networks and vastly improving their revenue models.

Voice over Broadband (VoB) is a new technology application for broadband networks that enables service providers to leverage their investments in broadband access networks to deliver not only high-speed data services, but also multiple lines of toll-quality voice over the same broadband pipe. These voice lines can be provisioned in a matter of seconds, utilizing the same copper or coax pair already installed in the home or business.

Although much of the early activity in broadband has been focused on small business customers, the business case for broadband cannot rely on business customers alone. Large and small service providers alike are focusing their efforts on the residential market, foot-printing entire geographies, enabling them to spread the infrastructure costs across a broader base of customers. More than 80 percent of today's broadband services have been deployed to the residential customer, primarily by incumbent telcos and cable operators. This growing installed base of residential subscribers is a prime target for Voice over Broadband services.

Voice Over Broadband: How It Works

Several equipment components comprise the broadband network access system. Regardless of the transport medium (DSL, cable, or wireless), when voice is carried over a broadband access network, it is packetized for efficient transmission in a manner similar to the method for transmission of high-speed data. A new type of equipment referred to as a "voice gateway" takes the circuit-switched voice signal from the Public Switched Telephone Networks (PSTN) or other voice services network, compresses it, and creates packets that can be transmitted to the access network over a regional transport network.

From the transport network, the signals go through an access node, which varies according to the particular access technology. One of the key functions of the access node is to aggregate the traffic from many broadband subscribers for efficient transmission to the transport network. In a DSL network, the access node is typically called a Digital Subscriber Line Access Multiplexer (DSLAM). For cable, access is through a Cable Modem Termination System (CMTS) and, for wireless, the Base Station Controller (BSC) serves this function.

The final component is the Customer Premises Equipment (CPE), which connects the user's information appliance--a telephone, computer, set-top box, etc.-to the broadband access network. In a voice-enabled DSL network, the CPE is typically called an Integrated Access Device (IAD) and is, generally, a 10 Baset router or modem for the data appliances and provides a number of analog phone ports for telephony appliances. Cable networks use a Media Terminal Adapter (MTA) and wireless requires a Wireless Network Interface Unit (WNIU) or Wireless Integrated Access Device (WIAD). The Fig illustrates the various CPE options based on network type.

A major shift in the distribution model is speeding up the pace of innovation for integrated access devices for the home. Service providers deploying Voice over Broadband will begin to ship voice-enabled CPE to every broadband customer, whether that customer subscribes to broadband voice services yet or not. This allows service providers to proactively market bundled voice and data services to an installed base of service ready customers. Thus, with large-scale deployments of Voice over Broadband services to the residence set for the second half of 2001, new ways to lower the cost, simplify installation, and leverage existing standards and data networking technologies in the home have become the critical requirement for this shift in the service provider distribution model.

The Customer Premise Challenge: Distributed CPE

While this new distribution model bodes well for the rapid ramp up of Voice over Broadband services, the customer premise remains a significant challenge. Packetized voice adds a new level of complexity to the delivery of broadband services to the home. For example, in a data-only environment, the DSL modem is located in or near the PC. When that same DSL pipe is being used to deliver voice and data services, where do you put the voice-enabled modem or Integrated Access Device (IAD)? Since all of a home's telephones are rarely located right next to a PC, how does a residential customer take advantage of the ability to use their broadband connection for high speed data and several voice lines?

Indeed, the VoB business case collapses, if residential customers have to pull new wiring to utilize their Voice over Broadband services in rooms where no PC is present. Several CPE vendors are pursuing innovative solutions to this problem. Two interesting approaches center on utilizing home networking technology to deliver broadband voice, as well as data, and/or pushing the IAD function into software.

Home networking technology has come a long way over the last two years. There is a growing installed base of standards-based home networking products, utilizing phoneline and wireless-based home networking technology. By using existing in-home wiring or wireless frequencies, standards like HPNA, Home RF, 802.11, and Bluetooth eliminate the need to pull additional wiring through the home. They also represent standards-based methods for networking data within the home that are becoming cheaper and more widely available. By building upon the existing work of these standards and expanding them to include broadband voice, CPE vendors will be able to provide a distributed architecture for Voice over Broadband services that allows derived voice services to be delivered to any phone, regardless of its proximity to the PC.

Another interesting solution is the "soft" IAD. Eliminating the need for a hardware-based modem, this type of customer premise device utilizes the processing power of the PC, requiring only a small, inexpensive, bridging device at each phone (similar to DSL's micro-filters) to deliver the derived voice services. With processing power increasing exponentially, the impact of the "soft" IAD on the PC's performance becomes virtually negligible.

Of course, there is a downside to both of these approaches. By leveraging data networking technologies or relying on PCs as the methods of delivery for packetized VoB services, service providers sacrifice the ability to provide lifeline services to residential customers. One of the great features of the traditional voice network is residential lifeline service. (Lifeline service is the ability to offer line-powered dial tone.) In the event of a power failure, the telephone will continue to operate and provide residences a "lifeline" to the outside world.

When power fails at the residence, packetized voice services are not available. Since lifeline service is included in every state Public Utility Commission local voice tariff, the inability to offer this service is problematic and would require a major effort to de-sensitize the public from this feature.

Packetized Residential Lifeline

However there is an alternative. A new patent-pending technology called Packetized Residential Lifeline (PRL) enables an emergency lifeline capability in the event of a power failure. PRL is deployed through a voice gateway and an IAD.

Ordinarily, if the power fails at the customer premises, the IAD or MTA ceases to function and is no longer able to process the incoming Voice over Broadband packetized voice. When this happens, PRL utilizes a Lifeline Interface Module (LIM) at the customer premises and the Lifeline Port Module (LPM) in the voice gateway at the service provider's premises to instantly switch the customer's phones to the backup, lifeline POTS circuit.

When power is restored at the customer premises and the IAD or MTA becomes functional, the packetized voice network automatically resumes operation. However, in a distributed architecture relying on a PC driven IAD or home networking technologies, cut-through to each RJ 11 is more complicated, making delivery of lifeline services much more difficult. The alternative option in this case is to provide an UPS system for the PC and/or IAD to enable lifeline.

The residential market represents a tremendous opportunity for Voice over Broadband services. However, there are several challenges at the customer premises that must be overcome for derived voice services to be widely deployed to residential customers. The viability of the residential market for Voice over Broadband services relies heavily on technology innovation to solve premises issues, including simplified installation of customer premises hardware and a distribution model that creates a large foot-print of voice-enabled customers. The foundation for this environment is standards-based, multi-vendor interoperability. Interoperability creates competition, which encourages rapid innovation, and enables accelerated deployment of new services. Service providers plan to provide their customers with CPE from multiple sources and any type of retail market will succeed only if vendors are dedicated to enabling standards-based, multi-vendor interoperability.

Brian Henrichs is the vice president of business development at General Bandwidth