Using Copper For High Quality Voice And Video Over IP

BY YOSSI SAAD

While IP is unquestionably the protocol of choice for connecting enterprise sites, it was not so long ago that it was first offered by the service providers to their enterprise customers. The superior flexibility, simplicity and attractive cost structure (compared to legacy TDM or ATM technologies), made IP and/or its �link layer� partner, �Ethernet,� services that prove to be both attractive to the end users and cost effective to the service providers. IP/Ethernet networks are being built worldwide and attractively priced services are being offered to customers. These developments promote the use of IP in the enterprise world for more than just carrying data. They can serve the organization�s entire communications needs including voice and video.

THE ROLE THE INFRASTRUCTURE PLAYS IN IMPLEMENTING VOICE AND VIDEO OVER IP
More and more businesses are migrating to IP-based communications and eliminating the need for separate voice and data networks. The key to deploying a successful IP network (whether it is used for communication with the outside world, used to utilize IP within the enterprise, or both) is having an infrastructure in place which can provide the necessary high-quality bandwidth to support all the voice and data communications over the network.

The most important question to ask when preparing to deploy high-quality voice and video over IP is if the existing physical transport media can support the necessary bandwidth. Obviously, if a fiber network is in place, the answer is yes.  However, if there is no fiber in place, a service provider or enterprise needs to carefully evaluate the technology alternatives to determine if they will provide the bandwidth.

Other infrastructure topics to address include making sure there is a mechanism to identify and prioritize different network traffic, and to support the various technical aspects of the individual traffic streams. Within a local area network this task is relatively straightforward, although simply �throwing bandwidth� at the problem is not enough since traffic queuing and prioritization are still key planning issues. Most up-to-date enterprise-class equipment has both the capability to handle multiple traffic streams and the support for high bandwidth over both copper (for inter-building connections) and fiber cables, which provide more than sufficient bandwidth.

This picture changes, however, when you examine the connectivity between sites over public or private networks. Traditional WAN services are TDM-based, quite expensive and often require companies to lease multiple circuits to carry different types of traffic. Cheaper alternatives such as best effort DSL-based services or oversubscribed cable bandwidth can save money, but do not offer the service level guarantees required for voice and video traffic. Inter-building connections based on copper are often too far away to support traditional copper LAN interfaces.

Fortunately, innovations in enterprise networks are making their way into the telecommunications infrastructure. High-capacity fiber backbones can carry both TDM and packet-based traffic with extra capacity created using coarse and dense-wave division multiplexing. The channelized nature of the SDH backbone supports different traffic types today as core networks are migrated over to routed Ethernet networks. IP router technology is also finding its way into the heart of the network, providing support for the IP sessions out to the end points at the subscriber.

The architecture of the telephone network is ideally suited to end-to-end transmission of voice, video and data. With the right switching equipment, individual as well as multicast traffic flows can be directed to subscribers.

HOW COPPER CAN PROVIDE THE NECESSARY BANDWIDTH TO SUPPORT VOICE AND VIDEO OVER IP BETWEEN AN ENTERPRISE SITE AND THE CO
A key barrier to the deployment of voice, video and data services has been the infrastructure of the last mile to the customer location. Video traffic in particular is very sensitive to delay and jitter as is voice to a lesser extent. Although quality is usually adequate for streaming of highly compressed content to a residence through a DSL connection, the quality and possible service guarantees are not sufficient for business-class services.

Since 85 percent of all buildings, globally, are connected to the public network by copper only, solving the quality issue for copper-based communication is key to delivering on the low cost promise of converged voice, video and data IP networks.

There are two ways to approach this problem. One is to replace the copper infrastructure with fiber. However, this is prohibitively expensive to individual locations, especially on a �build it and they will subscribe� basis. The second approach is to look for innovative technologies which can use the existing copper infrastructure for the last mile from either the CO or remote to the subscriber. 

In this latter case, the technology has to be spectrally compatible with other protected services in the network such as DSL, T1 etc. In addition, these technologies will only be cost-effective to deploy if they do not require the levels of circuit engineering and design associated with repeated T1 circuits. Finally, as business services, they must be symmetrical. There are two technologies today which meet these criteria, VDSL and G.SHDSL. VDSL is restricted to short distances, leaving G.SHDSL as the most attractive candidate. An updated version of this standard (G.SHDSL.bis) is being standardized these days by the ITU-T.

In order to create the bandwidth desired for newer services above T1 speeds, multiple circuits need to be bound together, and such technologies, such as T1 Inverse Multiplexing over ATM (IMA), have been available for some time.  However, not being originally designed for copper transmission, they have not been able to meet the delay and jitter requirements of voice and video traffic without requiring very carefully designed pre-qualified copper pairs.

A new standard designed to take multiple copper pairs and bond them together to enable optimized Ethernet delivery is being finalized these days by the IEEE 802.3ah task force known as Ethernet in the First Mile (EFM). While it provides basic performance using G.SHDSL.bis, an EFM system�s capabilities can be further enhanced by utilizing special �boosting� technologies such as Actelis Netoworks� MetaLOOP. This technology offers throughput, reach, delay and jitter characteristics far superior to any other approach, over POTS-quality copper. Actelis� MetaLIGHT systems can bond up to 16 pairs and deliver up to 67 Mbps of Ethernet traffic on any available copper between the end user and the central office or remote terminal.

Using this technology, carriers are now able to offer cost-effective services to the 85 percent of customers served only by copper, carrying their voice, video and data traffic with fiber-level service level agreements.

With support now possible for IP voice to any customer, incumbent and competitive carriers are able to offer value-added services to their customers, such as IP Centrex.  This allows them to move beyond being mere �bit pipes� and to plan new services and revenue growth areas beyond the commodity T1 and voice markets.

HOW COPPER CAN PROVIDE THE TRANSPORT FOR VOICE AND VIDEO OVER IP THROUGHOUT AN ENTERPRISE NETWORK
EFM and MetaLOOP technologies are also applicable in private copper networks where inter-building links are too far away for copper LAN interfaces on enterprise networking equipment. IP traffic, be it voice, video or data, can be combined with traditional PBX traffic and carried across existing private telephone lines to other sites. This is particularly useful in cases where the alternatives are over-priced services from a telecom supplier or expensive fiber trenching within the campus.

Creating ubiquitous connectivity for voice, video and data traffic across and between customers has always been considered a desirable, but capital intensive exercise. With innovations such as Actelis� MetaLOOP technology and IEEE EFM standards implemented in products like the Actelis� MetaLIGHT systems, ubiquitous IP networks can become a reality without the cost and delays of fiber trenching. Any kind of IP traffic can now be carried to any point on a carrier's network or in a campus environment, with the same level of quality of service as a fiber connection.

Yossi Saad is Actelis vice president of marketing & product management. Actelis Networks is a leading supplier of solutions that enable service providers and enterprises to deliver carrier-grade, new broadband services using existing copper plant. With the superior rate, reach and reliability of Actelis' standards-based, award-winning MetaLIGHT products, service providers and enterprises can deliver high bandwidth, symmetrical services to their customers and/or locations without further infrastructure investments. Founded in 1998 and headquartered in the Silicon Valley, Actelis Networks is backed by preeminent telecom investors, including New Enterprise Associates, The Walden International Investment Group, U.S. Venture Partners and The Carlyle Group.  Actelis is shipping generally available products to customers throughout the United States, as well as in Europe and Asia Pacific.  For more information, please visit the corporate Web site.