Telephony: T-1, PBX and Centrex

When I started this column more than 10 years ago, finding a match between what our industry needed to hear and what I had to say was about as easy as filling a glass of water from Lake Michigan. There was so much “new stuff,” and cable technical people were thirsty for knowledge. Now that we’ve been doing so well in adding residential telephony customers, I began wondering if the lake had been emptied—until I talked to some folks at Comcast. “2007 and 2008 are the years of commercial services,” said Jim Venne, director of Regional Sales Operations for the Chicago Region. The reason is the same as the one the Sundance Kid gave when asked why he robbed banks. “That’s where the money is!” Classic telephony Commercial services includes data access and video, as well as business telephony. Even for data, however, much of the technology is classic telephony. T-1 and T-3 links are connectivity mainstays, and even when we are talking about Gigabit Ethernet (GigE), it often means T-1 over an Ethernet link. In addition to being used for ties between corporate locations, T-1 links are the pipe that connects cell towers to the necessary land-based mobile switching centers. Similarly, although most new business telephony systems are sold as multimedia communications, the main application is still voice services.

The market for commercial services is huge, by some estimates more than $7 billion annually in regional markets alone. So why didn’t we get into this business from the start? In conversations I had with cable executives about 10 years ago, they would often say that it was better not to fight too many battles at once. They didn’t have any doubts about competing for residential phone service, but felt that if they offered business telephony (or any other commercial service), it would be the straw that pushed the telcos into residential video. Some arguments die naturally. T-1, two ways T-1 services can be offered by a cable company in two forms over an HFC plant: as a DOCSIS-based service using a T-1 modem or as an Ethernet-based service. Vendors offering implementations include Vyyo, Narad and Scientific Atlanta. Vyyo provides a system with modems using DOCSIS chipsets, while both Narad and Scientific Atlanta have Ethernet solutions.

Vyyo’s solution consists of DOCSIS compatible T-1 modems at a customers’ premises, connected over an HFC network to their headend-based XMTS T1 Access Concentrator. Both the modems and the access concentrator use Broadcom DOCSIS chipsets, but also incorporate proprietary technology to maintain T-1 timeslots and clocking. The XMTS interacts with the modems and a backbone transport network similarly to the way a cable modem termination system (CMTS) functions in a standard DOCSIS network.

Narad’s offering is an Ethernet switched solution that consists of Optical Network Distribution Switches (ONDSs), Narad Diplex Filters (NDFs), Narad Access Switches (NASs), and Broadband Interface Units (BIUs). The BIUs are customer premises located 100BaseT Ethernet modems that contain a pseudowire interface that converts T-1 to Internet protocol (IP) for transmission over an Ethernet network. NASs are Ethernet switches that bridge existing amplifiers and regenerate the Ethernet data. The ONDS is a switch located at a fiber node and is where the T-1 is switched to a fiber distribution network. Narad uses an upstream carrier in the 908 to 971 MHz band and a downstream carrier in the 1.02 to 1.08 GHz band to provide symmetrical data service and depends upon the NDF to separate Ethernet from the standard cable spectrum at the ONDS.

Like the Narad product, Scientific Atlanta’s BroadLAN Transport System is Ethernet-based and requires a T-1 to Ethernet interface from a partner company. Unlike Narad, it operates within standard upstream and downstream allocations. The hardware consists of a headend-based T-1200 or T-2400 Transport Modem Termination System and the customer premises C-1100 or C-1200 Client Transport Modem. It uses a 6 MHz channel in the 88-864 MHz downstream spectrum and another 6 MHz channel in the 5-42 MHz upstream. In the reverse path, subscriber information is multiplexed on up to 14 narrowband tones. The multiple tones provide immunity from “jammer” frequencies within the 6 MHz band. Potential gold mine For cable, business telephony is an unopened goldmine. In the beginning, the only place to get business phone service was the telco, and two flavors evolved. Private branch exchanges (PBXs) are telephony systems where the telephone switch is located at the customer premises. Their cousin is Centrex Service, where a group of lines in the same telco central office switch that serves residential customers is reserved for a business customer. Originally, the telco owned either type of system, and the size of the business was the leading parameter that determined the type of system. With deregulation, businesses could own their premises-based telephony switches, and cost and control became just as important. Today, PBXs are mostly sourced from private vendors or obtained from a service provider acting as a distributor for a private vendor. Centrex-type service comes from a service provider. In both cases, the service provider can be a cable company as well as a telco. A third flavor of business telephony, hosted PBX, is also possible. Similar to Centrex service, a hosted PBX is located in a network apart from the business being served. A hosted service, however, is usually based upon a network that only serves businesses.

Like T-1 implementations, business telephony can be provided by a cable company in two ways. A cable company can partner with an IP PBX vendor or with a hosted service, either as a distributor or in a marketing relationship where the cable company provides access lines and/or network connectivity. Alternatively, it can provide Centrex-type business services from a PacketCable network if business features are part of the feature set of its network. Whaleback is one company that offers the first type of solution, while CedarPoint offers the second.

The Whaleback CrystalBlue offering is a sort of hybrid between a customer premises PBX and a hosted PBX service that exists in a third-party network. An on-premises processor handles call switching and feature provisioning, but call completion is via a Whaleback gateway accessed over a broadband link from the business. In late January, Whaleback announced a “bandwidth resiliency” feature that provides hot swaps between two broadband links to guarantee uninterrupted service and/or route diversity. The business customer pays Whaleback a flat monthly fee per phone line and a per-line activation fee, which includes unlimited U.S. usage and maintenance for the processor and its feature software. The cable company receives revenue for each broadband line between the on-premises processor and the customer’s Internet service provider (ISP).

The CedarPoint Centrex offering is completely based upon the cable company’s PacketCable-compliant switch. In 2006, CedarPoint added a set of business features to its Safari product, to complement existing residential features. As such, Safari provides much the same functionality as traditional Class 5 switches with a Centrex offering. Safari also offers trunk connectivity to IP PBX offerings. Lots of lakes Going back to my glass of water analogy from the beginning of the column, it appears there are still a lot of commercial services lakes to fill this column’s waterglass, from both technology and marketing perspectives. Add cellular to the mix, and there’s no drought in sight for a number of years. Justin J. Junkus is president of KnowledgeLink and telephony editor for Communications Technology. Reach him at [email protected].