The Internet is not only changing the way we communicate in our daily life, but it is also fundamentally changing the way we conduct business. Information exchange today extends well beyond communication within a building or business campus, and the applications go well beyond e-mail and corporate Intranet. Rather, we swap engineering designs with remote offices, share inventory databases with suppliers, get proofs from our vendors, let employees work at home, take orders and ship products to customers—all over a private network or the Internet. These new business practices create a tremendous demand for high bandwidth access to the networks. A new class of bandwidth-intensive applications, such as videoconferencing, heightens demand even further, as these become the mainstream business practices.

Figure 1: Three types of access supported by the cable infrastructure: the Internet, private network and virtual private network—all of which connect end users to the respective networks through their headends. The virtual private network is represented by a private network and secured "tunnels" within the public Internet.

How does modern networking and access technology meet these demands? At the low end, today's telephony-based remote access is inexpensive, but too slow. At the high end, dedicated leased lines offer fast digital access, but at a cost that is prohibitive for small- and mid-sized businesses—a group that constitutes 60 percent of the business market.

The proximity of their cable infrastructures puts cable operators in an excellent position to deliver high-speed access to small- and mid-sized businesses. By leveraging their cable assets and the economics of the coaxial cable network, cable operators are poised to be formidable players in the local access market.

Market opportunity

Traditionally, local telephone operators have monopolized the local telecommunications market—today, a market approaching $100 billion. However, the Telecommunications Act of 1996 changed all that, and opened the market to competitors, including competitive local exchange carriers (CLECs) and long distance carriers.

Figure 2: A framework for business applications supported by cable access. The e nabling technologies are represented at the bottom, horizontal applications are in the middle and vertical applications are at the top.
Figure 3: To combat upstream noise, S-CDMA modems reduce channel capacity in the event of noise surges. This feature ensures reliable and continuous service, avoiding complete network shutdown and lengthy reboots. This feature allows operators to design a business system to prioritize one level of service, such as CBR, over a lower-level of service, such as UBR, so that the higher level of service is not impacted by upstream interference.

Dedicated data access, which provides business users with a constant, full-time connection to the Internet, is a small, yet fast-growing, segment of the local telephony market. Driven by the explosive growth of the Internet and private networks, dedicated access has been growing at a rate of more than 20 percent per year—today at nearly $10 billion. CLECs have been effective in capturing a segment of this market from the telcos.

Cable operators are in a unique position to offer a suite of economic broadband access solutions for small and mid-size businesses. While CLECs target large businesses in major cities, cable networks cover primarily residential areas, where small- and mid-size businesses are located. Their all-coax and hybrid fiber/coax (HFC) architectures are likely to offer better economies than all-fiber networks, when deployed in these residential areas. All of these factors provide cable operators unmatched competitive advantages in the business market.

Cable-based access networks

Cable operators can target two distinct access opportunities: Internet access and private/virtual private network (VPN) access (see Figure 2). In Internet access, the cable network is used to connect businesses to the Internet through the headend. The headend acts as a traffic concentrator for a point of presence (POP) on the Internet. The businesses' internal network is connected to the cable network through a cable modem via a hub or a router.

As an access to a private or virtual private network, the cable network connects vendors, business partners, customers, branch offices and employees' homes to a corporate network. Users are connected to the headend via the cable network, which connects to a private backbone with a dedicated leased line, in the case of a private network, or with secured "tunnels" through the Internet, in the case of a virtual private network. Such tunnels, implemented by network layer encryption of Internet Protocol (IP) data, allow transmission of mission-critical data across the Internet without compromising its security. Virtual private networks have the advantage of lower cost and higher flexibility over private networks, because VPNs don't require leased lines.

Business applications over cable

In general, business applications over cable are differentiated from residential applications by: (1) providing productivity enhancements as opposed to the entertainment focus of residential applications, (2) running over a wide area network (WAN), and (3) requiring high bandwidth, two-way connection. Figure 2 provides a framework for describing business applications over the cable access network. The underlying technologies supporting these applications include the cable modem, the coaxial cable network, virtual private network, and voice-over-IP.

Three categories of horizontal business applications can best be supported by a cable access network: collaborative applications, real-time broadband applications and commerce-related applications. Collaborative applications include groupware, workflow and whiteboard applications, which allow multiple users in disparate locations to share the same information concurrently. The information exchanged in these collaborative applications includes documents, images, business forms, chained discussions or video and audio streaming. The real-time applications include videoconferencing and IP telephony. Commerce-related applications include Web site hosting for advertising or electronic commerce and financial transactions such as point-of-sale, inventory control and credit verification.

Table 1: Business application requirements
Figure 4: Bandwidth and latency requirements for various broadband services. (All numbers are after data compression.)

Multiple vertical business applications can be supported by cable access. Figure 2 includes a list of eight vertical applications, including K-12 education, college campus access, telemedicine, real estate, work-at-home/telecommuting, retail and community and government access. All of these share a common characteristic: they are accessible to cable networks.

Design requirements

Because business applications provide productivity enhancements, there are specific implications in selecting a cable modem. Table 1 lists a set of requirements for business applications (page 90).

Reliability. By their nature, business applications demand highly reliable networks. To successfully enter the local market and capture market share from local telephone operators, cable operators must deliver highly reliable access service—a proven strategy by CLECs in recent years.

The most vulnerable aspect of a cable access service is the upstream channel, as a result of the noise in this portion of the spectrum. The upstream noise corrupts the quality of the physical layer transport, and potentially the data service, as well. Recent field trials conducted by the author's company with a major cable operator have shown that the upstream noise floor can vary as much as 10 dB to 20 dB in a period of 12 hours. Such noise fluctuations demand a cable modem with a robust upstream channel. With its higher noise threshold and outstanding immunity against white Gaussian noise, narrowband interference, and impulse noise, S-CDMA-based cable modems significantly enhance the reliability of cable access services.

The reliability of access services is predicated, not only on the higher noise threshold, but also on resiliency against noise fluctuations. In situations where the noise level exceeds the threshold, the cable modem system must have a rate-adaptive feature that responds to interference with a momentary reduced data rate, rather than a complete disruption of the access service. Figure 3 illustrates the rate-adaptive capability of an S-CDMA-based cable modem system, which reduces capacity to guarantee reliability and continuous service in a high-noise environment.

Security. Business applications over private and virtual private networks have privacy and competitive implications, thus requiring secured access channels. This implies three levels of security: in the modem, in the headend, and over the cable network. On the modem side, authorized users must be authenticated before accessing the network. In addition, a firewall can be integrated into a modem to enhance the security of the branch, home, or vendor offices in which the modem is deployed. At the headend, each connecting modem needs to be authenticated to ensure that it is authorized for both access and services. In addition, communication at the link and network layers over the cable infrastructure can be encrypted to improve security. Today, link and network layer encryption technology such as VPN is becoming available. Physical layer security can also be achieved through modulation techniques that incorporate spread spectrum techniques to ensure both data integrity and security.

Bandwidth symmetry. The vast majority of business applications impose equivalent demands on upstream and downstream bandwidth. For example, data exchange over a private network often involves two-way exchange of the same type of information between two corporate headquarters or between a corporation and its branch offices, customer premises, or employees' home offices. In addition, a business may need to request Web pages from the Internet or to host a Web site of its own.

Cable modem systems with limited upstream bandwidth impose severe limitations on the business applications that can be run over the network. Such systems do not effectively support symmetric business applications, such as groupware and videoconferencing, and also limit the downstream bandwidth available for other applications. Such symmetric applications demand a cable modem access system which supports true, two-way interactivity.