Broadband Availability

Broadband Availability
For some years the telecommunications industry has worked hard on various methods to provide high-capacity access to the Internet. The result of this heavy investment (some of which is less valuable now than its original cost) is generally a competitive environment of broadband access availability.

We can identify seven ways to obtain broadband connectivity (that is, appropriate for business VoIP applications) between on-premise LANs and managed WANs, as follows:

Leased digital links using legacy TDM technology are available as DS-1 (i.e., "Tl" as it is commonly known) at 1.5 Mbps, or DS-3, at 45 Mbps. Outside North America the equivalent multichannel digital services are El (at 2 Mbps) and E3 (at 34 Mbps). With the tariffs charged by the incumbent telcos these services are not attractive, but under competitive conditions may still have a role to play.

Switched ISDN channels are at basic (144 Kbps) or primary (1.5 or 2 Mbps) rates. ISDN-PRI was widely used in the early years of rapid growth with the ISP business but, again, is not now competitively priced in most areas.

DSL services are widely offered in many countries at attractive prices.

Cable modems (CMs) are linked by hybrid coaxial/optical fiber to the two-way network of the local monopoly cable TV carrier.

Digital cellular wireless services have moved into the 2.5G and 3G developments. These services have the advantage of mobility and may also be of limited usefulness for fixed locations.

Microwave radio services for broadband access are primarily of the point-to-multipoint type. These high-frequency technologies, such as local multipoint distribution services (LMDS), generated considerable interest when licenses were sold in the mid-1990s. Unfortunately, most of the new fixed-broadband radio carriers have collapsed financially and this choice is not widely available.

Extended Ethernet (i.e., native IP transmission) over optical fiber is available in many urban areas from multiple service providers.

We should note that "sky-based" communications services, whether from geostationary or low-earth-orbit satellites, are not suitable for any interactive VoIP applications, because of either significant transit delays or serious unbalance between the up and down-link data rates.

One major advantage that will become obvious with IP-Centrex is that customers can afford to rent a second broadband access link to their main locations, providing better availability of service than was feasible with legacy Centrex. On a fair accounting basis, the true cost of the copper wire component of a local loop (the traditional "last mile") is around $10 per month. The actual cost of local access bandwidth to support one IP-Centrex user, in a medium-sized office of 100 users, will be less than one-half of that amount. This leaves an ample margin to pay for a second access link, perhaps at a degraded bit rate, that is both physically and service-provider redundant.

Four of the service types that are summarized in the following sections are worthy of further consideration.

DSL Services
DSL services use up to several megahertz of bandwidth over the local loop, compared with conventional, single-carrier modems, which are restricted to the 3.4 kHz that is generally available for audio telephone signals. This means that DSL signals cannot pass through any switch (i.e., PBX or CO) and, because of high attenuation at the higher frequencies, the usable range is limited to a few miles over the standard 24 American Wire Gauge (AWG) copper wire.

In the customer's premises the DSL modem provides an Ethernet interface to the internal LAN, while at the serving carrier's site the DSL terminates on a digital subscriber line access multiplexer (DSLAM), which is linked directly to the IP or ATM WAN on the trunk side. With ADSL service, an analog channel is reserved for one conventional telephone line, below the frequencies employed for the DSL. But in a fully IP, packet-only access environment, which we can call the all-digital loop (ADL), the full bandwidth over the copper wires can be exploited and there is no need for frequency splitters at each end, resulting in lower equipment costs. This is illustrated in Figure 1 for the home office situation, to which dc power can be sent for the phones, because of the end-to-end copper loop.


Figure1:All-digital loop architecture.

Most DSL customers are currently using the service for Internet access from their homes and small businesses. In North America, in late 2002, there were about 4 million DSL users, compared with 7 million cable modem subscribers. In Britain and several other Western European countries, the adoption of DSL remained extremely low, because the incumbents were slow to "unbundle" local loops to competitive carriers and prices were kept too high. By contrast, in South Korea over 10 million customers use a DSL connection for Internet access.

We expect that monthly prices for ADSL will settle in the $30 to $SO range, with HDSL at less than $200, and that DSL will be, by far, the most common broadband access service for small offices, such as bank branches, medical clinics, and schools.

Cable Modems
Cable modems, which use the cable TV infrastructure to deliver broadband access, quickly became popular in North America and Western Europe, where there is a fairly high residential cable penetration, with prices of around $30 per month for nominal 6-Mbps service. Some cable carriers also offer a 128-Kbps access service at a lower cost (e.g., $18 per month) to compete with dial-up modems.

For business applications, such as IP-Centrex, CM for broadband access has two serious disadvantages:

- Cable TV is a shared service (like an extended, single-cable, LAN), with the worrisome implications of security risk and variable throughput.

- The typical cable TV operating company does not share the same sense of service reliability as an incumbent telco.

Next Generation Wireless Services
Next generation wireless services deliver data transmission rates over the digital cellular (or PCS) networks that are similar to those at the low end of wireline capabilities. For IP-Centrex applications these wireless networks primarily serve mobile users and can be valuable as "fixed mode cellular," providing local access redundancy for small offices. For example, it may be worth spending a few extra dollars for a wireless data service to back up a cable connection to a home office.

The so-called 2.5G data capability is now widely available with digital cellular services in two versions. The general packet radio service (GPRS) is an option with GSM that can deliver a data rate of up to 56 Kbps. With the CDMA services, mainly in North America, the clumsily named one times radio transmission technology ( IxRTT) offers up to 144 Kbps throughput. Pricing plans for these services usually add about $15 to the monthly bill, with additional charges for large data transfers.

Even though some mobile phone operators have spent many billions of dollars to acquire national licenses, third generation (3G) wireless data technology is not yet widely deployed. With 3G services, as an extension of GSM or CDMA, there is a promise of data rates from 144 Kbps (mobile) up to 2 Mbps (fixed).

One attraction of these data services is that they support the full range of mobile devices, including cell phones, PDAs, intelligent pagers, and laptop computers. With one-third of our work force engaged in telecommuting, at least on a part-time basis, the synergy between widely available digital wireless and IP-Centrex services will become invaluable.

Extended Ethernet
The extended Ethernet is the transmission of IP data packets over optical fiber, especially dense wavelength division multiplexed (DWDM) fiber, between the customer's premises and a managed network. This is an extremely competitive market in medium-to-large urban areas, with IP over DWDM being sold by ILECs, CLECs, cable companies, and electrical power distributors. Additionally, some organizations, such as municipal and regional governments, may have laid their own optical fiber links for specific applications. In this environment of bandwidth overcapacity, it is possible to obtain a 100-Mbps IP local access link for less than $500 per month, which is almost equivalent to the cost of a tariffed T1 link (i.e., 1.5 Mbps) from the incumbent telco. Against this low rental there will probably be an installation fee (or "service charge") of 10 month's rental, or a 3-year commitment to gain free installation.

Our three concerns with these financially attractive broadband, optical fiber solutions are:

- The QoS from the service provider may be diluted because of intense price competition between carriers.

- Some vendors are likely to withdraw from this market or fail commercially because margins may be too low to pay for ongoing network management and maintenance.

- The optical fiber network of any one carrier may not be able to serve all of the customer's locations in a given city. In spite of complicating affairs for management, we frequently have to cope with a multivendor situation