The middle ground

Broadband wireless access can help service providers differentiate by filling the gap between DSL and fiber

As the Internet and e-commerce grows in importance for businesses of all sizes, even today s small and medium-sized enterprises need access to high-speed data communications.

Unfortunately, these businesses tend to fall in a gap that currently is underserved by carriers. While large businesses have high-speed fiber access options, small offices/home offices can use residential access technologies such as cable modems or DSL.

With fiber, carriers have invested to build out local and nationwide networks. However, less than 5% of business buildings in the U.S. are connected by existing fiber. Therefore, mostly large businesses located in tall buildings in highly dense areas have access to fiber. Consequently, competitive local exchange carriers (CLECs) with extensive fiber routes have looked to broadband wireless access - having purchased local multipoint distribution service and other broadband wireless access licensed spectrum - as a means to extend fiber facilities in a way that maintains not only the high bandwidth but also the carrier-grade levels of quality.

Although cable modem and DSL access as residential options satisfy the needs of low-bandwidth users, these methods are not suited to the needs of small and medium-sized businesses. Broadband wireless access can meet current and future demand for high-speed data services for today s business customers that otherwise would fall in the gap. Similar to the growth of the PC market, in which PC and component manufacturers produced faster machines to appease the demands and applications of its users, now comes broadband wireless access to satisfy those users bandwidth demands.

Cable modems continue to gain momentum in the residential market because lines tend to be concentrated in these areas. However, cable TV operators cannot serve office parks in both urban and suburban areas, where small and medium-sized businesses are based.

Several years ago, ISDN was hailed as the technology to provide high-speed access to the masses. This never happened, in part because of mishandling by carriers in deploying and marketing the offering, and in part because of technological limitations. Besides bandwidth restrictions, DSL could suffer the same legacy as ISDN with limited deployments.

Furthermore, a major concern for CLECs in deploying DSL services is relying on the RBOC's copperbased plant. The deployment statistics for DSL bear this out - just more than 800,000 DSL links have been deployed to date, according to a TeleChoice estimate. This is in spite of pent-up demand for high-bandwidth data services.

CLECs still remain restricted by the limited RBOC deployments and must rely on them to provision service to its customers. The co-location of CLEC equipment (in the form of DSL access multiplexers), lease of RBOC facilities and the deployment time represent additional barriers.

And often there are customer service problems installing DSL because of inaccurate database information about the location and status of phone lines from the central office (CO) to the customer site. This results in installation delays and multiple service calls - inconveniences business users cannot afford.

These realities will continue to affect CLECs, even for those that price and market DSL services more aggressively to make them attractive to customers. The parallels to ISDN deployments continue.

A step beyond Broadband wireless was designed for data and meets the unique needs of data communications. It s a true packet-based technology, not a method of using another technology to provide packet service. In a way, next generation broadband wireless access approaches are similar to the Ethernet LAN within an office, but in a metropolitan area. To offer another analogy, frame relay did for data communications in a voice-switched WAN what broad-band wireless access accomplishes for integrated voice and data in the access portion of the network. Frame relay was intended to efficiently handle higher speed, bursty data and allocate bandwidth through statistical multi-plexing - the ability to oversubscribe services.

Employing a true point-to-multipoint architecture, more recent broadband wireless access system approaches create a network that acts as a wireless bus to allow carriers the ability to deliver broadband services on a shared basis to many users in a geographic area. The result is that business users in diverse locations use a single broadband pipe to receive higher speed broadband connections at lower costs.

In the access loop, the system allocates only the necessary bandwidth required by an end user at any given time, allowing the carrier to meet service level commitments, while at the same time freeing up unused bandwidth for other users. This bandwidth on demand also enables wireless CLECs to over-subscribe their spectrum and their equipment, taking advantage of the fluctuating nature of data services.

For example, broadband wireless access can provide the same guaranteed rate of 0.5 Mb/s in each direction that DSL offers but with the ability to also burst up to 5 Mb/s on demand or any other portion of 40 Mb/s pipe - something DSL cannot offer (Figure 1).

Because of the bursty nature of data communications, this full burst rate is available to users 99% of the time. In other words, not all users will use the network at the same time, and not all will need the same burst rate at the same time. Because of this, carriers can oversubscribe the network while still providing full service to users, which could result in an increase of revenues by a factor of six with no additional investment.

Bandwidth not used by one customer at any given moment can be used by another customer, and therefore, no bandwidth is wasted - again maximizing a carrier s revenue opportunities. In contrast, DSL offers only fixed bandwidth, and the physical nature of the connection to the customer premises means that the carrier cannot offer unused bandwidth to another customer.

In the access pipe, one criticism leveled at broadband wireless is its requirement for line-of-sight transmission within a 5-kilometer radius. However, line of sight isn't a significant drawback because the signal is sent from the top of one tall building to the tops of other mid-level to tall buildings - the types of buildings that usually house small and medium-sized businesses. Careful selection of base station sites can eliminate any line-of-sight challenges. As long as the signal can hit some corner of the customer s building, broadband service can be provided.

But this is not equivalent to DSL s limitation of distance from the CO and its use of dedicated facilities to every location, as seen in the DSL topology in Figure 2.

In a true point-to-multipoint broadband wireless access architecture seen in Figure 3 however, wireless CLECs can deliver higher data speeds (768 kb/s to 40 Mb/s), in an efficient and flexible wireless bus or shared architecture. This innovative approach lets these carriers achieve spatial statistical multiplexing - oversubscribing services over a group of geographically dispersed buildings.

Moreover, broadband wireless can reduce cost and time of deployment. Deploying a broadband wireless network entails placing a base station on top of a suitable building, obtaining a fiber link for the base station and installing the customer premises equipment (CPE) on customers buildings. The San Francisco Bay area with its thousands of buildings could be covered by just a few hubs, a deployment that can be accomplished in weeks with broadband wireless access rather than several years for wired connections (Figure 4. Of course, speed to market is essential for carriers offering broadband services, and these carriers can ill-afford to wait to take advantage of the vast potential of the market.

Broadband wireless is a cost-effective technology to deploy. The physical infrastructure is limited to base stations and CPE. No physical connections are needed - nor are the related hassles of digging up streets and sidewalks to bury lines. Because the customers aren't mobile, the need for initial nationwide coverage is not essential. This is a pay-as-you-grow technology. For more capacity, service providers can add base stations as they add customers.

An entry-level base station with 155 Mb/s capacity can be deployed for less than $200,000. One base station can cover 30 square kilometers and serve thousands of users. With this deployment model, a broadband wireless network can be deployed at a cost of approximately $2000 per customer. At price points similar to a DSL investment, while achieving fiber quality and speeds, a carrier can get a broadband wireless network up and running and generating revenue with a relatively low capital outlay.

Next generation broadband wireless access systems provide real-time bandwidth on demand at broadband speeds to meet the needs of business customers. With this flexibility and efficiency corresponding to increases in revenues and decreases in costs, these new systems are the ultimate enablers of broadband access to the underserved business community. While DSL is a reasonable step up from the 56 kb/s dial-up modems, it has insufficient speeds and deployment limitations to satisfy the ever-increasing data needs of small and medium-sized business.

The CLECs that will be successful in serving the gap of the business market are those that use broadband wireless to deliver differentiated services, which integrate high-speed, bursty data with voice offerings. Whether a carrier s objective is to become a facilities-based provider or to complement its local and national fiber networks, employing next generation broadband wireless access platforms not only improves the business case, but provides a competitive advantage in the long run.