In Wireless, Less Is More - Technology Information

Telecommunications, Nov, 2000 by Malcolm Wood

Low-power units could be the key to cost-effective advanced services.

With every technology leap, reality needs time to catch up with what dreamers envision for our future. That's what's happening while we wait for wireless systems to deliver on their bright promises. The payoff will be the ability to go beyond the realm of wireless conversations into the world of WAP (Wireless Application Protocol)-based handsets that display miniature versions of Web pages. We've all been enticed by the possibility of using these displays to check dot.com stocks, changing weather conditions or sports scores.

The only wrinkles are the lack of Web-enabled handsets and the inability of most conventional wireless networks to provide the high-quality signal coverage that data-intensive PCS applications require to perform these miracles. In some cases, the inadequacy will surface within networks that currently supply adequate coverage for less demanding voice and data services. In other cases, it will involve high infrastructure costs to offer coverage in new areas. Even worse, in remote or rural locations, it will make service at reasonable cost impractical. Regulatory restrictions on conventional RF facilities, related concerns about environmental health and safety, and the visual downside of huge transmission towers add another layer of complexity to these challenges. Unfortunately, resistance to wireless deployment can prevent network operators from making the upgrades necessary for dependable delivery of advanced services.

Paradigm Shift

The answer does not lie in building more and taller towers or sending out more powerful RF signals. One solution is an entirely new generation of economical, low-profile, low-power coverage units that resolve the issues of cost, logistics and local resistance.

Even in areas that have dense, highly developed wireless infrastructures, such as Japan and much of Europe, the introduction of WAP will reveal the limitations of conventional wireless networks. Future users of WAP-enabled handsets will discover they must remain stationary while accessing Web-based information. If they are inside a moving vehicle or even walking, the call will be dropped with annoying regularity. At the heart of the problem is the demanding nature of packet-based, data-heavy PCS applications. Because they require a uniformly high-quality signal, the effective size of wireless cells shrinks. Translation? The signal quality at the edge of a cell deteriorates to the point where packets are lost and calls are dropped.

To plug these holes and enhance network performance, successful operators could instead rely on a network of small-profile, low-power coverage units that support networks moving toward 3G services. This solution consists of the following components.

* A b-unit (base unit), which is attached to the network operator's BTS (base transceiver station).

* A cluster of c-units (coverage units), which provide coverage to the target area by transferring signals between handsets and the b-unit attached to the base station.

* A network management application that operates remotely from the network OMG (operation management center) and enables operators to configure and manage the network.

Colocated at a conventional base station, which is the source of the transmission, the b-unit transmits signals to and from clusters of c-units, which relay signals to and from the handsets. At any time within this network, a handset is receiving the signal from multiple c-units. Conversely, when the handset is transmitting, multiple c-units receive the signal and pass it on to the b-unit. This multiple-signal-source architecture makes it possible to reduce the system's power output and deploy units at a lower height than conventional wireless alternatives--all while maintaining robust coverage.

Since the units operate on only 0.8 watts of power, RE exposure is lower than for conventional mobile handsets. Consequently, they fall within FCC requirements for low-impact equipment. These units also reduce power consumption in mobile handsets and extend battery life. In a recent test trial, handsets were able to power-down in 92 percent of the coverage area, compared to only 10 percent for conventional networks, and signal coverage improved.

New Deployments

Because low-power units can be installed virtually anywhere, operators have greater flexibility in obtaining new sites and more leverage in negotiating site lease costs. Furthermore, this siting flexibility enables operators to deploy networks in areas previously inaccessible to traditional infrastructure equipment.

The low-power units also improve coverage performance. In one test, they raised system-wide performance to the degree that signals received by handsets met threshold requirements for 98 percent of the coverage area compared to 76 percent using conventional technology. These units can help operators deploy service in areas where they face siting challenges because they provide more flexible options and more homogenous signal levels throughout the network.