UWB by definition is any RF technology that uses a bandwidth in excess
of 500MHz or deviation greater than 25 percent of the center frequency.
UWB technology was and continues to be used for impulse applications
such as ground-penetrating radar and systems used by military and law
enforcement to see behind walls. In the WPAN world, UWB forms the basis
for the Wimedia specification.
While Wimedia is also intended to operate in a limited range,
think of it as Bluetooth on steroids. Most notably it can operate
legally in certain portions of the 3.1GHz to 10.6GHz range, permitting
it to offer high bandwidths without the interference issues typical of
the more crowded 2GHz spectrum. It is also compatible with current and
emerging mobile telephony standards such as Wimax. Because of its
ability to transfer data at speeds in excess of current Ethernet
networks, but also support voice, video and data, Wimedia could
ultimately replace Bluetooth.
Zigbee was born from a later addition to the 802.15 Bluetooth
specification called 802.15.4, which created a specification for a low
data rate, low power consumption and a more secure network device. In
2004, the Zigbee alliance, a group of over 100 companies, ratified the
Zigbee 1.0 specification. While compatible with the former IEEE
specification, it improves the functionality associated with
applications such as industrial control systems, building/home
automation and medical data collection.
Like Bluetooth, it operates in the ISM 2GHz band, but requires
significantly less overhead in terms of software code requirements to
create an application, hence a savings in power consumption and simpler
The Zigbee specification supports operation in one of three modes:
Router works similar to traditional Ethernet
routers providing connections based on source destination requirements
of the respective devices.
Zigbee Coordinator is
required to form a Zigbee network. The coordinator could be viewed as
similar to the Domain Name Server (DNS) in a large network, storing
information about the other devices of the network.
End Device is the simplest device on a Zigbee network. It can only
communicate to a coordinator or a router, however it can not pass data
through. This is used where a simple, inexpensive point-to-point
connection is all you need.
Other WPAN technologies
WPAN devices are not limited to various black-boxes. A German company
called Ident Technologies has developed a technology called Skinplex,
which permits the transmission of data using the human body as a
medium. Basically, a person carries a device that uses his skin as the
antenna. When he is in close proximity to a receiver, communications
can be reliably achieved. One of the current applications for this
technology is secure access to buildings, automobiles or other
situations that require verification. The system operates at low data
rates on a frequency of 195kHz. This is similar to the RFID systems
found in most retail stores.
WPANs might present some interesting applications in a
broadcast facility. Imagine a studio of WPAN-enabled devices where
there are no wires, and where equipment could be moved from studio to
studio without rewiring.
McNamara is president of Applied Wireless, Cape Coral, FL.