Biomedical Engineering Reference
In-Depth Information
Bluetooth,
802.11b,
Zigbee
802.11a
GPS
PCS
UWB
UWB
-41.3
-51.3
-53.3
-75.3
0.96
1.61
1.99
2.4
3.1
5
10.6
Frequency (GHz)
Fig. 1.3
Transmit spectrums for UWB and other wireless technologies
regulations on UWB transmit power allowing gated UWB transmission systems to
transmit at higher peak powers [
20
]. In March 2007, an international standard for
UWB communication was approved by the International Organization for Stan-
dardization (ISO) based on the Wi-Media UWB common radio platform [
21
,
22
].
Figure
1.3
depicts the frequency spectrum of UWB transmission together with
spectrums of other existing wireless technologies.
UWB communication systems can be divided into two major categories;
Impulse Radio-Ultra-Wideband (IR-UWB) and Multi Carrier-Ultra-Wideband
(MC-UWB). MC-UWB uses multiple sub carriers to transmit data using Orthog-
onal Frequency Division Multiplexing (OFDM). This technique is used by the
Wi-Media alliance for wireless multimedia transmission. MC-UWB technique
consumes large amount of power due to complex signal processing involved in
OFDM based transceivers. For example, the Wi-Media chipset by Aleron consumes
around 300 mW of power [
23
]; hence, it is not suitable for power stringent WBAN
applications.
IR-UWB systems transmit short pulses to transmit data. Pulsed nature of UWB
transmitters enables the use of simpler modulation schemes such as Pulse Position
Modulation (PPM) and On-Off-Keying (OOK). Simpler modulation schemes
enable less complex hardware systems implementing IR-UWB communication
systems and reduce the power consumption significantly. These are among many
advantages provided by the IR-UWB communication systems, making it a suitable
candidate for battery powered WBAN applications. Some of the major advantages
provided by the IR-UWB communication for WBAN applications are discussed in
the following section.
