Biomedical Engineering Reference
In-Depth Information
1.3 IR-UWB WBAN System and Advantages
(1) Low power consumption of IR-UWB transmitters
WBAN devices are considered as battery powered devices. Hence, the power
consumption of data transmission devices involved in a WBAN should be kept at a
minimum in order to extend the battery life. This is especially very critical for
implantable applications of WBAN, since replacing a device or a battery will
involve an invasive surgery.
IR-UWB transmitters use discrete pulses in order to transmit data [
24
], whereas
traditional narrow band transmitters use data modulated continuous wave signals
for wireless transmission. Because of the discrete pulse transmission, a significant
portion of the data transmission time in IR-UWB transmitters consists of a silent
period. As a result, the electronic components involved in pulse generation can be
operated at a low power mode. In contrast, traditional narrow band transmitters
operate continuously throughout the data transmission period for most of modu-
lation schemes. This difference of data mapping principal results in a significant
reduction in the power consumption UWB based wireless technologies for long
operation periods.
Implementation of an IR-UWB transmitter involves very few Radio Frequency
(RF) components compared to continuous wave transmitters. In fact, all digital
realizations of IR-UWB transmitters are achievable with the aid of state-of-the-art
Complementary Metal Oxide Semiconductor (CMOS) technology [
25
]. In con-
trast, traditional narrow band transmitters utilize high power consuming RF and
analog components, such as RF Power Amplifiers (PA) and analog Phase Locked
Loops (PLL), extensively due to the nature of the signal generation [
26
].
Furthermore, because of the easier data mapping in IR-UWB transmitter,
complex modulation schemes are not required for IR-UWB communication sys-
tems. This feature enhances the power savings significantly. Hence, IR-UWB
communication may provide a significant advantage over traditional narrow band
transmitters for power intensive WBAN applications.
(2) High data rate capability
IR-UWB radios map the data bits into very short (nano second duration) pulses.
This method implies a carrier-less data transmission scheme, where short pulses
represent a signal with a signal power that is spread in a large bandwidth in the
frequency domain. According to Shannon's capacity theorem, the data rate
capacity of a channel is linearly proportional to its channel bandwidth and loga-
rithmically proportional to increase in the Signal to Noise Ratio (SNR) of the
channel. This means that the IR-UWB signals are capable of delivering higher data
rates, using the high bandwidth property. A continuous wave based narrow band
signal has to operate at much higher frequencies in order to transmit at the same
data rates [
27
]. The use of higher frequencies in narrow band signals leads to
higher attenuation, which has to be compensated by increasing the transmit power.
