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UWB Receiver Architectures
for Wearable WBANs
receivers that have a number of fingers equal
to the available number of resolvable paths are
required, but they are impractical. On the other
hand, a single correlator that is matched to one
transmission path is very simple, but highly sub-
optimal (Arslan, Chen et al. 2006). Non-coherent
receivers are low-power solutions that do not
require channel estimation, and are suitable for
low-data rate applications (Chao and and Scholtz
2003). In these receivers, low-power consumption
is traded for degradation in bit error rate (BER)
performance. Non-coherent alternatives include
transmitted reference (TR) and energy detection
(ED) schemes (Stoica 2008).
Optimum receivers involve the correlation of
the received waveform with a locally generated
template waveform, and require channel estima-
tion, which add to the power consumption of the
receiver (Arslan, Chen et al. 2006). These require-
ments are precluded for non-coherent receivers,
where the detection process depends solely on
the received pulses (Chao and and Scholtz 2003;
Arslan, Chen et al. 2006).
The TR scheme is based on the transmis-
sion of a pair of pulses (one modulated and one
un-modulated), where at the receiver the un-
modulated pulse is used to detect the modulated
pulse. However, TR correlation receivers suffer
from the use of a noisy template (Stoica 2008).
Instead of sending reference pulses, the differential
transmitted reference (DTR) scheme uses the data
pulses of previous symbols for the correlation
with the received pulses. Hence, DTR achieves
a 3 dB performance gain over TR schemes. On
the other hand, DTR requires differential encod-
ing of the transmitted bits, which in turn requires
longer delay lines and higher power consumption
(Stoica 2008).
The energy detection (ED) correlation receiver
is another non-coherent receiver. In ED correla-
tion receivers, the correlator is replaced by a
squaring device. ED IR-UWB receivers can be
implemented with on-off keying (OOK) and pulse
Wireless pervasive healthcare has recently re-
ceived an increased attention in research, where
patients can monitor their health and take mea-
surements at home or office. Wireless healthcare
networks can provide real-time data acquisition via
medical sensor nodes attached to the human body
in the form of a wireless local body area network
(WBAN) (Bin, Huan-Bang et al. 2007; Bindra
2008). The data is then stored in a remote central
node. Ultimately, the use of wearable healthcare
systems is a promising solution not only for gait
analysis, but also for general health monitoring and
the early detection of abnormal conditions (Jova-
nov 2005). A promising technology for WBANs
that offers low-power consumption and robust
performance in dense-multipath environments is
the ultra wideband (UWB) technology (Di Renzo,
Buehrer et al. 2007). UWB systems, as defined
by the Federal Communications Commission
(FCC), are the systems with fractional bandwidths
that exceed 0.20 at the -10 dB level (Reed 2005).
The band allocated to UWB is 7.5 GHz, and the
frequency band allocated to UWB communica-
tions is 3.1- 10.6 GHz with different emission
limits for indoor and outdoor systems (Reed
2005; Arslan, Chen et al. 2006). Consequently,
the corresponding UWB pulses are very short,
typically on the order of nanosecond. The ultra-
fine time resolution of the UWB pulses allows for
location and tracking applications. Particularly,
the time-of-arrival (TOA) and time-difference-
of-arrival (TDOA) range estimation techniques
via the arrival time of the first detected path can
offer high accuracy range estimates (Reed 2005;
Arslan, Chen et al. 2006).
IR-UWB provides robustness in dense mul-
tipath environments (Arslan, Chen et al. 2006).
An optimum receiver is fully capable of exploiting
the rich multipath channel diversity. In order to
capture the signal energy, All-RAKE (ARAKE)
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