Biomedical Engineering Reference
In-Depth Information
Table 1
Different wireless technologies used in WBAN applications
Properties
Wireless technology
ZigBee
WLAN
MICS
Bluetooth
UWB
Frequency
2.4 GHz
2.4 GHz
401-406 MHz
2.4 GHz
3.1-10.6 GHz
Transmit
power (dBm)
0
10-30
−
16
0
−
41.3
Channel
bandwidth
2 MHz
22 MHz
300 kHz
1 MHz
500 MHz
Data rate
250 kbps
11 Mbps
200-800 kbps
1 Mbps
850 kbps up
to 20 Mbps
Range (m) 0-10 0-100 0-10 0-10 2
WBAN
wireless body area networks,
WLAN
wireless local area networks,
MICS
medical implant
communication system,
UWB
ultra-wideband
which drastically increases the amount of data that needs to be transmitted simul-
taneously. This, in turn, increases the demand for high data rate transmission of
physiological data. For example, a 128-channel neural recording system with 8-bit
sampling requires a data rate in excess of 10 Mbps [
3
]. Use of wired media for data
transmission is not feasible at all times. It restricts the movement of the patient and
involves painful surgical procedures (for example in WCE).
Table
1
shows some of the wireless technologies used in WBANs. Out of the
existing wireless physical layer technologies, UWB and WLAN standards are able
to cater for the data rate requirement of high data rate applications. The WLAN
standard is rarely used in WBAN applications because of its large power consump-
tion. The ZigBee standard defines the network, security, and application layer on
top of the IEEE 802.15.4 standard [
12
] which incorporates the physical and medium
access control (MAC) layers [
13
]. It operates in the 2.4-GHz unlicensed industrial,
scientific, and medical (ISM) band, alongside with WLAN and Bluetooth, making
the 2.4-GHz band more crowded. In the UWB standard, it is possible to choose the
operational bandwidth from a wide spectrum which ranges from 3.1 to 10 GHz. The
power consumption in a ZigBee-based sensor node is considerably high compared
to a UWB-based transmitter. For example, the Chipcon IC (CC2420), which is a
commercially available transceiver, consumes in order of 20 mW [
14
], even when
it is operating at lowest transmit power configuration. The MICS band cannot be
used for WBAN applications that require high data rates due to data rate restric-
tions. UWB stands out from the above technologies for WBAN sensor nodes due to
the low power requirements of the UWB transmitter, high data rate capability, and
reasonably uncomplicated circuit design.
Table
2
depicts some of the available WBAN platforms that are commonly
considered for WBAN applications. These devices operate using a low supply
voltage ranging from 2 to 3 V. From the available NB sensor platforms, Microsemi
(formerly Zarlink) platform provides the complementary metal oxide semiconductor
(CMOS)- based integrated circuit (IC) with the lowest power consumption for WBAN
applications. This IC is used in the Given Imaging's PillCam® series WCE devices
for low-power NB-based implant communication [
19
]. The MICA2DOT shown in
Search WWH ::
Custom Search