Biomedical Engineering Reference
In-Depth Information
6.6 On-Body Evaluation of the Dual-Band WBAN
Communication System
On-body evaluation of the dual-band communication system is performed in order
to demonstrate the performance of the MAC protocol under on-body multi sensor
communication scenarios. Multiple communication scenarios shown in Table
6.1
are developed based on the positioning of sensor nodes and coordinator node.
Network performance parameters, such as BER, sensor initialization delay are
experimentally evaluated for each scenario. All the experiments are carried out using
four sensor nodes. Sensor nodes are initiated in a random manner during the
experiments. All the sensor nodes transmit at a PRF of 100 MHz. PPB values for each
sensor node are controlled by changing the width of data bits generated by the micro-
controller modules of the sensor nodes. The transmit spectrums of all the sensor
nodes are set to fall within the FCC regulated spectral mask. Figure
6.11
depicts
shows the average UWB transmit spectrum for a sensor node used in the experiments.
6.6.1 BER Performance Analysis
BER analysis demonstrates the reliability of the dual-band communication system
under dynamic channel conditions. BER calculation is carried out in the following
manner. The micro-controller of a particular sensor node is programmed to send a
data bit sequence with a length of 10
8
bits in segmented data packets. This bit
sequence is known to both sensor node and coordinator node. When the coordi-
nator node receives data from a sensor node, it transfers the received data to a
Matlab program that calculates the BER. The Matlab program uses all the bits in a
data packet except the Sync portion for BER calculation. Four sensor nodes are
used in the BER experiments. All the sensor nodes are configured to transmit
continuously using the packet format shown in Fig.
6.1
a. BER for a particular
scenario shown in Table
6.1
is evaluated for various separation distances between
sensor nodes and the coordinator node.
BER values are evaluated for four scenarios. In the first three scenarios, BER
values are calculated by fixing the PPB values of each sensor node to 20, 50 and 100
PPBs in order to demonstrate the effect of PPB on BER. Dynamic BER allocation
procedure of the MAC protocol is disabled for these fixed PPB experiments. Sensor
initialization for the fixed PPB experiments is done using the maximum allowable
PPB value (100 PPB for these experiments) according to the sensor node initiali-
zation procedure described in
Chap. 3
. After initialization, sensor nodes go back to
sending data using the fixed PPB values assigned to each sensor node. A fourth
experiment is carried out in order to evaluate the BER when the dynamic BER
allocation procedure of the MAC protocol is enabled. Coordinator node assigns a
PPB value range from 20 to 100 PPB according to the procedure described in
Chap. 3
in an attempt to keep the BER threshold for each sensor node at 10
-4
or the closest
