Biomedical Engineering Reference
In-Depth Information
consider for this calculation. It was observed that the analog/RF front-end con-
sumes a current of 6 mA and digital communication with the micro-controller
consumes only a negligible amount of current in addition to the normal operational
current of the micro-controller.
It can be observed from Table
6.2
that the micro controller consumes the
largest portion of power among the main sections involved in data transmission.
Power consumption of the UWB transmitter is considerably low due to its low
duty cycled high data rate transmission. A similar experiment is carried out in [
14
]
in order to investigate the power consumption of a wireless sensor node based on a
2.4 GHz transceiver module. This investigation shows much higher levels of
power consumption compared to this design. Figure
6.21
demonstrates percentage
power consumption for each scenario shown in Table
6.2
.
6.8 Conclusion
This chapter describes the implementation of a dual-band MAC protocol and
evaluation of its various performance parameters such as BER, initialization delay
and power consumption. Pulse synchronization and bit synchronization play an
important role in accurate detection of UWB data. The unique pulse synchroni-
zation mechanism described in this chapter avoids the requirement of an ADC with
high sampling rate in order to sample narrow UWB pulses. On-body BER eval-
uation results presented in this chapter confirms the efficiency introduced by
multiple PPB scheme for short-range WBAN communications. A MAC protocol
can be designed to have dynamic allocation of the number of pulses per bit. This
ensures that the sensor nodes transmit data while maintaining an acceptable BER.
BER evaluation is carried out for various scenarios based on the position of the
sensor nodes, number of users and presence of body motion. It can be observed
from the results that the body motion adversely affects the BER performance of a
WBAN communication system. A multiple PPB scheme is able to compensate for
the changes in the BER levels that occur because of rapidly changing channel
conditions.
The dynamic PPB scheme described in this chapter ensures that sensor nodes
always transmit at the minimum PPB value while maintaining an acceptable BER
level. This mechanism enables the sensor nodes to operate at optimum power
consumption while maintaining a reliable data communication link. The cross
layer implementation of MAC protocol, together with the dual-band hardware
implementation of sensor node provides a power efficient communication system
that can be used efficiently in WBAN applications that require various data
transmission capabilities.
Acknowledgment The authors would like to thank Dr. Tharaka Dissanayake for his help in
designing the UWB antenna used for the high frequency simulations.
