Biomedical Engineering Reference
In-Depth Information
Fig. 9
Frame structure for transmit-only MAC protocol for wireless body area network (WBAN)
guard interval to prepare the receiver for data reception. The data frame overhead is
kept to a minimum in order to keep the transmission period short, thus reducing the
chances of collision.
Drawbacks:
Although the transmit-only MAC protocol addresses the problem of
high power consumption that arises because of the use of UWB receiver at the
WBAN sensor node, it has several drawbacks.
•
When the network traffic increases, the number of collisions that occur owing to
asynchronous transmission of pulses adversely affect the data delivery capability
in the network.
•
There is no feedback path to dynamically adjust the transmit power in accordance
with the changing channel conditions.
•
Rescheduling of the network requires manual intervention with the sensor nodes.
This MAC protocol can be further improved by the use of a narrowband receiver
in order to eliminate the issues regarding the network reconfigurations and network
expansion while achieving low power consumption in the sensor nodes. Such a MAC
protocol is suggested in [
41
]. The MAC protocol described in [
41
] uses a narrowband
receiver at the sensor node to receive feedback on properties, such as receive BER.
Comparison of UWB-Based MAC Protocols for WBAN
Applications
The MAC protocols discussed above have advantages in different areas when they are
used in WBAN applications. A summary of the selected MAC schemes discussed
in this section is tabulated in Table
2
on the basis of their performance attributes
described below.
•
Energy efficiency
—Factors affecting the energy efficiency of a MAC scheme
are energy wastage owing to protocol overhead,
idle listening,
collisions,
overemitting and overhearing.
•
QoS
—QoS is crucial in a WBAN system because of the sensitivity of the data
collected by sensor nodes. If the QoS is poor and the data reliability is low, this
could lead to a wrong diagnosis and it can be life threatening.
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