Biomedical Engineering Reference
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Sense -
Busy channel
detected +
Back-off
Sense -
Idle channel
detected
Preamble + Data
Beacon
Beacon
a
No
Data to send
Yes
Yes
Data transmission
Waits for random
back-off me
No
No
Back-off mer
expired
Preamble
detected
Yes
Preamble
detected
b
Fig. 4
Preamble sense multiple access (PSMA)-based medium access proposed in [
26
].
a
Data
transmission using a super frame structure.
b
Channel access mechanism
IEEE802.15.4a standard. The comparison shows that the suggested MAC proto-
col performs better in terms of throughput and energy consumption for WBANs
consisting of large number of sensor nodes.
Drawbacks:
The major drawback of this MAC protocol is that it assumes the pres-
ence of an IR-UWB-based receiver at the sensor node end in order to sense the
channel using PSMA mechanism. Hence, it ignores all the complexities that involve
in using an IR-UWB receiver at a WBAN sensor node that are mentioned above. It
also does not provide a solution for the case where two or more sensor nodes perform
preamble sense simultaneously, which leads to an eminent collision scenario.
MAC Protocol Based on Exclusion Regions
A MAC protocol developed based on transmit and receive antenna patterns and the
antenna directionality is proposed in [
29
]. An exclusion region (ER) is defined as
an area surrounding a receiver such that the transmitter sensor nodes within the
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