Biomedical Engineering Reference
In-Depth Information
Fig. 5
Exclusion region
(ER)-based ultra-wideband
(UWB) communication
ER cause interference to each other. However, the transmitter sensor nodes that
are not located inside an ER do not cause interference at the targeted receiver. In
this MAC protocol, the data communication of sensor nodes within the same ER is
resolved temporally using time hopping (TH)-codes, whereas the sensor nodes in
different ERs are allowed to transmit data concurrently. All the sensor nodes transmit
data asynchronously. The main objective of this MAC protocol is to minimize the
interference that can occur in a multiple UWB transmission environment, while
optimizing the throughput using concurrent transmissions in mutually exclusive ERs.
Figure
5
depicts the sensor communication using the ERs.
Drawbacks:
Although this MAC protocol addresses the issue of interference miti-
gation in UWB multiple access, it does not investigate the efficiency of important
factors such as pulse synchronization and multiple access for sensor nodes within
the same ER. It also assumes that a sensor node can determine whether it is within
the range of a certain ER by accurate ranging capabilities.
Uncoordinated Wireless Baseborn Access for UWB
Networks (UWB
2
)
The uncoordinated wireless baseborn access for UWB networks (UWB
2
) protocol
[
30
,
31
] utilizes orthogonal TH-codes in order to achieve multiple access in a shared
medium. In this protocol each node is identified using a unique TH-code that is
generated using the method provided in [
32
]. A common TH-code is used in order
to communicate control messages and sensor initialization.
At initialization, a sensor node sends a link establishment (LE) frame shown in
Fig.
6
a, using the common TH-code. In this LE frame, the sensor node proposes
a TH-code to be used for communication between the sensor and the coordinator.
The coordinator node then replies with a link control (LC) message and listens to
the TH-code allocated for the sensor node. The sensor initialization is followed by
the data communication using the suggested TH-code and the data frame format
shown in Fig.
6
b. The UWB
2
MAC protocol supports both acknowledged and un-
acknowledged data communication. The main advantage of this MAC protocol is
that it has avoided the requirement for CCA by using orthogonal TH-codes. Although
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