Biomedical Engineering Reference
In-Depth Information
Turn on
*
Waits and receive beacon on the NB
channel and synchronizes to super frame
structure
Waits random back-
off time
Sends RTS( Preamble sequence+Sensor ID)in
one of the first two time slots of the CAP
Waits random back-
off time
Listens to CTS on NB channel
Parent node sends CTS message(Sensor ID+ Data slot+
request to send data in max . allowable PPB )
CTS Received?
No
Yes
Initial BER adjustment
End of Initialization
Fig. 6.17
Sensor initialization procedure
sensor initialization, a sensor node uses the maximum allowable PPB value (100
PPB for this experiment) in order to transmit a Ready To Send (RTS) message.
After receiving a Clear To Send (CTS) message, a sensor node goes through a
BER compensation period where sensor node and coordinator node negotiate a
final PPB value to be used for that particular instance in order to transmit at a
minimum possible PPB value while keeping the BER below or equal to 10
-4
.
Initialization delay depends on many parameters, such as BER of the system at a
particular instance, congestion in the initialization slots of the super frame struc-
ture and propagation delay of the wireless signals. For this experiment initiali-
zation delay is measured from the time a sensor node receives the first beacon until
the time where the sensor node start data transmission. All the sensor nodes are
turned on at the same time. Initialization delay for a particular sensor node can be
expressed using the following equation.
