Information Technology Reference

In-Depth Information

E

=

H

×

n

×

N

×

(

n

+

n

×

0

75

+

n

+

n

×

0

75

)

pac

bits

bits

ack

ack

where
n
ack
is the total number of bits of the return packet. In order to evaluate the energy
E
for

the packets without ARQ and with CRC (AUX2, BCH3 and HAM2 packets) the average

number of hops has to be computed. The probability that a packet achieves
h
hops is the

product of success in the
h-1
hops and the probability of failure in the
h
th hop, if
h<H
.
If
h=H

the probability of a packet achieving
H
hops is the product of success in the
h-1
hops and the

probability of failure in the
h
th hop added to the probability of success in the
H
hops:

[

]

h

−

1

p

[

h

]

=

(

−

PER

)

(

PER

)

,

if

h

<

H

H

f

f

[

]

1

p

[

h

]

=

(

−

PER

)

h

−

(

PER

)

+

(

−

PER

)

h

,

if

h

=

H

H

f

f

f

Therefore, the average number of hops
H
can be evaluated as:

=
H

h

∑
=

H

p

[

h

]

×

h

H

1

Then the total energy consumed
E
for the packets with CRC and without ARQ is:

(

)

E

=

H

×

n

×

n

+

n

×

0

.

75

pac

bits

bits

For a Bluetooth ad hoc network to be considered energy efficient, the maximum amount

of data bits has to be transmitted with the minimum energy consumption. An energy

efficiency parameter η
may be defined as:

E

η

=

min

×

R

E

The energy efficiency for an adaptive scheme is evaluated using this equation, but the

energy
E
and the reliability
R
have to be evaluated in a different manner. For the ADP1

scheme the AUX2 packet is used for the first and second hops, the HAM2 packet for the

third, fourth and fifth hops and DH1 packet for the remaining hops of the sensor network. The

total energy
E
is the energy consumed by the different packets:

E

=

E

+

E

+

E

aux

2

ham

2

dh

1

The ene
rg
y consumed by the AUX2 packet is:

[

]

E

=

H

×

n

n

+

n

×

0

.

75

aux

2

pac

bits

bits

where the average number of hops
H
can be evaluated using
H=2
and
n
bits
is the number of

bits of the AUX2 packet. The energy consumed by the HAM2 packet is: