# Energy Efficiency in

Electronique - Appareils

24 nov. 2013 (il y a 5 années et 1 mois)

86 vue(s)

Energy Efficiency in
-
Hoc Networks

Chien
-
Jen Huang

& Min Chen

April 22, 2004

EE497A

2

Outline

Introduction

Physical layer design

Routing layer design

Cross
-
layer design issues

Conclusions

3

Introduction

-
hoc networks

Energy efficiency is one of the crucial
-
hoc

Energy constraint strategy is a global
issue, involving

most
layer stacks in the
network structure

4

Physical layer design

--
System model

The

whole

transmission period time

The total energy consumption for transmitting bits

The energy
-
constrained modulation problem finally can be modeled
as
:

Minimize

Subject to
delay constraint

peak
-
power constraint

tr
sp
on
T
T
T
T

E
L
tr
tr
sp
sp
on
on
T
P
T
P
T
P
E

tr
tr
on
c
t
T
P
T
P
P

)
)
1
((

L
E
E
bit
/

tr
on
T
T
T

max
0
max
)
1
(
0
P
P
P
c
t

tr
tr
sp
sp
on
c
amp
t
T
P
T
P
T
P
P
P

)
(
5

Physical layer design

--
Energy constraint problem for M
-
QAM

An upper bound of the symbol error probability for M
-
QAM in AWGN
channel is given in [5] as

SNR

Free space propagation model

We obtain the lower bound of the transmission energy as

2
1
2
3
)
2
1
1
(
4
)
1
2
3
(
)
2
1
1
(
4

b
e
Q
Pe
b
b
b
f
r
N
B
P
2
2

r
r
t
t
P
G
G
L
d
P
2
2
2
)
4
(

on
d
b
BT
L
f
on
t
t
BT
G
P
N
T
P
E
on
BT
L
on
)
2
1
(
4
ln
)
1
2
(
3
4
2
2

6

Physical layer design

--
Energy constraint problem for M
-
QAM
(cont’d)

The total energy consumption per bit as

Peak
-
power constraint

we can find a lower bound such that all satisfy the
peak
-
power constraint

Energy consumption optimal problem for M
-
QAM is modeled as

Minimize

Subject to

The optimal modulation constellation size is obtained from

by

L
T
P
T
P
T
P
E
tr
tr
on
c
on
t
total
/
)
)
1
((

c
t
P
P
P

max
)
1
(

min
T
min
T
T
on

total
E
T
T
T
T
T
tr
on

max
min
*
on
BT
L
b

b
M
2

*
on
T
7

Physical layer design

--
Numerical results

Fig. 1 versus Fig. 2 versus

T
T
on
/
total
E
total
E
b
8

Physical layer design

--
Further discussions

M
-
QAM versus M
-
FSK

QAM sacrifices transmit power to obtain higher bandwidth
efficiency

FSK sacrifices bandwidth for a reduction in transmit power

Coded versus uncoded modulation

Error control coding can reduce the required SNR for the same
performance requirement

Possible bandwidth expansion caused by error control coding
redundancy, and the extra energy consumption of the encoder

Power Control And
Routing Protocol In
Network Layer

10

Design Rules For Power Control
Routing Protocol

Routing with more
hops can save power

Many short hop may be
better than a few long ones

Routing with more
hops reduces
interference at every
node

hop
BC
AB
BC
AB
hop
Pt
Td
Td
d
d
T
Pt
Td
Pt
CGtGr
T
Td
Pt
d
CGtGr
Pt
2
1
Pr
Pr
)
(
Pr
2
,
Pr
1
1
Pr

Power P required to transmit over a distance d

11

Common Power Routing
Protocol (COMPOW)

Characteristics

Equal transmission power between every
node in the route

The common power is the minimal one which
can keep the connectivity of the route

Compatible to some other protocol

DHCP

Reverse ARP

12

COMPOW will be not efficient when the node in
the network is not uniformly distributed

13

Cluster Power Routing Protocol
(CLUSTERPOW)

Characteristic

Use power level clustering the nodes into
groups

The cluster may last for several levels

Every node in the same cluster level transmits
the same power to each other

Designed based on “distance vector routing”
algorithm

14

Property Of CLUSTERPOW

Clusterpow is adaptive to the network
distribution

The route is discovered with a non
-
decreasing
power levels

COMPOW is the special case of Clusterpow

Clusterpow at every fixed power level is loop
free

Clusterpow is loop free

15

Clusters in the ad hoc network

[7] V. Kawadia and P. R. Kumar, Power Control and Clustering in
IEEE INFOCOM 2003
.

16

Power Efficiency Issue In Cross
Layer

Device power issue

Increase hops number also increase the
device power consumption ( contradict to the
design rule)

Error propagation issue

simply relay case

Data is just amplified without any demodulation or
decoding when passing by the intermediate nodes
between source and destination

17

18

Power Efficiency Issue In Cross
Layer

regenerator case

Data will be demodulated, decoded or some other
processing which can improve the error rate when
passing by the intermediate nodes between source
and destination

Use regenerators may decrease the error rate but
also increase the processing power at every node

With error propagation, more hops are not
necessarily good

19

Simulation1:

Compare the cases of directly transmission, simply relay and
regenerator

4
-
QAM, pass loss exponent=4, dac=5m ,y=0m

2 hops routing, equal error rate in the final nodes

20

Simulation2:

Compare the cases of directly transmission, simply relay and
regenerator

4
-
QAM, pass loss exponent=4, dac=5m ,y=2m

2 hops routing, equal error rate in the final nodes

21

Conclusion

Optimizing the performance of each layer
is not necessarily optimizing the global
performance

Achieving the global performance, cross
layer issues should be taken into account

22

Questions?

23

References

[1] A. J. Goldsmith and S. B. Wicker, Design Challenges for Energy
-
Networks,
IEEE Wireless Communications Magazine
, pp. 8
-
27 Aug. 2002.

[2] A. Y. Wang, S. Chao, C. G. Sodini, and A. P. Chandrakasan, Energy Efficient Modulation and
MAC for Asymmetric RF Microsensor System,”
International Symposium on Low Power
Electronics and Design
, pp. 106
-
111, 2001.

[3] S. Cui, A. J. Goldsmith, and A. Bahai, Energy
-
constrained Modulation Optimization under
Energy Constraints,

ICC’03

[4] S. Cui, A. J. Goldsmith, and A. Bahai, Energy
-
constrained Modulation, submitted to IEEE
Trans. on Wireless Communications.

[5] J. G. Proakis,
Digital Communications,

4th Ed. New York: MxGraw
-
Hill, 2000.

[6] S. Hares, H. Yanikomeroglu, and B. Hashem, A Relaying Algorithm for Multihop TDMA TDD
Networks Using Diversity,
IEEE Vehicular Technology Conference 2003 (
VTC'F03
)
, Orlando,
Florida, USA, October. 2003.

[7] V. Kawadia and P. R. Kumar, Power Control and Clustering in Ad Hoc Networks,
IEEE
INFOCOM 2003
.

[8] Vikas Kawadia and P. R. Kumar, A Cautionary Perspective on Cross Layer Design, submitted
to
IEEE Wireless Communication Magazine
. July, 2003.

[9] Z. Sahinoglu and P. Orlik, Regenerator Versus Simple
-
Relay With Optimum Transmit Power
Control for Error Propagation,
IEEE Communications Letters
,

Vol. 7,

Issue 9,

pp. 416
-
418,
September 2003.

[10] Z. Sahinoglu,and P. Orlik, Optimum Power Compensation for Error Propagation in Relay
Assisted Wireless Networks,
IEEE Global Telecommunications Conference
, Vol. 1, pp. 382
-
386,
December 2003.