CorLayer: A Transparent Link Correlation

klapdorothypondMobile - Wireless

Nov 23, 2013 (3 years and 8 months ago)

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Oct 2013

1

CorLayer: A Transparent Link Correlation
Layer for Energy Efficient Broadcast

Shuai Wang
,
Song Min Kim, Yunhuai Liu,

Guang Tan, and Tian He


University of Minnesota







MobiCom 2013

The Need for Broadcast Operation

2

University of Minnesota

S
huai

Wang @ MobiCom’ 13

Code Dissemination

Global Time Sync

Routing Discovery

Data Collection

Wireless communication essentially occurs in a
broadcast medium.

Multi
-
path Routing

Opportunistic Forwarding

Network Coding

3

University of Minnesota

S
huai

Wang @ MobiCom’ 13

The Need for Broadcast Operation

Advanced designs exploit the benefit from
broadcast nature.

Motivation

Despite the fact that wireless communication essentially
occurs in a broadcast medium with concurrent
receptions


Existing
research predominately examine
separate statistics
for
individual links (channel) or path: ETX, PPR, LQI, RSSI


Little
research has been done to investigate the
joint
statistics involving concurrent wireless links (e.g. broadcast)


Because of the legacy assumption of



link
independence

4

University of Minnesota

S
huai

Wang @ MobiCom’ 13

Legacy Assumption

It is
assumed that wireless
reception
among concurrent
links are
independent
due
to
multipath induced fading.







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S

i.e., Packet loss at N2 is independent of packet loss at N1.

University of Minnesota

S
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Wang @ MobiCom’ 13

Unfortunately….

Legacy assumption no longer holds well because packet
loss due to the coexistence of wireless networks

6

University of Minnesota

S
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Wang @ MobiCom’ 13

7

The co
-
existence of
ZigBee

and Wi
-
Fi

University of Minnesota

S
huai

Wang @ MobiCom’ 13

The co
-
existence of
ZigBee

and Wi
-
Fi

8

W
ireless spectrum becomes crowded: 802.11b, 802.11g, and

802.15.4 all use the 2.4 GHz ISM band.

Interference becomes the major cause of pack loss instead of fading

25dB difference

University of Minnesota

11

19

University of Minnesota

S
huai

Wang @ MobiCom’ 13

Explosive Growth of Wi
-
Fi

9

1100%

Wi
-
Fi Hotspots in U.S.

University of Minnesota

University of Minnesota

S
huai

Wang @ MobiCom’ 13

Increasing Cross
-
Network Interference



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0.4
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R1

PRR
R2

R1

Noise(dbm)
Time (sec)
R2
Two receivers' PRR

The concurrent noise increase

I
nterference leads to correlated packet loss:

10

University of Minnesota

University of Minnesota

S
huai

Wang @ MobiCom’ 13

11

Furthermore, Correlated Shadow Fading


Closely located
devices may suffer
correlated lose
since
wireless signals suffer shadow fading when obstacles appear

in the propagation path of the radio waves.

University of Minnesota

S
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Wang @ MobiCom’ 13

Furthermore, Correlated Shadow Fading


12

University of Minnesota

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7
IM
SAA
2010
T
uto
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l

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ra
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7
0.4
0.8
0
200
400
0.8
-90
-80
0
200
400
-90
-80


R1

PRR
R2

R1

Signal(dbm)
Time (sec)
R2
Two receivers' PRR

The concurrent RSSI reduction

Closely

Located

Appearance of Obstacles

University of Minnesota

S
huai

Wang @ MobiCom’ 13





Synthetic Independent Trace

Empirical Trace

13

Wireless links are correlated!

0
20
40
60
80
100
1
2
3
4
5
6
7
8
9
Packet Sequence Number
Receiver
0
20
40
60
80
100
1
2
3
4
5
6
7
8
9
Packet Sequence Number
Receiver
University of Minnesota

IM
SAA
2010
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7
1

Source node

9

Receivers

100

Packets

University of Minnesota

S
huai

Wang @ MobiCom’ 13

How Link Correlation Affects Broadcast



(a) Negative Correlated:

(b) Positive Correlated:

In order to accurately
estimate
the broadcast performance,

we
MUST

consider link correlation.

Link quality:
0.8

# of packets need to
be retransmitted:
4


Link quality:
0.7

# of packets need to
be retransmitted:
3


14

University of Minnesota

S
huai

Wang @ MobiCom’ 13

The expected number of transmissions :

Theoretical Analysis

E[ ]

1 2
1
(K (u))
1 1
(u)
(e ) (e ) (K (u))
M M
i
i i
i i i
p
p p p

 

  
 
15

Transmissions due to
Link Quality

1
1
(e )
M
i
i
p


Reduced transmissions by
Link Correlation

2
1
(K (u))
1
(e ) (K (u))
M
i
i
i i
p
p p




University of Minnesota

S
huai

Wang @ MobiCom’ 13


: the probability that all nodes in K(u) successfully
receive a packet. .

(K (u))
i
p
K
i
(u) is a subset of N(u) with size
i
, where N(u) is node
u
’s
one
-
hop neighbor set.

16

University of Minnesota

S
huai

Wang @ MobiCom’ 13

1
1
(u) M 1
(e )
M
i
i
p


  

Special Case


when links are independent:

The Property of

(u)

1 2
1
(K (u))
1 1
(u)
(e ) (e ) (K (u))
M M
i
i i
i i i
p
p p p

 

  
 
Property

1:

Property

2:

The higher the link correlation
-


1
(K (u))
(K (u))
i
i
p
p

The fewer the transmissions
-


(u)

Link Blacklisting for Better Correlation

17

The average number of transmissions before blacklisting is
mainly concentrated around 4.5 and it's 2.4 after blacklisting.

University of Minnesota

S
huai

Wang @ MobiCom’ 13

1
2
3
4
5
6
7
0.0
0.2
0.4
0.6
0.8
1.0


Cumulative fraction of test sets
Number of transmissions
Before blacklist
After blacklist
2.4

4
.
5

Empirical Study
:

IM
SAA
2010
T
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ra
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Sm
a
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Sp
a
c
e
s
7
IM
SAA
2010
T
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ri
a
l

T
ra
d
i
ti
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l


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7
Blacklisting leads to a significant reduction in transmission!

CorLayer:

Goals


Goals:
Design a supporting layer by blacklisting low correlated
links to help upper layer protocols save transmissions.

18

University of Minnesota

S
huai

Wang @ MobiCom’ 13

Neighbor Discovery

CorLayer

Broadcast Protocols

Original Physical

Topology

Updated Logical

Topology

19

CorLayer:

Challenges


How to guarantee the network connectivity when
blacklisting is executed?


A localized light
-
weight algorithm for connectivity check.



How to blacklist links thus the updated topology
can benefit the upper layer broadcast protocols?


Assess the cost of covering one
-
hop neighbors, taking
link correlation into consideration.


University of Minnesota

S
huai

Wang @ MobiCom’ 13

CorLayer:

Design


Connectivity Check

20

Key Idea


link blacklisting requires the existence of an

alternative path.

W

U

V

Asynchronously Blacklisting


two
-
phase locking is used

to avoid a race condition.

University of Minnesota

S
huai

Wang @ MobiCom’ 13

CorLayer:

Design


Link

Blacklisting

University of Minnesota

S
huai

Wang @ MobiCom’ 13

Key Idea
-

Triangular Blacklisting Rule:

blacklisting a link if the source node could take fewer

transmissions via an alternative path.

U

V

W

x

z

y

21

22

CorLayer:

Design


Link

Blacklisting

University of Minnesota

S
huai

Wang @ MobiCom’ 13

Key Idea
-

Triangular Blacklisting Rule:

blacklisting a link if the source node could take fewer

transmissions via an alternative path.

W

U

V

Direct Broadcast

Cost for 1st Hop

Cost for 2nd Hop

N(u)-{v}
(u)
| N(u) 1|


(w)
| N(w) |

N(u)-{v}
(u) {v}
(u)
(w)
(u) (u) +
| N(u) 1| | N(w) |
N


 



(u) {v}
(u) (u)
N
 


(u)

(u) {v}
(u)
N


U

V

W

x

U

V

W

x

Evaluation

Testbed Settings





23

University of Minnesota

S
huai

Wang @ MobiCom’ 13

Platform

Location

Environment

Nodes/APs

MICAz

UMN

Lab

36/5

TelosB

SIAT

Office

30/8

GreenOrbs

TRIMPS

Outdoor

20/0

Physical Size

Degree

Channel

Power

8m*2.5m

7~23

Ch16

-
25dBm

18m*13m

6~21

Ch16, Ch26

-
25dBm

15m*5m

4~13

Ch16

-
25,
-
19.2dBm

23

Supported Protocols (1/2)

24

University of Minnesota

S
huai

Wang @ MobiCom’ 13


Integrated Protocols:

I.
Tree based:

1). S
-
Tree:
A.
Juttner

et al. Mobile Networks and Application’05

2). C
-
Tree:
K.
Alzoubi

et al. HICSS’02

II.
Cluster based:

3). Cluster:
J. Wu
et al. Wireless Communication and Mobile
Computing’03

4). Intermediate:
J. Wu
et al. Telecommunication Systems’01

5). Clustering:
I.
Stojmenovic

et al. TPDS’02

6). P
-
Clustering:
T. J. Kwon
et al. SIGCOMM’02

III.
Multiple point relay:

7). MPR:
A.
Qayyum

et al. HICSS’02

8


9). Min
-
id MPR, MPRCDS:
C.
Adjih

et al.

INRIA
-
Rapport’02

Supported Protocols (2/2)

25

University of Minnesota

S
huai

Wang @ MobiCom’ 13


Integrated Protocols:

IV.
Pruning based:

10
-
11). SP, DP:
H. Lim
et al. Computer Communications
Journal’01

12
-
13). PDP, TDP:
W. Lou
et al. TMC’02

14). RNG:
J.
Cartigny

et al. IJFCS’03

V.
Location based:

15). CCH:
M. T. Sun
et al. CS
-
NMC’05

VI.
Network Coding:

16). COPE:
S.
Katti

et al. SIGCOMM’06

16). CODEB:
E. L. Li
et al. INFOCOM’07


Evaluation Metrics:


T
he total number of transmissions needed to deliver one packet to all
the nodes in the network.


Extensive evaluation with
16

protocols run on
3

testbeds!

Evaluation


Main Performance Results


26

S-Tree
C-Tree
Cluster
Intermediate
Clutering
P-Clutering
MPR
Min-id MPR
MPRCDS
SP
DP
Pruning
TDP
RNG
CCH
CODEB
0
5
10
15
20

Number of Transmissions
University of Minnesota

S
huai

Wang @ MobiCom’ 13

38%

48
%

52%

49%

36%

39%

On average, CorLayer reduces transmissions by
47%
!

Evaluation


Impact of blacklisting rules


R_:
R
andom Blacklisting;


WL_:
W
orst
L
ink Blacklisting;


CorLayer_: Our Design;


27

R_MPR
WL_MPR
CorLayer_MPR
R_Cluster
WL_Cluster
CorLayer_Cluster
R_Pruning
WL_Pruning
CorLayer_Pruning
R_CODEB
WL_CODEB
CorLayer_CODEB
0
5
10
15
20

Number of Transmissions
R_: CorLayer Saves

R_

50%

Transmissions!

WL_: CorLayer Saves “WL_”
20%
Transmissions!

MPR

Cluster

Pruning

Network
Coding

University of Minnesota

S
huai

Wang @ MobiCom’ 13

Conclusion


We have presented CorLayer, a link correlation
-
based layer
that enhances the energy efficiency of reliable broadcasting.



We integrated CorLayer transparently with sixteen state
-
of
-
the
-
art broadcast algorithms and evaluated the design on
three real
-
world multi
-
hop testbeds.



The results indicate that with CorLayer, reliable broadcast
avoids unnecessary transmissions caused by wireless links
that are less positively correlated.

28

University of Minnesota

S
huai

Wang @ MobiCom’ 13

Thank you!



Q&A

29

University of Minnesota

S
huai

Wang @ MobiCom’ 13