Augmenting mobile 3 g using wifi

Augmen'ng
Mobile
3G
Using
WiFi

By:
Aruna
Balasubramanian,
Ratul
Mahajan,
Arun

Venkataramani

Presenter:
Ke
Huang

Tuesday, April 12, 2011 1

Demand
for
mobile
access
growing

www.totaltele.com

h+p://www.readwriteweb.com

2


Demand
for
mobile
access
growing

www.totaltele.com

h+p://www.readwriteweb.com

900
million
mobile
broadband
subscrip'ons
today….

www.3gamericas.org

2


Mobile
demand
is
projected
to
far

3


Mobile
demand
is
projected
to
far

www.rysavy.com
Current
spectrum 409.5
MHz
Unallocated
spectrum
230
MHz
(including
whitespaces)
Projected
demand
by
800
MHz
–

2016
1000
MHz

3


Mobile
demand
is
projected
to
far

www.nyCmes.com
www.rysavy.com
Current
spectrum 409.5
MHz
Unallocated
spectrum
230
MHz
(including
whitespaces)
Projected
demand
by
800
MHz
–

2016
1000
MHz

3


Mobile
demand
is
projected
to
far

www.nyCmes.com
www.rysavy.com
Current
spectrum 409.5
MHz
Unallocated
spectrum
230
MHz
(including
whitespaces)
Projected
demand
by
800
MHz
–

2016
1000
MHz

www.nyCmes.com
“In
light
of
the
limited
natural
resource
of
spectrum,
we
have
to
look
at

the
ways
of
conserving
spectrum”
-‐-‐
Mark
Siegel
(AT&T)

Reducing
cellular
spectrum
u'liza'on
is
key! 3


How
can
we
reduce
spectrum
usage?
blogs.chron.com

1.
Behavioral

2.
Economic

3.
Technical
4


How
can
we
reduce
spectrum
usage?
blogs.chron.com

1.
Behavioral

www.usatoday.com

2.
Economic

3.
Technical
4


Augmen'ng
Mobile
3G
using
WiFi

Oﬄoad
data
to
WiFi
when
possible

Focus
on
vehicular
mobility

5


Oﬄoading
3G
data
to
WiFi

6


Related
work
on
mul'ple
interfaces
Improving
performance
using
handoﬀs
based
on

current
condi'ons
Reducing
power
consump'on
by
switching

across
mul'ple
interfaces

7


Related
work
on
mul'ple
interfaces
Improving
performance
using
handoffs
based
on

current
condi'ons
Reducing
power
consump'on
by
switching

across
mul'ple
interfaces

This
work:
1.How
much
3G
data
can
be
offloaded
to
WiFi?
2.How
to
offload
without
hur'ng
applica'ons?
7


Contribu'ons
Measurement:

Joint
study
of
3G
and
WiFi

connec'vity
Across
three
ci'es:
Amherst,
Seagle,
SFO

System:
Wiﬄer,
to
oﬄoad
3G
data
to
WiFi
while

respec'ng
applica'on
constraints

Deployed
on
20
vehicles

8


Measurement
setup
Testbed:
Vehicles
with
3G
and
WiFi
(802.11b)
radios
Amherst:
20
buses
+
1
car,
Seagle:
1
car,
SFO:
1
car

Soiware:
Simultaneously
probes
3G
and
WiFi
for

Availability,
loss
rate,
throughput

Dura'on:
3000+
hours
of
data
over
12+
days

9


Open
WiFi
availability
low,
but
useful
Availability

=
frac'on
of
1-‐second
intervals
when
at
least

one
packet
received

Availability
(%)

10


Open
WiFi
availability
low,
but
useful
Availability

=
frac'on
of
1-‐second
intervals
when
at
least

one
packet
received

86%

Availability
(%)

10


Open
WiFi
availability
low,
but
useful
Availability

=
frac'on
of
1-‐second
intervals
when
at
least

one
packet
received

86%

Availability
(%)

11%

10


Open
WiFi
availability
low,
but
useful
Availability

=
frac'on
of
1-‐second
intervals
when
at
least

one
packet
received

86%

Availability
(%)

11% 7%

10


Open
WiFi
availability
low,
but
useful
Availability

=
frac'on
of
1-‐second
intervals
when
at
least

one
packet
received

86%

Availability
(%)
3G+WiFi
combinaCon
be+er
than
sum
pf
parts
11% 7%

10


WiFi
loss
rate
is
higher
Loss
rate
=
Frac'on
of
packets
lost
at
10
probes/sec

Cumulative
fraction WiFi

3G

11


WiFi
loss
rate
is
higher
Loss
rate
=
Frac'on
of
packets
lost
at
10
probes/sec

Cumulative
fraction 28%
WiFi

3G

11


WiFi
loss
rate
is
higher
Loss
rate
=
Frac'on
of
packets
lost
at
10
probes/sec

Cumulative
fraction 28%
WiFi

8%
3G

11


WiFi
(802.11b)
throughput
is
lower
Throughput
=
Total
data
received
per
second

WiFi
Cumulative
fraction
3G Upstream

WiFi
Cumulative
fraction
3G Downstream

12


WiFi
(802.11b)
throughput
is
lower
Throughput
=
Total
data
received
per
second

WiFi
Cumulative
fraction
3G Upstream
0.35

WiFi
Cumulative
fraction
3G Downstream

12


WiFi
(802.11b)
throughput
is
lower
Throughput
=
Total
data
received
per
second

WiFi
Cumulative
fraction
3G Upstream
0.35 0.72

WiFi
Cumulative
fraction
3G Downstream

12


Implica'ons
of
measurement
study
Strawman
augmenta'on:
Use
WiFi
when

available
Can
oﬄoad
only
~11%
of
the
'me
Can
hurt
applica'ons
because
of
WiFi’s
higher
loss

rate
and
lower
throughput

13


Key
ideas
in
Wiﬄer
Increase
savings
for
delay-‐ Reduce
damage
for
delay-‐
tolerant
applica'ons sensi've
applica'ons
Problem:
Using
WiFi
only
Problem:
Using
WiFi

when
available
saves
whenever
available
can

ligle
3G
usage hurt
applica'on
quality
Solu'on:
Exploit
delay-‐ Solu'on:
Fast
switch
to
3G

tolerance
to
wait
to

when
WiFi
delays

oﬄoad
to
WiFi
when

availability
predicted exceed
threshold

14


Predic'on-‐based
oﬄoading
D
=
Delay-‐tolerance
threshold
(seconds)
S
=
Data
remaining
to
be
sent
(bytes)

Each
second,
1. If
(WiFi
available),
send
data
on
WiFi

2. Else
if
(W(D)
<
S),
send
data
on
3G

3. Else
wait
for
WiFi.

15


Predic'on-‐based
oﬄoading
D
=
Delay-‐tolerance
threshold
(seconds)
S
=
Data
remaining
to
be
sent
(bytes)

Each
second,
1. If
(WiFi
available),
send
data
on
WiFi

2. Else
if
(W(D)
<
S),
send
data
on
3G Predicted
WiFi

transfer
size
in

3. Else
wait
for
WiFi. next
D
seconds

15


Predic'ng
WiFi
capacity
History-‐based
predic'on
of
#
of
APs
using
last
few

AP
encounters

WiFi
capacity
=
(expected
#APs)
x
(capacity
per
AP)
Simple
predictor
yields
low
error
both
in
Amherst

and
Seagle

16


Predic'ng
WiFi
capacity
History-‐based
predic'on
of
#
of
APs
using
last
few

AP
encounters

WiFi
capacity
=
(expected
#APs)
x
(capacity
per
AP)
Simple
predictor
yields
low
error
both
in
Amherst

and
Seagle

Negligible
beneﬁts
with
more
sophis'cated
predic'on,
eg

future
loca'on
predic'on
+
AP
loca'on
database
16


Fast
switching
to
3G
Problem:
WiFi
losses
bursty
=>
high
retransmission
delay

Approach:
If
no
WiFi
link-‐layer
ACK
within
50ms,
switch
to
3G
Else,
con'nue
sending
on
WiFi

17


Wiffler
implementa'on

Wiffler

proxy

§ Predic'on-‐based
offloading
upstream
+
downstream
§
Fast
switching
only
upstream
Ø Implemented
using
signal-‐upon-‐ACK
in
driver

18


Evalua'on
Roadmap
Predic'on-‐based
oﬄoading
Deployment
on
20
DieselNet
buses
in
150
sq.
mi

region
around
Amherst
Trace-‐driven
evalua'on
using
throughput
data

Fast
switching
Deployment
on
1
car
in
Amherst
town
center
Trace-‐driven
evalua'on
using
measured
loss/delay

trace
using
VoIP-‐like
probe
traﬃc

19


Deployment
results
Data
offloaded
to
WiFi
Wiffler’s
predic'on-‐based
offloading 30%
WiFi
when
available 10%
File
transfer
size:
5MB;
Delay
tolerance:
60
secs;

Inter-‐transfer
gap:
random
with
mean
100
secs

20


Deployment
results
Data
offloaded
to
WiFi
Wiffler’s
predic'on-‐based
offloading 30%
WiFi
when
available 10%
File
transfer
size:
5MB;
Delay
tolerance:
60
secs;

Inter-‐transfer
gap:
random
with
mean
100
secs

%
Cme
good
voice
quality

Wiffler’s
fast
switching 68%
WiFi
when
available
(no
switching) 42%
VoIP-‐like
traffic:
20-‐byte
packet
every
20
ms

20


Trace-‐driven
evalua'on
Parameters
varied
Workload,
AP
density,
delay-‐tolerance,
switching
threshold

Strategies
compared
to
predic'on-‐based
oﬄoading:
WiFi
when
available
Adapted-‐Breadcrumbs:
Future
loca'on
predic'on
+
AP
loca'on

database
Oracle
(Imprac'cal):
Perfect
predic'on
w/
future
knowledge

21


Wiﬄer
increases
data
oﬄoaded
to
WiFi
Workload:
Web
traces
obtained
from
commuters

22


Wiﬄer
increases
data
oﬄoaded
to
WiFi
Workload:
Web
traces
obtained
from
commuters

14%
WiFi
when

available
yields

ligle
savings

22


Wiffler
increases
data
offloaded
to
WiFi
Workload:
Web
traces
obtained
from
commuters

Wiffler
close
to

42% Oracle

14%

22


Wiffler
increases
data
offloaded
to
WiFi
Workload:
Web
traces
obtained
from
commuters

Wiffler
close
to

42% Oracle
Sophis'cated

14% predic'on
yields

negligible
benefit

22


Wiffler
increases
data
offloaded
to
WiFi
Workload:
Web
traces
obtained
from
commuters

Wiffler
close
to

42% Oracle
Sophis'cated

14% predic'on
yields

negligible
benefit

Wiffler
increases
delay
by
10
seconds
over
Oracle.

22


Even
more
savings
in
urban
centers

23


Fast
switching
improves
quality
of

delay-‐sensi've
applica'ons

24


Fast
switching
improves
quality
of

delay-‐sensi've
applica'ons

58%

24


Fast
switching
improves
quality
of

delay-‐sensi've
applica'ons

58%
40%

24


Fast
switching
improves
quality
of

delay-‐sensi've
applica'ons

73%

58%
40%

24


Fast
switching
improves
quality
of

delay-‐sensi've
applica'ons

73%

58%
40%

30%
data
oﬄoaded
to
WiFi
with
40ms
switching
threshold
24


Future
work
Reduce
energy
to
search
for
usable
WiFi

Improve
performance/usage
by
predic'ng
user

accesses
to
prefetch
over
WiFi

Incorporate
evolving
metrics
of
cost
for
3G
and

WiFi
usage

25


Summary
Augmen'ng
3G
with
WiFi
can
reduce
pressure
on

cellular
spectrum

Measurement
in
3
ci'es
confirms
WiFi
availability
and

performance
poorer,
but
poten'ally
useful

Wiffler:
Predic'on-‐based
offloading
and
fast
switching

to
offload
without
hur'ng
applica'ons

26


Summary
Augmen'ng
3G
with
WiFi
can
reduce
pressure
on

cellular
spectrum

Measurement
in
3
ci'es
confirms
WiFi
availability
and

performance
poorer,
but
poten'ally
useful

Wiffler:
Predic'on-‐based
offloading
and
fast
switching

to
offload
without
hur'ng
applica'ons

Questions?
26


Thank you!


Augmenting mobile 3 g using wifi

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