Enhancing Worker Digital Experience: A Hands-on Workshop for Partners
Augmenting mobile 3 g using wifi
1. Augmen'ng
Mobile
3G
Using
WiFi
By:
Aruna
Balasubramanian,
Ratul
Mahajan,
Arun
Venkataramani
Presenter:
Ke
Huang
Tuesday, April 12, 2011 1
2. Demand
for
mobile
access
growing
www.totaltele.com
h+p://www.readwriteweb.com
2
Tuesday, April 12, 2011 2
3. Demand
for
mobile
access
growing
www.totaltele.com
h+p://www.readwriteweb.com
900
million
mobile
broadband
subscrip'ons
today….
www.3gamericas.org
2
Tuesday, April 12, 2011 2
5. 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
Tuesday, April 12, 2011 3
6. 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
Tuesday, April 12, 2011 3
7. 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
Tuesday, April 12, 2011 3
8. How
can
we
reduce
spectrum
usage?
blogs.chron.com
1.
Behavioral
2.
Economic
3.
Technical
4
Tuesday, April 12, 2011 4
9. How
can
we
reduce
spectrum
usage?
blogs.chron.com
1.
Behavioral
www.usatoday.com
2.
Economic
3.
Technical
4
Tuesday, April 12, 2011 4
10. How
can
we
reduce
spectrum
usage?
blogs.chron.com
1.
Behavioral
www.usatoday.com
2.
Economic
3.
Technical
4
Tuesday, April 12, 2011 4
11. Augmen'ng
Mobile
3G
using
WiFi
Offload
data
to
WiFi
when
possible
Focus
on
vehicular
mobility
5
Tuesday, April 12, 2011 5
18. 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
Tuesday, April 12, 2011 7
19. 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
Tuesday, April 12, 2011 7
20. 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
Tuesday, April 12, 2011 8
21. 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
Tuesday, April 12, 2011 9
22. Open
WiFi
availability
low,
but
useful
Availability
=
frac'on
of
1-‐second
intervals
when
at
least
one
packet
received
Availability
(%)
10
Tuesday, April 12, 2011 10
23. Open
WiFi
availability
low,
but
useful
Availability
=
frac'on
of
1-‐second
intervals
when
at
least
one
packet
received
86%
Availability
(%)
10
Tuesday, April 12, 2011 10
24. Open
WiFi
availability
low,
but
useful
Availability
=
frac'on
of
1-‐second
intervals
when
at
least
one
packet
received
86%
Availability
(%)
11%
10
Tuesday, April 12, 2011 10
25. Open
WiFi
availability
low,
but
useful
Availability
=
frac'on
of
1-‐second
intervals
when
at
least
one
packet
received
86%
Availability
(%)
11% 7%
10
Tuesday, April 12, 2011 10
26. 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
Tuesday, April 12, 2011 10
27. WiFi
loss
rate
is
higher
Loss
rate
=
Frac'on
of
packets
lost
at
10
probes/sec
Cumulative
fraction WiFi
3G
11
Tuesday, April 12, 2011 11
28. WiFi
loss
rate
is
higher
Loss
rate
=
Frac'on
of
packets
lost
at
10
probes/sec
Cumulative
fraction 28%
WiFi
3G
11
Tuesday, April 12, 2011 11
29. WiFi
loss
rate
is
higher
Loss
rate
=
Frac'on
of
packets
lost
at
10
probes/sec
Cumulative
fraction 28%
WiFi
8%
3G
11
Tuesday, April 12, 2011 11
30. WiFi
(802.11b)
throughput
is
lower
Throughput
=
Total
data
received
per
second
WiFi
Cumulative
fraction
3G Upstream
WiFi
Cumulative
fraction
3G Downstream
12
Tuesday, April 12, 2011 12
31. WiFi
(802.11b)
throughput
is
lower
Throughput
=
Total
data
received
per
second
WiFi
Cumulative
fraction
3G Upstream
WiFi
Cumulative
fraction
3G Downstream
12
Tuesday, April 12, 2011 12
32. 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
Tuesday, April 12, 2011 12
33. 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
Tuesday, April 12, 2011 12
34. 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
Tuesday, April 12, 2011 12
35. 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
Tuesday, April 12, 2011 13
36. 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
Tuesday, April 12, 2011 14
37. 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
Tuesday, April 12, 2011 15
38. 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
Tuesday, April 12, 2011 15
39. 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
Tuesday, April 12, 2011 16
40. 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
Tuesday, April 12, 2011 16
41. 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
Tuesday, April 12, 2011 17
42. Wiffler
implementa'on
Wiffler
proxy
§ Predic'on-‐based
offloading
upstream
+
downstream
§
Fast
switching
only
upstream
Ø Implemented
using
signal-‐upon-‐ACK
in
driver
18
Tuesday, April 12, 2011 18
43. 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
Tuesday, April 12, 2011 19
44. 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
Tuesday, April 12, 2011 20
45. 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
Tuesday, April 12, 2011 20
46. 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
Tuesday, April 12, 2011 21
47. Wiffler
increases
data
offloaded
to
WiFi
Workload:
Web
traces
obtained
from
commuters
22
Tuesday, April 12, 2011 22
48. Wiffler
increases
data
offloaded
to
WiFi
Workload:
Web
traces
obtained
from
commuters
14%
WiFi
when
available
yields
ligle
savings
22
Tuesday, April 12, 2011 22
49. Wiffler
increases
data
offloaded
to
WiFi
Workload:
Web
traces
obtained
from
commuters
Wiffler
close
to
42% Oracle
14%
22
Tuesday, April 12, 2011 22
50. 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
Tuesday, April 12, 2011 22
51. 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
Tuesday, April 12, 2011 22
53. Fast
switching
improves
quality
of
delay-‐sensi've
applica'ons
24
Tuesday, April 12, 2011 24
54. Fast
switching
improves
quality
of
delay-‐sensi've
applica'ons
58%
24
Tuesday, April 12, 2011 24
55. Fast
switching
improves
quality
of
delay-‐sensi've
applica'ons
58%
40%
24
Tuesday, April 12, 2011 24
56. Fast
switching
improves
quality
of
delay-‐sensi've
applica'ons
73%
58%
40%
24
Tuesday, April 12, 2011 24
57. Fast
switching
improves
quality
of
delay-‐sensi've
applica'ons
73%
58%
40%
30%
data
offloaded
to
WiFi
with
40ms
switching
threshold
24
Tuesday, April 12, 2011 24
58. 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
Tuesday, April 12, 2011 25
59. 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
Tuesday, April 12, 2011 26
60. 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
Tuesday, April 12, 2011 26