Resource sharing in mobile wireless networks

1
Resource sharing in mobile wireless networks

• Maria Papadopouli
• Computer Science Department
• Columbia University
• http//www.cs.columbia.edu/maria

2
Academic background

• Columbia University
• Ph.D. candidate Fall 1996-
• advisor Prof. Golubchik
  Fall 19961998
• advisor Prof. Schulzrinne
  Fall 1998-
• New York University
• M.S. Computer Science May
  1994
• University of Crete
• B.S. Computer Science June
  1992

3
References on resource sharing in mobile ad hoc
networks
with Prof. Schulzrinne

• Effects of power conservation, wireless coverage
  cooperation on data dissemination among
  wireless devices , ACM MobiHoc 2001
• Performance analysis of 7DS a data dissemination
  prefetching tool for mobile users, IEEE
  Sarnoff 2001, best paper/poster award
• 7DS in mobile ad hoc networks, Globecom 2000
• Performance of data dissemination among mobile
  devices, journal submission, 2002
• Design implementation of a P2P data
  dissemination prefetching tool for mobile
  users, Metro 2001
• Network connection sharing in ad hoc wireless
  network among collaborative hosts, Nossdav 1999

4
References on video on demand
with Prof. Golubchik

• "A Scalable Video on Demand server for a Dynamic
  Heterogeneous Environment", Lecture Notes in
  Computer Science, Springer 1998
• "Support  of VBR Video Streams Under Disk
  Bandwidth Limitations", ACM SIGMETRICS
  Performance Evaluation Review 1997
•  (with also J.C-S. Lui), "A survey of approaches
  to fault tolerant design of video on demand
  servers Techniques, analysis and comparison",
  Special issue of Parallel Computing Journal on
  Parallel Data Servers and Applications 1998

5
Outline

• Introduction
• Background on wireless data access
• Motivation
• Overview of 7DS
• Performance analysis on 7DS
• Conclusions
• Future work

6
Background

• Fast growth in pervasive computing devices
• Fast wireless data services growth
• Base stations for wireless WAN will not keep pace
• Regulatory, environmental cost barriers for a
  dense deployment
• Users experience intermittent connectivity
  limited data access

7
Mobile information access

• Dependency on infrastructure
• Wireless WAN
• eg 802.11, 3G, CDPD, GSM, Bluetooth, Ricochet
• Infostations (Rutgers)
• When a client is in the proximity of the server,
  it access the data
• Peer-to-Peer
• Routing in mobile, ad hoc sensor networks

8
Mobile information access

• Interactivity model
• Synchronous
• Users directly access or request the data
• Asynchronous (using prefetching)
• Hoarding (Coda CMU, Seer UCLA)

9
Limitations of infostations wireless WAN

• No communication infrastructure
• eg field operation missions, tunnels,
  subway
• Emergency
• Overloaded
• Expensive
• Wireless WAN access with low bit rates high
  delays

10
Limitations of ad hoc networks

• All hosts cooperative
• Complete path for the communication of two hosts

11
Limitations of hoarding

• Only files
• Files exist prior to disconnection
• No dynamic generated information

12
Wireless data services

• Delay tolerant
• Location-dependent services
• User location hints at data needs
• Overhead to discover, access update local data

13
Challenge

• Accelerate data availability enhance
  dissemination discovery of information under
  bandwidth changes intermittent connectivity to
  the Internet due to host mobility
• considering power, bandwidth memory
  constraints of hosts

14
Our Approach

• Increase data availability by enabling devices to
  share resources
• Information sharing
• Message relaying
• Bandwidth sharing
• Self-organizing
• No infrastructure
• Exploit host mobility

15
Outline

• Introduction
• Background on wireless data access
• Motivation
• Overview of 7DS
• Simulations Analysis on 7DS
• Information dissemination
• Message relaying
• Bandwidth sharing
• Conclusions
• Future work

16
7DS

• Application
• Zero infrastructure
• Relay, search, share disseminate information
• Generalization of infostation
• Sporadically Internet connected
• Coexists with other data access methods
• Communicates with peers via a wireless LAN
• Power/energy constrained mobile nodes

17
Examples of services using 7DS
news
WAN
events in campus, pictures
where is the closest Internet café ?
pictures, measurements
service location queries
schedule info
autonomous cache
18
Information sharing with 7DS
cache miss
Host C
WLAN
cache hit
data
Host B
Host A
19
7DS options
Cooperation Server to client Peer to peer
Querying active (periodic) passive
20
Outline

• Introduction
• Simulations Analysis on 7DS
• Information dissemination
• Message relaying
• Bandwidth sharing
• wireless LAN
• video on demand environment
• Conclusions
• Future work

21
Simulation environment
pause time 50 s mobile user speed 0 .. 1.5
m/s host density 5 .. 25 hosts/km2 wireless
coverage 230 m (H), 115 m (M), 57.5 m
(L) ns-2 with CMU mobility, wireless
extension randway model
querier
wireless coverage
dataholder
randway model
22
Simulation environment
pause time 50 s mobile user speed 0 .. 1.5
m/s host density 5 .. 25 hosts/km2 wireless
coverage 230 m (H), 115 m (M), 57.5 m
(L) ns-2 with CMU mobility, wireless
extension
querier
wireless coverage
1m/s
pause
mobile host
data holder
23
Simulation environment
pause time 50 s mobile user speed 0 .. 1.5
m/s host density 5 .. 25 hosts/km2 wireless
coverage 230 m (H), 115 m (M), 57.5 m
(L) ns-2 with CMU mobility, wireless
extension
wireless coverage
v1
24
Dataholders () after 25 min
high transmission power
P2P
Mobile Info Server
Fixed Info Server
2
25
Scaling properties of data dissemination
wireless coverage

R
R
2 km
If cooperative host density transmission power
are fixed, data dissemination remains the same
26
Scaling properties of data dissemination (contd)
wireless coverage
R
R/2
For fixed wireless coverage, the larger the
density of cooperative hosts, the more efficient
the data dissemination
27
Average delay (s) vs. dataholders ()
Fixed Info Server
one server in 2x2 high transmission power
4 servers in 2x2 medium transmission power
28
Average Delay (s) vs Dataholders ()Peer-to-Peer
schemes
high transmission power
medium transmission power
29
Scaling properties of data dissemination (contd)
L
wireless coverage of info server
r
v
L
x
x
R
30
Modeling Fixed Info Server as diffusion-controlled
process

• trapping model with particles C and T (traps)
• particles C perform random walk in 2D space
• particles T static, randomly distributed in space
  of infinite capacity
• particles T absorb C when C step onto them

querier ? particle C
fixed info server ? trap
trapping ? receiving data

• survival probability fn at long times n
• log (fn) ? -A?n

31
Fixed Info Serversimulation and analytical
results
high transmission power
Probability a host will acquire data by time t
follows 1-e-a?t
32
Outline

• Introduction
• Background on wireless data access
• Motivation
• Overview of 7DS
• Performance analysis on 7DS
• Information dissemination
• Message relaying
• Network connection sharing
• Conclusions
• Future work

33
Message relaying with 7DS
WAN
Gateway
WLAN
Message relaying
Host B
Host A
34
Message relaying

• Take advantage of host mobility to increase
  throughput
• Hosts buffer messages forward them to a gateway
• Hosts forward their own messages to cooperative
  relay hosts
• Restrict number of times hosts forwards

35
Messages () relayed after 25 min (average
number of buffered messages 5)
2
36
Outline

• Introduction
• Background
• Motivation
• Overview of the system
• Performance analysis
• Information dissemination
• Message relaying
• Network connection sharing
• Conclusions
• Future work

37
Network connection sharing
Host F
WAN
Host E
Host A
thin WAN links
Hosts A B dual-homed They act as gateways to
WAN for hosts C D
Host D
Wireless LAN
Host C
Host B
38
Network connection sharingprotocol
Host E
WAN

• C sends request for gateway
• B A respond advertising their bandwidth in WAN
  link
• 4. C selects least loaded gateway (eg A)
• 5. A ? C admission control

thin wireless WAN links
Host A
Host D
WLAN
Host B
Host C
39
Benefits using network connection sharing

• Statistical multiplexing for bursty traffic
• Increase bandwidth utilization of the WAN links
• 80 bandwidth utilization for Pareto traffic
• Load balancing across gateways
• For shared data applications
• Reduction of replicated data
• Increase quality of service

40
Outline

• Introduction
• Background on wireless data access
• Motivation
• Overview of the system
• Performance analysis
• Information dissemination
• Message relaying
• Network connection sharing
• Conclusions
• Future work

41
Conclusions

• Dominant parameters
• density of cooperative hosts
• wireless coverage density of cooperative hosts
  their mobility
• For fixed cooperative hosts density
  transmission power
• scale area performance
  same
• For fixed wireless coverage density
• Density of cooperative host ?
  performance ?

42
Conclusions (contd)

• Probability a host will acquire data by time t
  in
• Fixed Info Server 1-e-a?t
• Peer-to-Peer 1-e-at
• Message relaying is beneficial
• Probability a message will reach the Internet ?
• Utilization of available throughput ?
• by taking advantage of host mobility

43
Future work

• Location-dependent applications services
• Actual traces models for user mobility, access
  patterns data locality
• Enhanced power conservation mechanism
• Security micro-payment issues
• Extension of network connection protocol
• Generalization of diffusion models for P2P
• Adaptive scalable algorithms for information
  discovery

44
Summary of contributions in video on demand

• Novel multimedia retrieval scheduling algorithms
• In multi-disk environments
• adapt to bandwidth changes
• maximize data retrieval for all streams
• using replication and multi-resolution
• In single-disk environments
• allocate disk bandwidth in a fair manner

45
Thank you!
46
Future work short term

• More on power conservation for data dissemination
  
• Peer-to-peer scheme using diffusion controlled
  processes
• Prototype
• Deployment of 7DS in CU campus in Bremen
• Public release of the code
• Collaborations
• IBM, HP, Bertelsmann Limewire (Gnutella)

47
Future work longer term

• Information discovery dissemination in
  pervasive computing
• Model abstractions for the quality of
  information
• Tight energy, bandwidth
• Privacy security for mobile, peer-to-peer
  applications
• Scaling structural properties

48
Preventing DoS attacks
Host Q
Host R
receives query
verifies Qs answer
decides to cooperate
49
Electronic check payment
Host Q
Host R
verify R is known to the bank authorized for
7ds
receive e-check verify it is genuine store
e-check
50
Token-based payment
Host Q
Host R
check token counter
verify Rs public key
receive query
increase token counter
increase token counter send data
51
Information discovery dissemination in
pervasive computing

• Query data locality
• No need of infrastructure use 7DS
• Query routing required
• Use infrastructure of gateways that create
  peer-to-peer overlay hierarchies in
  self-organizing manner based on query demand
  resources
• Castro, Greenstein, Muntz, Bisdikian,
  Kermani, Papadopouli Locating Application Data
  Across Service Discovery Domains, MOBICOM01

52
7DS Implementation

• Cache manager (3k lines)
• GUI server (2k lines)
• HTTP client methods (24k lines)
• Proxy server (1k lines)
• UDP multicast unicast (1k)
• Web client server (2k)
• Jar files used (xerces, xml,lucene, html parcer)

53
Message relayed to gateway after 25 min
2
54
Network connection sharing summary
Client
Gateway

• Requests for network connection
• Gateway selection
• Load balancing criteria

• Advertisement of gateway availability
• Admission control using Measured sum Jamin et
  al
• u? ? vr
• v measured load
• r (peak) rate requested
• uutilization target
• ?bandwidth of WAN link

55
Gateway selection mechanism

• Load balancing criteria
• Reduction of the maximum difference in
• the average load over an interval t across the
  gateways
• maxiLi(t)-miniLi(t)/b
• Li(t) average traffic measured at gateway i
  over interval t
• Greedy algorithm Choose the least loaded gateway

56
Network connection sharing
Bandwidth Utilization () Pkt dropping rate () Load balancing criteria ()
Exponential 66 0.002 2
Pareto 81 9 2
Pareto exponential 312 s(ON), 325s
(OFF) Pareto, shape par. 1.2 Flows 64kb/s,
0.6 s int., avg hold time 5 min Perfect load
balancing 0
57
Pareto traffic measurement policy
T(s), S(s) Link Utilization() Pkt loss Rate ()
60, 400 31 0.09
30, 400 37 0.2
3, 400 81 10
58
Information discovery dissemination in
pervasive computing

• Without infrastructure
• 7DS exploits query data object locality host
  mobility
• Cooperation among hosts based on resources
• With infrastructure
• Gateways create peer to peer overlay hierarchies
  in self-organizing manner
• Participate based on query demand resources
• Castro,Greenstein,Muntz (UCLA),
  Bisdikian,Kermani(IBM), Papadopouli(Columbia
  Un.), Locating Application Data Across Service
  Discovery Domains, MOBICOM01

59
Information discovery in pervasive computing
Castro, Greenstein, Muntz (UCLA), Bisdikian,
Kermani (IBM), Papadopouli (Columbia Un.),
Locating Application Data Across Service
Discovery Domains, MOBICOM 2001.

• Dynamic nature of the environment
• uncertainty, errors, timeliness redundancy
• Local autonomy
• Partial knowledge, local decisions to achieve a
  global effect
• Self-organization to minimize administration
  overhead
• Adaptive, scalable algorithms protocols

60
Epidemic model

• Carrier is infected, hosts are susceptible
• Transmit to any give host with probability
  hao(h) in interval h
• Pure birth process
• Ttime until data has spread among all mobiles
• ET1/a S

N-1
i1
61
7DS implementation

• Initial Java implementation on laptop
• Compaq Ipaq (Linux or WinCE)
• Inhand Electronics
• ARM RISC board
• Low power
• PCMCIA slot for storage, network or GPS

62
Mobility models

• User mobility
• Randway
• Random direction
• Boundless simulation area
• Gauss-Markov
• with history of previous move

• Group mobility
• Column mobility
• Pursue mobility
• Nomadic community mobility

63
Subway model

• Passengers arrive at subway stations
• Poisson process 1/l1-3min
• ride 2-6 stops
• 1 min to leave the platform
• Subway line
• 10 stops
• Train with 6 cars
• Arrives at a stop every 5 minutes
• Percentage of dataholders after they leave the
  subway for 1/l 3 min is 65

64
Types of attacks in ad hoc networks

• Basic mechanisms
• MAC layer
• Routing mechanisms
• Malicious users agree to forward messages but
  fail to do so
• False routing information messages
• Selfishness service enforcement issues

• Security mechanisms
• Distributed trusted server under the control of
  malicious party
• Public key maliciously replaced

65
Service enforcement

• Lock out mechanism for selfish or misbehaving
  users
• Denial of service attacks
• Locked out node moves away where his behavior is
  not reported
• Virtual micro currency mechanism
• Incentives to cooperate
• Discouraged from overloading the network
• terminodes.org (EPFL), mojonation.net

66
Virtual micro currency

• Nodes remunerate each other for the services they
  provide to each other
• terminodes.org (EPFL), mojonation.net

67
Information discovery dissemination in
pervasive computing

• Dynamic nature of the environment
• Uncertainty, errors, timeliness redundancy
• Local autonomy
• Partial knowledge, local decisions to achieve a
  global effect
• Self-organization
• Minimize administration overhead
• Adaptive, scalable algorithms protocols

68
Wireless WAN access

• Spectrum is very expensive

Location what cost
UK 3G 590/person
Germany 3G 558/person
Italy 3G 200/person
New York Verizon (20MHz) 220/customer

• 3G bandwidth is very low (64kbs)

69
Avantgo wireless service provider
70
Vindigo wireless service provider
71
NYC wireless public infrastructure