Transcript manet-part2x

Mobile Ad-Hoc Networks – Part II (cont.)
Thomas Plagemann
Based on presentation from Matthias Hollick
(Technische Universität Darmstadt)
Outline = today’s highlights
Part I:
Introduction and Motivation
 Terminology, Basics and Applications
 Ad Hoc vs. the Internet Model
Understanding Ad Hoc Routing
 Characteristics of Ad Hoc Communication
 Ad Hoc Routing Paradigms
Part II:
Selected Ad Hoc Routing Protocols




The Ad Hoc On-demand Distance Vector Protocol (AODV)
Dynamic Source Routing (DSR)
Location Aided Routing (LAR)
Optimized Links-State Routing (OLSR)
Our Research – Optimized forwarding in MANETs
 Problem and Solution Space
3
Dynamic Source Routing (DSR)
• Shares some principles with AODV
– When node S wants to send a packet to node D, but does
not know a route to D, node S initiates a route discovery
– Source node S floods Route Request (RREQ)
– Each node appends own identifier when forwarding RREQ
– Following an example for a route discovery from source S
to destination D
Y
Z
S
B
A
E
F
C
J
G
H
I
K
M
L
D
N
4
Route Discovery in DSR
Y
Z
S
E
F
B
C
M
J
A
L
G
H
K
I
D
N
Represents a node that has received RREQ for D from S
5
Source: Nitin Vaidya
Route Discovery in DSR
Y
Broadcast transmission
[S]
S
E
F
B
C
M
J
A
L
G
H
K
I
[X,Y]
Z
D
N
Represents transmission of RREQ
Represents list of identifiers appended to RREQ
Source: Nitin Vaidya
Route Discovery in DSR
Y
Z
S
E
[S,E]
F
B
C
A
M
J
[S,C]
H
L
G
K
I
D
N
• Node H receives packet RREQ from two neighbors:
• potential for collision
7
Source: Nitin Vaidya
Route Discovery in DSR
Y
Z
S
E
F
B
[S,E,F]
C
M
J
A
L
G
H
I
[S,C,G] K
D
N
• Node C receives RREQ from G and H, but does not forward
• it again, because node C has already forwarded RREQ once
Source: Nitin Vaidya
Route Discovery in DSR
Y
Z
S
E
[S,E,F,J]
F
B
C
M
J
A
L
G
H
K
I
D
[S,C,G,K]
N
• Nodes J and K both broadcast RREQ to node D
• Since nodes J and K are hidden from each other, their
• transmissions may collide
Source: Nitin Vaidya
Route Discovery in DSR
Y
Z
S
E
[S,E,F,J,M]
F
B
C
M
J
A
L
G
H
K
I
D
N
• Node D does not forward RREQ, because node D
• is the intended target of the route discovery
Source: Nitin Vaidya
Route Discovery in DSR
• Route Reply (RREP)
– Destination D on receiving the first RREQ, sends a (RREP)
– RREP is sent on a route obtained by reversing the route
appended to received RREQ
– RREP includes the route from S to D on which RREQ was
received by node D
– Route Reply can be sent by reversing the route in Route
Request (RREQ) only if links are guaranteed to be bidirectional
– If unidirectional (asymmetric) links are allowed, then
RREP may need a route discovery for S from node D
• Unless node D already knows a route to node S
11
Route Reply in DSR
Y
Node S on receiving RREP, caches
the route included in the RREP
S
E
Z
RREP [S,E,F,J,D]
F
B
C
M
J
A
L
G
H
K
I
•
Represents RREP
control message
D
N
12
Source: Nitin Vaidya
Data Delivery in DSR
When node S sends a data packet to D, the entire route is
included in the packet header (hence the name source
routing) Intermediate nodes forward according this route
DATA [S,E,F,J,D]
S
Y
Z
E
F
B
C
M
J
A
L
G
H
K
I
• Packet header size grows with route length
D
N
Source: Nitin Vaidya
Common features of DSR and AODV
• Both discover routes only in the presence of
data packets in the need for a route to the
destination
• Route discovery is based on query and rely
cycles and route information is stored in all
intermediate nodes on the route
– Route table entires (AODV), route caches (DSR)
14
[Source: http://www.cs.ucla.edu/classes/fall03/cs211/lectures/lec1029.ppt]
High level difference
• DSR uses source routing, but AODV uses a
table-driven routing framework and
destination sequence # to prevent loops and
determine route freshness.
• DSR does not rely on any timer-based
activities, but AODV does.
• DSR uses routing cache aggressively, and
maintains multiple routes per dest. AODV
uses one route per destination.
15
[Source: http://www.cs.ucla.edu/classes/fall03/cs211/lectures/lec1029.ppt]
Differences between DSR and AODV
• DSR has access to greater amount of routing
information than AODV by the virtual of SR. AODV
can gather limited information.
– DSR: in a single query-reply cycle, source learns route to
each intermediate node in the route in addition to the dest.
Each intermediate node also learns route to other nodes on
the route. Promiscuous listening also helps to learn the
route to every node on the route
– AODV: no source routing or promiscuous listening. It
causes AODV to rely on a route discovery flood more often,
generating more network overhead
16
[Source: http://www.cs.ucla.edu/classes/fall03/cs211/lectures/lec1029.ppt]
Difference (cont.)
• DSR uses route caching aggressively and
replies to all requests reaching a destination
from a single request cycle. Source learns
many alternative routes to the destination,
useful when the primary route fails. This
saves overhead due to discovery flood.
• AODV maintains at most one entry per dest.
In the routing table. The destination replies
only once to the request arriving first and
ignores the rest.
17
[Source: http://www.cs.ucla.edu/classes/fall03/cs211/lectures/lec1029.ppt]
Difference (cont.)
• DSR does not have explicit mechanism to expire
stale routes in the cache (except that some are
deleted by RERR) or prefer fresher routes. RERR
backtracks the data packet that meets a failed link.
Nodes not on the upstream route of this data packet
but using the failed link are not notified promptly.
• AODV is more conservative, the fresher route is
always chosen. The route deletion using RERR is
also conservative. Using the predecessor list, RERR
packets reach all nodes using a failed link on its
route to any destination.
18
[Source: http://www.cs.ucla.edu/classes/fall03/cs211/lectures/lec1029.ppt]
Outline = today’s highlights
Part I:
Introduction and Motivation
 Terminology, Basics and Applications
 Ad Hoc vs. the Internet Model
Understanding Ad Hoc Routing
 Characteristics of Ad Hoc Communication
 Ad Hoc Routing Paradigms
Part II:
Selected Ad Hoc Routing Protocols




The Ad Hoc On-demand Distance Vector Protocol (AODV)
Dynamic Source Routing (DSR)
Location Aided Routing (LAR)
Optimized Links-State Routing (OLSR)
Current Research – Optimized forwarding in MANETs
 Problem and Solution Space
19
Location-Aided Routing (LAR)
• Exploits location information to limit scope of flooding
for route request
– Location information may be obtained using GPS
• Expected Zone is determined as a region that is
expected to hold the current location of the destination
node (D)
– Expected region determined based on potentially old
location information, and knowledge of the destination’s
speed
• Route requests limited to a Request Zone that contains
the Expected Zone and location of the sender node (S)
20
Expected Zone in LAR
• S = Source node, D = Destination node
• X = last known location of node D, at time t0
• Y = location of node D at current time t1, unknown to
sender S
• r = (t1 - t0) * estimate of D’s
speed
r
X
Y/D
S
Expected Zone
21
Request Zone
• LAR’s limited flooding
– A node forwards a route
request only if it belongs to the
request zone
– The request zone should
include
• expected zone
• other regions around the
expected zone
– No guarantee that a path can
be found consisting only of the
hosts in a chosen request
zone.
• timeout
• expanded request zone

Trade-off between
 latency of route
determination
 the message overhead
Membership of Request Zone
• How a node determine
if it is in the request
zone for a particular
route request
•LAR scheme 1
•LAR scheme 2
Request Zone in LAR-1
Network Space
Request Zone
r
B
A
X
Y/D
S
24
Operation of LAR-1
• Only nodes within the request zone forward route requests
– Node A does not forward RREQ, but node B does
– Request zone explicitly specified in the route request
– Each node must know its physical location to determine whether
it is within the request zone
Request Zone
r
B
A
S
X
Y/D
25
Operation of LAR-1
• Only nodes within the request zone forward
route requests
• If route discovery using the smaller request
zone fails to find a route, the sender initiates
another route discovery (after a timeout)
using a larger request zone
– the larger request zone may be the entire network
• Rest of route discovery protocol similar to
DSR
26
Request Zone and Operation in LAR-2
S knows the location (Xd, Yd) of
node D at time t0
Node S calculates its distance
from location (Xd, Yd): DISTs
Node I receives the route request,
calculates its distance from location
(Xd, Yd): DISTi
For some parameter δ,
If DISTs + δ ≥ DISTi, node I replaces
DISTs by DISTi and forwards the
request to its neighbors; otherwise
discards the route request
LAR Variations: Adaptive
Request Zone
• Each node may modify the request zone included in the
forwarded request
– Modified request zone may be determined using more recent
information and may differ from original request zone
B
S
Request zone adapted by B
Request zone defined by sender S
Until now a route request explicitly specified a request zone
• Implicit Request Zone: A node X forwards a route request received from Y if
node X is deemed to be closer to the expected zone as compared to Y
28 to
• The motivation is to attempt to bring the route request physically closer
the destination node after each forwarding
Location-Aided Routing
• The basic proposal assumes that, initially, location
information for node X becomes known to Y only during a
route discovery
– This location information is used for a future route discovery
– Each route discovery yields more updated information which is
used for the next discovery
• Variations
– Location information can also be piggybacked on any message
from Y to X
– Y may also proactively distribute its location information
• LAR Summary – Advantages
– Reduces the scope of route request flood
– Reduces overhead of route discovery
• LAR Summary – Disadvantages
– Nodes need to know their physical locations
– Does not take into account possible existence of obstructions for
radio transmissions
29
Outline = today’s highlights
Part I:
Introduction and Motivation
 Terminology, Basics and Applications
 Ad Hoc vs. the Internet Model
Understanding Ad Hoc Routing
 Characteristics of Ad Hoc Communication
 Ad Hoc Routing Paradigms
Part II:
Selected Ad Hoc Routing Protocols




The Ad Hoc On-demand Distance Vector Protocol (AODV)
Dynamic Source Routing (DSR)
Location Aided Routing (LAR)
Optimized Links-State Routing (OLSR)
Current Research – Optimized forwarding in MANETs
 Problem and Solution Space
30
Optimized Link State Routing
(OLSR)
• Links state routing in general: Each node …
–
–
–
–
…
…
…
…
periodically floods status of its links
re-broadcasts link state information received from its neighbor
keeps track of link state information received from other nodes
uses this information to determine next hop to destinations
– Link state routing is proactive
– Local information is disseminated network wide
• Reduction of overhead of flooding link state information if
fewer nodes to forward the information
– A broadcast from X is only forwarded by selected nodes, socalled multipoint relays (MPR)
– MPRs should globally optimize flooding by optimizing it locally
31
Link State Routing (eg, OSPF)
• Each node periodically floods
status of its links
• Each node re-broadcasts link state
information received from its neighbour
• Each node keeps track of link state
information received from other nodes
• Each node uses above information to
determine next hope to each destination
24 retransmissions to diffuse
a message up to 3 hops
Retransmission node
[Source: Qamar A Tarar: OLSR Protocol]
32
OLSR – Multipoint Relays
MPR Definitions
 A node is selected with two rules
 Any 2-hop neighbor must be covered by at least one multipoint relay
 The number of multipoint relays should be minimized (per node)
 A node forwards the flooding packets with the following rules
 Forward if the packet has not already been received
 The node is multipoint relay of the last emitter
A simple heuristic for computing MPRs
 Start with an empty MPR set
 Add to the MPR set each neighbor that is the only one
covering some 2-hop neighbor (must be an MPR anyway)
 Until all 2-hop neighbors are covered repeat:
 Add to the MPR set a neighbor that covers a maximum of still
uncovered 2-hop neighbors
33
OLSR – MPR Selection (1)
• What are MPRs of node A ?
F
B
A
C
G
J
E
H
K
D
M
Source: Nitin Vaidya
OLSR – MPR Selection (2)
• Nodes C and E forward information received
from A
– What are MPRs of node E?
F
B
A
C
G
J
E
H
K
D
M
35
Source: Nitin Vaidya
Node that has broadcast state information from A
OLSR – MPR Selection (3)
• Nodes A and H are multipoint relays for node
E
– A has forwarded the link state message already
F
B
A
C
G
J
E
H
K
D
M
36
Source: Nitin Vaidya
Node that has broadcast state information from A
OLSR – MPR Selection (4)
• Node E and K are multipoint relays for node H
– Node K forwards information received from H in the
next step
– E has already forwarded the same information once
F
B
A
C
G
J
E
H
K
D
M
37
Source: Nitin Vaidya
Node that has broadcast state information from A
Flooding LSR vs. OLSR
24 retransmissions to diffuse
a message up to 3 hops
Retransmission node
[Source: Qamar A Tarar: OLSR Protocol]
11 retransmission to diffuse a
message up to 3 hops
Retransmission node
38
Neighbor sensing
• Each node periodically broadcasts its HELLO
messages:
– Containing the information about its neighbors and their link
status
– Hello messages are received by all one-hop neighbors
• HELLO message contains:
– List of addresses of the neighbors to which there exists a
valid bi-directional link
– List of addresses of the neighbors which are heard by
node( a HELLO has been received )
• But link is not yet validated as bi-directional
39
[Source: Jacquet, P., Park Gi Won: Optimized Link State Routing Protocol for Ad Hoc Networks]
Neighbor sensing (cont.)
• HELLO messages :
– Serves Link sensing
– Permit each node to learn the knowledge of its neighbors up
to two-hops (neighbor detection)
– On the basis of this information, each node performs the
selection of its multipoint relays (MPR selection signaling)
– Indicate selected multipoint relays
• On the reception of HELLO message:
– Each node constructs its MPR Selector table
40
[Source: Jacquet, P., Park Gi Won: Optimized Link State Routing Protocol for Ad Hoc Networks]
OLSR Core Protocol
Functionality
• Link Sensing
– Periodic HELLO messages: a local link set, describing links
between "local interfaces" and "remote interfaces" is defined
• MPR Selection and MPR Signaling
– Nodes select a subset of their neighbors such that a broadcast
message, retransmitted by these selected neighbors, will be
received by all nodes 2 hops away
– MPR calculation bases on HELLO messages
• Topology Control Message Diffusion (Link State Messages)
– Topology control messages carry sufficient link-state information
to allow route calculation to all nodes in the network
• Route Calculation:
– Bases on link state information + interface configuration
– The routing table can be calculated at each node
• The OLSR standard specifies all messages + mechanisms
41
Summary OLSR
• Target networks
– Large, dense networks
– Low latency for route discovery (proactive)
– Various extensions exist, so-called auxilliary
functions to complement the core functionality of
OLSR
• Multipoint relays reduce the flooding overhead
because
– … only MPRs forward control messages
– … MPRs may flood partial link state, that is, only
MPRs generate link state information including MPR
Selector information
• A MPR Selector of node X is a node which has selected
its 1-hop neighbor, node X, as its multipoint relay
42
Outline = today’s highlights
Part I:
Introduction and Motivation
 Terminology, Basics and Applications
 Ad Hoc vs. the Internet Model
Understanding Ad Hoc Routing
 Characteristics of Ad Hoc Communication
 Ad Hoc Routing Paradigms
Part II:
Selected Ad Hoc Routing Protocols




The Ad Hoc On-demand Distance Vector Protocol (AODV)
Dynamic Source Routing (DSR)
Location Aided Routing (LAR)
Optimized Links-State Routing (OLSR)
Current Research – Optimized forwarding in MANETs
 Problem and Solution Space
43
On the Forwarding Capability of Mobile Handhelds for Video
Streaming over MANETs
Stein Kristiansen, Morten Lindeberg, Daniel Rodríguez-Fernández
and Thomas Plagemann
Application Domain Emergency &
Rescue
Using head mounted
camera
Streaming live video
Command & Control
Center
Mobile Ad-Hoc Network
45
DT-Stream project
Funded by the Norwegian Research Council
Video Streaming over MANETs
•
Challenges:
–
–
–
–
•
Dynamic network, mobility, route changes, route breaks, higher error rates
Restricted amount of resources
Evaluation
….
M. Lindeberg, S. Kristiansen, T. Plagemann, V. Goebel: “Challenges
and techniques for video streaming over mobile ad hoc networks”,
Multimedia Systems Journal, 2010
–
Over 100 papers analysed
46
Related Work
•
Jan et al. “Video streaming experiment on deployed ad hoc network”,
TridentCom´07
–
–
–
–
–
•
Xue et al. “revisiting multimedia streaming in mobile ad hoc networks”,
NOSSDAV´06
–
–
–
–
–
•
300 Kbps CBR stream
1 Laptop and 1 – 4 Zaurus SL-C1000
Stream reception at intermediate nodes affects considerable e2e packet loss
Jitter & delay increase with hop-count
No reports about resource consumption
Study of CPU consumption and intra-node delay on laptops with different OS´s
Video streams 128 – 2000 Kbps
HW & OS significantly affect forwarding capacity
Saturation point of forwarding node down to 512 Kbps
Copy to and from NIC introduces up to 2.83 ms for 1500 B UDP packets
Resource consumption of forwarding handheld nodes
–
Our earlier work Halvorsen et al. Mobimedia 2008 (see next transparencies)
47
Phone to stream video in MANETs?
Published at
MobiMedia 2008
48
Capacity of Nodes
• Action clip, 400x240, 1000Kbps, MPEG-4
Server node
Intermediate node
Client node
• CPU of N770 is a severe bottleneck
49
What about recent Smart Phones?
•
CPU: 252MHz TI OMAP 1710
•
Connectivity:
– 802.11g WLAN
– Bluetooth 1.2
Memory and storage:
– 64 MB RAM
– 128MB flash
– up to 1GB RS-MMCMemory
and storage
•
•
•
•
CPU: TI OMAP 3430: ARM CortexA8 600 MHzPower, DMA, DSP
(430 MHz TI C64x+)
Connectivity
– 802.11b/g
– Bluetooth
– GSM
Memory and storage:
– 256 MB RAM
– 768 MB flash
50
– 32 GB internal strorage
extensible with 16 GB
Experiment Set-up
•
Experience from earlier experiments:
–
–
–
–
Avoid interferences from other network
Avoid route changes
Focus on forwarding node server & client should not be bottleneck
Logg as much as possible
Monitor
2.2 GHz Intel Centrino Duo Core
2 GB RAM
Bomb shelter
M
S
Sender
2.6 GHz Intel Centrino Duo Core
3 GB RAM
R
F
Forwarder
Nokia N900
Receiver
2.6 GHz Intel Centrino Duo core
3 GB RAM
Hard-wired routes
51
Experiment Set-up (cont.)
• 3 classes of experiments
– FW: forwarding only
– FWENC: forwarding & encoding
– FWDEC: forwarding & decoding
• Foreman video
– 352x288, 12 sec
– Low motion and high motion
part
– Pre-encoded:
•
•
•
•
128 Kbps 1 – 40 streams
256 Kbps 1 – 20 streams
512 Kbps 1 – 10 streams
1024 Kbps 1 – 5 streams
52
Experiment Set-up (cont.)
NTP
tshark
Monitor
2.2 GHz Intel Centrino Duo Core
2 GB RAM
Bomb shelter
M
S
Sender
2.6 GHz Intel Centrino Duo Core
3 GB RAM
R
F
Forwarder
Nokia N900
mp4trace, RTP
Gstreamer
sar
Receiver
2.6 GHz Intel Centrino Duo core
3 GB RAM
Hard-wired routes
etmp4, tcpdump
53
Results
Per packet processing more
important than per byte processing
-Delay in F
-Packet loss & PSNR
Different saturation points:
-FW: 2 Mbps
-FWENC & FWDEC: 3 Mbps
Drastic increase of delay beyond
saturation point due to
retransmissions
54
Results (cont.)
Saturation point impacts
Transmission rate
Saturation is not visible
as CPU load
Paradoxon: higher workload
leads to higher performance
and lower CPU load
250 MHz vs. 500/600 MHz
55
Results (cont.)
2 – 10 1024 Kbps streams
2 1024 Kbps streams
Frequency and voltage
scaling to save energy
Implemented kernel
module change bus
frequency
Saturation point remains
but better performance
-1.01 Mbps more
- 10 ms less delay
56
Conclusions
• Real world experiments are tedious (no surprise)
– Maemo has still problems in ad-hoc mode
• N900:
–
–
–
–
Forward 3 1024 Kbps without quality loss
CPU is not the bottleneck anymore
Introduces substantial delay over saturation
Where is the bottleneck???
• Ongoing & future work
– Strategies for routing & streaming in unstable MANETs
(ns3)
– Larger testbed studies
– Extending ns3 with node model
57
MAC Layer Support for Delay Tolerant Video Transport in
Disruptive MANETs
Morten Lindeberg, Stein Kristiansen, Vera Goebel and Thomas Plagemann
University of Oslo, Department of Informatics
[mglindeb, steikr, goebel, plageman]@ifi.uio.no
Background and Motivation
• Emergency and rescue scenarios
• Video streaming services can improve
communication and operational efforts
– E.g., firemen wearing head-mounted cameras
• Infrastructure destroyed or not existing
• Solution: Mobile ad hoc networks with
possible disruptions
59
Target Scenario
• Mimic realistic scenario
• Enforce store-carry-forwarding
60
Use existing technology?
• Video encoding:
– H.264 significantly reduce bandwidth requirements
• Transport:
– TCP does not work well
• Network:
– IP + MANET routing: OLSR
• Wireless:
– IEEE 802.11 ad hoc mode
61
Transport: Overlay Solution
• A delay tolerant overlay
–
–
–
–
–
Store-carry-forward paradigm
Dts-Overlay
Inspired by MOMENTUM [1]
Messages are sent hop-by-hop
Route through carrier nodes
when no route exist
• Problem: packet loss
[1] Cabrero, S., Paneda, X.G., Plagemann, T., Goebel, V.: Overlay solution for
multimedia data over sparse MANETs. In: International Wireless Communications and
Mobile Computing Conference, IWCMC (2009)
62
Packet loss
• OLSR routes with broken links
– In essence, lower layers are not delay tolerant
• Address Resolution Protocol (ARP)
1.
ARP will loose packets if no nodes reply with
matching MAC address to the broadcasted IP
address
• IEEE MAC 802.11
1.
2.
Packets silently dropped after final retransmission
.. or if queue exceeds limit
63
Solution
• ARP Support:
– Avoid packet loss by only forwarding when address is
resolved
• MAC Support (IEEE 802.11b):
– MAC Return: Do not drop packet after final retransmission, hand it to Dts-Overlay
– Link Adapt: Do not forward if the MAC transmission
queue is filling (link is probably down)
– Reduce non-meaningful re-transmissions (MAC retransmission limit)
64
Implementation
• Implemented in ns-3 (network simulator)
• Workload:
–
–
–
–
Foreman CIF resolution (352x288)
12 second duration on repeat
H.264 baseline profile
Target bitrate 256 kb/s
• Wireless model:
–
–
–
–
IEEE 802.11b ad hoc mode
DSSS modulation
Friis propagation loss model
Constant speed propagation delay model
65
Evaluation
• Metrics:
1.
2.
3.
4.
Packet reception (Rxv)
Buffered packets (Buf )
Packet loss (Pl)
Sum of bytes (video) at PHY layer (Txtot)
• Present average from five different runs 3600 s duration
• Main-Studies (3600 s duration):
– ER (custom scenario)
– Sparse MANET (1250 m x 1250 m, 20 nodes, random walk)
– Dense MANET (250 m x 250, 20 nodes and additional
workload, random walk)
66
Results: Pre-Study
• Address Resolution
– Affect packet loss substantially!
– We achieve lowest packet loss with Dynamic
ARP!
– .. wait for ARP resolution before using a link
Pl
Default
Static
Dynamic
39.3 %
31.7 %
19.5 %
67
Configurations
C3
C4
C5
C6
C7
Re-trans.
7
3
3
3
3
MAC
Return
No
No
No
Yes
Yes
Link Adapt
No
No
Yes
No
Yes
68
Lowering
retransmission limit
cause packet loss
Link Adapts
improves further,
even reduces total
transmission ov by
4%
MAC Return close
to eliminates all
packet loss
Results: ER
100%
90%
80%
70%
60%
50%
40%
30%
Pl
Buf
Rx
Deploying Link
Adapt does not
affect packet
reception much
20%
10%
0%
C3
C4
C5
C6
C7
69
Tendencies areSparse
the same, high
standard deviation (mobility)
Results:
MANET
Switch to single run
160000
Sent
C3
C4
C5
C6
C7
140000
MAC Return
improves
reception
With even less
transmissions
than default
configuration
900
C3
C4
C5
C6
C7
800
700
120000
Txt (MB)
Packet count (#)
600
100000
80000
500
400
60000
300
40000
200
20000
100
0
0
0
500 1000 1500 2000 2500 3000 3500
Time (s)
0
500 1000 1500 2000 2500 3000 3500
Time (s)
70
Results:
Dense
MANET
Not much loss really,
although some
duplicates for MAC Return
TxTot (MB)
Link Adapt has
strong effect on
transmissions
160
140
120
100
80
TxTot (MB)
60
40
20
0
C3
C4
C5
C6
C7
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Conclusion
• MAC Support Evaluation:
– MAC Return drastically reduce packet loss
– Allow us to lowering MAC retransmission limit
– Link Adapt lowers overhead of transmissions
that are not meaningful
• Usability is strengthened through evaluation
also in a dense MANET
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Future work
• Cross-layer interaction framework for
improved architectural support
• Real-world experiments
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Outline
Part I:
Introduction and Motivation
 Terminology, Basics and Applications
 Ad Hoc vs. the Internet Model
Understanding Ad Hoc Routing
 Characteristics of Ad Hoc Communication
 Ad Hoc Routing Paradigms
Part II:
Selected Ad Hoc Routing Protocols




The Ad Hoc On-demand Distance Vector Protocol (AODV)
Dynamic Source Routing (DSR)
Location Aided Routing (LAR)
Optimized Links-State Routing (OLSR)
Current Research – Optimized forwarding in MANETs
 Problem and Solution Space
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Final Quiz
•
•
•
•
•
What is the difference between AODV and DSR?
What are the strength and weaknesses of LAR?
How does OLSR optimize flooding?
What are the purposes of Hello messages in OLSR?
Can we use smartphones to create MANETs for
video streaming? What are the challenges?
• Why can ARP loose packets? How many
retransmissions on the link of a wireless network are
meaningful?
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Additional Readings
• Ad hoc tutorial
– Supplemental information may be obtained
at Prof. Nitin Vaidya’s site
http://www.crhc.uiuc.edu/~nhv (e.g. some
excellent tutorials on ad hoc
communication networks). The slides on
DSR, LAR, and OLSR are based on his
tutorial.
• IETF Standardization
– MANET WG
http://www.ietf.org/html.charters/manetcharter.html
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Acknowledgements
from Matthias Hollick
• Acknowledgements for the ad hoc part go to
various sources:
–
–
–
–
–
–
–
–
–
N. Vaidya @ UIUC
C. Perkins @ Nokia
S. Corson @ UMD
P.R. Kumar @ UIUC
D. Johnson @ Rice
Zhenqiang Ye @ UCR
R. G. Herrtwich @ DaimlerChrysler
WWRF
Former colleagues of the Mobile Networking Group
@ KOM
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Copyright Notice
• This document has been distributed by the contributing
authors as a means to ensure timely dissemination of
scholarly and technical work on a non-commercial
basis. Copyright and all rights therein are maintained
by the authors or by other copyright holders,
notwithstanding that they have offered their works here
electronically.
• It is understood that all persons copying this
information will adhere to the terms and constraints
invoked by each author's copyright. These works may
not be reposted without the explicit permission of the
copyright holder.
78