Scalable Geographic Routing for Mobile Ad-hoc Networks (Joint work with Xiaojing Xiang and Zehua Zhou)

1
Scalable Geographic Routing for Mobile Ad-hoc
Networks(Joint work with Xiaojing Xiang and
Zehua Zhou)

• Xin Wang
• Assistant Professor
• Director, Wireless and Networking Systems Lab
  (WINS)
• http//www.cse.buffalo.edu/xwang8

2
Mobile Communications Today Tale of 2 Networks

• Cellular Telecommunications Networks
• Tailored for voice very low bandwidth
• Devices not suitable for Internet and computing
  applications
• Despite high penetration, Internet access has
  fizzled
• Wireless Enterprise Networks
• Tailored for best-effort data traffic high
  bandwidth, no controls
• Supports general computing and data networking
  applications
• Gaining density in hot-spots, but no ubiquitous
  coverage

Wireless Controllers
Access Router
3
Tomorrow Common Net, Common Apps

3G CellularNetworks
RadioController

AccessRouter
UrbanNetworks

• Outdoor Areas
• High Mobility

AggregationRouter

• Broadband Distribution Networks
• High Speed Pico Cells
• WiMAX

Presence
EnterpriseNetworks
Location
AccessRouter

• 802.11
• Local Mobility
• Packet Voice
• High Data Rates

Core InternetBackbone
AggregationRouter
AggregationRouter
Authentication

HomeNetworks
AccessRouter

• DSL/Cable
• High Speed Internet Access
• Community
• networks

Ad HocNetworks
4GRadios

• Allow Peer-to-Peer Communications
• Self Configuring

4
Focus of Talk

• Scalable geographic routing protocols for Mobile
  Ad Hoc networks

5
Talk Overview

• Background and motivation
• Self-adaptive geographic unicast routing
• Scalable geographic multicast routing
• On-going and future work

6
Background

• Mobile Ad Hoc Networks (MANET)
• Self organized networks with no fixed
  infrastructure
• Example applications disaster area, military,
  sensor networks, wireless mesh networks
• May need to traverse many hops due to limited
  radio range
• Routing find a packet
  delivery path
• Unicast one-to-one
• Multicast one-to-many
  or manyto-many

7
Challenge of MANET Routing

• Host mobility leads to dynamic topology
• Rate of link failure/repair increases with moving
  speed
• Topology and routing path maintenance become more
  difficult with the increase of path length and
  node density
• Mobile devices have very limited energy, and
  small devices such as sensors have very limited
  per-node resources

8
Existing Unicast Routing Protocols

• Proactive protocols (DSDV, OLSR)
• Actively track network topology changes, not
  suitable for high mobility
• Maintain routes continuously, large overhead when
  there is no traffic
• Reactive protocols (DSR, AODV, TORA, FLR)
• Maintain routes only if needed
• May need network-wide flooding to discover
  routes, larger delay due to searching for path
  before sending packet
• Hybrid protocols (ZRP, SHARP)
• Combine the proactive and reactive approaches

• Geographic routing protocols (GPSR, GFG)
• Make use of location information to reduce
  routing overhead
• Only need to be aware of local topology

9
Information Required for Geographic Routing

• A nodes own position obtained through
  positioning service such as GPS
• The position of the destination determined
  through some location service
• The positions of all neighbors learned through
  periodic beacons sent by neighbors

10
GPSR Greedy Perimeter Stateless Routing (Karp00)

• Local topology construction
• Periodically send beacons to
  announce node position to
  neighbors
• Carry sender position with data packets
• Two forwarding formats
• Greedy forwarding
• Make local optimal forwarding decision,
  choose the neighbor closest
  to the destination as next hop.
• Perimeter forwarding
• Without neighbor closer to destination,
  route around the perimeter of
  void area using a
  planar sub-graph
  (no crossed-edges exist)
  calculated from local
  topology until greedy
  forwarding can be
  resumed

D
x
D
x
11
Problems with Classical Geographic Routing

• Proactive fixed-interval beaconing for positions
• Generate unnecessary overhead and consume energy
• Create collisions with normal data transmissions
• Beaconing interval affects accuracy of the local
  topology and routing performance
• Outdated topology gt non-optimal routing,
  transmission failures gt more network resource
  consumption
• Continuous retransmissions due to inaccurate
  position
• Reduce link throughput and fairness, and increase
  collisions gt further delay and energy consumption

12
Performance Improvement

• Change Beacon Sending Interval
• Send out beacons only after moving a certain
  distance
• Send beacons more frequently, e.g. piggyback
  position with packets (Are the sending nodes the
  best next hop? )

Does not consider traffic conditions. May
generate unnecessary beacons.

• Do not use Beacons (CBF03, BLR04)
• Focus only on finding the forwarding node in
  greedy mode
• No recovery strategy
• No consideration of path maintenance

13
Our Contributions

• Propose two geographic routing protocols
• On-demand alleviate unnecessary overhead due to
  proactive beacons
• Introduce more flexible position distribution
  mechanisms more updated topology, more efficient
  routing and less failure
• Introduce a self adaptive routing approach
  robust to topology changes and adaptive to traffic

14
Importance of adaptivity some analysis

• Positions obtained through beacons become
  outdated
• Depending on mobility and position distribution,
  a large fraction of positions may be outdated.
• Analysis assumptions
• Node B sends beacons periodically to refresh its
  position at A
• Neighbor area of A centered at A, within
  transmission range R
• Moving area of B centered at B, within maximum
  moving distance r
• Parameters

Neighbor time-out interval t
Relative moving speed
Current distance between A, B
Maximum moving distance of B after t
15
Different Scenarios
R
R
r
z
z
A
B
R
r
A
B
z
B
A
r
Same as this case
16
Probability of Moving Out of Range
Case 1
Case 2
Case 3
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Percentage of positions that are out-of-range
Timeout
Vmax 4s 6s 8s 10s 12s 14s
10m/s 3.57 5.49 7.51 9.64 11.88 14.27
20m/s 7.51 11.88 16.80 22.43 29.19 38.26
30m/s 11.88 19.51 29.19 42.94 55.38 65.24
40m/s 16.80 29.14 47.37 62.22 72.89 80.07
50m/s 22.43 42.94 62.22 75.00 82.64 87.24
18
Proposed Geographic Routing Protocols

• Beaconless Interactive Geographic Routing (BIGR)
• BTGR Beacon-on-Trigger Geographic Routing

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Beaconless Interactive Geographic Routing (BIGR)

• There is no beacon, routing path is built
  on-demand
• Route searching phase
• Forwarding decision made through the cooperation
  of forwarding node and its neighbors
• How to find next hop without positions of
  neighbors? How to recover from geographic routing
  void?
• Route optimization phase
• Forwarding path optimized jointly by sending node
  and its neighbors

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Route Searching

• Every node keeps a next hop table

Destination F
Dests position, time (xF, yF), t
NextHop C
New position, time (xnew, ynew), tnew
Old position, time (xold, yold), told
Transmission mode greedy or recovery
A
F
Next hop table for node B
B
C
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How to find next hop?

• When a node (C) does not have next hop
  information, broadcast REQ

S
E
F
B
M
L
C
J
A
G
H
D
I
K
N
Within neighborhood
Represents a node that receives a packet for the
first time
Dest DestPos SendPos Hop
D XD, YD Xc, Yc 1
REQ message with
22
Forwarding Node Selection

• Reply sending nodes closer to destination
  respond after a backoff, and the backoff time is
  smaller for a node closer to destination
• Reply suppression a node cancels its reply if it
  overhears packet forwarding, or overhears reply
  sent by node closer to destination
• Multiple replies select the node closer to the
  destination as next hop

S
E
F
B
M
L
C
J
A
G
H
D
I
K
N
Dest Sender SendPos Hop
D G XG, YG 1
REPLY message
23
Packet Sending

• Cs next hop table

Destination D
Dests position, time (xD, yD), t
NextHop G
New position, time (xnew, ynew), tnew
Old position, time (xold, yold), told
Transmission mode greedy
S
E
F
B
M
L
C
J
A
G
H
D
I
K
N
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Recovery from Local Void

• Without local topology, cannot use perimeter
  forwarding. How to recover?
• Broadcast REQ to N-hop neighbors

F
E
S
B
M
C
L
J
A
D
H
I
K
G
N
Dest DestPos SendPos Hop
D XD, YD Xc, Yc 2
REQ message with
25
Finding Path in Recovery Mode

• Reply sending
• If one-hop neighbor is nearer to destination, it
  replies with Hop 1 Otherwise continues
  broadcasting REQ
• A two-hop neighbor nearer to destination replies
  (reverse path), Hop 2 The one-hop neighbor
  records the next hop to the destination (D) as
  the REPLY sender (G), forwards REPLY to REQ
  sender ( C)
• Reply suppression drop the REPLY if having
  forwarded/overhead one from the node closer to
  destination
• Multiple replies select the node closer to
  destination

Dest Sender SendPos Hop
D G XG, YG 2
Reply message
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Position Update and Route Optimization

• Update next hop position when overhearing packet
  forwarding by next hop (carrying sending node
  position)

• Validate next hop
• Estimate next hop
• If both old and new positions are fresh
• If only new position is available, it will be
  used as the estimated position
• Search for new route
• If both old and new positions are outdated
• If estimated position is out of transmission
  range or no longer closer to destination than
  current forwarding node

• Optimize rerouting path three cases
• Assumption current forwarding path is from B to
  C, neighboring node A overhears from both node B
  and C

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Case 1 A is the destination

• As A is the destination, B should sent packet
  directly to A, so A sends CORRECT to B
• B sets its next hop to A

A
B
C
Old path
Old position
Current position
New path
28
Case 2 Greedy Mode Forwarding
A
F

• If A is closer to F than C is to F, A sends
  CORRECT to B
• B compares As and Cs positions to F, and sets
  its next hop to A if it is closer to F

B
C
Greedy
Old position
Current position
Old path
New path
29
Case 3 Recovery Forwarding
F

• If A is closer to F than it is to B and C, A
  sends CORRECT to B
• If B is the first hop of recovery, if A is closer
  to F than B is to F, then A is closer to F than
  both B and C
• If B is the last hop of recovery, if A is closer
  to F than C is to F, then A is closer to F than
  both B and C
• B compares A and Cs positions relative to F, if
  A is closer to F, B sets its next hop to A
• If B is the first hop of recovery, change mode to
  greedy

A
D
B
C
Recovery mode
Greedy
Old position
Current position
Old path
New path
30
Proposed Geographic Routing Protocols

• Beaconless Interactive Geographic Routing (BIGR)
• BTGR Beacon-on-Trigger Geographic Routing

31
BTGR Beacon-on-Trigger Geographic Routing

• Beacons are generated on demand triggered by
  data traffic, non-optimal route
• Adaptive to traffic
• Send beacon periodically when overhearing data
  forwarding or requested by neighbor
• Stop beaconing if there is no traffic
• Route optimization
• Broadcast a beacon upon detecting non-optimal
  path
• Topology maintenance
• Only maintain positions of neighbors on demand
• Packet forwarding
• Forward if positions are fresh
• Request position update otherwise

32
Beacon Triggering by Non-optimal Path

• Route validation
• Delete invalid neighbors
• Update the positions of other members based on
  estimation
• Route optimization also three cases
• The first two cases are similar to that of BIGR
• Case 3 When A overhears forwarding from B to C
  using perimeter mode
• If A is closer to the destination than the
  position where the perimeter mode started, B
  should resume greedy forwarding earlier
• A broadcasts a beacon to refresh its position, B
  will send future packets to A

33
Impact of Mobility

• Delivery ratio Control
  overhead

34
Impact of Mobility (cont)
Total transmissions Average end-to-end
delay
GPSR has significantly higher transmission
redundancy and end-to-end delay due to outdated
position.
35
Summary

• Propose two self-adaptive on-demand geographic
  routing protocols
• Alleviate unnecessary overhead due to proactive
  beacons
• More efficient position distribution and very
  robust to topology change packet transmission
  delay is reduced more than three times at high
  mobility as compared to GPSR
• Outperform existing geographic protocols in all
  test scenarios, including mobility, node density
  and traffic load

36
Talk Overview

• Background and motivation
• Self-adaptive geographic unicast routing
• Scalable geographic multicast routing
• On-going and future work

37
Existing Multicast Routing Protocols

• Tree-based (AMRIS, MAODV, LAM)
• Utilize network resources efficiently
• Mesh-based (FGMP, CAMP, ODMRP)
• Robust

Difficult to scale due to overhead for route
searching, group membership management, and
tree/mesh maintenance over dynamic topology

• Geographic multicast (LGT, DSM, PBM)
• Reduce topology maintenance overhead, but not
  scalable

38
Why Is Geographic Multicast Difficult to Scale?

• Putting the information of all group members into
  packet header creates excessive overhead for
  large group
• Relying on location service to obtain positions
  for all group members adds more overhead

39
Our Contributions

• Design an efficient on-demand hierarchical group
  membership management scheme
• Avoid the need to build and maintain tree/mesh
  structure
• Avoid the need for periodical network-range
  flooding of source information, and location
  searches for group members

40
Some Concepts
Home zone

• Zone
• Network terrain is divided into square zones
• Member Zone
• A Zone with group members
• Zone Leader
• Manage membership in a member zone
• Home Zone
• Zone in which all zone members track the
  addresses and Zone IDs of sources

Source
Zone leader
Group member
Other nodes
41
Membership Reporting in Local Zone

• A group member sends REFRESH to leader to report
  its membership
• If leader is known, unicast
• If leader is not known, elect leader
• Leader election (on demand)
• Flood the REFRESH, indicating leader information
  is requested
• A leader will send back a LEADER message
• If no LEADER is received, the member announces
  itself as the leader and floods a LEADER message
  within the zone

Zone leader
Group member
Other nodes
42
Membership Management within Zone

• A member
• Sends REFRESH to leader periodically and when
  joining /leaving group, carrying its membership
  and position
• A leader
• Sends LEADER periodically within the zone to
  announce its leadership, carrying the positions
  and group IDs of the multicast members
• States maintenance
• Nodes in the member zone save the information of
  multicast group members in the zone
• Group members and zone leader keep source
  information

43
Moving between Zones

• When a node moves into a new zone
• Clears old zones information
• If the node is a group member
• Will continue receiving packets forwarded by old
  zone
• Sends REFRESH to new zone leader
• When a leader is moving out of a zone
• Hands leadership to other nodes

44
Source Announcements

• A source
• At session initiation time, floods an ANNOUNCE,
  with address, position, and group ID
• Later piggybacks its information with the
  multicast packets
• A node interested in being a member
• Records source information
• For joining, send REFRESH to its leader

45
Home Zone

• Function of Home zone
• Maintains addresses and zone IDs of sources
• A source sends its zone ID to home zone when
  moving to new zone floods source info to whole
  zone
• Searching for Home zone
• Source announces its current zone as home zone
• Sets sequence number to 0, sequence number
  increases upon home zone change
• Other nodes search home zone with increasing
  ring
• Home zone election
• When a node receives a message addressed to home
  zone with sequence number different from record
  (due to zone update or zone announcement from a
  new source)
• If the message has larger sequence number, update
  its home zone info otherwise, forward the
  message to recorded home zone
• A home zone node sends SOURCE to message sender
  to update senders home zone information

46
Membership Management at Upper Tier

• If the leader knows the source location
• Sends report on group membership to the source
• Aggregates reports for different sources
  located at the same host node
• If a leader does not know source location, or the
  source information is outdated
• Sends REPORT to home zone, which will forward the
  report to the source zone
• A home zone node sends a SOURCE message to the
  leader to update leaders source information
• Source records the member zones

47
Empty Zone Handling

• Member zone
• The departing leader notifies the source
• Home zone
• The last node announces the new zone it is moving
  to as the home zone floods source information
  within new home zone sends ANNOUNCE to network
  with sequence number of home zone increased by one

48
Multicast Packet Delivery

• Source
• Sends packets to all member zones and members in
  its zone
• Aggregates transmissions and sends one copy if
  several members share next hop
• Intermediate nodes
• Take similar action
• If the message includes their current zone,
  replace zone ID in the message with the IDs of
  the members in the zone.

Home Zone
Source
Zone leader
Group member
Other nodes
49
Impact of mobility

• Delivery ratio Control overhead

50
Scalability
Group size Network size
51
Summary

• Design a scalable geographic multicast routing
  scheme
• Scalable and robust group membership management
  and packet forwarding in terms of group size,
  network range and mobility
• Avoid the need to build and maintain the
  tree/mesh structure over dynamic topology
• Avoid network-range flooding of source
  information and location searches for the group
  members

52
Tomorrow Common Net, Common Apps

3G CellularNetworks
RadioController

AccessRouter
UrbanNetworks

• Outdoor Areas
• High Mobility

AggregationRouter

• Broadband Distribution Networks
• High Speed Pico Cells

Presence
EnterpriseNetworks
Location
AccessRouter

• 802.11
• Local Mobility
• Packet Voice
• High Data Rates

Core InternetBackbone
AggregationRouter
AggregationRouter
Authentication

HomeNetworks
AccessRouter

• DSL/Cable
• High Speed Internet Access

Ad HocNetworks
4GRadios

• Allow Peer-to-Peer Communications
• Self Configuring

• Unifies access technologies (wireless and
  wireline)
• End-to-end Internet Service
• common mobility management and control
• common transport infrastructure
• common services infrastructure

53
On-going and Future Work

• Cross-Layer Optimization and Design of Mobile and
  Wireless Systems
• Create infrastructure and algorithms to enable
  more optimal performance of the wireless system,
  by adopting an integrated, multi-layer approach
• On-going projects
• Power control and energy efficient transmissions
  in mobile Ad Hoc networks
• Architecture design and cooperative resource
  management for IP-based radio access network

54
On-going and Future Work (cont)

• Next Generation Mobile Wireless Network
  Infrastructure and Service
• Development of network infrastructure and
  services over emerging radio and computing
  technologies.
• On-going projects
• Sensor Network Applications and Services
• Programmable Wireless Networking and Service
  Infrastructure Design
• Scalable and Resilient Wireless Mesh Network
  Design
• Context-aware Mobile Computing and Wireless
  Services
• Architecture and Design for Heterogeneous Networks

55

Q A
56

• Architecture and Design for Heterogeneous
  Networks
• Enable end-to-end communications over
  heterogeneous networks WPAN, WLAN, WMAN, W-WAN,
  and Internet.
• Secure and Cooperative Routing over Ad Hoc
  Networks
• Provide security and incentive to enable the
  relay-based hop-by-hop transmissions.

57
Case 3 Recovery Forwarding

• Suppose A overhears from B and C
• Packet was forwarded for destination F from B to
  C using recovery mode
• If B is the last hop of recovery
• If A is closer to F than C, then A is closer to F
  than both B and C
• A sends COREECT to B
• B compare A and Cs positions to F
• B sets its next hop to A if it is closer to F
• Remain in recovery mode, a better path

F
A
D
B
C
Recoverymode
Old position
Current position
Old path
Overall, if A is closer to F than Both B and C,
it sends CORRECT to B
New path
58
Beacon Triggering by Data Traffic

• Three types of beacons (for position information)
• BEACON message
• REQ (Carrying position)
• Data packets (Carrying position)
• Beacon request
• Receiving REQ
• Overhearing data transmission
• Beacon sending
• Only if the request interval is smaller than
  threshold
• For packet sending
• Use local topology information for forwarding if
  request sent interval is smaller than threshold
• Otherwise, send REQ to neighbor

59
Route Optimization (cont)

• Optimization procedure depends on scenarios
• Case 1 A is the destination of the packet
• Case 2 Packet was forwarded for destination F
  from B to C using greedy mode
• Case 3 Packet was forwarded for destination F
  from B to C using recovery mode

F
F
A
A
D
A
C
B
B
C
B
C
Greedy mode
Recovery mode
Case 1
Case 2
Case 3
60
Route Searching

• How to find a path without beacon?
• Depend on forwarding states greedy or recovery
  
• Greedy forwarding
• Find a neighbor closest to the destination
• Recovery forwarding
• How to forward when there is no neighbor closer
  to the destination?

61
Destination D
Dests position, time (xD, yD), t
NextHop G
New position, time (xnew, ynew), tnew
Old position, time (xold, yold), told
Transmission mode greedy
62
Membership Management in Local Zone

• Membership reporting by mobiles nodes
• Leader election
• Moving between different zones

63
Membership Management at Upper Tier

• A source needs to record the member zones
• Source announcement
• Home zone election
• Zone membership reporting