Xin Wang Assistant Professor Director, Wireless and Networking Systems Lab (WINS) SUNY, Buffalo
description
Transcript of Xin Wang Assistant Professor Director, Wireless and Networking Systems Lab (WINS) SUNY, Buffalo
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)SUNY, Buffalo
http://www.cse.buffalo.edu/~xwang8
Future -Common Network, Common Applications
Core InternetBackbone
AuthenticationAuthentication
PresencePresenceLocationLocation
AggregationRouter
AggregationRouter
AggregationRouter
AggregationRouter
AggregationRouter
AggregationRouter
AccessRouterAccessRouter
AccessRouterAccessRouter
3G CellularNetworks
RadioController
RadioController Access
RouterAccessRouter
UrbanNetworks
HomeNetworks
EnterpriseNetworks
4GRadios
Ad HocNetworks
4G AirInterface
4GRadios
• DSL/Cable• Community wireless networks
• Broadband Distribution Networks• High Speed Pico Cells• Broadband Wireless
• 802.11++• Local Mobility• Packet Voice• High Data Rates
• Outdoor Areas• High Mobility
• Allow Peer-to-Peer Communications• Self Configuring
Talk Overview
Background and motivationPart I: Self-adaptive geographic unicast
routingPart II: Scalable geographic multicast
routingOn-going and future work
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 many–to-many
Challenges of MANET Routing
Host mobility leads to dynamic topologyRate 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
Existing Unicast Routing Protocols
Proactive protocols (DSDV, OLSR)– Maintain routes continuously, large overhead when
there is no traffic– Actively track network topology changes, not suitable
for high mobility
Geographic routing protocols (GPSR, GFG) – Make use of location information to reduce routing overhead– Only need to be aware of local topology
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
Information Required for Geographic Routing
The position of the destination: determined through location service
A node’s own position: obtained through positioning service such as GPS
The positions of all neighbors: learned through periodic beacons sent by neighbors
Forwarding Formats
Greedy forwarding– Make local optimal forwarding
decision, choose the neighbor closest to the destination as next hop.
D
x
x
D
Perimeter forwarding (GPSR)– Calculate a planar sub-graph
(no crossed-edges exist) from the local topology
– Route around the perimeter of void area (that does not have neighbor closer to the destination) until greedy forwarding can be resumed
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 => non-optimal routing, transmission
failures => more network resource consumption
Continuous retransmissions due to inaccurate position – Reduce link throughput and fairness, and increase
collisions => further delay and energy consumption
Possible 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 (CBF’03, BLR’04) – Focus only on finding the next hop for greedy
forwarding, and there is no recovery strategy– Do not have a good strategy to cache the path
detected or perform any route optimization.
Talk Overview
Background and motivationPart I: Self-adaptive geographic unicast
routingPart II: Scalable geographic multicast
routingOn-going and future work
Our Contributions
Propose two self-adaptive routing protocolsBIGR: Beaconless Interactive Geographic Routing BTGR: Beacon-on-Trigger Geographic Routing
– On demand: alleviate unnecessary overhead due to proactive beacons
– More flexible position distribution: more updated topology, more efficient routing and less failure
– Self adaptive: adaptive to traffic pattern and robust to topology changes
Importance of updated positions: some analysis Positions obtained may become outdated
– A mobile may move out of transmission range before the position is timed out and removed from neighbor table.
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 distance r Neighbor time-out interval t
B’s speed relative to A
Current distance between A, B
Maximum distance traveled by B after t
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Probability of Moving Out of Range
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Probability of the mobile moving out-of-range (expressed in percentages)
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
Timeout
Proposed Geographic Routing Protocols
BIGR: Beaconless Interactive Geographic Routing
BTGR: Beacon-on-Trigger Geographic Routing
Route searching phase
Route optimization phase
– Forwarding decision made through the cooperation of forwarding node and its neighbors
– Forwarding path optimized jointly by sending node and its neighbors
Beaconless Interactive Geographic Routing (BIGR)
There is no beacon, routing path is built on-demand
How to find next hop without positions of neighbors?
Route Searching
After a route searching, a node keeps a record for next hop
Destination F
Dest’s position, time (x_F, y_F), t
NextHop C
New position, time (x_new, y_new), t_new
Old position, time (x_old, y_old), t_old
Transmission mode greedy or recovery
B
A F
C
Next hop table for node B
Nex
t-ho
p po
siti
on
How to find next hop?
When a node (C) does not have next hop information, broadcast REQ
REQ message with
A node that receives a packet for the first time
Dest DestPos SendPos
Hop
D XD, YD Xc, Yc 1
Within neighborhood
B
A
SE
H
J
D
C
G
I K
M
N
LF
Forwarding Node Selection Reply sending: nodes closer to destination respond after a
competition delay, and the delay is smaller for a node closer to destination
REPLY message Dest Sende
rSendPos
Hop
D G XG, YG 1
B
A
SE
H
J
D
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I K
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LF
Multiple replies: select the node closer to the destination as next hop
Reply suppression: a node cancels its reply if it overhears packet forwarding, or overhears reply sent by node closer to destination
Packet Sending
C’s next hop table
Destination D
Dest’s position, time (x_D, y_D), t
NextHop G
New position, time (x_new, y_new), t_new
Old position, time (x_old, y_old), t_old
Transmission mode greedy
B
A
SE
H
J
D
C
G
I K
M
N
LF
Recovery from Local Void
Without local topology, cannot use perimeter forwarding. How to recover?
B
A
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J
D
C
IK
M
N
L
G
REQ message with Dest DestPo
sSendPos
Hop
D XD, YD Xc, Yc 2
E
Broadcast REQ to N-hop neighbors
Finding Path in Recovery Mode Reply sending:
Dest Sender SendPos
Hop
D G XG, YG 2B
S F
H
J
D
C
IK
ML
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E
Reply suppression: drop the REPLY if having forwarded/overhead one from the node closer to destination
– 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;
Multiple replies: select the node closer to destination
Reply message
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 routing path: three cases
Case 1: A is the destination
As A is the destination, B should send packet directly to A, so A sends CORRECT to B
B C
A
Old position
CORRECT
Current position
Old path
New path
AMove
B sets its next hop to A
CORRECT
Case 2: Greedy Mode Forwarding
If A is closer to F than C is to F, A sends CORRECT to B
Old position
Current position
Old path
New path
B C
A
A
Move F
Greedy B compares A’s and C’s positions
to F, and sets its next hop to A if
it is closer to F
A
Case 3: Recovery Forwarding
If A is closer to F than that from 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
F
D
CB
CORRECT
A
Move
Recovery mode
Greedy
Old position
Current position
Old path
New path
B compares A and C’s 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
Proposed Geographic Routing Protocols
BIGR: Beaconless Interactive Geographic Routing
BTGR: Beacon-on-Trigger Geographic Routing
BTGR: Beacon-on-Trigger Geographic Routing
Position distribution: through beacons Packet forwarding
– Send packet through greedy forwarding in general.
– Use perimeter forwarding in recovery mode.
Topology maintenance– Only maintain positions of neighbors when there is
traffic
Beacon generation: triggered by data traffic and route optimization– 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
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 those of BIGR– Case 3: When A overhears forwarding from B to C
using perimeter mode If A is closer to the destination than that of the node
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
Performance Studies
Setup:– Tool: GlomoSim– Network size: 3000 m x 1000 m, 300 nodes– Traffic: 30 CBR with rate 8kbps each– Mobility model: Random Waypoint
Measures:– Packet delivery ratio
The ratio of packets delivered to those originated by the source– Control overhead
The number of control messages over the number of packets received– Average number of data packet transmissions
The total number of packet transmissions accumulated from each hop over the total number of packets received
– Average end-to-end delay Average time interval for packets to traverse from source to
destination
Performance: Impact of Mobility
Delivery ratio Control overhead
BIGR and BTGR delivery ratios are not impacted by speedBIGR more actively updates the position as speed increases
Performance: Impact of Mobility (cont)
Total transmissions Average end-to-end delay
Our protocols have significantly lower transmission redundancy and end-to-end delay than GPSR due to more updated topology.
Summary of Part I
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
Talk Overview
Background and motivationPart I: Self-adaptive geographic unicast
routingPart II: Scalable geographic multicast
routingOn-going and future work
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)– Only consider packet forwarding scheme– Reduce topology maintenance overhead, but not scalable
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
Our Contributions
Design an efficient on-demand hierarchical group membership management scheme
Use geographic forwarding to avoid building and maintaining tree/mesh structure
Introduce the home zone to avoid periodical network-range flooding of source information
Combine group membership management with location service to avoid location searches for group members
Track the addresses and Zone IDs of sources
Home zone
Terms Used in SGMP
Member Zone Group member
Zone leader
Source
SGMP: Basic Principles
Zone LeaderMember
Join
Source
Join
Member ZoneMemberData
SourceData
Packet sending: geographic unicasting, and the packet for a zone is sent towards the zone center.
(RERESH) (REPORT)
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
Home Zone Management
Home zone information update
Home zone searching
Home zone election
– Other nodes: search home zone with ring of increasing size.
– Source: announces its current zone as home zone, and sets sequence number to 0; Sequence number increases by one each time home zone changes.
– Will be triggered when a node receives a message addressed to home zone with ID different from record (due to zone update or zone announcement from a new source)
– A source sends its zone ID to home zone when moving to new zone– The first home zone node floods source info to whole zone
Membership Management within Zone
A member
A leader
– Sends REFRESH to leader periodically and when joining /leaving group, carrying its membership and position
– Floods LEADER periodically within the zone to announce its leadership, carrying its own position and the positions and group IDs of the multicast members
Membership Management at Upper Tier
Home Zone
Leader knows source location
Membership report
SOURCEmessage
Leader does not know source locationor
Source information is outdated
Source: records the member zones
Moving between Zones
When a node moves into a new zone– Clears old zone’s 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
Empty Zone Problem
S
r p
2
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kNkN
k
ppk
NP
)1(1
1
dSN :networkin nodes ofNumber
2 :zone of Area r
S :network of Aread :density Node
20 40 60 80 100
100m 74.885 56.282 44.864 36.865 30.853
200m 36.857 19.208 10.985 6.5467 3.9951
400m 6.4964 0.9643 0.1605 0.0281 0.0051
600m 0.5930 0.0112 0.0002 5.4E-06 1.2E-07
m2400 x m2400S 2nodes/km:Density
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
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 information of the members in the zone. Zone leader
Group member
Other nodes
Source
Performance: Impact of mobility
Delivery ratio Control overhead
SGMP has up to 35% higher delivery ratio and 20 % lower overhead at high mobility
Performance: Scalability
Group size Network size
SGMP has higher delivery ratio under all group sizes, and has more than 2.5 times higher delivery ratio for large network sizes.
Summary of Part II
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
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
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
Q & A
Home Zone Election
Home ZoneSEQ = 1
Home ZoneSEQ = 0
When a node receives a message carrying home zone ID different from that in its record– If the message has larger sequence number, update its home zone info; otherwise, forward the
message to recorded home zone
Forwardto home zone with larger SEQ
Membership report
SOURCEmessage
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
Impact of node density
Impact of node density (cont)
Impact of traffic load
Impact of traffic load (cont)
… Tomorrow – Common Net, Common Apps
Core InternetBackbone
AuthenticationAuthentication
PresencePresenceLocationLocation
AggregationRouter
AggregationRouter
AggregationRouter
AggregationRouter
AggregationRouter
AggregationRouter
AccessRouterAccessRouter
AccessRouterAccessRouter
3G CellularNetworks
RadioController
RadioController Access
RouterAccessRouter
UrbanNetworks
HomeNetworks
EnterpriseNetworks
4GRadios
Ad HocNetworks
4G AirInterface
4GRadios
• DSL/Cable• High Speed Internet Access
• Broadband Distribution Networks• High Speed Pico Cells• 802.11++
• Local Mobility• Packet Voice• High Data Rates
• Outdoor Areas• High Mobility
• 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
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.
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
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?
Membership Management in Local Zone
Membership reporting by mobiles nodes Leader election Moving between different zones
Membership Management at Upper Tier
A source needs to record the member zones
Source announcementHome zone electionZone membership reporting
Protocol Overview
Group membership management
Packet forwarding
– At local zone tier, a leader will collect the positions and membership of the member nodes in the zone.
– At upper tier, the leader will represent the member zone to join a multicast tree.
– At upper tier, the source sends a packet to member zones; At lower tier, the first node in the zone that receives the data packet forwards it to the group members.
– Both data and control packets are generally transmitted through geographic unicasting; Packets for a zone are sent towards the zone center
Location of group members is combined with groupmembership management