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Efficient Geographic Routing in Multihop Wireless Networks

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Efficient Geographic Routing. in Multihop Wireless Networks ... detour. Example of NADV with Lossy Links. Need to avoid nodes in the gray zone. Link cost: ETX ... – PowerPoint PPT presentation

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Title: Efficient Geographic Routing in Multihop Wireless Networks


1
Efficient Geographic Routingin Multihop Wireless
Networks
  • Seungjoon Lee
  • Department of Computer Science,
  • University of Maryland, College Park
  • Joint work with Bobby Bhattacharjee, Suman
    Banerjee
  • MobiHoc05
  • Presented by Ting-Yu Lin

2
Outline
  • Motivation
  • New Link Metric for Geographic Routing
  • Definition of Normalized Advance (NADV)
  • Example of NADV
  • Optimality of NADV in Idealized Environments
  • NADV with Various Types of Link Cost
  • Link Cost Estimation
  • Simulation Results
  • Conclusions

3
Routing in Wireless Networks
Minimum-cost path
S
T
Shortest path
  • Shortest path is not always the best.
  • We want to find a minimum-cost path
  • ETX (Expected Transmission Count), Delay,
    Transmission energy consumption

4
Cost-based Routing
S
T
Shortest-hop path
5
Cost-based Routing
S
T
Shortest-hop path cost12
2
4
3
3
  • ETX, Delay, Transmission energy consumption

6
Cost-based Routing
Alternative path cost9
3
2
1
1
2
S
T
Shortest-hop path cost12
2
4
3
3
  • ETX, Delay, Transmission energy consumption
  • Relatively easy to incorporate in on-demand
    routing
  • How to find low-cost paths using geographic
    routing?

7
Geographic Routing
  • Uses location information
  • Each node knows its location (e.g., using GPS).
  • Sources know the locations of destinations.
  • Neighbor location is known through periodic
    messages.
  • Next-hop Decision
  • Greedy Forwarding
  • Recovery Operation
  • To overcome local minima, or voids
  • All operations are local (in contrast to DSR,
    etc.)

8
Greedy Geographic Forwarding
D(S)
S
T
n
D(n)
Maximize advance ADV(n) D(S) - D(n)
9
Greedy Geographic Forwarding
Advance ADV(n) D(S) - D(n)
S
T
n
Our goal gt Maximize advance vs. Use low-cost link
gt Trading-off proximity and link cost
10
Example of Greedy Forwarding
S
T
n
Area with high error rate
  • ADV does not consider link quality.
  • We want BOTH large advance AND low link cost.

11
Normalized Advance (NADV)
  • Definition NADV(n) ADV(n)/Cost(n)
  • Advance per unit cost
  • as link cost, then
  • (expected advance per transmission)
  • Goal
  • Use NADV as link metric in geographical routing,
    such that a node forwards packets to the neighbor
    with largest NADV.

12
Benefits of NADV
  • Applicable to many cost types
  • E.g., ETX, transmission energy consumption, link
    delay
  • General framework
  • Different routing strategies depending on
    objectives
  • E.g., Min-latency path, min-energy path
  • Opportunity for Adaptive Routing
  • Due to local next-hop decision in geographic
    routing

detour
C
S
A
B
T
Cost increase
13
Example of NADV with Lossy Links
  • Need to avoid nodes in the gray zone
  • Link cost ETX

14
Example of NADV with Lossy Links
  • Need to avoid nodes in the gray zone
  • Link cost ETX

Best for NADV
Best for ADV
Sender
Destination
15
Path Optimality using NADV (theoretical base)
  • Goal
  • Minimize the sum of link costs on the path.
  • Assumptions (Idealized Environment)
  • We can find a node at an arbitrary point (high
    density).
  • Link cost increasing convex function of
    distance.
  • E.g., Required transmission power is larger for
    longer distance
  • Optimal Strategy
  • To choose nodes only on the straight line between
    S and T.
  • To choose nodes on an equidistant basis (all
    links have the same distance ADVx optimal
    interval).
  • To choose the neighbor with minimum Costx/ADVx,
    or maximum NADVxADVx/Costx

16
Proposed WISE (Wireless Integration Sublayer
Extension)
  • Located on top of MAC.
  • Closely coordinates with MAC for efficient link
    cost estimation.
  • Provides simple primitives for upper-layer
    protocols.

17
NADV with Various Cost Types
  • Link Error Rate
  • ETX 1/(Packet Success Ratio)
  • NADV ADV/ETX ADV (Packet Success Ratio)
  • Seada04, Zorzi03
  • Link Delay
  • Transmission time due to different link
    transmission rate
  • NADV ADV/(Transmission Time)
  • Packet Transmission Power
  • NADV ADV/Cpower

18
Link Cost Estimation
  • NADV requires link cost estimation.
  • E.g., Packet error rate estimation using SNR or
    probe messages
  • Fast and accurate estimation with lower overhead
    is desirable
  • PER estimation schemes
  • Probe messages
  • SNR
  • where
    SNR
  • Self monitoring
  • Detailed estimation schemes are in the paper.
  • Multiple schemes for various operating
    environments

19
Simulation Experiments (ns-2)
  • Scenarios
  • 100 stationary nodes randomly placed in
    1km-by-1km square (250m tx range)
  • One pair of src-dst (900 meters) CBR traffic 1
    pkt every 2 seconds
  • Multiple sources
  • Mobile nodes
  • Link cost types
  • ETX
  • Link cost is a function of distance
  • Link delay
  • Transmission energy consumption
  • Random link cost
  • Link cost is NOT a function of distance

20
Delivery Ratio vs. Link Error RateNADV Achieves
High Delivery Ratio.
  • Link Metric ADV/ETX

Higher packet error rate
21
Simulation ResultRetransmissions vs. Link Error
Rate
  • 100 stationary nodes in 1km-by-1km square (250m
    tx range)
  • One pair of src-dst (900 meters) CBR traffic 1
    pkt every 2 seconds.
  • Uniformly random assignment of link error
    probability 0max-PER.

22
Simulation Result (using link estimation
schemes)Delivery Ratio vs. Link Error Rate
  • 100 stationary nodes in 1km-by-1km square (250m
    tx range)
  • One pair of src-dst (900 meters) CBR traffic 1
    pkt every 2 seconds.
  • Change in background noise values

Delivery Ratio
23
Random Link CostNADV Finds Good Paths.
  • Assign link cost randomly between 1 and 6
  • Not a monotonic function of distance
  • Link Metric NADV ADV/(Random Link Cost)
  • Modify AODV to find a minimum-cost path (AODV).
  • To minimize the sum of all link costs on the path.

24
Random Link CostNADV Finds Good Paths.
  • Assign link cost randomly between 1 and 6
  • Not a monotonic function of distance
  • Link Metric NADV ADV/(Random Link Cost)
  • Modify AODV to find a minimum-cost path (AODV).
  • To minimize the sum of all link cost on the path.
  • NADV is comparable to AODV and optimal routing
  • Even with local, greedy decision for the next
    hop.
  • Even when link cost is not a function of distance.

25
Random Link CostNADV Finds Good Paths.
  • Assign link cost randomly from 1,6
  • Not a function of distance
  • Modify AODV to find a minimum-cost path.

26
Simulation ResultComparison with AODV
  • Assign link cost randomly from 1,6
  • Not a function of distance
  • Modify AODV to find a minimum-cost path.

Randomly choose 50 of links and increase the
cost by 50.
27
Simulation ResultExperiment with Link Cost
Change
  • Generic cost
  • Random variable in 16
  • Cost change during the communication

detour
S
T
Cost increase
28
Related Work
Geographic Routing GPSR, face routing
Link Error DeCouto03
Link Delay Awerbuch04
Xmit Energy Banerjee02
Other Cost
29
Related Work
Seada04 Zorzi03
SP-PowerStoj01
Geographic Routing GPSR, face routing
Link Error DeCouto03
Link Delay Awerbuch04
Xmit Energy Banerjee02
Other Cost
30
Related Work
NADV (Normalized Advance)
Seada04 Zorzi03
SP-PowerStoj01
Geographic Routing GPSR, face routing
Link Error DeCouto03
Link Delay Awerbuch04
Xmit Energy Banerjee02
Other Cost
31
Conclusions
  • Normalized Advance (NADV)
  • General Link Metric for Geographic Routing
  • Applicable to various cost types
  • Optimal
  • Requires cost estimation schemes
  • Performance Improvement
  • Up to 5 times higher delivery ratio
  • Comparable to optimal routing
  • Future works
  • Hybrid use of link costs
  • Experiments on a real testbed
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