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Dual-Region Location Management for Mobile Ad
Hoc Networks
Yinan Li, Ing-ray Chen, Ding-chau Wang
Presented by Youyou Cao
Introduction
• MANET: A self-organizing and self-configuring infrastructureless network of mobile devices connected by Wireless
• Problem: No good scalable location management for MANET yet!
Existing location management scheme
• Each node is assigned a home region(serve as location servers) through hashing
• Drawback: need to contact location server even source and destination nodes are close to each other
Home region of destination node
Destination node
Source node
How to improve?
• Periodically exchange location info with neighboring nodes in its local region
• If a node in the local region knows the location of destination node
Local region of source node
Source node
Destination node
Local region of destination node
- Only local location info of the neighbor is needed
How to improve?
• Even better, source node might be within the local region of the destination node
Source node
Destination node
Local region of destination node
- Only need local info from the node itself!
How to improve?
• Further question: how to define home and local region size?• Previous work:
- Define home region size statically at design time• Our work:
- Dynamically determine the optimal home region size and local region size
- in order to minimize the overall network cost incurred by location management and data packet delivery
System Design
• Assumptions:
- Mobile nodes knows their location, moving direction, moving speed via GPS
- Density of mobile nodes are high enough so there is at least one location server in each node’s home region
Dual-Region Mobility Management (DrMoM)
• Global Partition: Equally sized rectangular region
• Each node is permanently assigned a home region by hashing
• Home region center is fixed, Home region size is dynamically chosen based on node mobility and service characteristics.
Dual-Region Mobility Management
• Local region center moves when node moves, local region size chosen dynamically
• Local region location updates follow a threshold-based approach, ie, notice neighbors when its current location is outside of the transmission rage of its last updated location
Increase :
- Chance of successful location query increase
- Larger overhead for location queries and updates
Key Parameter: home region size
Key Parameters: local region size
Increase :
- Chance of locate destination node using only local info increase
- Cost of location inquiry packet delivery increase
- Rate of location updates of the home region decrease
Location Table
Each node maintain two tables:
• Home region location table
- Stores location information of nodes for which it serves as a location server
• Local region location table
- Stores location information of nodes for which it is within their location region
Greedy geographical packet forwarding
For each hop, select the node that is closest to the destination within its one hop neighbors
Performance Model
• Goal: minimize total communication cost incurred by DrMoM- Total number of wireless transmissions per time unit
• Impact of using this metric:- Small saving in cost can be significant over time
- Larger probability of successful packet deliveries
- Shorter average packet delay
- Maximize the lifetime of a MANET
Performance Model
• Assumptions:- Use modified random way point mobility model to simulate the movement of mobile nodes
- Hash function maps any mobile node uniformly to any rectangular region with equal probability
Notation
Broadcast cost b(R): the number of wireless transmissions to cover the entire region
: Average # of hops between node and its home region: Average distance between a node and its home region in a m*m square area
Location Update Cost
:The cost for local region location updates: broadcast updates to its neighbors
:The cost for home region location updates: send updates messages to home region first, then broadcast
Location Query Cost
the cost for local region location query: broadcast and collect reply from local neighbors
the cost for home regionlocation query: send request and get response from home region
Probability that local regionlocation query fails
Node densityProbability that a neighbor of S is also in local region or home region of D
Data Packet Delivery Cost
Upper bound: Upper bound:
p1(p2) : – probability that S is within the local(home) region of D
Case 1: A valid entry for D exists in Case 2: A valid entry for D exists in
Case 3: No valid entry for D exists in or
Home Region Maintenance Cost
When node B enter the home region of node A, A’s home region nodes broadcast the message to their neighbors
Total Communication Cost
Data Packet Rate Local region location update rate
Home region location update rate Home region maintenance rate
Performance Comparison
Total communication cost incurred per time unit by DrMoM vs SLURP and RUDLS as a function of φ, ν, n
Conclusion
• Designed a dual-region location management scheme to minimize overall network cost incurred for location management and data packet delivery that outperforms state-of-the-art schemes
• Dynamically identify and apply optimal and to each mobile node based on runtime mobility and service characteristics
• Application: build lookup table of optimal and at static time, check and apply optimal value at runtime
Future work
• Consider other mobility model rather than random movement
• Use stochastic Petri Net modeling technique• How to select trustworthy nodes as location
server when there is attack• Extend the design notion to other location-
based services in MANET