A Message Ferrying Approach for Data Delivery in Sparse Mobile Ad Hoc Networks

1
A Message Ferrying Approach for Data Delivery in
Sparse Mobile Ad Hoc Networks

• W. Zhao, M. Ammar and E. Zegura (Georgia
  Institute of Technology)
• Proceedings of ACM MobiHoc 2004
• Presented by Park, Seon-yeong

2
Introduction 1/2

• Sparse Mobile Ad Hoc Networks
• Network partitions can last for a significant
  period
• E.g., earthquake disaster area

Mobile Ad Hoc Node
Radio transmission Range
3
Introduction 2/2

• Previous Approaches for Sparse Mobile Ad Hoc Nets
• Radios with longer transmission ranges to
  maintain network connectivity
• Node mobility to help deliver data
  store-carry-forward
• Reactive schemes
• Rely on inherent movement
• Contention of limited buffers due to a large
  number of redundant messages (Epidemic routing)
• Proactive schemes
• Modify nodes trajectories
• Difficult to support multiple simultaneous
  transmissions

4
Overview of Message Ferrying 1/3

• Message Ferrying (MF)
• Proactive mobility-assisted approach
• Components
• Message ferries
• Special nodes with responsibility for carrying
  data between regular nodes
• Move around the deployed area according to known
  routes
• Fewer resource constraints
• Equipped with renewable power, large memory and
  powerful processors
• Regular nodes
• Assigned tasks in the deployment area
• Limited resources such as battery and memory

5
Overview of Message Ferrying 2/3

• Applications of Message Ferrying
• Low throughput and large delay as compared to
  connected networks are acceptable
• Examples
• Crisis-driven
• Battlefield or disaster applications
• Geography-driven
• ZebraNet project
• Cost-driven
• Cost effective alternatives such as DakNet
  project
• Service-driven
• Privacy or anonymity service for message delivery

6
Overview of Message Ferrying 3/3

• Two MF Schemes
• Node-Initiated MF (NIMF)
• Nodes periodically move and communicate with a
  ferry
• Ferry-Initiated MF (FIMF)
• Ferries move proactively to meet nodes

7
Node-Initiated MF - Overview

• Message Delivery in Node-Initiated MF

Ferry route
Send/recv msg.
Send/recv msg.
s
D
D
Destination
s
Source
8
Node-Initiated MF Operations 1/2

• Ferry Operations
• Move according to a well-known ferry route
• Periodically broadcast by ferry or conveyed by
  other out-of-band means
• Broadcast short range Hello messages periodically
• On reception of an Echo message from a node
• Exchange messages with the node

9
Node-Initiated MF - Operations 2/2

• Node Operations
• WORKING mode
• Move according to assigned task
• GO_TO_FERRY mode
• Determine by Trajectory control
• SEND/RECV mode
• Exchange messages with the ferry
• GO_TO_WORK mode
• Return to its location prior to the detour when
  completing message exchange or ferry has moved
  out of range
• Switch to SEND/RECV mode from other modes when
  nodes meet the ferry unintentionally without
  proactive movement

10
Node-Initiated MF - Node Trajectory 1/5

• Node Trajectory Control
• Balance between data delivery and performance
  degradation in assigned tasks
• To minimize message drops while reducing the
  negative impact of proactive movement
• Assumptions
• Time is divided into fixed-length slots
• All messages have same size and timeout value T

11
Node-Initiated MF - Node Trajectory 2/5

• Message Drops
• Occur when message time out buffer overflow
• Message drop rate

12
Node-Initiated MF - Node Trajectory 3/5
td
F
N

• Message Drops (cont.)
• Move to ferry when
• Ferry periodically broadcasts in Ferry_Status
  with message generation and drop rate to all nodes

a
(1)
13
Node-Initiated MF - Node Trajectory 4/5

• Working Time Percentage (WTP)
• Percentage of time a node is free to work on
  assigned tasks, Wi
• Move to ferry when
• Wi gt ?
• Node i modifies its trajectory only when
• (1) and (2) are both true

(2)

• ? predefined threshold

14
Node-Initiated MF - Node Trajectory 5/5

• Message Drop Rate
• Message timeout
• Regular node and message ferry
• Message timeout rate during time slot t
• a(t) mi(ta), ta t - T
• Buffer overflow
• Regular node
• Buffer overflow rate during time slot t
• b(t) mi(tb),
• Message drop rate

drop
drop

• Bi node buffer size
• ? length of a time slot

15
Ferry-Initiated MF Overview 1/2

• Message Delivery in Ferry-Initiated MF

Ferry route
Ferry Location
New route
Service_Request (Nodes Location Info.)
Location_Update (New Location)
Send/recv msg.
16
Ferry-Initiated MF Overview 2/2

• Assumption
• Ferry moves faster than nodes
• Nodes are equipped with a long range radio for
  control messages
• Nodes long range radio lt ferrys long range radio

17
Ferry-Initiated MF - Operations 1/2

• Node Operations
• DISASSOCIATED mode
• No requested service from ferry
• Send Service_Request to the ferry
• Node notification control mechanism
• ASSOCIATED mode
• Send Location_Update to notify the ferry of
  nodes new location
• On reception of a Hello message from the ferry,
  exchange messages with the ferry
• In both mode, nodes can exchange messages with
  the ferry when nodes meet the ferry
  unintentionally

18
Ferry-Initiated MF - Operations 2/2

• Ferry Operations
• IDLE mode
• Follow a specific default route
• Periodically broadcast location info. to nodes
  via long rage radio
• WORKING mode
• After reception of Service_Request from a node
• Compute new ferry route whenever receiving
  Service_Request and Location_Update
• Ferry trajectory control mechanism
• On reception of an Echo message from a node,
  exchange messages with the node
• In both mode, the ferry can exchange messages
  with a node when ferry meets the node
  unintentionally

19
Ferry-Initiated MF Node Notification 1/3

• Node Notification Control
• To control the transmission of notification
  messages while reducing message drops and energy
  consumption
• Notification msg. Service_Request,
  Location_Update

20
Ferry-Initiated MF Node Notification 2/3

• Service_Request message
• Message drops
• Ferry location
• df lt
• df distance from a node to the ferry
• system parameter, lt Rl )
• Energy consumption
• vi lt
• vi notification message rate (NMR)
• Average number of notification messages
  sent per second
• predefined threshold
• Sending Service_Request message only when (1),
  (3) and (4) are true

(1)
?
(3)
?
?
?
(4)
?
21
Ferry-Initiated MF Node Notification 3/3
F

• Location_Update message
• Ferry location
• df lt Rl dn gt Rs
• dn nodes distance to the location it reported
  to the ferry
• Rs transmission range of nodes short range
  radio
• Energy consumption
• vi lt
• Sending Location_Update message only when
• (4) and (5) are both true

Location_Update
Rs
N
dn
(5)
?
(4)
22
Ferry-Initiated MF - Ferry Trajectory 1/3

• Default Ferry Route
• To maximize a chance to meet nodes at every
  location
• Area is divided into a grid of square cells and
  the ferry scan through the cells in a row-by-row
  order

Deployment area
F
Default ferry route
Rl
N
Rl transmission range of nodes long
range radio
23
Ferry-Initiated MF - Ferry Trajectory 2/3

• Ferry Trajectory Control
• To decide the trajectory to meet nodes with the
  goal of minimizing message drops
• Ferry route problem
• Finding the route that minimizes DP

• node is own message drop rate
  during time slot t
• drop rate in the ferry for
  destination i during time slot t
• t0 current time slot
• si latency for node i
• k number of requesting nodes

24
Ferry-Initiated MF - Ferry Trajectory 3/3

• Two heuristics
• Nearest Neighbor (NN)
• Ferry always visits the closest node
• Traffic-aware (TA)
• Ferry tries to minimize the expected message
  drops
• 2H-opt heuristic of traveling salesperson
  problem (TSP)
• Ferry might miss the node!
• Ferry assumes that it has finished the visit with
  the node and recomputes its route to meet with
  remaining nodes

25
Performance Evaluation 1/5

• Methodology
• ns simulator
• Communication range
• Short range radio
• 802.11 DCF as MAC layer
• 250m transmission range and 0.282W transmit power
• Long range radio
• Simplified model of no loss or delay
• Transmission power for distance d is proportional
  to dk (k 4)
• Nodes
• 40 nodes on 5000m x 5000m area
• 25 source destination nodes are randomly chosen
  every 20 sec.
• Movement of random waypoint model
• Maximum speed 5m/s and pause time 50 sec.
• Buffer size 400 messages
• For FIMF, long range radio 500kbps

26
Performance Evaluation 2/5

• Ferry
• Speed 15m/s
• Default route is a rectangle with (1250, 1250)
  and (3750, 3750)
• Messages
• 500 byte size msg. and timeout 8000 sec.
• Epidemic routing vs. MF
• Default parameter settings

27
Performance Evaluation 3/5

• Impact of Node Buffer Size

28
Performance Evaluation 4/5

• Impact of Node Mobility
• Random way point (RW)
• Randomly picked
• destination
• Limited random (LRW)
• Movement within
• 400x400 area
• Area based (AB)
• 10 nodes moving
• according to RW
• Other nodes LRW

29
Performance Evaluation 5/5

• Impact of transmission range on FIMF

30
Conclusion

• Efficient Data Delivery in Sparse Mobile Ad Hoc
  Networks
• Message ferries exploitation of non-randomness
  to help deliver data
• By using ferry, source can send messages to
  destination even there is no end-to-end path
• Two variation of MF scheme
• Node-Initiated MF (NIMF)
• Ferry-Initiated MF (FIMF)
• Improve date delivery and energy efficiency as
  compared to flooding-style routing (Epidemic
  routing)