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SGF: A State-Free Gradient-Based Forwarding Protocol for Wireless Sensor Network. Pei Huang, Xi Yang, Yongdong Tan Southwest Jiaotong University Presented by Ming-Tsung Hsu. Outline. Introduction Related Work The SGF Protocol Simulation Results Conclusion. Introduction. - PowerPoint PPT Presentation
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SGF: A State-Free Gradient-Based
Forwarding Protocol for Wireless Sensor
Network
Pei Huang, Xi Yang, Yongdong TanSouthwest Jiaotong University
Presented by Ming-Tsung Hsu
Outline Introduction Related Work The SGF Protocol Simulation Results Conclusion
IntroductionTypes of routing protocols Table-Driven
Maintenance cost for topology changing On-Demand
MANET Scalability and robustness
Position-Based State-free GPS for geographic information
Gradient-Based State-free Low-cost
Introduction (cont’d) State-free Gradient-Based Forwarding
(SGF) protocol sink broadcasts an ADV message to set up the
cost field Source node broadcasts an Open RTS (ORTS) Neighbors whose cost is smaller than that of
the sender will participate in the competition for becoming the next hop
The best one will first respond to the sender with Competing CTS (CCTS)
Related Work Position-Based
Beacon-based the sender must have its own position, the position of its a
ll neighbors (through beaconing) Dynamic Forwarding Delay
Gradient-Based “Gradient” means a direction state, set towards t
he neighboring nodes through which a destined sink is reached
GRAB (GRAdient Broadcast) uses the energy cost as the gradient
The SGF Protocol Cost Field Concept State-Free Minimum-Cost Unicast Setting Dynamic Response Wait Timer Recovery
Cost Field Concept Cost Field
The minimum energy overhead needed to forward a packet from itself to the sink along the optimal path
Each node sets its cost to the sink as ∞ Sink broadcasts an ADV message containing its
own cost of 0 Upon hearing an ADV message from node N,
node M has a path with cost LN + CN,M LN is the cost of node N, and CN,M is the cost form N to M
If the new cost is smaller than its current cost LM, LM = LN +CN,M Broadcasts an ADV message with its new cost
State-Free Minimum-Cost Unicast An ORTS is broadcasted by the node M
Carries the minimum cost of the node to the sink Neighboring node
sets a CCTS Response timer only if the cost at this node is smaller than that of the sender
The node (R) that assigns the shortest time value will first respond with Competing CTS (CCTS) Other neighbors sensing the signal will cancel their
timers
S
K
N
R PM
Sink
State-Free Minimum-Cost Unicast (cont’d) After received a valid CCTS, the sender M will
extract the responder cost from the CCTS and reset its cost
Subsequent packets (DATA, ACK) are in accordance with 802.11 DCF semantics (DATAACK)
S
K
N
R PM
Sink
Update LM
Setting Dynamic Response Wait Timer
WC,WE, WR are used to tune the weight of each parameter (In simulations, they are assigned 0.5, 0.4 and 0.1 respectively)
CMax denote the maximum cost of a single hop
Setting Dynamic Response Wait Timer (cont’d)
1. The transmission power?
2. Time out?
3. 802.11? (Data, Ack)?
Recovery - Retreat Mechanism N has received data from M N's ORTS timer expired if no response is received
Retransmit ORTS seven times The node sets its cost to infinity and goes to sleep
M will try to relay it because its local ID matches the value of lastID contained in the message header
If M cannot find another next hop Request all nodes whose minimum costs are derived from it to explore their
new next hop goes to sleep
The process will be performed till an upriver node (say S) finds a next hop (maybe K).
S
K
NP
MSink
ORTS 7 times
M Counting?
Simulation Results -Settings ns-2 Single source node and Single sink 1000x1000m 512 bytes per 10 seconds
