an adaptive tdma slot assignment protocol in ad hoc sensor networks akimitsu kanzaki, takahiro hara...
DESCRIPTION
3 Introduction Motivation E-ASAP prevents the excessive increase of unassigned slots By minimizing each node’s frame length.TRANSCRIPT
An Adaptive TDMA Slot Assignment Protocol
in Ad Hoc Sensor Networks
Akimitsu Kanzaki, Takahiro Hara and Shojiro NishioACM Symposium on Applied Computing, 2005
(ACM SAC’05)
2
Outline
Introduction Related Work
USAP(Unifying Slot Assignment Protocol) USAP-MA(USAP-Multiple Access) ASAP(Asaptive Slot Assignment Protocol)
E-ASAP (Extend ASAP) Simulation Results Conclusion
3
Introduction
Motivation E-ASAP prevents the excessive increase of
unassigned slots By minimizing each node’s frame length.
4
Related Work- USAP(Unifying Slot Assignment Protocol)MILCOM’96
N frames=Cycle
M slots
The first slot in each frame is reserved to transmit control packet
5
Related Work- USAP(Unifying Slot Assignment Protocol) When a new node joins the network
It firstly collects NMOPs by listening the network channel for a cycle
It recognizes the slot assignments in its contention area.
Disadvantage of USAP N(frame) and M(slot) should be large enough The channel utilization usually becomes low
Due to a large number of unassigned slots.
MILCOM’96
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Related Work- USAP-MA(USAP-Multiple Access)
MILCOM’99
Frame Length= 8
Frame Length= 4
Frame Length= 8
Frame Length= 4
Double frame length
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Related Work- USAP-MA(USAP-Multiple Access)
Advantage of USAP-MA USAP-MA improves the channel utilization
By reducing unassigned slots with consideration of the number of nodes and the network topology.
Disadvantage of USAP-MA The channel utilization is still low
Unassigned slots in the later part if frame when frame length is double
USAP-MA does not offer When and how to change the frame length How to select a slot assigned to a new node
MILCOM’99
Frame Length= 8
Frame Length= 4
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Related Work- ASAP(Asaptive Slot Assignment Protocol) Set the frame length for a new node
Base on the number of nodes in its contention area
Minimize the number of unassigned slots to improve the channel utilization
Packet Format Transmit mode
Data packet (DAT) Contain the information on the frame length and slots
assigned to the sender Maximum frame length of the sender and its neighbor
AINA 2003
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Related Work- ASAP(Asaptive Slot Assignment Protocol) Packet Format
Control mode Request packet (REQ)
A requests the information on the frame length and assigned slots of all nodes in its contention area.
Information packet (INF) Contain the information on the frame length of B and slots
assigned to the sender and C Suggestion packet (SUG)
A sends to its neighbors to announce the frame length and its assigned slot.
Reply packet (REP) B transmits to confirm of receiving SUG
AINA 2003
A
CB
New node
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REQ
INF
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Related Work- ASAP(Asaptive Slot Assignment Protocol) Packet Format
Control mode Request packet (REQ)
A requests the information on the frame length and assigned slots of all nodes in its contention area.
Information packet (INF) Contain the information on the frame length of B and slots
assigned to the sender and C Suggestion packet (SUG)
A sends to its neighbors to announce the frame length and its assigned slot.
Reply packet (REP) B transmits to confirm of receiving SUG
AINA 2003
A
CB
New node
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SUG
REP
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Related Work- ASAP(Asaptive Slot Assignment Protocol) Setting the frame length and grasping slot
assignment After collecting INFs from all neighbors, new node
sets its frame length. New node adopts the maximum frame length among all
nodes in the contention area
AINA 2003
Frame Length= 8
Frame Length= 4
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Related Work- ASAP(Asaptive Slot Assignment Protocol) Selecting an assigned slot Getting an unassigned slot (GU)
Releasing multiple assigned slots (RMA)
Doubling the frame (DF)
1 a2 b3 d4 c5 a6 b7 e
Double
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Related Work- ASAP(Asaptive Slot Assignment Protocol) Disadvantage of ASAP
Frame length in the whole network tends to increase Frame length of a new node is set as the maximum
frame length among nodes in its contention area.
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E-ASAP (Extend ASAP)
Each node assigns a slot to itself in the frame of the minimum length
Frame Length= 8
Frame Length= 4
hc
f
d
g
i
1j
5
6
4
2
1
3
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E-ASAP (Extend ASAP)
Information held by node h in E-ASAP
h 1 hop 2 hop
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E-ASAP (Extend ASAP)-Slot AssignmentSlot Assignment
Steps: New node collects INFs transmitted by its neighbors
Try to assign a slot to itself in the minimum frame length of 4 slots
New node searches a slot Getting an unassigned slot (GU)
If the first slot is not assigned to any neighbors, and some unassigned slots are found.
Releasing multiple assigned slots (RMA) If the first slot is not assigned to any neighbors and all the other slots a
re assigned to other nodes in its contention area Doubling the frame (DF)
If no slot is available in the current frame length, new node doubles the frame and tries again to assign a slot
RMA and GU
a b
Unassigned slot
a b cd a b e
Multiple slots
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E-ASAP (Extend ASAP)
New node
1/83/4
3/4
0/4
2/4
1/4
a
bc d
eDoubleDouble
2/8 , 6/8
RMARMA
b
New nodeNew nodeGUGU
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E-ASAP (Extend ASAP)- Detecting of conflictDetecting of conflict
a
b
c
d
e
f g
3
1
2
3 5
4
4New node
conflict
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E-ASAP (Extend ASAP)- Solution to solve conflictSolution to solve conflict
Deleting a conflicting slot
Divide the assignment
Delete slot 3 of a
Divide slots
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Frame Length= 8
E-ASAP (Extend ASAP)-Solution to solve conflictSolution to solve conflict
Doubling the frame and dividing the assignment
Frame Length= 8Frame Length= 4 Double
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E-ASAP (Extend ASAP)- Releasing Slot AssignmentReleasing Slot Assignment
When a node exits from the network It releases slots assigned to itself, and its neighbors
detect the exit After reconfiguring the slot assignment information
The neighbors of the exiting node temporarily release their own assigned slots
And search for slots that can be assigned to themselves by Getting an unassigned slot (GU)
If a neighbor finds a slot which can assign to itself in the shorter frame than the current one It updates its own assignment
Each neighbor updates its own assignment transmits in its contention area.
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E-ASAP (Extend ASAP)-SimulationSimulation
Simulation Environment Each node in the network does not move. Initially 2 nodes, and this number increases one
by one until 50 nodes are present. The number of nodes then decreases one by one in the
reverse order ASAP and E-ASAP
New node listens to the channel for 128 slots for collecting information
USAP: frame length 50 slots
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E-ASAP (Extend ASAP)-SimulationSimulation
Average channel utilization
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E-ASAP (Extend ASAP)-SimulationSimulation
Control traffic
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E-ASAP (Extend ASAP)-SimulationSimulation
Setting delay (control mode changes to transmit mode)
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E-ASAP (Extend ASAP)-ConclusionConclusion
E-ASAP is a TDMA slot assignment protocol To improve the channel utilization. To decreases the number of unassigned slots Efficiently assign slots to nodes
When a node appears and disappears from the network Future Work
To consider a frame format to accommodate the movement of nodes.
To extend E-ASAP to adapt the change of network environment Such as traffic load
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