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Tiny Ad hoc Routing Protocol (TARP)
Ashikur Rahman and Pawel Gburzynski
Department of Computing ScienceUniversity of Alberta
Email: ashikur@cs.ualberta.ca
Features & Assumptions
• Controlled Flooding as a routing scheme
• Simple• Flexible• Low cost• No control packets• Some tunable parameters• Fixed communication range• Bi-directional flows
Protocol in Brief
• Reactive Broadcast-based • Converge to a narrow strip of nodes along the
shortest path
S D
Two controlling rules
• Duplicate Discard (DD) rule
Retransmission Count
Source ID
Sequence noSession ID
Destination ID
knsDS ,,,,• Packet signature
• Packet Header,
Packet signature + r + h + some more fields
• Packet signatures are stored in DD Cache.
First Rule (Cont.)
hrtT avgr
• Expiry time of an entry, Tr
hrtFT avgcr • Average transmission time, tavg
taavgaavg tCtCt )1(
Initially
C
Lctavg
Second Rule
• Sub Optimal Path Discard (SPD) rule
• Has it’s own (SPD) cache
• Each entry is a tuple, dssddksk CChhDS ,,,,,
Discard Counters
Hop count between <s,k>
Hop count between <d,k>
• Target Avoid forwarding via sub- optimal path
Second Rule (Cont.)
hSKhDK
hbS
K
D
bDKSKds hhhC • Number of Packets to be discarded by K,
bDKSKbds hhhmC
• mb is called mobility factor
• Value of mb indicates aggressiveness
Example: SPD Rule.
S
KL M
DZ
SPD Buffer at:
hb mb
D 0 0
S 0 0
SPD Cache at x:
hb mb hSX CDS hDX CSD
M 0 0 0 0 0 0
L 0 0 0 0 0 0
K 0 0 0 0 0 0
Z 0 0 0 0 0 0
Packet P1 from D to S
S
KL M
DZ
SPD Cache at x:
hb mb hSX CDS hDX CSD
M 0 0 0 0 1 0
L 0 0 0 0 2 0
K 0 0 0 0 3 0
Z 0 0 0 0 1 0
SPD Buffer at:
hb mb
D 0 0
S 2 1
Packet P2 from S to D
S
KL M
DZ
SPD Cache at x:
hb mb hSX CDS hDX CSD
M 2 1 3 2 1 0
L 2 1 2 2 2 0
K 2 1 1 2 3 0
Z 2 1 1 0 1 0
SPD Buffer at:
hb mb
D 2 1
S 2 1
Packet P3 from D to S
S
KL M
DZ
SPD Cache at x:
hb mb hSX CDS hDX CSD
M 2 1 3 2 1 2
L 2 1 2 2 2 2
K 2 1 1 2 3 2
Z 2 1 1 0 1 0
SPD Buffer at:
hb mb
D 2 1
S 2 1
Packet P4 from S to D
S
KL M
DZ
SPD Cache at x:
hb mb hSX CDS hDX CSD
M 2 1 3 2 1 2
L 2 1 2 2 2 2
K 2 1 1 2 3 2->1
Z 2 1 1 0 1 0
SPD Buffer at:
hb mb
D 2 1
S 2 1
Packet P5 from D to S
S
KL M
DZ
SPD Cache at x:
hb mb hSX CDS hDX CSD
M 2 1 3 2->1 1 2
L 2 1 2 2 2 2
K 2 1 1 2 3 1
Z 2 1 1 0 1 0
SPD Buffer at:
hb mb
D 2 1
S 2 1
Packet P6, P7
S
KL M
DZ
SPD Cache at x:
hb mb hSX CDS hDX CSD
M 2 1 3 0 1 2
L 2 1 2 2 2 2
K 2 1 1 2 3 0
Z 2 1 1 0 1 0
SPD Buffer at:
hb mb
D 2 1
S 2 1
Second Rule (Cont.)
• Can be best viewed as series of light bulbs.• Nodes on shortest path always turned on• Nodes on sub optimal path are periodically turned on/off• Frequency of turning on/off varies.
S D
Second Rule (Cont.)
• Lower value of mb will cause more flooding.
• Higher value of mb will narrow down the width of
the forwarding node strip.
bDKSKtbds hhhtdmC )(
Dynamic quantity
•The constant need not to be static
Experimental Result
Couple of MAC Issues
• Hidden Node Problem
A B C
• Four way handshake RTS/CTS/DATA/ACK ineffective.
• Does not even use two-way handshake DATA/ACK.
• Without feedback retransmission is impossible.
Fuzzy Acknowledgement
• Sender will reserve bandwidth for a duration of:– SIFS + ACK tx time
• Recipient of the packet will send ACK after SIFS• Thus Multiple recipients will be allowed to send ACK
almost at the same time.• Exactly 3 things can happen
– No activity – A valid ACK– A short period of burst activities
• Fuzzy ACK not vary reliable, merely gives a hint.
Sample Scenario
Cross Layer Interaction
• For Recipient MAC Should I send ACK?• For Sender MAC Should I retransmit?• Retransmission decision is done statistically:
• RF related to probability of lying on the optimal path
• If RF > RFthreshold retransmit.
)(
)()(
fwdSKD
ackSKD
SKD n
nRF
Effect of RFthreshold
Performance Improvement
Future Direction
• Solution to Hidden node problem yet to be
uncovered.• Incorporation of power consumption into heuristics
facilitating path identification.
Question/Comment
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