A new Cooperative Strategy for Deafness Prevention in Directional Ad Hoc Networks
Andrea Munari, Francesco Rossetto, and Michele Zorzi
University of Padova, Italy
IEEE ICC 2007
Outline
Introduction Related Work Antenna Model Cooperative MAC (CMAC) Simulation Conclusions
Introduction
Wireless ad hoc networks are radio-based systems that do not need an access point or base station to operate.
When antenna arrays are employed. Directional transmissions enable a spatial reuse of the channel.
Introduction
Deafness A terminal is said to be deaf if it does not
answer an RTS message addressed to it.
A BRTS
Introduction
Deafness in directional RTS
A
D
E
B
C
F
I can’t hear anything.
Introduction
In Omni-directional RTS
A
D
E
B
C
F
I can’t send to B.
I can’t send to B.
I can’t send to B.
I can’t send to B,C.
I can’t send to B,C,D.
Related Work
Circular RTS/CTS Mechanism (CRCM) RTS and CTS packets are broadcast omni-direc
tionally by means of a sequence of directional transmissions.
A
B RTS
CTS
DATA
Motivation There is still some deafness problems in
directional transmissions.
A
D
E
B
C
F
I can’t hear anything.
I can’t send to A.
I can’t send to A.
I can’t send to A,B.
I can’t send to B,C.I don’t hear
anything.
Goal
CMAC proposes a cooperation scheme among nodes, trying to inform terminals that go back to idle mode after a transmission about communications that have started in the meantime.
Antenna Model
Each node can decode more than one packets simultaneously, provided that they come from different directions.
Each node can’t receive anything during the transmission.
Cooperative MAC (CMAC)
CMAC employs three solutions to let the nodes have a fair image of their neighbors’ state Circular delivery of RTS and CTS. Multiple Receptions. Cooperation among nodes.
Cooperative MAC
Cooperation among nodes The main cause of deafness is a mistaken idea o
f the network activity. This mechanism helps the nodes to know the ne
w links built during the transmission. Each node maintains an internal table, called C
ommunication Register (CR), where all the known ongoing communications are reported.
Cooperative MAC
A
D
E
B
C
F
Node id Time Left
A 5
Node id Time Left
A 4
B 10
Node id Time Left
B 10Node id Time Left
B 6
Node id Time Left
A 5
I should be update A’CR.
Node id Time Left
B 6Node id Time Left
A 4
Node id Time Left
B 6
Collaboration frame
Simulation
Simulator OPNET (version 11.5)
Parameters
Nodes 10 (in single hop)
Area 1500m x 1000m
Antennas 8 antennas
Data rate 1 Mbits/s
Traffic rate Poison traffic at nominal rates of 8,16,25,50,100,150 packets/s
Packet sizes
RTS 240 bits
CTS 240 bits
Collaboration 120 bits
Data 10240 bits
ACK 120 bits
CRCM MUD L-CMAC B-CMAC
Circular delivery of RTS/CTS O O O O
Multiple receptions O O O
Cooperation among nodes O O
The overhead of collaboration frames
O
Interference is generated by collaboration frames
O
The size of collaboration frames
120 bits (fixed)
Optimal
The low bound of CMAC
The upper bound of CMAC
MultiUser Detection
Simulation
Link failures vs. load (10 nodes)
Link Failures=
RTS theof All
RTSfault totalThe
Simulation
Power consumption vs. load (10 nodes)
Simulation
Throughput vs. effective load (10 nodes)
Throughput=
ratebit * timeSimulation
bitssent ly Successful
Load=
ratebit * timeSimulation
bitssent Totally
Conclusion
The cooperation in this paper is used for telling the nodes correct information.
The impact of our solutions on multihop networks and routing is an interesting problem and is part of our future work.
Thank you~
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