A Cooperative Diversity- Based Robust MAC Protocol in wireless Ad Hoc Networks Sangman Moh, Chansu...
Transcript of A Cooperative Diversity- Based Robust MAC Protocol in wireless Ad Hoc Networks Sangman Moh, Chansu...
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A Cooperative Diversity-Based Robust
MAC Protocol in wireless Ad Hoc
NetworksSangman Moh, Chansu Yu
Chosun University, Cleveland State UniversityKorea, Cleveland
IEEE TPDS, March 2011
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OutlineO IntroductionO Background O Cooperative Diversity MACO Performance EvaluationO Conclusion and Future Work
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IntroductionO In wireless ad hoc networks, signal fading
and interference are two major obstacles in realizing their full potential in delivering signals.
O Cooperation among the nodes is considered critically important in addressing these problems.
O It may be difficult to maximize the performance unless nodes are coordinated to cooperate at lower levels.O MAC- and PHY- layer
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Introduction O Recently, some researches in developing
cooperative MAC algorithms O Path-centric medium access O MAC-layer packet relaying
O is determined in a proactive mannerO is used to forward frames at higher bit ratesO but not enhance the communication
reliability, especially in interference-rich environment
O Cooperative communicationO enhance the link reliability
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IntroductionO Cooperative communication exploits
diversity offered by multiple users, known as multiuser or cooperative diversity.
O It dramatically improves bit error rate (BER).O More reliable transmissionO Higher throughput
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Background
OCooperative DiversityOCooperative Diversity in
Wireless Ad Hoc Networks
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Cooperative DiversityO Two types of cooperative diversity
algorithmsO Repetition-based
O Amplify-and-forwardO Decode-and-forward
O Space-time-codedO Distributed space-time coding (DSTC)O Space-time coding (STC) (multiantenna
system)O Space-time block coding (STBC)
(multiantenna system)
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DSTC
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Cooperative Diversity in Wireless Ad Hoc NetworksO Azgin et al. proposed Cooperative
MAC (C-MAC) and the corresponding routing protocols for wireless ad hoc network. (GlobeCom 2005) O Relaying start (RS)O Relay acknowledgement (RA)O Relay broadcasting (RB)O Transmission start (TS)O RTS-CTS-RS-RA-RB-TS-ACK
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Cooperative Diversity MAC
O Overview
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A Simple Cooperative scheme
O The authors proposed in ICC 2007.O Based on DCF of the IEEE 802.11
standardO If a primary link is reliable enough to
successfully transmit frames, no cooperative transmission is enabled.
O If it fails, the sender retransmits the frame but cooperatively with its partnerO When to cooperate
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A case for simple scheme
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Problems of simple scheme
O Twice longer than that without cooperation
O An RTS failure can be due to collisions/interference from other nodes’ communication
O The RTS/CTS exchange effectively eliminates the problem associated with “the hidden terminals”.
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Cooperative Diversity MAC
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State transition diagrams
Sender
Receiver
Partner
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Partner Selection and Its Propagation
O Every node proactively selects its partner by monitoring or overhearing its neighbors with respect to link quality.
O Measure and record the link quality while receiving a frame
O The neighbor with the best link quality among all neighbors is chosen as its partner.
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Why choose the neighbor with the best link quality?O Three reasons behind this choice
O Communication between a node and its partner must be highly reliable.
O A partner with the best link quality is most probably the closest node.
O It ensures that the sender and the partner share the same communication environment so that they can make a consistent decision on cooperation.
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Performance Evaluation
O Using ns-2 simulatorO 50 mobile nodes move over a square area
of 300X1500 m2
O Each simulation runs for 900 seconds. O Source-destination pairs are randomly
selected.O Mobile nodes are assumed to move
randomly with the node speed of 0-5 m/secO Pause time between moves varies from 0
to 900 seconds.
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Performance Comparison
This is due to the complex interplay among MAC- and routing-layer protocols in MANET environment
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Overhead and cooperation efficiency
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Impact of environment noise
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Effect of network traffic on packet delivery ratio
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Conclusions and Future Work
O This paper proposed CD-MAC and discusses design issues and performance benefits in wireless ad hoc network.
O When a communication link is unreliable, a sender transmits its signal together with its partner delivering the signal more reliably.
O As a future work, exploiting cooperative diversity based on multichannel interfaces will be investigated.