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Cooperative Communication. Xu Jiaming. Outline. Introduction Cooperative Routing Power and Delay trade-off in Cooperative Networks Conclusion. Introduction. Two fundamental aspects of Wireless Networks multipath fading Interference. Multipath fading. Time diversity
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Cooperative Communication Xu Jiaming
Outline • Introduction • Cooperative Routing • Power and Delay trade-off in Cooperative Networks • Conclusion
Introduction • Two fundamental aspects of Wireless Networks • multipath fading • Interference
Multipath fading • Time diversity Coding and Interleaving • Frequency diversity CDMA, OFDM • Spatial diversity MISO, SIMO, MIMO
Interference • TDMA Graph Coloring • Contention-based mechanisms Aloha, CSMA, etc • CDMA Multiuser Detection (SIC)
Summary Building better bit pipes Allocating bit pipes wisely Can we exploit the interference? Opportunistic Communication Cross-layer Wireless Resource Allocation
Can we exploit the interference? • What is the basic characteristic of wireless medium which causes the interference? • Cooperative communication • Cooperative diversity
Summary Building better bit pipes Allocating bit pipes wisely Opportunistic Communication Cooperative Communication Cooperative Networks Cross-layer Wireless Resource Allocation
Cooperative Routing • Cooperative communication is a cross-layer issues. • Cooperative Routing • Reduce power consumption • Reduce Delay
What we learn? • Power and Delay trade-off in Wireless Networks • Transmit the information to nodes far away • low delay but high power consumption • Transmit the information to nearby nodes • High delay but low power consumption • Transmitter makes a choice according to current channel state and buffer occupancy.
Power and Delay Tradeoff Curve Power Time Savings Non-cooperative Cooperative Energy Savings Delay
Conclusion • Cooperative Communication. • Research Trends • Coded-based Cooperation • Capacity of Cooperative networks Relay S D relay
Coded Cooperation • BC mode • Relay can decode • Destination may not • MAC mode • Relay re-encodes/transmits • Source transmits • New information • Repeats previous information • Destination decodes correlation
Modeling and Mathematics Mathematical Heavy We Capacity Modeling Mathematical Low New Capacity
Cooperative Routing • Cooperative communication is a cross-layer issues. • Cooperative Routing in static wireless networks. • Information is routed from s to d in a sequence of time slots • Each time slot • Broadcasting mode • Cooperation mode • Multistage decision problem
Cooperation Graph • reliable set of nodes that have information at kth stage • set of nodes that will be added to reliable set in the next transmission
Cooperative Routing benefits • Restrict the cooperation to nodes along the optimal non-cooperative route. • Energy savings
Alternative view toward Cooperative Routing • Cooperative communication increases the transmission range.