Download - Cooperative Communication
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 diversityCoding and Interleaving
• Frequency diversityCDMA, OFDM
• Spatial diversityMISO, SIMO, MIMO
Interference
• TDMAGraph Coloring
• Contention-based mechanismsAloha, CSMA, etc
• CDMAMultiuser Detection (SIC)
Summary
Building better bit pipes Allocating bit pipes wisely
Opportunistic Communication
Can we exploit the interference?
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
Cross-layer Wireless Resource Allocation
Cooperative Communication
Cooperative Networks
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
Pow
er
Delay
Non-cooperative
Cooperative
Energy Savings
Time Savings
Conclusion
• Cooperative Communication.• Research Trends
• Coded-based Cooperation • Capacity of Cooperative networks
D
Relay
S 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 decodescorrelation
Modeling and Mathematics
We Capacity
New Capacity
Mathematical Heavy
ModelingMathematical Low
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
kS
kU
1k k kS S U
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.