Cooperative Communication

1
Cooperative Communication

• Xu Jiaming

2
Outline

• Introduction
• Cooperative Routing
• Power and Delay trade-off in Cooperative Networks
• Conclusion

3
Introduction

• Two fundamental aspects of Wireless Networks
• multipath fading
• Interference

4
Multipath fading

• Time diversity
• Coding and Interleaving
• Frequency diversity
• CDMA, OFDM
• Spatial diversity
• MISO, SIMO, MIMO

5
Interference

• TDMA
• Graph Coloring
• Contention-based mechanisms
• Aloha, CSMA, etc
• CDMA
• Multiuser Detection (SIC)

6
Summary
Building better bit pipes
Allocating bit pipes wisely
Can we exploit the interference?
Opportunistic Communication
Cross-layer Wireless Resource Allocation
7
Can we exploit the interference?

• What is the basic characteristic of wireless
  medium which causes the interference?
• Cooperative communication
• Cooperative diversity

8
Summary
Building better bit pipes
Allocating bit pipes wisely
Opportunistic Communication
Cooperative Communication
Cooperative Networks
Cross-layer Wireless Resource Allocation
9
Cooperative Routing

• Cooperative communication is a cross-layer
  issues.
• Cooperative Routing
• Reduce power consumption
• Reduce Delay

10
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.

11
Power and Delay Tradeoff Curve
Power
Time Savings
Non-cooperative
Cooperative
Energy Savings
Delay
12
Conclusion

• Cooperative Communication.
• Research Trends
• Coded-based Cooperation
• Capacity of Cooperative networks

Relay
D
S
relay
13
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
14
Modeling and Mathematics
Mathematical Heavy
We
Capacity
Modeling
Mathematical Low
New Capacity
15
Thank You!
16
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

17
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

18
Cooperative Routing benefits

• Restrict the cooperation to nodes along the
  optimal non-cooperative route.
• Energy savings

19
Alternative view toward Cooperative Routing

• Cooperative communication increases the
  transmission range.