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Cooperative Wireless Networks Hamid Jafarkhani Director Center for Pervasive Communications

Explore the shift from point-to-point to many-to-many communications in wireless networks for seamless connectivity. Learn about cooperative strategies, relay networks, beamforming, and interference management technologies.

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Cooperative Wireless Networks Hamid Jafarkhani Director Center for Pervasive Communications

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  1. Cooperative Wireless Networks Hamid Jafarkhani Director Center for Pervasive Communications and Computing www.cpcc.uci.edu

  2. Center’s Focus and Goal CPCC was established in 2000 To facilitate research in emerging communications technologies To dramatically change the way people access and use information Need for ubiquitous communications to anywhere at anytime results in many challenges in Circuits/Systems Communications/Signal processing Networking Goal: Higher throughput and better connectivity 2

  3. Focus and Goal Need for ubiquitous communications to anywhere and any device at anytime to the internet to the cloud to home to PC, tablet to TV to car to your body Goal: Internet of things through wireless access 3

  4. Characteristics of Machine-to-Machine Net Very large number of nodes (Trillion ?) Sensor networks are used more often Body area networks are gaining more attention Self organized and autonomously operated Operating through different domains (wireless and wired) seamlessly Low latency Low power 4

  5. Mobile Video Traffic • The number of mobile devices exceeded the world’s population in 2012 • Machine-to-machine (M2M) modules will exceed the world’s population in 2016 (7.3 billions) • Mobile video traffic was 52% of the mobile traffic in 2011 (70% in 2016) • Mobile video traffic in 2016 will be 13 times the entire mobile traffic in 2011 • The top 1% of mobile data subscribers generated 24% mobile data traffic in 2011 (35% in 2016) 5

  6. Landscape in 2025 • Billions of (trillion?) devices • Today: more than a billion wireless subscribers • 100 times growth in mobile traffic • more users & more traffic per user • 10 times increase in device density • 10 times less power consumption (Bits/Joule) • Today, Internet/Telecom infrastructure consumes 3% of the world’s energy • Same connectivity everywhere (edge vs center) 6

  7. Need for a Paradigm Shift • Current wireless networks include many users and many data transmitted simultaneously, but we allocate independent resources through routing, scheduling, … to send A’s message to B without interference • What if we “literally” allow simultaneous transmission? Point-to-Point  Many-to-Many Competition  Cooperation 7

  8. Many-to-Many 8

  9. Many-to-Many 9

  10. Technologies • Interference Management • Interference cancellation • Interference alignment • Cognitive Communications • Massive MIMO • Context-Aware Networking • Cooperative Communications • Multiple base station transmission/reception • Relay networks • Virtual MIMO • Network coding 10

  11. Relay Networks 11

  12. Cooperative Strategies • Amplify and forward • Decode and forward • Coded cooperation • Compress/estimate and forward • Distributed space-time coding • Distributed beamforming 12

  13. Comparing MIMO and Distributed Beamforming • Differences: • Antennas can share power in MIMO (total power constraint). • Antennas know the transmitted signals perfectly in MIMO. • Consequences: • Individual (separate) power constraints and a non-convex optimization problem. • Distributed solutions. An analytical closed-form solution exists despite the non-convex nature of the problem. 13

  14. Relay Networks withQuantized Feedback 14

  15. Distributed Beamforming with Limited Feedback • The problem can be modeled as a source coding problem. • The solution is a vector quantizer. • We need to design the optimal codebook for the vector quantizer. 15

  16. Simulation Results 16

  17. Beamforming in Relay-Interference Networks • So far, the main goal of cooperation has been the delivery of a point-to-point message. • What if we want to shift the paradigm to a many-to-many scenario? 17

  18. Beamforming in Relay-Interference Networks 18

  19. CSI Knowledge 19

  20. Summary • Traditional diversity definitions are not good enough to compare the asymptotic reliability of different cooperative communication systems. • Despite interference, multi-user relay networks can provide the same diversity as single-user networks. • In terms of diversity, relay selection is an optimal codebook using quantized feedback information. • Very low-rate CSI quantizers exist that achieve full diversity asymptotically with zero feedback rate. 20

  21. Conclusions • There is still need for ubiquitous communications to anywhere and any device at anytime • There is a paradigm shift from point-to-point communication to many-to-many communication • There is a paradigm shift from competition to cooperation 21

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