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. 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 with Quantized 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