Survey of Wireless Network-on-Chip Systems Master’s Project Defense Xi Li

1. Report Advisor: Dr. Vishwani D. Agrawal Report Committee: Dr. Shiwen Mao and Dr. JitendraTugnait Department of Electrical and Computer Engineering Auburn University, AL 36849 USA Survey of Wireless Network-on-Chip SystemsMaster’s Project DefenseXi Li Xi's M.E.E Presentation

2. Outline ※ Background ※ Problem Statement ※ General Solution ※ Contribution - Experimental Results and Analysis Latency vs. Injection Rate Latency vs. Number of Virtual Channels ※ Conclusion Xi's M.E.E Presentation

3. Background Xi's M.E.E Presentation

4. ※ Network-on-Chip (NoC) is an approach to designing the communication subsystem between IP cores on a single chip, modules are interconnected via switches (routers) ※ Size: mm-scale ※ Numbers of processors: dozens of or even hundreds of ※ Communication method:“Point-to-point” and “packet-based (usually in flit)” ※ Layered protocol (MAC layer, network layer) ※ Modules’ structures should be as simple as possible ※ Variety kinds of topologies are used in NoC Xi's M.E.E Presentation

5. A 4 by 4 regular mesh NoC topology Xi's M.E.E Presentation

6. Problem Statement Xi's M.E.E Presentation

7. ※ High latency and power consumption will be introduced due to 1) the multi-hop in the communication path between two nodes and 2) high injection rate. ※ More nodes in a chip, more hops and higher injection rate will be in the communication. Many hops, high injection rate, and results a high latency Xi's M.E.E Presentation

8. General Solutions Xi's M.E.E Presentation

9. ※ Wireless link is introduced – reduce the number of hops in the path ※ Some outstanding transmission ways: UWB, mm-wave, CNT Xi's M.E.E Presentation

10. ※ Pure Wireless vs. Hybrid Wireless NoC system • Pure: All nodes are fully connected via wireless • Limited wireless source • Limited transmission range • Therefore, hard to use in practice • Hybrid: Combination of wired and wireless • Reduce the number of hop • Alleviate latency • Therefore, always used Xi's M.E.E Presentation

11. ※ Structure※ Wireless insertion※ Routing scheme and communication protocol Xi's M.E.E Presentation

12. ※ Structure of Hybrid Wireless NoC system: Hierarchical • Bottom level: nodes form to a cluster via wired link • Top level: some clusters are connected by wireless (sometimes, clusters in neighbor are still connected by wired) Structure of hybrid wireless NoC Xi's M.E.E Presentation

13. ※ Wireless insertion:Using SA (simulated annealing) to get the optimal configuration – the placement of the wireless links ? ? ? ? Xi's M.E.E Presentation

14. ※ Routing scheme and communication protocol • Should be as simple as possible • Routing schemes’ examples: Location-based (LBR), dimension-ordered, path length-based and some other adopting router scheme • Communication protocol: multi-channel protocol (combination of TDM and FDM) • Other used communication schemes: pulse position modulation, biphase modulation, on-off key modulation… Xi's M.E.E Presentation

15. Contribution Xi's M.E.E Presentation

16. ※ Experiment • In this section, performance of both traditional NoC (wired) and wireless NoC will be simulated; then, a comparison between them will me make. • Some parameters: • injection rate: bit/cycle per node • latency: cycle • virtual channel Xi's M.E.E Presentation

17. ※ Latency vs. Injection Rate (wired) 8 by 8 regular mesh: Xi's M.E.E Presentation

18. ※ Latency vs. Injection Rate (wired) • In order to reduce the distance between two nodes in wired communication, we can increase the concentration of the network. • Concentration stands for the number of nodes that share a single router. E.g. concentration 4 means a router is shared by 4 nodes. Xi's M.E.E Presentation

19. ※ Latency vs. Injection Rate (wired) A 4 by 4 cmesh NoC topology Xi's M.E.E Presentation

20. A 4 by 4 regular mesh NoC topology Xi's M.E.E Presentation

21. ※ Latency vs. Injection Rate (wired) • therefore, in cmesh topology, the average distance • can reduce. 8 by 8 cmesh hop 8 by 8 regular mesh hop Xi's M.E.E Presentation

22. ※ Latency vs. Injection Rate (wired) 8 by 8 cmesh: Xi's M.E.E Presentation

23. ※ Latency vs. Injection Rate (wired) • However, since every router has more work to do, latency is still introduced • Therefore, there is a trade-off between the distance and number of nodes per router if we use wired link. Comparison between8 by 8 regular mesh and cmesh: Xi's M.E.E Presentation

24. ※ Latency vs. Injection Rate (wireless) • Therefore, wireless NoC is needed • Here, we use a kind of topology to simulate wireless NoC system – flattened butterfly topology Xi's M.E.E Presentation

25. ※ Latency vs. Injection Rate (wireless) A 4 by 4 flattened butterfly NoC topology Xi's M.E.E Presentation

26. ※ Latency vs. Injection Rate (wireless) 256 nodes 64 nodes Xi's M.E.E Presentation

27. ※ Latency vs. Number of Virtual Channels (wired) 8 by 8 regular mesh Xi's M.E.E Presentation

28. ※ Latency vs. Number of Virtual Channels (wireless) Wireless NoC (64 nodes) Xi's M.E.E Presentation

29. ※ Comparison between wired and wireless Xi's M.E.E Presentation

30. Conclusion Xi's M.E.E Presentation

31. ※ Conclusion • Comparison with traditional wired NoC, wireless NoC has a great improvement in performance (latency, maximum injection rate, so that the throughput) • In wireless NoC, before a specific level of injection rate, the latency increment is tiny. • Virtual channel plays a more important role in wireless NoC than in traditional NoC. Xi's M.E.E Presentation

32. ※ Future work • Devices’ manufactory • Topology and communication protocol • Other aspect: fault tolerant and reconfiguration Xi's M.E.E Presentation

33. Thank You Xi's M.E.E Presentation

34. Question? Xi's M.E.E Presentation