Xiaofei Wang Taekyoung Kwon, Yanghee Choi MMLAB, Seoul National University 2008.01.15

1. Xiaofei Wang Taekyoung Kwon, YangheeChoi MMLAB, Seoul National University 2008.01.15 Exploring Spectrum-aware On-demand Multi-path Routing in Multi-radio Multi-hop Cognitive Radio Networks Multimedia and Mobile Communication Laboratory

2. Outline • Introduction to CRN • Multi-radio Multi-path Routing in CRN • Evaluation • Conclusion Multimedia and Mobile Communication Laboratory

3. Outline • Introduction to CRN • Multi-radio Multi-path Routing in CRN • Evaluation • Conclusion Multimedia and Mobile Communication Laboratory

4. 1. Introduction to CRN • Cognitive Radio Network • Dynamic spectrum access • Opportunistically utilize spectrum resources • Active monitoring, tuning, working Multimedia and Mobile Communication Laboratory

5. Primary Users (PU), Secondary Users (SU) • PU can start transmission anytime • SU has to use bands occupied by no PU Art of SU’s life in CRN : Jump and fill in the blanks! Multimedia and Mobile Communication Laboratory

6. Outline • Introduction to CRN • Multi-radio Multi-path Routing in CRN • Evaluation • Conclusion Multimedia and Mobile Communication Laboratory

7. 2. Multi-radio Multi-path • Everything becomes difficult in “multi-hop” • No one knows what happens 1-hop away! • Much tougher in CRN B C A D E Multimedia and Mobile Communication Laboratory

8. Fundamental issues in multi-hop CRN • Route Connectivity • Achievable End-to-end Throughput • PU’s insertion and SU’s recovery • Let’s us multi-radio multi-path strategy • To provide higher probability of route survival • To achieve times of end-to-end throughput • “Spectrum-wise disjoint paths” • To avoid intra-path & inter-path interference Multimedia and Mobile Communication Laboratory

9. Multiple Cognitive Radios • 1 for control signaling, M for data traffic • “Share” mode • “Switch” mode • 1 + N bands, N ≥ M • Multiple Paths • Split transmission manner • Duplicated transmission manner Multimedia and Mobile Communication Laboratory

10. Multi-path in Multi-radio Multi-hop CRN Multimedia and Mobile Communication Laboratory

11. Spectrum Pool • All parameters of licensed/unlicensed bands • Radio and Band Usage Table (RBT) • B: Several available bands • I: Number of flows that are using this band in this SU • N: Number of flows that are using this band within 1- hop neighbors • R: Which radio is using this band in this SU • “X” will be used to indicate PU occupation • Periodical exchange of hello message Multimedia and Mobile Communication Laboratory

12. A Multi-radio Multi-hop CRN Example • Existing SU flows: • Current PU traffics: • P1 : b1 • P2 : b4 • P3 : b5 Multimedia and Mobile Communication Laboratory

13. Route Discovery (DSR-like) • Attach its own RBT into the RREQ • New RREQ_ID or old RREQ_ID but with hop count ≤ previous one  rebroadcast (multipath) A B RREQ with RBTS RREQ with RBTS, A, B RREQ with RBTS, A S D RREQ with RBTS RREQ with RBTS, E RREQ with RBTS, E, F F E Multimedia and Mobile Communication Laboratory

14. RREQs arrives at D • First RREQ •  Primary Path (PP) • Later RREQs •  Candidate Path (CP) • Radio & band selection • Preference: • Idle radio > “Share” > “Switch” • RBTs should be updated after every comparison! Multimedia and Mobile Communication Laboratory

15. RBTS& RBTA RBTS’ & RBTA’ • RBTA’ & RBTB RBTA’’ & RBTB’ • RBTB’ & RBTD RBTB’’ & RBTD’ … • … Multimedia and Mobile Communication Laboratory

16. Path Evaluation Metrics: • Hop Count: • NPP: Hop count of PP • NCP: Hop count of CP • Band Overlapping Factor: FCP • α: weight factor • balancing how we emphasize the jointness of paths Multimedia and Mobile Communication Laboratory

17. Finally, two paths are established: • Primary Path: • Secondary Path: ( selected from CPs) • Data Striping: • Packets will be splitted and transmitted throughput different paths simultaneously • Dual path: odd / even Multimedia and Mobile Communication Laboratory

18. Recovery: 2 New radio&band is assigned, let’s keep going E3 ---- 3F 2 1 b3 b4 X 1 1 3 3 2 b2 b1 Stop transmitting to me, go other path! b1 Who is involved in this PU insertion? P4 D E F S Multimedia and Mobile Communication Laboratory

19. Outline • Introduction to CRN • Multi-radio Multi-path Routing in CRN • Evaluation • Conclusion Multimedia and Mobile Communication Laboratory

20. 3. Evaluation • MPMR vs. MPSR(SMR) vs. SPMR • NS2 • 802.11a, 6Mbps, UDP • 7 orthogonal channels from 11a: • 36, 44, 52, 60, 149, 157, 165 • 3 radios • 2 paths Multimedia and Mobile Communication Laboratory

21. Maximum End-to-end Throughput: • MPMR achieves much high end-to-end throughput • MPSR uses single radio, low throughput • SPMR uses one path, limited high throughput MPSR( ) Multimedia and Mobile Communication Laboratory

22. Recovery Evaluation • P4 begins at 3 sec. • E detects the insertion • is interrupted • E and F re-select b2 • ~120 ms 2 E3 ---- 3F Multimedia and Mobile Communication Laboratory

23. There is a degradation of throughput, for all • MPSR achieves low throughput ( let’s ignore it…) • SPMR transmission is terminated • MPMR keeps high speed transmission MPSR(SMR) SPMR MPMR Multimedia and Mobile Communication Laboratory

24. Outline • Introduction to CRN • Multi-radio Multi-path Routing in CRN • Evaluation • Conclusion Multimedia and Mobile Communication Laboratory

25. 4. Conclusion • Multi-path Routing in Multi-radio Multi-hop Cognitive Radio Networks • Route Discovery • Radio/Band Selection • Route Recovery • Finally • Higher route connectivity • Higher end-to-end throughput Multimedia and Mobile Communication Laboratory

26. Currently • Massive simulations • Detailed evaluation • Future Work • More efficient radio & band selection algorithm • More evaluation metrics of paths • Faster route recovery of SS’s traffic • Try to cancel the extra radio for control signal • This is the most practical problem! Multimedia and Mobile Communication Laboratory

27. Q&A Thank You! Multimedia and Mobile Communication Laboratory