STR Radios and STR Media Access
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The document discusses the development of a new centralized MAC protocol called Janus for full duplex wireless communication, which promises a significant throughput improvement. Janus achieves a 150% throughput gain compared to traditional half-duplex systems by leveraging self-interference cancellation and centralized scheduling. It highlights the transition from traditional wireless design assumptions and the potential benefits of full duplex technology in modern wireless LANs.
STR Radios and STR Media Access
- 1. doc.: IEEE 802.11-13/1421r1 Submission November 2013 Philip Levis, Stanford UniversitySlide 1 STR Radios and STR Media Access Date: 2013-11-12 Name Affiliations Address Phone email Philip Levis Stanford University 412 Gates Hall, 353 Serra Mall, Stanford, CA 94305 650-725-9046 pal@cs.stanford.edu Authors:
- 2. doc.: IEEE 802.11-13/1421r1 Submission November 2013 Philip Levis, Stanford UniversitySlide 2 Abstract Single antenna, in-band STR is coming. Janus is a centralized STR MAC that uses communication rounds and explicitly schedules all frame transmissions. Full duplex promises a 100% throughput gain, Janus provides a 150% throughput gain. Full duplex networks can benefit from more centralized MAC algorithms and protocols.
- 3. doc.: IEEE 802.11-13/1421r1 Submission November 2013 Philip Levis, Stanford UniversitySlide 3 Wireless Today “It is generally not possible for radios to receive and transmit on the same frequency band because of the interference that results. Thus, bidirectional systems must separate the uplink and downlink channels into orthogonal signaling dimensions, typically using time or frequency dimensions.” - Andrea Goldsmith, “Wireless Communications,” Cambridge Press, 2005.
- 4. doc.: IEEE 802.11-13/1421r1 Submission November 2013 Philip Levis, Stanford UniversitySlide 4 Talk in a Nutshell • Single antenna, in-band, STR is coming – Breaks a fundamental assumption in most wireless designs – Current best: WiFi with a shared RX/TX antenna (200mW, 80MHz @ 2.4GHz, 110dB of cancellation) • How full duplex changes the MAC layer
- 5. doc.: IEEE 802.11-13/1421r1 Submission Why Half Duplex? • Self-interference is millions to billions (60-90dB) stronger than received signal • If only we could “subtract” our transmission... November 2013 Philip Levis, Stanford UniversitySlide 5
- 6. doc.: IEEE 802.11-13/1421r1 Submission First Prototype: Antenna Cancellation November 2013 Philip Levis, Stanford UniversitySlide 6
- 7. doc.: IEEE 802.11-13/1421r1 Submission First Prototype: Antenna Cancellation November 2013 Philip Levis, Stanford UniversitySlide 7 ~30dB self-interference cancellation Enables full-duplex when combined with digital (15dB) and hardware (25dB) cancellation.
- 8. doc.: IEEE 802.11-13/1421r1 Submission First Prototype 4 antennas, 1 mW, 5MHz @ 2.4GHz November 2013 Philip Levis, Stanford UniversitySlide 8 Digital interference cancellation Antenna cancellation Hardware cancellation Jung Il Choi, Mayank Jain, Kannan Srinivasan, Philip Levis and Sachin Katti. “Achieving Single Channel, Full Duplex Wireless Communication.” In Proceedings of the 16th Annual International Conference on Mobile Computing and Networking (Mobicom 2010).
- 9. doc.: IEEE 802.11-13/1421r1 Submission Why Half Duplex? • Self-interference is millions to billions (60-90dB) stronger than received signal • If only we could “subtract” our transmission... November 2013 Philip Levis, Stanford UniversitySlide 9
- 10. doc.: IEEE 802.11-13/1421r1 Submission Second Design November 2013 Philip Levis, Stanford UniversitySlide 10
- 11. doc.: IEEE 802.11-13/1421r1 Submission Second Prototype 2 antennas, ~100 mW, 20MHz @ 2.4GHz November 2013 Philip Levis, Stanford UniversitySlide 11 Mayank Jain, Jung Il Choi, Taemin Kim, Dinesh Bharadia, Kannan Srinivasan, Siddharth Seth, Philip Levis, Sachin Katti and Prasun Sinha. “Practical, Real-time, Full Duplex Wireless.” In Proceedings of the 17th Annual International Conference on Mobile Computing and Networking (Mobicom 2011).
- 12. doc.: IEEE 802.11-13/1421r1 Submission Third Design November 2013 Philip Levis, Stanford UniversitySlide 12 • One antenna – Circulator • Adaptive cancellation – Bank of delay lines – Handles frequency selective interference, isolation • 110dB of cancellation – 20dBm, -90dBm noise floor – 80MHz @ 2.4GHz Dinesh Bharadia, Emily McMillin, and Sachin Katti. “Full Duplex Radios.” In Proceedings of ACM SIGCOMM (2013).
- 13. doc.: IEEE 802.11-13/1421r1 Submission Implications November 2013 Philip Levis, Stanford UniversitySlide 13
- 14. doc.: IEEE 802.11-13/1421r1 Submission Full Duplex MAC November 2013 Philip Levis, Stanford UniversitySlide 14 symmetric AP-centric asymmetric asymmetric failure client-centric asymmetric
- 15. doc.: IEEE 802.11-13/1421r1 Submission Janus • MAC layer for full duplex wireless LANs • Entirely AP-centric and AP-scheduled • Provides per-client fair share of channel – Fairness of time, not bits – Nodes with lower SNR receive lower throughput • Full duplex promises 100% throughput gain, Janus provides a 150% gain November 2013 Philip Levis, Stanford UniversitySlide 15
- 16. doc.: IEEE 802.11-13/1421r1 Submission Janus Cases November 2013 Philip Levis, Stanford UniversitySlide 16 symmetric AP-centric asymmetric asymmetric failure client-centric asymmetric
- 17. doc.: IEEE 802.11-13/1421r1 Submission Janus Overview November 2013 Philip Levis, Stanford UniversitySlide 17
- 18. doc.: IEEE 802.11-13/1421r1 Submission Probe Phase November 2013 Philip Levis, Stanford UniversitySlide 18
- 19. doc.: IEEE 802.11-13/1421r1 Submission Collection Phase November 2013 Philip Levis, Stanford UniversitySlide 19
- 20. doc.: IEEE 802.11-13/1421r1 Submission Schedule + Data Phase November 2013 Philip Levis, Stanford UniversitySlide 20
- 21. doc.: IEEE 802.11-13/1421r1 Submission ACK Phase November 2013 Philip Levis, Stanford UniversitySlide 21
- 22. doc.: IEEE 802.11-13/1421r1 Submission Scheduling Full Duplex November 2013 Philip Levis, Stanford UniversitySlide 22 Optimal solution is NP-complete (intractable) Simple greedy heuristic performs well (90%).
- 23. doc.: IEEE 802.11-13/1421r1 Submission Throughput November 2013 Philip Levis, Stanford UniversitySlide 23 90% gain 150% gain
- 24. doc.: IEEE 802.11-13/1421r1 Submission Decomposing Gains November 2013 Philip Levis, Stanford UniversitySlide 24 Benefits from centralization Benefits from SINR map Contraflow is a full duplex CSMA/CA protocol.
- 25. doc.: IEEE 802.11-13/1421r1 Submission Multiple APs November 2013 Philip Levis, Stanford UniversitySlide 25
- 26. doc.: IEEE 802.11-13/1421r1 Submission Full Duplex/Janus • Single-antenna STR is coming • Can benefit from more centralized MAC • Tradeoff between MIMO and STR • Janus shows 150% throughput gain over half-duplex network • Prior results showed full duplex reduces hidden terminals by 88% November 2013 Philip Levis, Stanford UniversitySlide 26 Jae Young Kim, Omid Mashayekhi, Hang Qu, Maria Kazandjieva, and Philip Levis. “Janus: A Novel MAC Protocol for Full Duplex Radios.” Stanford University CSTR 2013-02 7/23/13. http://hci.stanford.edu/cstr/reports/2013-02.pdf
- 27. doc.: IEEE 802.11-13/1421r1 Submission Future Wireless LAN • High performance wireless LANs are typically managed today – Meraki, Aruba, Aerohive, Proxim, etc. – Frequency planning, careful placement – Management software on ad-hoc network? • An increasing confluence between mobile telephony and wireless LANs – What is the right level of control/centralization? November 2013 Philip Levis, Stanford UniversitySlide 27
- 28. doc.: IEEE 802.11-13/1421r1 Submission Straw Poll • Should HEW explore a MAC layer with more centralized scheduling, with the purpose of better enabling future in-band STR as well as simplifying management and provisioning? (Y/N/A) November 2013 Philip Levis, Stanford UniversitySlide 28
- 29. doc.: IEEE 802.11-13/1421r1 Submission November 2013 Philip Levis, Stanford UniversitySlide 29 References • Jung Il Choi, Mayank Jain, Kannan Srinivasan, Philip Levis and Sachin Katti. “Achieving Single Channel, Full Duplex Wireless Communication.” In Proceedings of the 16th Annual International Conference on Mobile Computing and Networking (Mobicom 2010). • Mayank Jain, Jung Il Choi, Taemin Kim, Dinesh Bharadia, Kannan Srinivasan, Siddharth Seth, Philip Levis, Sachin Katti and Prasun Sinha. “Practical, Real-time, Full Duplex Wireless.” In Proceedings of the 17th Annual International Conference on Mobile Computing and Networking (Mobicom 2011). • Dinesh Bharadia, Emily McMillin, and Sachin Katti. “Full Duplex Radios.” In Proceedings of ACM SIGCOMM (2013). • Jae Young Kim, Omid Mashayekhi, Hang Qu, Maria Kazandjieva, and Philip Levis. “Janus: A Novel MAC Protocol for Full Duplex Radios.” Stanford University CSTR 2013-02 7/23/13. http://hci.stanford.edu/cstr/reports/2013-02.pdf • Nikhil Singh, Dinan Gunawardena, Alexandre Proutiere, Bozidar Radunovic, Horia Vlad Balan, and Peter Key, Efficient and Fair MAC for Wireless Networks with Self-interference Cancellation, in WiOpt 2011, May 2011