1. Jesús Alonso-Zárate, Elli Kartsakli, Luis Alonso, and Christos Verikoukis May 2010, Cape Town, South Africa, ICC 2010 Coexistence of a Novel MAC Protocol for Wireless Ad hoc Networks and the IEEE 802.11

2. 2/28 ICC 2010 Cape Town, South Africa jesus.alonso@cttc.es Outline 1)Introduction 2)802.11 overview 3)DQMAN overview 4)Coexistence Methodology 5)Simulation Results 6)Conclusions

3. 3/28 ICC 2010 Cape Town, South Africa jesus.alonso@cttc.es Outline 1)Introduction 2)802.11 overview 3)DQMAN overview 4)Coexistence Methodology 5)Simulation Results 6)Conclusions

4. 4/28 ICC 2010 Cape Town, South Africa jesus.alonso@cttc.es Introduction Context: Wireless Local Area Networks (ad hoc) Focus: Medium Access Control protocols (MAC protocols) 1999: IEEE 802.11 and the Distributed Coordination Function (DCF) Since then  letter soup (a,b,g,e,n, …), but few changes to MAC MAC very inefficient for high number of users or heavy data traffic Result: vast amount of new MAC protocols have been proposed

5. 5/28 ICC 2010 Cape Town, South Africa jesus.alonso@cttc.es Introduction Problem and motivation: 1)Higher performance, at the cost of 2)Non-backwards compatibility Contribution: 1)Methodology for the coexistence of DQMAN and the DCF 2)Methodology can be applied to other MAC protocols.

6. 6/28 ICC 2010 Cape Town, South Africa jesus.alonso@cttc.es Outline 1)Introduction 2)802.11 overview 3)DQMAN overview 4)Coexistence Methodology 5)Simulation Results 6)Conclusions

7. 7/28 ICC 2010 Cape Town, South Africa jesus.alonso@cttc.es The IEEE 802.11: Overview DCF  mandatory access method Based on CSMA (listen-before-talk) Collision Resolution Algorithm  Binary Exponential Backoff (BEB) Defines two modes of operation: 1)Basic access  transmission of data + ACK 2)Collision Avoidance access  adds a handshake RTS/CTS Reduces the duration of collisions (long data packets) Protection against hidden terminals

8. 8/28 ICC 2010 Cape Town, South Africa jesus.alonso@cttc.es The IEEE 802.11: The BEB algorithm Slotted backoff Random backoff counter in the interval [0,CWi] CW min  minimum size of the contention window CW MAX  maximum size of the contention window Backoff counter decreased by one unit after each slot if channel sensed idle, otherwise, the counter is frozen

9. 9/28 ICC 2010 Cape Town, South Africa jesus.alonso@cttc.es The IEEE 802.11: Basic Access Clear Channel Assessment (CCA)  Distributed Inter Frame Space (DIFS) Short Inter Frame Space (SIFS)  propagation, processing, turnaround delays Virtual Carrier Sensing  Network Allocation Vector (NAV) Positive ACK (ACK timeout in case of error)

10. 10/28 ICC 2010 Cape Town, South Africa jesus.alonso@cttc.es The IEEE 802.11: Collision Avoidance Inclusion of handshake: RTS: Request to Send CTS: Clear to Send

11. 11/28 ICC 2010 Cape Town, South Africa jesus.alonso@cttc.es Outline 1)Introduction 2)802.11 overview 3)DQMAN overview 4)Coexistence Methodology 5)Simulation Results 6)Conclusions

12. 12/28 ICC 2010 Cape Town, South Africa jesus.alonso@cttc.es DQMAN: Overview I 1)DQMAN  extension of DQCA 2)DQCA requires a central coordination point 3)Approach in DQMAN: 1)Master-Slave, 2)Self-organizing, 3)Spontaneous, 4)Passive (no explicit clustering overhead), 5)Dynamic CLUSTERING. 4)Master, slave and idle stations. 5)Masters pretend to be temporary infrastructure for their local neighborhood 6)Clusters are temporary

13. 13/28 ICC 2010 Cape Town, South Africa jesus.alonso@cttc.es DQMAN: Overview II Time+ Station 3: SLAVE Station 2: SLAVE Station 1: SLAVE Station 0: MASTER FBP Data from 1 to 3 ACK Contention Window Slaves with data to transmit select a minislot at random where to send an Access Request Sequence (ARS) Busy tones Feedback information about the state of each of the access minislots. With this information, stations can execute the MAC protocol rules in a distributed manner SIFS Short Inter Frame Space 123

14. 14/28 ICC 2010 Cape Town, South Africa jesus.alonso@cttc.es Outline 1)Introduction 2)802.11 overview 3)DQMAN overview 4)Coexistence Methodology 5)Simulation Results 6)Conclusions

15. 15/28 ICC 2010 Cape Town, South Africa jesus.alonso@cttc.es Coexistence Assume that DQMAN stations are dual Default access: DCF of the IEEE 802.11 Standard Dual stations → special RTS → dual-RTS: If the destination is a DCF station, it responds with a CTS If the destination station is a dual station it can initiate a DQMAN phase by becoming master For the DQMAN phase, legacy stations should remain silent by properly updating the NAV with the FBP → dual-CTS

16. 16/28 ICC 2010 Cape Town, South Africa jesus.alonso@cttc.es Coexistence Format of regular RTS and CTS packets Frame ControlDurationRx. AddressTx. AddressCRC Frame ControlDurationRx. AddressCRC RTS CTS Protocol Version Type of frame (control) Subtype: RTS or CTS B0B1B15 … B8B9 … B8: To AP B9: From AP 16 Control Flags (1-bit)

17. 17/28 ICC 2010 Cape Town, South Africa jesus.alonso@cttc.es Coexistence Dual-RTS and Dual-CTS (FBP) Frame ControlDurationRx. AddressTx. AddressCRC Frame ControlDurationRx. AddressCRC RTS CTS Protocol Version Type of frame (control) Subtype: RTS or CTS B0B1B15 … B8B9 … B8: To AP B9: From AP 16 Control Flags (1-bit)

18. 18/28 ICC 2010 Cape Town, South Africa jesus.alonso@cttc.es Coexistence Dual-RTS and Dual-CTS (FBP) Frame ControlDurationRx. AddressTx. AddressCRC Frame ControlDurationRx. AddressCRC RTS CTS Protocol Version Type of frame (control) Subtype: RTS or CTS B0B1B15 … B8B9 … B8: To AP B9: From AP 16 Control Flags (1-bit)

19. 19/28 ICC 2010 Cape Town, South Africa jesus.alonso@cttc.es Coexistence Dual-RTS and Dual-CTS (FBP) Frame ControlDurationRx. AddressTx. AddressCRC Frame ControlDurationRx. AddressCRC RTS CTS Protocol Version Type of frame (control) Subtype: RTS or CTS B0B1B15 … B8B9 … B8: To AP B9: From AP 16 Control Flags (1-bit)

20. 20/28 ICC 2010 Cape Town, South Africa jesus.alonso@cttc.es Coexistence Time+ d-Station 3: M d-Station 2 Station 1 d-Station 0 RTS d CTS d

21. 21/28 ICC 2010 Cape Town, South Africa jesus.alonso@cttc.es Time+ d-Station 3: M d-Station 2 Station 1 d-Station 0 DATA RTS d CTS d DATA CTS d Backoff NAV Coexistence A minimum DCF operation time is now performed to enable access to legacy stations NAV

22. 22/28 ICC 2010 Cape Town, South Africa jesus.alonso@cttc.es Outline 1)Introduction 2)802.11 overview 3)DQMAN overview 4)Coexistence Methodology 5)Simulation Results 6)Conclusions

23. 23/28 ICC 2010 Cape Town, South Africa jesus.alonso@cttc.es Simulation Results MTO 5 DQMAN dual stations + 5 legacy stations

24. 24/28 ICC 2010 Cape Town, South Africa jesus.alonso@cttc.es Simulation Results 5 DQMAN dual stations + 5 legacy stations

25. 25/28 ICC 2010 Cape Town, South Africa jesus.alonso@cttc.es Simulation Results 5 DQMAN dual stations + 5 legacy stations

26. 26/28 ICC 2010 Cape Town, South Africa jesus.alonso@cttc.es Outline 1)Introduction 2)802.11 overview 3)DQMAN overview 4)Coexistence Methodology 5)Simulation Results 6)Conclusions

27. 27/28 ICC 2010 Cape Town, South Africa jesus.alonso@cttc.es Conclusions Lots of MAC protocols with high performance for WLAN IEEE 802.11 is there  Backwards compatibility is a must Coexistence methodology presented in this paper DQMAN with IEEE 802.11 In simulation, it works! Can be extended to any other MAC protocol Next step: try a real testbed to see if it works.

28. Jesús Alonso-Zárate jesus.alonso@cttc.es www.cttc.es Questions? Thanks for your kind attention!