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Coexistence of a Novel MAC Protocol for Wireless Ad hoc Networks and the IEEE 802.11

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

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Coexistence of a Novel MAC Protocol for Wireless Ad hoc Networks and the IEEE 802.11

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

  2. Outline Introduction 802.11 overview DQMAN overview Coexistence Methodology Simulation Results Conclusions

  3. Outline Introduction 802.11 overview DQMAN overview Coexistence Methodology Simulation Results Conclusions

  4. 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. Introduction • Problem and motivation: • Higher performance, at the cost of • Non-backwards compatibility • Contribution: • Methodology for the coexistence of DQMAN and the DCF • Methodology can be applied to other MAC protocols.

  6. Outline Introduction 802.11 overview DQMAN overview Coexistence Methodology Simulation Results Conclusions

  7. 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: • Basic access  transmission of data + ACK • Collision Avoidance access  adds a handshake RTS/CTS • Reduces the duration of collisions (long data packets) • Protection against hidden terminals

  8. The IEEE 802.11: The BEB algorithm • Slotted backoff • Random backoff counter in the interval [0,CWi] • CWmin minimum size of the contention window • CWMAX 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. 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 (ACKtimeout in case of error)

  10. The IEEE 802.11: Collision Avoidance • Inclusion of handshake: • RTS: Request to Send • CTS: Clear to Send

  11. Outline Introduction 802.11 overview DQMAN overview Coexistence Methodology Simulation Results Conclusions

  12. DQMAN: Overview I • DQMAN  extension of DQCA • DQCA requires a central coordination point • Approach in DQMAN: • Master-Slave, • Self-organizing, • Spontaneous, • Passive (no explicit clustering overhead), • Dynamic CLUSTERING. • Master, slave and idle stations. • Masters pretend to be temporary infrastructure for their local neighborhood • Clusters are temporary

  13. DQMAN: Overview II Contention WindowSlaves with data to transmit select a minislot at random where to send an Access Request Sequence (ARS) 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 FBP FBP Station 0: MASTER Data from 1 to 3 Station 1: SLAVE Station 2: SLAVE ACK Station 3: SLAVE Busy tones SIFS Short Inter Frame Space 1 2 3 Time+

  14. Outline Introduction 802.11 overview DQMAN overview Coexistence Methodology Simulation Results Conclusions

  15. 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. Coexistence Format of regular RTS and CTS packets RTS Frame Control Duration Rx. Address Tx. Address CRC CTS Frame Control Duration Rx. Address CRC 16 Control Flags (1-bit) … … Protocol Version Type of frame (control) Subtype:RTS or CTS B0 B1 B8 B9 B15 B8: To APB9: From AP

  17. Coexistence Dual-RTS and Dual-CTS (FBP) RTS Frame Control Duration Rx. Address Tx. Address CRC CTS Frame Control Duration Rx. Address CRC 16 Control Flags (1-bit) … … Protocol Version Type of frame (control) Subtype:RTS or CTS B0 B1 B8 B9 B15 B8: To APB9: From AP

  18. Coexistence Dual-RTS and Dual-CTS (FBP) RTS Frame Control Duration Rx. Address Tx. Address CRC CTS Frame Control Duration Rx. Address CRC 16 Control Flags (1-bit) … … Protocol Version Type of frame (control) Subtype:RTS or CTS B0 B1 B8 B9 B15 B8: To APB9: From AP

  19. Coexistence Dual-RTS and Dual-CTS (FBP) RTS Frame Control Duration Rx. Address Tx. Address CRC CTS Frame Control Duration Rx. Address CRC 16 Control Flags (1-bit) … … Protocol Version Type of frame (control) Subtype:RTS or CTS B0 B1 B8 B9 B15 B8: To APB9: From AP

  20. Coexistence RTSd d-Station 0 Station 1 d-Station 2 CTSd d-Station 3: M Time+

  21. Coexistence DATA Backoff RTSd d-Station 0 NAV NAV Station 1 DATA Backoff d-Station 2 CTSd CTSd CTSd Backoff d-Station 3: M A minimum DCF operation time is now performed to enable access to legacy stations Time+

  22. Outline Introduction 802.11 overview DQMAN overview Coexistence Methodology Simulation Results Conclusions

  23. Simulation Results 5 DQMAN dual stations + 5 legacy stations MTO

  24. Simulation Results 5 DQMAN dual stations + 5 legacy stations

  25. Simulation Results 5 DQMAN dual stations + 5 legacy stations

  26. Outline Introduction 802.11 overview DQMAN overview Coexistence Methodology Simulation Results Conclusions

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

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