Opportunistic Media Access Control and Rate Adaptation for Wireless Ad Hoc Networks

1
Opportunistic Media Access Control and Rate
Adaptation for Wireless Ad Hoc Networks

• Jianfeng Wang1, Hongqiang Zhai1,
• Yuguang Fang1 and Maria C. Yuang2
• 1Department of Electrical and Computer
  Engineering
• University of Florida, USA
• 2Department of Computer Science and Information
  Engineering
• National Chiao Tung University, Taiwan

2
Outline

• Background and Motivation
• To address channel variations in CSMA/CA based
  WLANs and multihop ad hoc networks
• Our approach
• Opportunistic media access and rate adaptation
  with the use of multiuser diversity
• Performance evaluation
• Conclusion

3
Background

• Time-varying wireless channel
• Fading and interference
• Negative effects of channel variations
• Head-of-Line blocking
• False link breakage, thus unnecessary rerouting
• Poor end-to-end TCP performance
• Existing solutions
• Rate Adaptation ARF1, RBAR2, OAR3
• Power Control PCMA4, PCDC5
• Cons Mitigate rather than utilize channel
  variations. Inefficient or unfair!

4
Motivation

• Utilize multiuser diversity (Like Qualcomms
  HDR6)

5
Basic ideas of our approach

• Channel state dependent queue management
• Both efficiency and fairness are considered
• Probe channel conditions of multiple candidate
  receivers by multicast-RTS
• Channel aware media access with collision
  avoidance
• Rate adaptation and packet bursting

6
Link layer queue management
F1
F2

FN
F Target weight C Channel quality X Output
E.g., proportional fairness
7
Channel probing with Multi-cast RTS

• Extend unicast RTS ( in de facto 802.11) to
  multi-cast RTS
• Probe channel conditions of multiple candidate
  receivers simultaneously

8
Channel aware media access by prioritized CTS
9
Rate adaptation and packet bursting

• Receiver uses measured SINR to determine
  appropriate data rate and reports it to sender by
  CTS
• Set transmission opportunity (TXOP) according to
  channel condition and received throughput

10
Throughput scaling with the number of flows
11
Impact of Ricean parameter K and mobile speed
12
TCP throughput and fairness
13
Multihop performance

• Throughput of onehop flows and multihop flows

14
Conclusion

• Provide a simple but efficient MAC protocol
• Utilize multiuser diversity in ad hoc networks
• Easily incorporated in the 802.11 standard with
  minor changes
• Throughput is significantly improved without
  sacrifice of the fairness

15
Selected references

• A. Kamerman and L. Monteban, WaveLAN II A
  high-performance wireless LAN for the unlicensed
  band, Bell Labs Technical Journal, pages
  118-133, 1997 .
• G. Holland, N. H. Vaidya and P. Bahl, A
  Rate-Adaptive MAC Protocol for Multi-Hop Wireless
  Networks, in Proc. of ACM MOBICOM2001, 2001
• B. Sadeghi, V. Kanodia, A. Sabharwal, and E.
  Knightly, Opportunistic Media Access for
  Multirate Ad Hoc Networks, in Proc. of ACM
  MOBICOM2002, 2002.
• J. Monks, V. Bharghavan, and W. Hwu, A Power
  Controlled Multiple Access Protocol for Wireless
  Packet Networks, in Proc. IEEE INFOCOM01, April
  2001.
• A. Muqattash and M. Krunz, Power Controlled Dual
  Channel (PCDC) Medium Access Protocol for
  Wireless Ad Hoc Networks, in Proc. IEEE
  INFOCOM03, 2003
• P. Bender, P. Black, M. Grob, R. Padovani, N.
  Sindhushayana, and A. Viterbi, "CDMA/HDR a
  Bandwidth Efficient High Speed Wireless Data
  Service for Nomadic Users," IEEE Communications
  Magazine, Vol. 38, No. 7, July 2000.