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Introduction Antenna Model Assumed antenna system Omni antenna Tx/Rx from all directions (360 degrees) Directional antenna Can point its main lobe towards any specified direction Do not consider power control Fixed beamwidth
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Using Directional Antennas for Using Directional Antennas for Medium Access Control in Ad Medium Access Control in Ad Hoc NetworksHoc Networks
Romit Roy Choudhury, Xue Yang, Romit Roy Choudhury, Xue Yang, Ram RamanathanRam Ramanathan. . and Nitin H. Vaidyaand Nitin H. Vaidya
University of lllinois at Urbana-ChampaignUniversity of lllinois at Urbana-Champaign
MOBICOM 2002
OutlineOutline IntroductionIntroduction Problems with Basic DMACProblems with Basic DMAC Multi-Hop RTS MAC ProtocolMulti-Hop RTS MAC Protocol Simulation Simulation Future work & ConclusionFuture work & Conclusion
IntroductionIntroductionAntenna ModelAntenna Model
Assumed antenna system Assumed antenna system Omni antennaOmni antenna
Tx/Rx from all directions (360 degrees)Tx/Rx from all directions (360 degrees) Directional antennaDirectional antenna
Can point its main lobe towards Can point its main lobe towards any specified dirany specified directionection
Do not consider Do not consider power controlpower control Fixed beamwidth Fixed beamwidth
Introduction Introduction Antenna ModelAntenna Model
A
Directional modeOmni mode
B
Benefits of directionalityBenefits of directionality Spatial Spatial reusereuse Higher transmission Higher transmission rangerange
Problems with Basic DMACProblems with Basic DMAC Hidden terminal problemsHidden terminal problems
Hidden terminal due to asymmetry in gainHidden terminal due to asymmetry in gain
BE FARTSCTS DATARxRTS
Problems with Basic DMACProblems with Basic DMAC
DeafnessDeafness
A
B
DC
DATADATA
DATA
Multi-Hop RTS MAC ProtocolMulti-Hop RTS MAC Protocol
Protocol Description : Multi-Hop RTSProtocol Description : Multi-Hop RTS Direction-Omni (DO) NeighborDirection-Omni (DO) Neighbor Direction-Direction (DD) NeighborDirection-Direction (DD) Neighbor
C D
TX RX
DD Neighbor
C D
TX RX
DO Neighbor
CTS
RTS
RTS
Multi-Hop RTS MAC ProtocolMulti-Hop RTS MAC Protocol
D
G
BRTS
F
C
RxDATA RXA
Simulation ResultsSimulation Results
SimulationSimulation
Future Work & Future Work & ConclusionConclusion
Rely lessRely less on the upper layers for beamfor on the upper layers for beamforming information ming information
ReplaceReplace the omni mode operation (tone) the omni mode operation (tone) Performance of the system improve in terPerformance of the system improve in ter
ms of aggregate ms of aggregate throughputthroughput and end-to-e and end-to-end nd delaydelay
Thank You !!Thank You !!
Problems with Basic DMACProblems with Basic DMAC Hidden terminal problemsHidden terminal problems
Hidden terminal due to unheard RTS/CTSHidden terminal due to unheard RTS/CTS
D
B FEDATA RTSCTS DATA
DATA
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