on reservation-based mac protocol for ieee 802.11 wireless ad hoc networks with directional antenna...

On Reservation-Based MAC Protocol On Reservation-Based MAC Protocol for IEEE 802.11 Wireless Ad Hoc for IEEE 802.11 Wireless Ad Hoc Networks With Directional AntennaNetworks With Directional Antenna

Author : Author :

Jin-Jia Chang, Jin-Jia Chang, StudentStudent Member, IEEEMember, IEEE

Wanjiun Liao, Wanjiun Liao, Fellow, IEEEFellow, IEEE

Jiunn-Ru Lai, Jiunn-Ru Lai, Member, IEEEMember, IEEE

Speaker : Huei-Rung TsaiSpeaker : Huei-Rung Tsai

IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY 2011IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY 2011

OutlineOutline

• Introduction

• Minor-Lobe Problem in Directional Antennas

• Goals

• RDMAC Protocol

• Performance Evaluation

• Conclusions

IntroductionIntroduction

• The antenna of wireless network device – Omnidirectional antennas

– Directional antennas

• The advantage of using directional antennas– Reduce the interference problem

– Reduce energy consumption

– Increase the network throughput (spatial reuse)

RR


• The communication condition of directional antennas – Data-link layer

– Physical layer

TT RR TT

Data-link LayerData-link Layer Physical LayerPhysical Layer


• In the IEEE 802.11– Collision avoidance

• Carrier sense multiple access with collision avoidance (CSMA/CA)

– Hidden terminal problem• RTS/CTS exchange before each data transmission

– For omnidirectional antenna system

• In directional antenna system– New problems of location-dependent carrier sensing

• Directional hidden terminal problem

• Deafness problem

AA BBDATA

RTSC


• Several protocols have been proposed to solve the location dependent carrier-sensing problem

[3] T. Korakis, G. Jakllari, and L. Tassiulas, “A MAC protocol for full exploitation of directional antennas in ad hoc wireless networks,” in Proc. ACM MobiHoc, 2003, pp. 98–107.

• Circular directional RTS/CTS

[4] H. Gossain, C. Cordeiro, and D. P. Agrawal, “MDA: An efficient directional MAC scheme for wireless ad hoc networks,” in Proc. IEEE Globecom, 2005, p. 3637.

• Diametrically opposite directional RTS/CTS

• Criticism–Every node known the location information of its neighbor in a priori

–Do not take into account the effect of the minor-lobe problem

Minor-Lobe Problem in Directional AntennasMinor-Lobe Problem in Directional Antennas

• Minor-Lobe Problem in Directional Antennas

Main-lobe

Minor-lobes

Back lobe

Side lobe

• Interference From Minor Lobes


TT RR

NN

• Interference From Minor Lobes– When transmitter’s main lobe overlaps with receiver’s minor lobe, the

node pair is regarded as within the interference


RR

InterferenceTT

• Interference From Minor Lobes


NN

TT RR TT RR

NN

Interference

Interference


• Mitigating Interference From Minor Lobes– Virtual Carrier Sensing (VCS)

– Physical Carrier Sensing (PCS)

• VCS in Practical Directional Antenna Systems– Requires successfully decoding frames

– VCS cannot identify the existence of minor lobes


TT RR

Safe !!NN


• PCS in Practical Directional Antenna Systems– Energy-detection-based mechanism

– When the signal strength exceeds a threshold, then we consider that existence of an ongoing transmission

• PCS is faster and more sensitivity than VCS, but when a node detects no signal, it doesn’t mean that it is real safe

GoalsGoals

• Propose a MAC protocol called reservation-based directional medium access control (RDMAC), solved these problems– Location-dependent carrier sensing

– Minor-lobe interference

• RDMAC can operate without – Prior information on neighboring nodes’ location

– Centralized synchronization mechanism

AssumptionAssumption

• The network environment exist two kinds of node– Omnidirectional antenna nodes

– RDMAC nodes

• Each RDMAC node can display two kinds of transmission– Omnidirectional transmission (ORTS/OCTS)

– Directional transmission (DRTS/DCTS/DDATA/DACK)

• Each RDMAC node maintains three table – Network access vector (NAV) table

– Directional network access vector (DNAV) table

– Neighbor table

RDMAC protocolRDMAC protocol

EE

DDCC

Omnidirectional antenna nodes

RDMAC node

FF

BB

ORTS:•Notify receiver node and neighboring node

DRTS:•Let neighboring nodes test the antenna gain threshold

OCTS:•Response transmitter node •Notify the direction of the antenna beam to transmitter and neighboring node

DRTS DCTS

ORTS OCTS

AA

Contention PeriodContention Period

Contention PeriodContention Period


EE

DDCC


RDMAC node

FF

BBAA

DRTS DCTS

ORTS OCTS


EE

DDCC


RDMAC node

FF

BBAA

Transmission PeriodTransmission Period

DDATA

DDATA


EE

DDCC


RDMAC node

FF

BBAA

Transmission PeriodTransmission Period

DACK

DACK


A

ContentionPeriod(tCP)

TransmissionPeriod(tTP)

B

C

D

E

F

OROR

OCOC

NAV

DRDR

DCDC

NAV

NAV

NAV

OROR

OCOC

DRDR

DCDC

Back off

DDATADDATA

DDATADDATA

DACKDACK

DACKDACK

time


A

ContentionPeriod(tCP)

TransmissionPeriod(tTP)

B

C

D

E

F

Free Period(tFP)

NAV

NAV

NAV

NAV

OROR

OCOC

DATADATA

ACKACK

NAV

NAV

OROR

OCOC

time

Performance EvaluationPerformance Evaluation

• Evaluate the performance result through ns-2 simulations

Static nodes 50

Area 2000 × 2000 m2

Frame size 1460 Byte

Physical data rate 54 Mb/s

Transmission range 250 m

Sidelobe beamwidth main beamwidth × 2

Backlobe beamwidth main beamwidth × 1

Interference range main beamwidth × 2

DIFS 28 μs

Contention period 500 μs

Performance EvaluationPerformance Evaluation

ConclusionsConclusions

• This paper proposed a new MAC mechanism called RDMAC for IEEE 802.11 DCF-based multihop wireless networks with directional antennas– Reduce the location-dependent carrier-sensing

– Reduce the interference problems caused by minor lobes

– Eliminates the requirements of a centralized synchronization mechanism and prior location information on neighboring nodes

on reservation-based mac protocol for ieee 802.11 wireless ad hoc networks with directional antenna...

Documents

minorlobe problem slide

lobe slide

directional antennas

r r introduction

interference problem

receivers minor lobe

directional antenna

directional rtscts criticism