A MAC Protocol for Mobile Ad Hoc Networks Using Directional Antennas

컴퓨터 및 정보통신공학 강 창 호

목차

• ABSTRACT• INTRODUCTION• DIRECTIONAL ANTENNAS IN AD HOC

NETWORKS• SIMULATION MODEL• SIMULATION RESULTS• CONCLUSION

ABSTRACT

ABSTRACT

• Ad hoc network of mobile wireless terminals(with multiple directional antennas)– Reduce the radio interference– Improving the packet throughput

• Problem– Frequent node movements

• Locating and Tracking

INTRODUCTION

INTRODUCTION

• Mobile Ad Hoc Network• Medium Access Control(MAC)• CSMA , CSMA/CA• DBTMA, FAMA, CARMA• Bandwidth utilization and throughput• MAC protocol

– Using directional antennas

INTRODUCTION

• Typical MAC protocols– Using omnidirectional antennas– Need to communicate

• Neighbors located in any direction

Directional antenna

• Reduce the interference– Nodes lying outside its directional pattern

• Can eliminate the interfering signals– From directions other than the signal source

Directional antenna

• Finding the desired direction• Reception using a directional antenna• Mobile terminal

– May have limitations of size– And the complexity/cost of communication

hardware

Propose a MAC protocol

• Use directional antennas• In an ad hoc network• Where the mobile nodes• Do not have nay location information• Use an RTS/CTS exchange

DIRECTIONAL ANTENNAS IN AD HOC NETWORKS

Model Description

• N mobile terminals(nodes)– Radio tranceivers– Share the same wireless channel– Transmission range

• Transmission power• Antenna gain• Receiver sensitivity• Channel characteristics• Noise

Model Description

• M directional antennas– Conical radiation pattern– Spanning an angle of 2π/M radians– Maintain this orientation at all times

• Correctively span• non-overlapping beam directions

Model Description

– Active and Passive mode– Use only active antenna– Complete attenuation

• Outside the conical pattern

– At any given time• Only one radio transceiver per node• Transmit and receive only one packet

MAC Protocol Using Directional Antennas

MAC Protocol Using Directional Antennas

• TRSS : total received signal strength• ST : sensing threshold• DSN : data source node• DDN : data destination node• OLN : other listening node• OTH : off-the-air

Defer and transmit

• Monitoring• TRSS > ST

– Wait util TRSS < ST – Wait for LongIFS– Wait for random access backoff period

Defer and transmit

• TRSS < ST– For atleast LongIFS– Initiate transmission

• TRSS > ST (for backoff period)– Backoff delay is canceled

Proposed MAC protocol

DSN

DDN

OLN

OLN

OLNDefer and transmit an RTS packet all antennas

Begin an OTH period

Transmit CTS packet on all antennas

ActivePassive

Begin or extend an OTH2 period

RTS

DATARTSRTS

RTS

RTS

CTSCTS

CTSCTS

M.PActive

Passive

Passive

Passive

M.PActive

Passive

Passive

Passive

SIMULATION MODEL

SIMULATION MODEL

• Indoor radio propagation model• Multipath fading• Parameterized radio receiver

charateristics

SIMULATION MODEL

• nxn square grid• N2 stationary wireless nodes• Specified by the user

– Transmitter power– Receiver sensitivity for carrier sensing– Minimum signal-to-interference– Grid spacing

SIMULATION RESULTS

PARAMETER1

• 15x15 uniform grid• 225 node ad hoc network

PARAMETER2

Parameter Values used

Grid size 200m

Transmitter power 50 dBm

Carrier sense threshold(ST) -70 dBm

Noise floor -90 dBm

Minimum SIR 20 dB

Packet size 1000 bytes

Node speed 10 m/s

Total bandwidth 1 Mb/sec

Result 1

Move randomly with a speed of 3 m/s

Result 2

Movement speed (m/s)

CONCLUSION

CONCLUSION

• Use directional antennas• Use variation of the RTS/CTS exchange• Improve the throughput