Angular MAC: a framework for directional antennas in wireless mesh networks

Erdem Ulukan and Özgür Gürbüz

Faculty of Engineering and Natural Sciences,

Sabanci University, Turkey

ACM Journal of Wireless Networks vol. 14 no.2 (April 2008)

(SCI 2008=0.741)

Outline Introduction Proposed Mechanism – Angular MAC Evaluation Analysis – Throughput Enhancement Conclusion

Introduction Capacity of wireless mesh networks can be enhanced

through the use of smart directional antennas. High quality links Throughput enhancement by spatial reuse

Lots of previous works suffer from Hidden terminal problem Deafness problem Head-of-line blocking problem

Each node is equipped with a multi-beam antenna. The multi-beam antenna either transmit or receive data

packets at a time, but not both.

Introduction – Antenna Model

a a01

2 3

Introduction – Related Work

D-CSMA All nodes are 1-hop neighbor.

Nasipuri, A., Ye, S., You, J., & Hiromoto, R. E. A MAC protocol for mobile ad hoc networks using directional antennas. IEEE WCNC, 2000.

a01

2 3

c01

2 3

b01

2 3

d01

2 3

Directional RTSDirectional CTS

Data (ab)Directional RTS

Directional CTS

Data (cd)

Introduction – Related Work

D-CSMA Deafness problem

Nasipuri, A., Ye, S., You, J., & Hiromoto, R. E. “A MAC protocol for mobile ad hoc networks using directional antennas.” IEEE WCNC, 2000.

a01

2 3

c01

2 3

b01

2 3

d01

2 3

Directional RTS

Data (cd)

Deafness in node c

Introduction – Related Work

Head-of-line blocking problem Result from transmission queue (FIFO) Optimal scheduling is ab, ac

Kolar, V., Tilak, S., & Abu-Ghazaleh, N. B. “Avoiding head of line blocking in directional antenna.” IEEE LCN, 2004.

a01

2 3

c01

2 3

b01

2 3

d01

2 3Data (cd)

Queue(1)

Queue(2)

Goal Proposed Angular MAC (ANMAC)

Hidden terminal problem is alleviated Deafness problem is prevented Head-of-line blocking problem is alleviated

Proposed Mechanism Angular MAC (ANMAC)

All nodes are single hop.

a01

2 3

c01

2 3

b01

2 3

d01

2 3

AN-RTS

[1,a,b]

[2,a,b][3,a,b]

[3,a,b]

[0,a,b]

Data (ab)

[b,a,2,1,3]

AN-CTS

[b,a,3,1,3]

[b,a,0,1,3]

[b,a,1,1,3]

Proposed Mechanism Angular MAC (ANMAC)

Tdefer=SIFS+TACK

a01

2 3

c01

2 3

b01

2 3

d01

2 3Data (dc)

ANRTStimed to c

a to b ANRTS

SIFS

ANCTS

SIFS

DATA

SIFS

ACK

DIFS

CW

SIFS

ANCTS

SIFS

DATA

SIFS

ACK

DIFS

DIFS

CW

Tdefer

Proposed Mechanism Angular MAC (ANMAC)

Network Allocation Notification (NAN)

a01

2 3

c01

2 3

b01

2 3

d01

2 3Data (cd)

NAN

ANRTStimec to d

a to b ANRTS

SIFS

ANCTS

SIFS

DATA

SIFS

ACK

SIFS

DIFS

CW

SIFS

ANCTS

SIFS

DATA

SIFS

ACK

DIFS

DIFS

CW

NANTdefer

Evaluation

Simulator OPNET

Competitions 802.11b

D-CSMA

Parameters

Physical layer data rate 11 Mbps

Packet generate rate 1450 bytes at a Poisson distribution

All transmissions are single hop.

Cross-like Topology

Cross-like Topology

Random Topology

Analysis – Throughput Enhancement (Contention Window)

According to success ratio (Nc/Ns) for tuning optimal contention window to maximize the throughput.

Nc – the number of collided packets

Ns – the number of successful packets

Define τ– the probability that a node transmits in a randomly chosen slot p – the probability that a transmitted packet encounters a collision Ps – the probability of successful transmission

ss

c

P

p

N

Nratio Success

From: IEEE Std 802.11 Figure. 51

Analysis

m

i

W

kki

ii

iki

i

b

bW

kWb

0

1

0,

0,,

1

Figrue. Markov Chain model for the backoff window size

i,wi-2 i,wi-1

i as backoff stagek as backoff time counterW as CWmin

Wi as 2iW, i (0,∈ m), so CWmax=2mW

0,00,0,0,0,1

0,00,0,0,1

,

1

0 ,

},{lim

bp

pbbpbpb

mibpbbpb

kiPLetb

m

mmmm

iiii

kki

)1,0( /}0,|,{P

),1( )1,0( /}0,1|,{P

],0[ )1,0( /)1(}0,|,0{P

],0[ )2,0( 1}1,|,{P

00

mm

ii

i

WkWpmkm

miWkWpiki

miWkWpik

miWkkiki

Analysis

n

n

n

ss

c

nP

p

N

N

)1(1)1(

)1(1ratio Success 1

1

Evaluation for Contention channel enhancements

Omni 802.11b Directional ANMAC-LS

Optimal CWmin is for 802.11b.

Conclusion ANMAC’s contributions are

self configuring nature with neighbor discovery immunity to deafness optimal selection and dynamic adaptation of contention window to

maximize the network throughput

Thank you~