CONTENTION FREE MAC PROTOCOL BASED ON PRIORITY IN UNDERWATER ACOUSTIC COMMUNICATION

Hui-Jin Cho, Jung-Il Namgung, Nam-Yeol Yun, Soo-Hyun Park, Chang-Hwa Kim and Young-Sun Ryuh

IEEE Oceans 2011 Speaker : Chuan-Heng, Chi

Outline • Introduction • Related work• Goals• Proposed MAC protocol• Network environment• PR-MAC • Simulation • Conclusion

Introduction

• The world's oceans cover over 70 % of its surface• Underwater Wireless Sensor Networks (UWSNs)

Introduction • Underwater sensor network technology can be applied in

many fields• Data acquisition• Underwater exploration• Unattended environmental monitoring systems• Prevention of natural disasters• Military purpose

Introduction • The battery cannot be recharged in simple way• How to reduce the energy consumption is importance

Sensor

Introduction • Transmission rate• WSN: 3 x 108 m/s • UWSN: 1500 m/s• Propagation delay

A

B

Propagation delay

B A

Introduction • Problem • Long propagation delay

RTS

RTS

RTS

CTS

CTS

DATA

DATA

RTS

CTS

A

B

C

Related work• Slotted FAMA

RTS

RTS

RTS

CTS

CTS

DATA

DATA

RTS

CTS DEFERS TRANSMISSIONS

A

B

C

MaximumPropagation Delay+CTS

Goals• We propose appropriate MAC Protocol for underwater

acoustic communications• Minimizing conflicts• Reducing energy loss

Proposed MAC protocol• We propose the Priority Reservation MAC (PR-MAC) protocol• Long propagation delay • Minimizing the conflict• Energy loss

Network environment • Assumption • Time synchronization of each node is conducted before• Each node’s ID assumed to be unique

PR-MAC

Random access period(R1)

Transmission cycle period

(C1) (C2) (Cn)

Transmission cycle period

Slot reservation period Data transmission period

‧‧‧‧‧

Random access period(R2)

time

time

‧‧‧‧‧

PR-MAC

• Random access period• Every node waits for random backoff time to broadcast own information

(include node ID, RSSI, Power status)

D B A C E

A

B

C

D

E

A

A

A C

C

C E

E

B

B

B D

D

C

C

C

B

B

B

Random access period(contention)

Active mode

Random access period(R1)

Transmission cycle period

(C1) (C2) (Cn)‧‧‧‧‧

Random access period(R2)

time

A

A

A C

C

C

B

B

B

PR-MAC• Priority decision

D B A C E

A AA

C CC

EE

B

B

B

A

B

C

D

E

A

A

A C

C

C E

E

B

B

B D

D

C

C

C

B

B

B

A

A

A C

C

C

B

B

B

AA

D D

E

D

E

C

B

D

B

D

E

C

1 2 354

PR-MAC

Random access period(R1)

Transmission cycle period

(C1) (C2) (Cn)

Transmission cycle period

Slot reservation period Data transmission period

‧‧‧‧‧

Random access period(R2)

time

time

‧‧‧‧‧

Slot reservationperiod Data transmission period

Transmission cycle period(contention free)

A

A

A

A

B

C

D

E

(A,2)

C

C

C

(C,10)

E

D B A C E

E

(E,2)

(no data)

B

B

B

(B,6)

A

A

E

rx-rx collision from A,E

B

B

B

C

C

C

Active mode Sleep mode

PR-MAC

Transmission cycle period

Slot reservation period Data transmission period

time

‧‧‧‧‧

Simulation

Parameter Value

Transmission range 1km

Data rate 1kbps

Network size 10km×10km

Nodes 20~200

Reservation message packet size 100 bits

Data packet size 3000 bits

Reservation slots 1 sec

Data slots 4 sec

Simulation • UASN-MAC

Transmission cycle period

Slot reservation period Data transmission period

time

‧‧‧‧‧

Competitive method

Simulation • UWAN-MAC

Simulation

Simulation

Simulation

Conclusion • In this paper, we proposed PR-MAC protocol suitable for

underwater acoustic communication• minimizing collision• reducing energy consumption