ript: a receiver-initiated reservation-based protocol for underwater acoustic networks

RIPT: A Receiver-initiated Reservation-based Protocol for Underwater Acoustic Networks

Nitthita Chirdchoo, Wee-Seng Soh, Kee Chaing Chua

IEEE JOURNAL ON SELECTED AREAS IN COMMUNICATIONS, VOL. 26, NO. 9, DECEMBER 2

008

Outline

IntroductionReceiver Initiated Packet Train (RIPT)

ProtocolSimulation and ResultsConclusion

Introduction

In terrestrial, typically assume the propagation delay is negligible busy signal, handshaking mechanism

In contrast, underwater communication resulting in propagation delay and narrow available

bandwidth may not be practical to set aside a separate

frequency band for transmitting busy signals

RIPT Protocol Overview

Long propagation delay, node takes much longer to receive control packets higher collision rate, and again, low throughput

It appears that receiver-initiated reservations are better because a receiver knows exactly when the

current handshake will endUtilized a receiver-initiated 4-way

(RTR/SIZE/ORDER/DATA) handshake

4-Way Handshaking

Initiated by RTR Packet

It contains receiver’s ID and number of data slots reserved

at the receiver (Mtrain) inter-node propagation delay from itself to each

of its neighbors a flag to indicate whether the receiver has any

DATA packet to broadcast

Nodes have same propagation delay granting priority to node with smaller node ID

Transmission Time of SIZE PacketReceive RTR

First Hop Neighbor Calculate

ORDER Packet

It contains the total slots assigned to each neighboring, and the order of transmission

Each of the neighboring nodes is assigned a unique priority randomly

Mtrain = 4

Broadcast Packet (Nb)

Receiver resends the information on broadcast packets

Improve the chances of its neighbors to be ready for them

After ORDER packet transmitting, receiver transmits its broadcast packets, if any

DATA Train Transmission

Adaptive Train Size

If the receiver finds that its Mtrain is not large enough increases Mtrain by 2 for the next round

If it finds that there are sufficient slot requests to fill up its Mtrain

decreases Mtrain by 1

There should be a maximum limit for Mtrain, avoid any receiver from capturing the channel f

or too long

When to Initiate an RTR Packet

The timing of initiating RTR packets is an important issue

Pick the exponential distribution for the time between RTR-initiations

Fairness Bit

To avoid same node acting as a receiver before other neighboring fairness bit

If a node has released from a handshaking loop while acting as a receiver set bit to ‘0’, and will not initiate any RTR packet reset once only the node has served as sender if a node has set ‘0’ for longer than tlimit ,it will res

et back to ‘1’

Simulation and Results

The effect of Mtrain and Tavg

offered load per node = 0.07

Throughput

Transmission and Collision

Delay

Conclusion

They proposed and studied a new MAC protocol for multi-hop underwater acoustic networks – RIPT

Random access handshaking protocol that addresses long propagation delay utilizing receiver-initiated reservations