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
