1. Exploring Random Access and Handshaking Techniques in Large- Scale Underwater Wireless Acoustic Sensor Networks Peng Xie and Jun-Hong Cui Computer Science &Engineering Department University of Connecticut

2. Medium Access Control (MAC) Contention-free Protocols Contention-based Protocols –Random Access: ALOHA, slotted ALOHA –Collision Avoidance with Handshaking MACA,MACAW

3. Network Model B is the only receiver, all other nodes are senders

4. Performance Metrics Throughput –The number of effective bits, i.e., the size of all data packet successfully received by the receiver. Communication Overhead –Ratio of the total number of bits sent by the sender to the number of effective bits received by the receiver.

5. Modeling Random Access Random Access for Underwater Sensor Networks –Same as random access for radio-based network –Node sends packets whenever it has data –A packet is successfully delivered if no collision occurs at the receiver side

6. Modeling Random Access (Cont’d) The sending data process of each node follows Poisson Distribution with data rate λ Data packet duration T p Data packet size S p Number of nodes in the network: n

7. Modeling Random Access (Cont’d) One data packet transmission –Success Probability –Average throughput of the whole networks –Communication overhead

8. Modeling Random Access (Cont’d) Trains of packets (m packets in a burst) –Success probability –Throughput –Communication overhead

9. Modeling RTS/CTS for Underwater Sensor Networks Infeasibility of RTS/CTS in Underwater Sensor Networks

10. Modeling RTS/CTS (Cont’d) Modifying RTS/CTS for Underwater Sensor Networks –When a sender receives CTS, the sender has to wait for the CTS to propagate the whole transmission range of the receiver. –The probability of data packet collision still exists, but can be negligible.

11. Modeling RTS/CTS (Cont’d) Maximum data rate –Time of one transmission: T Θ =T cts +T prop +T trans –Max data rate: λ t =min(1/ T Θ, λ(n-1)) Throughput: m×S p × λ t Communication overhead

12. General Parameter Setting –Bit rate: 10kbps –Distance between the sender and the receiver: 50 m –Transmission range: 100m –Data packet size: 40B –Control packet size: 4B –Number of network: 5 –Data rate: 1-5 packets/s

13. Performance Comparison :Non- Burst-Traffic Effect of Data Rate

14. Performance Comparison :Non- Burst-Traffic Effect of Transmission Range

15. Performance Comparison :Non- Burst-Traffic Effect of network density

16. Performance Comparison :Non- Burst-Traffic Effect of Transmission Distance

17. Performance Comparison :Non- Burst-Traffic Effect of Packet Size

18. Performance Comparison : Burst- Traffic

19. Conclusions The performance of random access and RTS/CTS are affected by many factors, such as transmission range, data generation, traffic burst, packet size and network topology. NO absolute winner for all network conditions.