1. Junfeng Xu, Keqiu Li, and Geyong Min IEEE Globecom 2010 Speak: Huei-Rung, Tsai Layered Multi-path Power Control in Underwater Sensor Networks

2. Outline  Introduction  Goals  Overview  Problem Formulation  Layered Multi-path Power Control (LMPC) scheme  Simulation  Conclusions

3. Introduction  Underwater Sensor Networks (USNs) enable a wide range of important applications  oceanographic data collection  scientific ocean sampling  pollution and environmental monitoring  disaster prevention  assisted navigation  distributed tactical surveillance

4. Introduction  USNs have posed many problems in the design and deployment  limited available bandwidth  large propagation delay  high bit error rates  energy efficiency (especially in the deep ocean)  Many mechanisms have recently been proposed to improve energy efficiency in USNs  design of low-power chipset  optimization of energy model  optimization of source scheduling  development of multi-path communications (MPC)

5. Introduction  Most of the existing mechanisms assume that the sound decay as the propagation distance increases, but ignore the noise attenuation in the deep underwater environment  Noise comes from the ocean surface, such as shipping, wind, thermal and turbulence, thus the bottom of the ocean is much ”quieter” than the surface

6. Goals  Taking noise attenuation into account to propose a smart Layered Multi-path Power Control (LMPC) scheme  build an energy-efficient tree-based multiple path  control energy consumption at different nodes in USNs to guarantee the lower energy consumption and higher reliability  avoiding retransmission

7. Overview Radio Channel Acoustic Channel Source Node Cross NodeSurface Gateway

8. Network Architecture  Multiple copies of the same packet are transmitted along multiple paths from a source node to the gateways  Different copies of the packet are forwarded to the sink from the gateways using the radio channel  Sink combine copies to generate the original packets

9. Problem Formulation Energy consumed at a node transmission power length of data packet data rate of transmission link L j The objective statement packet error ratedata ratepower

10. LMPC scheme  Build the energy-efficient tree (EET)  Distribute transmission power on the EET with the proper packet error ratio (PER)

11. LMPC scheme  Build the energy-efficient tree (EET)  binary tree

12.  Distribute transmission power on the EET with the proper PER LMPC scheme average received signal SNR of node N ij AWGN follows normal distribution, instantaneous received signal SNR

13. LMPC scheme  Distribute transmission power on the EET with the proper PER For QPSK modulation, the bit error ratio(BER) is The packet error rate (Pr ij ) of node N ij Aggregated PER of L i

14. LMPC scheme  Distribute transmission power on the EET with the proper PER average power on path L i

15. LMPC scheme no need of retransmission ensure that P r in the range of the average PER of the solution trees The problem can be written as follows

16. LMPC scheme

17. Simulation  Use NS-2.29 to evaluate the performance the proposed scheme

18. Simulation Scenario 1Scenario 2

19. Conclusions  Motivated by the noise attenuation in deep water, this paper has proposed a layered multi-path power control (LMPC) mechanism for USNs in the underwater environment  communication plate is divided into multiple layers  crossed nodes multicast data packets to the next hops  each node can control transmission power itself