Design Of Efficient And Reliable Transmission Protocol For Underwater Sensor Network Based On Network Coding

With the growing prosperity of Marine economy,the role of the underwater acoustic communication is becoming more and more important,However,the traditional point-to-point underwater acoustic communication has a single function,so it is necessary to endue underwater acoustic communication with the function of networking.Underwater sensor network can play a greater role in Marine oil and gas exploitation,Marine environment monitoring,underwater vehicle networking and other aspects.Due to the limitations of underwater acoustic channel in the Marine environment,for example,the propagation speed of underwater sound is only about 1500 m/s,which is 5 orders of magnitude lower than the propagation speed of electromagnetic wave.The multipath effect and doppler effect can greatly increase the communication delay and bit error rate.The bandwidth of underwater acoustic communication is extremely low.These limitations make underwater acoustic communication more challenging than terrestrial communication.The purpose of reliable data transmission is to enable the receiving node to successfully receive the data sent to it.The main schemes for this purpose are Automatic Repeat-reQuest(ARQ)and network coding.ARQ can achieve reliable data transmission in a low-noise environment,but if the environment is extremely bad,it will be trapped in continuous retransmission,which greatly reduces the transmission efficiency.However,network coding is a redundancy mechanism and has a high fault tolerance to the harsh environment.Many literatures also put forward their own strategies and suggestions based on these two schemes.In this paper,under the framework of underwater acoustic network,the following research contents and innovations are made to solve the problem of unreliable transmission.1.Apply the concept of ocean computing,put intelligent data processing in the front end,and compress the image data according to the characteristics of underwater images,which can significantly reduce the amount of data to be transmitted.Reducing the amount of original image data by half without affecting the quality of the data.2.Using a hybrid scheme of network coding and selective retransmission.At the sending end,the forward error correction code is first used to encode the data.Although some redundant data are transmitted,the receiver can recover the original data by decoding even if some packets are lost due to channel instability or conflicts,thus reducing the number of retransmission.In the case of a poor channel,if the receiver does not recover the original data,it uses a selective retransmission algorithm to send a NACK to notify the sending node to send the lost data packet.Especially for multi-hop networks,network performance is significantly improved.3.Improved the selection of retransmission.In the case that no acknowledgement packet is received,all packets will be retransmitted.However,after coding,the packets will be doubled.If all packets are retransmitted,unnecessary network overhead and energy consumption will be increased.So in this article,network performance is improved by retransmitting the last packet when the acknowledgement packet is not received.Based on the reliability transmission protocol proposed in this paper,the image denoising and compression algorithm can be used to alleviate the problem of inconvenient underwater charging.It only transmits the characteristic information to reduce the amount of data and achieve efficient transmission.The idea of hop-by-hop coding can be applied to multi-hop networks,which greatly increases the application range and reliability.