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Slot-Time Optimization Scheme for Underwater Acoustic Sensor Networks

수중음향 센서네트워크를 위한 슬롯시간 최적화 기법

  • 이동원 ;
  • 김선명 (금오공과대학교 컴퓨터소프트웨어공학과) ;
  • 이해연 (금오공과대학교 컴퓨터소프트웨어공학과)
  • Received : 2013.11.29
  • Accepted : 2014.04.11
  • Published : 2014.04.30

Abstract

Compared to a terrestrial communication, the high BER(Bit Error Ratio) and low channel bandwidth are the major factor of throughput degradation due to characteristics of underwater channel. Therefore, a MAC protocol must be designed to solve this problem in UWASNs(Underwater Acoustic Sensor Networks). MAC protocols for UWASNs can be classified into two major types according to the contention scheme(Contention-free scheme and Contention-based scheme). In large scale of sensor networks, a Contention-based scheme is commonly used due to time-synchronize problem of Contention-free scheme. In the contention-based scheme, Each node contends with neighbor nodes to access network channel by using Back-off algorithm. But a Slot-Time of Back-off algorithm has long delay times which are cause of decrease network throughput. In this paper, we propose a new scheme to solve this problem. The proposed scheme uses variable Slot-Time instead of fixed Slot-Time. Each node measures propagation delay from neighbors which are used by Slot-time. Therefore, Slot-Times of each node are optimized by considering node deployment. Consequently, the wasted-time for Back-off is reduced and network throughput is improved. A new mac protocol performance in throughput and delay is assessed through NS3 and compared with existing MAC protocol(MACA-U). Finally, it was proved that the MAC protocol using the proposed scheme has better performance than existing MAC protocol as a result of comparison.

무선 센서네트워크의 데이터 전송을 위해서 각 노드는 백오프(Back-off)기법을 이용하여 이웃노드와 채널을 경쟁한다. 수중음향 센서네트워크에서도 일반적으로 백오프를 이용하여 노드 간 채널을 경쟁한다. 그러나 수중음향 센서네트워크의 백오프에 이용되는 슬롯타임(Slot-time)은 무선 센서네트워크와는 달리 매우 긴 지연시간을 갖는다. 따라서, 수중음향 센서네트워크에서는 긴 슬롯타임에 의해 각 노드간의 통신성능 저하 문제가 발생한다. 본 논문에서 제안하는 기법은 실제 노드가 배치된 상태를 이웃 노드와의 전파지연 시간을 이용하여 계산하고, 슬롯타임을 노드 스스로 최적화한다. 이러한 방법을 통해 각 노드들 간의 통신에 낭비되는 시간을 줄이고 네트워크 성능을 향상 시킨다. 본 논문에서는 제안하는 기법을 구체적으로 기술하고 제안하는 기법과 기존의 연구와의 성능차를 확인한다. 성능 비교결과 제안하는 기법이 기존의 기법에 비하여 우수한 성능을 갖는 것을 확인 하였다.

Keywords

References

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