09-10-2010, 12:01 PM
[attachment=5478]
This article is presented by:
Omar O. Aldawibi, Bayan S. Sharif and Charalampos C. Tsimenidis
School of Electrical, Electronic and Computer Engineering
Newcastle University, NE1 7RU, UK
ABSTRACT
Underwater acoustic networks (UAN) are becoming an integral part of a wide range of applications, such as those used for exploration and maintenance in the offshore oil and gas industry, surveillance for homeland security, subsea mine counter measures, marine environmental assessment and diving activities. For UAN, efficient and effective media access control (MAC) is a very important requirement to address the challenges of dense network deployment and shared communication media. Several types of MAC protocols have been developed for radio networks; however, they are not directly adaptable to UAN due to the significant differences between terrestrial radio and underwater acoustic channels. In this paper, we propose a scheduling protocol according to distance awareness to combat propagation delays for ad hoc UAN. The network module and related assumptions are outlined, and a performance analysis, looking at packet transmission probability, maximum saturation throughput and average end to end delay, is also presented. Analytical and practical scenarios and simulations, including network topology, parameters and results, have been discussed.
INTRODUCTION
Underwater acoustic networks have become a powerful technique for aquatic applications, and have recently attracted a great deal of attention from the networking research community . Efficient and effective media access control (MAC) is very important due to dense network deployment and shared communication media. With it, better performance of underwater acoustic networks can be achieved . Different applications require different types of MAC protocols. Several types of MAC protocols have been developed for radio networks; however, they are not directly adaptable to UAN due to the significant differences between terrestrial radio and underwater acoustic channels. MAC protocols can be generally divided into two categories . contention-free protocols and contentionbased protocols. Contention-free protocols include TDMA, FDMA and CMDA, where communication channels are separated into time, frequency or code domains. FDMA is unsuitable for underwater channels because of limited available bandwidth. Furthermore, synchronization in TDMA and the near-far problem in CDMA are two other issues to consider. Consequently, a feasibility study of these protocols in underwater acoustic networks is not easy . Contention-based protocols include random access methods and collision avoidance .In random access the sender transmits the packet without coordination, so packet collision avoidance is totally probabilistic; while in the collision avoidance protocol, the sender and receiver capture the channel through control packets exchanged between them before the data packet has been transmitted . Protocols such as CSMA with collision avoidance based on RTS/CTS protocols are widely used. The performance of random access methods based on RTS/CTS approaches in underwater acoustic networks is determined by several factors. Some research has shown that RTS/CTS-based protocols outperform random access approaches in underwater acoustic networks in terms of energy efficiency. However, the use of a RTS/CTS-based protocol to eliminate packet collision completely results in large energy consumption due to the long propagation delay in underwater acoustic networks. In order to avoid collision completely, two conditions must be satisfied: 1) the duration of the RTS should be greater than the maximum propagation delay; and 2) the duration of CTS should be two times greater than the maximum propagation delay, plus the hardware transmit-toreceive transmission time. These two conditions are easy to apply in terrestrial radio networks. However, it is too expensive to apply them to ad hoc underwater acoustic networks due to the fact that large propagation delay makes the size of the control packets large
This article is presented by:
Omar O. Aldawibi, Bayan S. Sharif and Charalampos C. Tsimenidis
School of Electrical, Electronic and Computer Engineering
Newcastle University, NE1 7RU, UK
Distance Awareness Scheduling for Single-Hop
Underwater Ad-Hoc Network
Underwater Ad-Hoc Network
ABSTRACT
Underwater acoustic networks (UAN) are becoming an integral part of a wide range of applications, such as those used for exploration and maintenance in the offshore oil and gas industry, surveillance for homeland security, subsea mine counter measures, marine environmental assessment and diving activities. For UAN, efficient and effective media access control (MAC) is a very important requirement to address the challenges of dense network deployment and shared communication media. Several types of MAC protocols have been developed for radio networks; however, they are not directly adaptable to UAN due to the significant differences between terrestrial radio and underwater acoustic channels. In this paper, we propose a scheduling protocol according to distance awareness to combat propagation delays for ad hoc UAN. The network module and related assumptions are outlined, and a performance analysis, looking at packet transmission probability, maximum saturation throughput and average end to end delay, is also presented. Analytical and practical scenarios and simulations, including network topology, parameters and results, have been discussed.
INTRODUCTION
Underwater acoustic networks have become a powerful technique for aquatic applications, and have recently attracted a great deal of attention from the networking research community . Efficient and effective media access control (MAC) is very important due to dense network deployment and shared communication media. With it, better performance of underwater acoustic networks can be achieved . Different applications require different types of MAC protocols. Several types of MAC protocols have been developed for radio networks; however, they are not directly adaptable to UAN due to the significant differences between terrestrial radio and underwater acoustic channels. MAC protocols can be generally divided into two categories . contention-free protocols and contentionbased protocols. Contention-free protocols include TDMA, FDMA and CMDA, where communication channels are separated into time, frequency or code domains. FDMA is unsuitable for underwater channels because of limited available bandwidth. Furthermore, synchronization in TDMA and the near-far problem in CDMA are two other issues to consider. Consequently, a feasibility study of these protocols in underwater acoustic networks is not easy . Contention-based protocols include random access methods and collision avoidance .In random access the sender transmits the packet without coordination, so packet collision avoidance is totally probabilistic; while in the collision avoidance protocol, the sender and receiver capture the channel through control packets exchanged between them before the data packet has been transmitted . Protocols such as CSMA with collision avoidance based on RTS/CTS protocols are widely used. The performance of random access methods based on RTS/CTS approaches in underwater acoustic networks is determined by several factors. Some research has shown that RTS/CTS-based protocols outperform random access approaches in underwater acoustic networks in terms of energy efficiency. However, the use of a RTS/CTS-based protocol to eliminate packet collision completely results in large energy consumption due to the long propagation delay in underwater acoustic networks. In order to avoid collision completely, two conditions must be satisfied: 1) the duration of the RTS should be greater than the maximum propagation delay; and 2) the duration of CTS should be two times greater than the maximum propagation delay, plus the hardware transmit-toreceive transmission time. These two conditions are easy to apply in terrestrial radio networks. However, it is too expensive to apply them to ad hoc underwater acoustic networks due to the fact that large propagation delay makes the size of the control packets large
