Interference cancellation and network coding for underwater communication systems

It is widely believed that wider access to the aquatic environment will enhance human knowledge and understanding of the world's oceans which constitute the major part of our planet. Hence, the current development of underwater sensing and communication systems will produce scientific, economic and social benefits. New applications will be enabled, such as deeper ocean observation, environmental monitoring, surveying or search and rescue missions. Underwater communications differ from terrestrial communications due to the unpredictable and complex ocean conditions, relying on acoustic waves which are affected by many factors like large propagation losses, long latency, limited bandwidth capacity and channel stability, posing great challenges for reliable data transport in this kind of networks. The aim of this project is to design a future underwater acoustic communication system for dense traffic situations investigating the possibility of Medium Access with Interference Cancellation and Network Coding. The main efforts focus on reliability, low energy consumption, storage capacity, throughput and scalabilit

Medium access control, error control and routing in underwater acoustic networks: a discussion on protocol design and implementation

The journey of underwater communication which began from Leonardo’s era took four and a half centuries to find practical applications for military purposes during World War II. However, over the last three decades, underwater acoustic communications witnessed a massive development due to the advancements in the design of underwater communicating peripherals and their supporting protocols. Successively, doors are opened for a wide range of applications to employ in the underwater environment, such as oceanography, pollution monitoring, offshore exploration, disaster prevention, navigation assistance, monitoring, coastal patrol and surveillance. Different applications may have different characteristics and hence, may require different network architectures. For instance, routing protocols designed for unpartitioned multi-hop networks are not suitable for Delay-Tolerant Networks. Furthermore, single-hop networks do not need routing protocols at all. Therefore, before developing a protocol one must study the network architecture properly and design it accordingly. There are several other factors which should also be considered with the network architecture while designing an efficient protocol for underwater networks, such as long propagation delay, limited bandwidth, limited battery power, high bit error rate of the channel and several other adverse properties of the channel, such as, multi-path, fading and refractive behaviors. Moreover, the environment also has an impact on the performance of the protocols designed for underwater networks. Even temperature changes in a single day have an impact on the performance of the protocols. A good protocol designed for any network should consider some or all of these characteristics to achieve better performance. In this thesis, we first discuss the impact of the environment on the performance of MAC and routing protocols. From our investigation, we discover that even temperature changes within a day may affect the sound speed profile and hence, the channel changes and the protocol performance vary. After that we discuss several protocols which are specifically designed for underwater acoustic networks to serve different purposes and for different network architectures. Underwater Selective Repeat (USR) is an error control protocol designed to assure reliable data transmission in the MAC layer. One may suspect that employing an error control technique over a channel which already suffers from long propagation delays is a burden. However, USR utilizes long propagation by transmitting multiple packets in a single RTT using an interlacing technique. After USR, a routing protocol for surveillance networks is discussed where some sensors are laid down at the bottom of the sea and some sinks are placed outside the area. If a sensor detects an asset within its detection range, it announces the presence of intruders by transmitting packets to the sinks. It may happen that the discovered asset is an enemy ship or an enemy submarine which creates noise to jam the network. Therefore, in surveillance networks, it is necessary that the protocols have jamming resistance capabilities. Moreover, since the network supports multiple sinks with similar anycast address, we propose a Jamming Resistance multi-path Multi-Sink Routing Protocol (MSRP) using a source routing technique. However, the problem of source routing is that it suffers from large overhead (every packet includes the whole path information) with respect to other routing techniques, and also suffers from the unidirectional link problem. Therefore, another routing protocol based on a distance vector technique, called Multi-path Routing with Limited Cross-Path Interference (L-CROP) protocol is proposed, which employs a neighbor-aware multi-path discovery algorithm to support low interference multiple paths between each source-destination pair. Following that, another routing protocol is discussed for next generation coastal patrol and surveillance network, called Underwater Delay-Tolerant Network (UDTN) routing where some AUVs carry out the patrolling work of a given area and report to a shore based control-center. Since the area to be patrolled is large, AUVs experience intermittent connectivity. In our proposed protocol, two nodes that understand to be in contact with each other calculate and divide their contact duration equally so that every node gets a fair share of the contact duration to exchange data. Moreover, a probabilistic spray technique is employed to restrict the number of packet transmissions and for error correction a modified version of USR is employed. In the appendix, we discuss a framework which was designed by our research group to realize underwater communication through simulation which is used in most of the simulations in this thesis, called DESERT Underwater (short for DEsign, Simulate, Emulate and Realize Test-beds for Underwater network protocols). It is an underwater extension of the NS-Miracle simulator to support the design and implementation of underwater network protocols. Its creation assists the researchers in to utilizing the same codes designed for the simulator to employ in actual hardware devices and test in the real underwater scenario

Data Transmission with Reduced Delay for Distributed Acoustic Sensors

This paper proposes a channel access control scheme fit to dense acoustic sensor nodes in a sensor network. In the considered scenario, multiple acoustic sensor nodes within communication range of a cluster head are grouped into clusters. Acoustic sensor nodes in a cluster detect acoustic signals and convert them into electric signals (packets). Detection by acoustic sensors can be executed periodically or randomly and random detection by acoustic sensors is event driven. As a result, each acoustic sensor generates their packets (50bytes each) periodically or randomly over short time intervals (400ms~4seconds) and transmits directly to a cluster head (coordinator node). Our approach proposes to use a slotted carrier sense multiple access. All acoustic sensor nodes in a cluster are allocated to time slots and the number of allocated sensor nodes to each time slot is uniform. All sensor nodes allocated to a time slot listen for packet transmission from the beginning of the time slot for a duration proportional to their priority. The first node that detect the channel to be free for its whole window is allowed to transmit. The order of packet transmissions with the acoustic sensor nodes in the time slot is autonomously adjusted according to the history of packet transmissions in the time slot. In simulations, performances of the proposed scheme are demonstrated by the comparisons with other low rate wireless channel access schemes.Comment: Accepted to IJDSN, final preprinted versio

Underwater Wireless Sensor Networks: How Do Acoustic Propagation Models Impact the Performance of Higher-Level Protocols?

Several Medium Access Control (MAC) and routing protocols have been developed in the last years for Underwater Wireless Sensor Networks (UWSNs). One of the main difficulties to compare and validate the performance of different proposals is the lack of a common standard to model the acoustic propagation in the underwater environment. In this paper we analyze the evolution of underwater acoustic prediction models from a simple approach to more detailed and accurate models. Then, different high layer network protocols are tested with different acoustic propagation models in order to determine the influence of environmental parameters on the obtained results. After several experiments, we can conclude that higher-level protocols are sensitive to both: (a) physical layer parameters related to the network scenario and (b) the acoustic propagation model. Conditions like ocean surface activity, scenario location, bathymetry or floor sediment composition, may change the signal propagation behavior. So, when designing network architectures for UWSNs, the role of the physical layer should be seriously taken into account in order to assert that the obtained simulation results will be close to the ones obtained in real network scenarios

Throughput modeling of single hop CSMA networks with non-negligible propagation delay

Cataloged from PDF version of article.We analyze the performance of the CSMA protocol under propagation delays that are comparable with packet transmission times. We propose a semi-Markov model for the 2-node CSMA channel. For the 2-node case, the capacity reduces to 40% of the zero-delay capacity when the one-way propagation delay is 10% of the packet transmission time. We then extend this model and obtain the optimum symmetric probing rate that achieves the maximum network throughput as a function of the average propagation delay, d¯, and the number of nodes sharing the channel, N. The proposed model predicts that the total capacity decreases with d¯−1 as N goes to infinity when all nodes probe the channel at the optimum rate. The optimum probing rate for each node decreases with 1/N and the total optimum probing rate decreases faster than d¯−1 as N goes to infinity. We investigate how the short-term unfairness problem in CSMA worsens as the propagation delay increases and propose a back-off mechanism to mitigate this issue. The theoretical results presented in this paper can be used as a benchmark for the performance improvements provided by algorithms that have already been developed

Transmission Scheduling Technique for A Propagation transfer using Sensing Protocol Under water Acoustic Wireless Sensor Networks.

 As detector nodes square measure typically powered devices, the vital aspects to face concern the way to cut back the energy consumption of nodes, so the network lifespan may be extended to cheap times. Mobile underwater networks with acoustic communications square measure faced with many distinctive challenges like high transmission power utilization, giant propagation delay and node quality. In which Protocol multichip wireless network that uses multiple channel and dynamic channel choice technique. The comparison is conceded out by means that of analytical models, that square measure wont to confine the activities of a node that acts in line with either thought-about specifically for the underwater acoustic surroundings. The delay-aware opportunist transmission planning rule has been principally designed for underwater mobile detector networks. It uses passively obtained native info to reinforce the probabilities of synchronic transmissions whereas reducing collisions. Together with that, a straightforward performance mechanism that allows multiple outstanding packets at the sender facet, facultative multiple transmission sessions has been projected, that successively considerably improves the turnout. Every node learns neighboring node’s propagation delay info and their expected transmission schedules by passively overhearing packet transmissions through the institution of the new developed Macintosh protocol referred to as DOTS. This protocol principally aspires to attain higher channel utilization by harnessing each temporal and spatial recycle. The simulation results exemplify that DOTS provides truthful, medium access even with node quality. Thence this protocol additionally saves transmission energy by avoiding collisions whereas increasing turnout. It additionally achieves a turnout many times over that of the Slotted FAMA, whereas providing connected savings in energy. understanding that protocol is additional suited to given network setting and square measure expected to be of facilitate in planning novel protocol that presumably surmount presently out there solutions. Node monitor native underwater activities and report collected detector knowledge exploitation acoustic multi-hop routing to alternative mobile nodes for collaboration or just to a far off knowledge assortment center