263 research outputs found
Medium access control, error control and routing in underwater acoustic networks: a discussion on protocol design and implementation
No full textThe 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
Multipath Routing With Limited Cross-Path Interference in Underwater Networks
No full textMultipath routing protocols trade off the effort of replicating data packets through multiple routes for improved delivery ratio or end-to-end delay. These advantages are especially valuable for those underwater networking applications where reliable data delivery justifies a higher resource consumption. In this letter, we argue that choosing multipath routes according only to the node- and link-disjoint paradigms may lead to excessive interference in underwater networks, even in the presence of MAC protocols based on interference avoidance. We show that it is more convenient to directly choose multipath routes that cause little interference to one another, and propose a multipath routing protocol that distributedly implements this concept. We simulate our solution in underwater network scenarios, and show that it achieves better packet delivery ratio and fewer interference-induced packet losses with respect to standard multipath routing approaches, even when the latter are stacked on top of interference-avoiding MAC protocols
MACA-APT: A MACA-based adaptive packet train transmission protocol for underwater acoustic networks
No full textIn wireless communications, collision is one of the principal sources of energy wastage, which often makes collision avoidance strategies preferred for medium access control (MAC) protocols. In this paper, we propose a collision avoidance-based MAC protocol called MACA-based Adaptive Packet Train (MACA-APT), which has been designed specifically for underwater acoustic networks (UANs). The design explicitly accounts for prominent characteristics of UANs such as long propagation delays and typically high bit error rates. In particular, the former is compensated via the transmission of multiple consecutive packets to multiple different receivers; the latter, instead, is tackled by embedding a cross-layer Stop-&-Wait ARQ scheme within MACA-APT.
The performance of the proposed protocol is evaluated via simulations and compared to another MAC protocol, also based on MACA, showing that MACA-APT achieves better performance for low to intermediate packet generation rates, and equivalent performance at higher rates. Moreover, we assess the impact of the packet train size on the performance of either protocol. This result is a first step towards the design of adaptive multi-packet multi-receiver MAC protocols for underwater networks
Underwater delay-tolerant routing via probabilistic spraying
No full textWe propose underwater delay-tolerant routing via probabilistic spraying (UDTN-Prob), a routing protocol for underwater delay-tolerant networks based on the store-and-forward paradigm. Our protocol exploits limited statistical knowledge of the time between two subsequent contacts between pairs of network nodes in order to filter the packets injected into the network, so that only those with a sufficiently high chance of being delivered to their intended destination within a given deadline are actually transmitted. In addition, the foreseen duration of a contact is estimated via a preliminary packet exchange, so that the nodes get a fair share of the contact time to exchange their own data. The transmission is protected against channel-induced packet losses via an automatic repeat query scheme modified to adapt itself to typical underwater transmission times and to the variation of round-trip times induced by node mobility. We simulate the protocol using the DESERT Underwater libraries, that make it possible to accurately reproduce the nodes’ behavior and mobility patterns. Our results show that the proposed protocol achieves significantly better performance than spray-and-wait, which is currently the most typical choice among store-and-forward protocols. Moreover, we show that a two-hop statistical knowledge of the node contact process yields marginally higher utility with respect to a simpler one-hop knowledge, which is also much easier to collect or estimate
On the performance of unsynchronized distributed MAC protocols in deep water acoustic networks
No full textRecent simulation software such as WOSS [1] and similar packages make it possible to perform accurate simulations of underwater acoustic networks by taking into account the actual behavior of sound propagation. In this paper, we focus on deep-water acoustic networks, and employ WOSS to compare the performance of three MAC protocols based on random access. The final goal of this effort is to test several network scenarios and baseline protocol approaches, and to understand which is more likely to offer top performance in underwater networks. In fact, it is still a partly open question whether or not there is a medium access control (MAC) protocol that is "good" in most if not all scenarios and network arrangements; or, at least, if any MAC protocol would be able to emerge as the de facto choice for most applications and network topologies. In this paper, we perform a comparison of MAC protocols in deep-water scenarios, in order to extend previous analyses, which targeted mainly shallow water networks. We will consider three types of medium access control: random access with instantaneous carrier sensing [1], transmitter-side tone-driven contention [2], and 3-way Request-To-Send/Clear-To-Send (RTS/CTS)-based access [3]
Performance Analysis of On-Demand Routing Protocols in Wireless Mesh Networks
No full textWireless Mesh Networks (WMNs) have recently gained a lot of popularity due to their rapid deployment and instant communication capabilities. WMNs are dynamically self-organizing, self-configuring and self-healing with the nodes in the network automatically establishing an adiej hoc network and preserving the mesh connectivity. Designing a routing protocol for WMNs requires several aspects to consider, such as wireless networks, fixed applications, mobile applications, scalability, better performance metrics, efficient routing within infrastructure, load balancing, throughput enhancement, interference, robustness etc. To support communication, various routing protocols are designed for various networks (e.g. ad hoc, sensor, wired etc.). However, all these protocols are not suitable for WMNs, because of the architectural differences among the networks. In this paper, a detailed simulation based performance study and analysis is performed on the reactive routing protocols to verify the suitability of these protocols over such kind of networks. Ad Hoc On-Demand Distance Vector (AODV), Dynamic Source Routing (DSR) and Dynamic MANET On-demand (DYMO) routing protocol are considered as the representative of reactive routing protocols. The performance differentials are investigated using varying traffic load and number of source. Based on the simulation results, how the performance of each protocol can be improved is also recommended.Wireless Mesh Networks (WMNs), IEEE 802.11s, AODV, DSR, DYMO
On the impact of the environment on MAC and routing in shallow water scenarios
No full textIn this paper, we investigate the impact of environmental changes on Medium Access Control (MAC) and routing protocols for underwater acoustic networks. We carry out the evaluation using the ns2-Miracle network simulator and the WOSS extensions, which interface the simulator to the Bellhop ray tracing software. We further extend the simulator to take into account the change of environmental parameters during the day, and to be able to generate random realizations of surface waves. We start by discussing how the acoustic propagation pattern changes due to changing temperature conditions, and show the impact of such variability on the performance of two random access protocols, namely CSMA-ALOHA and DACAP. As CSMA-ALOHA proves best in our simulation, we consider this protocol in a converge-casting scenario, where all nodes have to deliver their data to a centrally placed sink. In this scenario, we show that keeping the routes fixed is not the best strategy because of time-varying propagation effects, and that even infrequent route updates (once every 3 hours) achieve much better results in terms of throughput, delivery delay, and average route length than static routes
Jamming-resistant multi-path routing for reliable intruder detection in underwater networks
No full textIn this paper, we discuss the performance of multi-path routing techniques in underwater acoustic networks applied to an intruder detection scenario. We assume that a network of submarine sensors is deployed close to a surveilled harbor, with the task to detect outbound surface boats. The communications take place in the 4 to 8 kHz band, in order to favor long-haul transmissions. This band is highly affected by the noise originating from the boat propellers. Therefore, we resort to jamming-resilient techniques such as multi-path transmissions. The latter is accomplished by restricted flooding, and by an adaptive form of source routing as an alternative.
Our results show that the inherent redundancy of multi-path routing offers an effective shield against excessive packet losses in the presence of strong jamming. This increases the probability that data packets containing detection information are promptly delivered to the desired sinks, with respect to the performance of static, single-path routing. In particular, restricted flooding achieves the best delivery ratio at the price of a very high number of generated replicas, whereas adaptive source routing trades off a lower delivery ratio for a lower overhead
On ARQ strategies over random access protocols in underwater acoustic networks
No full textIn this paper, we introduce a mechanism to improve the performance of ARQ over underwater links. Our scheme aims at reproducing a Selective Repeat ARQ strategy: to do this, it sets up a form of time-division duplex link between the transmitter and its receiver, by leveraging on the propagation delay incurred by underwater sound. In fact, such delay typically allows to interlace the transmission of data and ACK packets in such a way that the two operations do not interfere or cause nodes to be deaf to the transmissions of each other. We consider two different versions of our protocol (in terms of channel access persistence) and compare them against ALOHA and CSMA with and without ARQ, in both static and mobile scenarios. We conclude that in multiuser networks our form of Selective Repeat ARQ outperforms other ACK-based protocols at low and intermediate traffic
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