UDTN-RS : A new underwater delay tolerant network routing protocol for coastal patrol and surveillance

The Coastal Patrol and Surveillance Application (CPSA) is developed and deployed to detect, track and monitor water vessel traffic using automated devices. The latest advancements of marine technologies, including Automatic Underwater Vehicles, have encouraged the development of this type of applications. To facilitate their operations, installation of a Coastal Patrol and Surveillance Network (CPSN) is mandatory. One of the primary design objectives of this network is to deliver an adequate amount of data within an effective time frame. This is particularly essential for the detection of an intruder's vessel and its notification through the adverse underwater communication channels. Additionally, intermittent connectivity of the nodes remains another important obstacle to overcome to allow the smooth functioning of CPSA. Taking these objectives and obstacles into account, this work proposes a new protocol by ensembling forward error correction technique (namely Reed-Solomon codes or RS) in Underwater Delay Tolerant Network with probabilistic spraying technique (UDTN-Prob) routing protocol, named Underwater Delay Tolerant Protocol with RS (UDTN-RS). In addition, the existing binary packet spraying technique in UDTN-Prob is enhanced for supporting encoded packet exchange between the contacting nodes. A comprehensive simulation has been performed employing DEsign, Simulate, Emulate and Realize Test-beds (DESERT) underwater simulator along with World Ocean Simulation System (WOSS) package to receive a more realistic account of acoustic propagation for identifying the effectiveness of the proposed protocol. Three scenarios are considered during the simulation campaign, namely varying data transmission rate, varying area size, and a scenario focusing on estimating the overhead ratio. Conversely, for the first two scenarios, three metrics are taken into account: normalised packet delivery ratio, delay, and normalised throughput. The acquired results for these scenarios and metrics are compared to its ancestor, i.e., UDTN-Prob. The results suggest that the proposed UDTN-RS protocol can be considered as a suitable alternative to the existing protocols like UDTN-Prob, Epidemic, and others for sparse networks like CPSN

Energy minimisation through iterative multihop routing in MANETs

Power control is one of the most important issues to be considered in ad hoc networks. Indeed, the choice of the transmission power will have an impact on the received signal strength, on the number of hops required to reach destination nodes, the overall connectivity of the network and their battery life. In this paper, we address the problem of power control so as to miminise the total network energy consumption and provide an optimum routing strategy. We consider CDMA as the communication channel to achieve multiple communications at a given time slot while guarantying a collision free medium access control. We propose a new iterative method which adaptively performs routing, power control and data rate optimisation. Ourapproach minimises the overall network energy consumption under signal to interference ratio constraints. We show that the total energy consumption is reduced when the algorithm is initialised with a routing table resulting from the mimumum spanning tree approach. However, we show that this optimum solution can be approximated when the algorithm is initialised with a very basic routing algorithm

Assessing students in second life - some options

This paper examines various options for assessing students within a virtual world such as Second Life. Although many learning activities are being set for students in virtual worlds and considerable effort is being made to construct elaborate 3D worlds for students to explore, less effort has been expended in developing tools that can assist in the assessment of student learning within the 3D environment. Examples of assessment tasks set using the Sloodle Set, QuizHUD and scripted prims (3D objects) will be discussed.Geoffrey Crisp, Mathew Hillier and Shamim Joarde

Joint power control and spreading gain optimisation for minimising the energy consumption in CDMA based ad hoc networks

This paper addresses the impact of the spreading gain on the efficiency of mobile Ad Hoc networks using Code Division Multiple Access (CDMA) as a mode of transmission. In particular, we concentrate on the trade off between the increase in transmission datarate, hence decrease of transmission time, and the necessary power needed to reach acceptable levels of interference in the system. We formulate this trade off as an optimisation problem with associated constraints, where the cost function is the overall energy consumed inthe network and the constraints are the acceptable signal to interference ratio for each node. The solution to this optimisation problem provide optimal values for both the transmission spreading gains and powers that need to be allocated to each node in order to minimise the total energy consumption of the network

REER-H : a reliable energy efficient routing protocol for maritime intelligent transportation systems

The Underwater sensor network (UWSN), also known as Marine Sensor Network (MSN), is gaining increasing attention due to its applications in the monitoring of the marine environment and assisting Marine Intelligent Transportation Systems (MITS). Such systems provide in-vehicle assistance services (i.e., traffic monitoring and driver alerts) by gathering transportation and environmental information. Though very promising, there are several barriers to developing energy-efficient communication protocols for heterogeneous MSN, including selecting optimal routing paths twinned with the lifetime of these sensor nodes along the path, which are restricted due to the limited energy storage capacity. Hereby, the selection of an optimal route path also necessitates harvesting and management of the sensor nodes' energy. To facilitate this, the current work presents REER-H, a Reliable Energy Efficient Routing protocol with Harvesting for cluster-based MSN capable of multi-source energy harvesting and an incorporated energy management technique. Incorporating three separate layers of the protocol stack, namely, network, MAC, and physical layers, REER-H uses its proposed adaptive scheduling technique to support collision-free data transmission by assigning adaptive time slots based on demand and data load. Also, the proposed integrated energy harvesting and management solves the energy hole problem and enhances the overall network lifetime. In comparison to the existing cooperative and cluster-based energy-efficient routing protocols for underwater maritime communication, the simulated results using Network Simulator-3 (NS3) reveal that the proposed scheme remarkably enhances the overall network performance in terms of packet delivery ratio, throughput, lifetime energy consumption, and end-to-end delay for MSN. © 2000-2011 IEEE