Tuleen Boutaleb

A Novel Cooperative Opportunistic Routing Scheme for Underwater Sensor Networks.

Increasing attention has recently been devoted to underwater sensor networks (UWSNs) because of their capabilities in the ocean monitoring and resource discovery. UWSNs are faced with different challenges, the most notable of which is perhaps how to efficiently deliver packets taking into account all of the constraints of the available acoustic communication channel. The opportunistic routing provides a reliable solution with the aid of intermediate nodes’ collaboration to relay a packet toward the destination. In this paper, we propose a new routing protocol, called opportunistic void avoidance routing (OVAR), to address the void problem and also the energy-reliability trade-off in the forwarding set selection. OVAR takes advantage of distributed beaconing, constructs the adjacency graph at each hop and selects a forwarding set that holds the best trade-off between reliability and energy efficiency. The unique features of OVAR in selecting the candidate nodes in the vicinity of each other leads to the resolution of the hidden node problem. OVAR is also able to select the forwarding set in any direction from the sender, which increases its flexibility to bypass any kind of void area with the minimum deviation from the optimal path. The results of our extensive simulation study show that OVAR outperforms other protocols in terms of the packet delivery ratio, energy consumption, end-to-end delay, hop count and traversed distance.

Void-Handling Techniques for Routing Protocols in Underwater Sensor Networks: Survey and Challenges

From the view of routing protocols in underwater sensor networks (UWSNs), the presence of communication void, where the packet cannot be forwarded further using the greedy mode, is perhaps the most challenging issue. In this paper, we review the state of the art of void-handling techniques proposed by underwater geographic greedy routing protocols. To this, we first review the void problem and its negative impact on the category of the geographic greedy routing protocols, which does not entail any void recovery technique. It is followed by a discussion about the constraints, challenges, and features associated with the design of void-handling techniques in UWSNs. Afterward, currently available void-handling techniques in UWSNs are classified and investigated. They can be classified into two main categories: 1) location-based and 2) depth-based techniques. The advantages and disadvantages of each technique along with the recent advances are then presented. Finally, we present a qualitative comparison of these techniques and also discuss some possible future directions.

Performance analysis of a DTIRC-LED illumination structure

The Dielectric Total Internal Reflecting Concentrator (DTIRC) is a type of non-imaging optic that has been used in the past to increase the collection efficiency of photovoltaic (PV) cells and photodetectors. It does this by redirecting energy impinging on its largest aperture to a smaller aperture to which the absorber is attached. This paper explores the use of non-imaging optics for light emission control when combined with a Light Emitting Diode (LED). In this case, the smallest aperture of the concentrator acts as its input and the largest aperture as the output. This allows control of the angular characteristics of the emitted light beam and an increase of the illuminance at the target plane, which is of particular relevance in applications such as illumination and optical wireless communications. Its compact size and design characteristics make the DTIRC a more desirable geometry compared to other non-imaging optics when used as a first or secondary optic to control the emission characteristics of a light source. This paper reports the correlation between simulation and experimental results that validate the ability of DTIRCs to collimate the output beam of extended light sources.

An Opportunistic Void Avoidance Routing Protocol for Underwater Sensor Networks

An Underwater Sensor Network (UWSN) has many unique features that makes it different from terrestrial network. This includes lower bandwidth, longer propagation delay, dynamic topology, high error rate, and energy constraint. To overcome the limitations of such an environment, opportunistic routing has recently attracted much attention due to its ability to improve the performance of UWSNs in terms of packet delivery ratio and energy saving. With the aid of opportunistic data routing, underwater sensors can collaboratively route a packet towards the destination which is a more adequate approach for sparse and lossy channels. In this paper, we propose a new routing protocol, called Opportunistic Void Avoidance Routing (OVAR), to address the void problem and high bit error rate without relying on any positioning system. OVAR is able to efficiently bypass all kinds of void areas with the lowest possible cost (including energy and delay) while prioritising the group of candidate nodes with the highest packet advancement. Given the density of neighbours (sparse or dense), each forwarding node is able to hold a trade-off between packet advancement and energy consumption by adjusting the number of nodes in its forwarding set. OVAR is also able to select the forwarding set in any direction from the sender without including any hidden node. The results of our extensive simulation study show that OVAR outperforms other protocols in terms of packet delivery ratio, energy consumption, and average end-to-end delay.

Analysis of uniformity of illumination of a freeform lens when combined with different optical sources

This paper presents the performance analysis of a freeform lens that can be used as a first or secondary optic when combined with a point or an extended light source. The light source can be an LED. The purpose of the optic is to increase uniformity of illumination within the footprint. The analysis is performed on the freeform lens when combined with: (i) an isotopic or a Lambertian point light source (ii) an isotropic or a Lambertian extended light source. This paper shows that through a design based on energy mapping between a light source and a target plane it is possible to achieve uniform illumination. The ZEMAX ray tracing simulation shows that the uniformity reduces gradually when the size of the light source increases. The results indicate that a freeform lens combined with a point source can generate over 95% uniformity.

Novel non-imaging optic design for uniform illumination

The Dielectric Totally Internally Reflecting Concentrator (DTIRC) has been developed in the past for wireless infrared communications and solar energy applications. This paper proposes a novel non-imaging optic design based on the DTIRC family of concentrators for use in illumination applications. The novel optic can be integrated with a light emitting diode (LED) and can be tailored to meet specific requirements. The proposed optic can be used as a first or secondary optic to provide uniform illumination within a circular footprint with a desired radius. The results from this work show that, with the optimised DTIRC, it is possible to achieve a uniformity of illuminance of over 95%.

An inherently void avoidance routing protocol for Underwater Sensor Networks

The presence of void area in the routing path is perhaps the most challenging issue from the routing protocol perspective in 3D acoustic Under-Water Sensor Networks (UWSN). In this paper, we propose a new routing protocol, called Inherently Void-Avoidance Routing (IVAR), to address the void problem without relying on any positioning system. IVAR is able to efficiently bypass void areas by properly selecting the forwarding nodes using only the local information, i.e. depth and number of hops to the sink. It inherently excludes all the routes leading to a void area and therefore does not need to switch to recovery mode. In dense scenarios, IVAR can deliver packets using a shorter distance compared to other unicast routing protocols. A fitness factor is employed to evaluate the appropriateness of each node for packet forwarding to confine the scope of the forwarding nodes. In sparse networks with many possible void areas, IVAR is also able to find the best, or close to, path, if any, with minimum communication overhead. The results of our extensive simulation study for sparse to dense networks demonstrate that IVAR outperforms other recently proposed protocols in terms of packet delivery ratio, average hop count, and propagation deviation factor.

A New Scheduling Scheme for Voice Awareness in 3G LTE

3G Long Term Evolution (LTE) is an all internet protocol (IP) based network and one of its main aims is to improve mobile multimedia services. This is achieved through streamlining the system for packet services. This leads to improvements in the form of higher bit rates, lower latencies, and a variety of service offerings. However, more challenging technical difficulties may be expected to arise when voice traffic flows over an LTE network. There is a major change in the way voice is transmitted in LTE in that it is transmitted in packets instead of through circuits. This has led to the development of new types of resource management schemes, which are quite challenging. In this paper, we propose a new scheduling algorithm for voice traffic over LTE. This algorithm takes into account Voice over Internet Protocol (VoIP) parameters and shows, through simulations, an improvement in overall performance based on throughput and block error rate of up to 30 percent.

Optimal beam radius for LED-based indoor positioning algorithm

Indoor positioning systems have the potential to replicate the success of outdoor positioning systems, but owing to the expensive and less accurate technology currently available for indoor positioning, they have not been able to take-off. LED-based Visible Light Communication (VLC) systems can solve this problem, but owing to complex algorithms and unoptimized parameter values the desired accuracy has not yet been achieved. This research addresses the problem of overlapping light radiation regions, which leads to lower accuracy in a VLC system, and proposes an algorithm to accurately determine the position of a device with respect to pre-positioned LEDs when it is receiving signal from multiple transmitting LEDs. To check the accuracy of this Optimal Beam Radius Indoor Positioning (OBRIP) algorithm numerous possible positions of a device uniformly distributed in a room with an indoor positioning system have been simulated to calculate the error in position estimation. Also, from the simulations, optimal values for beam radius, for a given number of LEDs in an array, separation between adjacent LEDs in an array for different room shapes has been calculated.

Performance Comparison of a Freeform Lens and a CDTIRO When Combined With an LED

This paper compares the features and performance of two secondary optics when combined with an LED. The aim and application of the secondary optic are explained in the introduction section. Sections 2 and 3 introduce two optics: A freeform lens and a novel circular dielectric totally internally reflecting optic (CDTIRO), which can provide uniform illumination. The design process, ray tracing simulations and experimental performance of the freeform lens are described in detail in Section 2. The ray tracing simulation and experimental performance of the CDTIRO are presented in Section 3. Section 4 presents a comparison of the features of both lenses and their performance. Both optics can produce over 95% uniformity within an illuminated area. However, the uniformity produced by the freeform lens reduces abruptly compared with the CDTIRO when some parameters such as size and the position of the light source are changed.