Ignas G. Niemegeers

Cognitive radio emergency networks - requirements and design

Currently deployed wireless emergency networks possess low spectrum efficiency, similar to their civilian wireless counterparts. Its due to the traditional radio frequency partitioning where each service has uniquely assigned bandwidth. To alleviate the problem one can propose dynamic channel assignment as a promising foundation for physical and link layer design of future wireless emergency communication networks. Here we identify functional requirements and system specifications for mobile ad hoc emergency networks built on top of cognitive radio. We also propose a simple Cognitive Radio medium access control protocol applicable to our network model, adopted from distributed channel assignment algorithm of IEEE 802.11

Fairness in Wireless Networks:Issues, Measures and Challenges

The pervasiveness of wireless technology has indeed created massive opportunity to integrate almost everything into the Internet fabric. This can be seen with the advent of Internet of Things and Cyber Physical Systems, which involves cooperation of massive number of intelligent devices to provide intelligent services. Fairness amongst these devices is an important issue that can be analysed from several dimensions, e.g., energy usage, achieving required quality of services, spectrum sharing, and so on. This article focusses on these viewpoints while looking at fairness research. To generalize, mainly wireless networks are considered. First, we present a general view of fairness studies, and pose three core questions that help us delineate the nuances in defining fairness. Then, the existing fairness models are summarized and compared. We also look into the major fairness research domains in wireless networks such as fair energy consumption control, power control, topology control, link and flow scheduling, channel assignment, rate allocation, congestion control and routing protocols. We make a distinction amongst fairness, utility and resource allocation to begin with. Later, we present their inter-relation. At the end of this article, we list the common properties of fairness and give an example of fairness management. Several open research challenges that point to further work on fairness in wireless networks are also discussed. Indeed, the research on fairness is entangled with many other aspects such as performance, utility, optimization and throughput at the network and node levels. While consolidating the contributions in the literature, this article tries to explain the niceties of all these aspects in the domain of wireless networking.

Research Issues in Ad-Hoc Distributed Personal Networking

This paper discusses the research issues that need to be addressed in order to create a personal distributed environment where people interact with various companion, embedded, or invisible computers not only in their close vicinity but potentially anywhere. These systems are called personal networks (PNs). They constitute a category of distributed systems with very specific characteristics. They are configured in an ad hoc fashion, as the opportunity and the demand arise, to support personal applications. PNs consist of communicating clusters of personal digital devices, devices shared with other people and even infrastructure-based systems. At the heart of a PN is a core Personal Area Network (PAN), which is physically associated with the owner of the PN. Unlike the present PANs that have a geographically limited coverage, the Personal Operating Space, PNs have an unrestricted geographical span, and incorporate devices into the personal environment regardless of their geographic location. In order to do this they need the services of infrastructure-based networks and ad-hoc networks to extend their reach. A PN extends and complements the concept of pervasive computing. We show that PNs introduce new design challenges due to the heterogeneity of the involved technologies, the need for self-organization, the dynamics of the system composition, the application-driven nature, the co-operation with infrastructure-based networks, and the security hazards. We discuss the impact of these problems on network design, assess present and proposed solutions, and identify the research issues.

IEEE 802.11ah: Advantages in standards and further challenges for sub 1 GHz Wi-Fi

The rapid developments in Internet-of-Things (IoT) and Machine-to-Machine (M2M) communication make it necessary to design communication systems operating in different wireless spectrum as an alternative to highly congested wireless access systems. In addition, the deployment of wireless smart meter devices is ramping up and it is expected that such devices will flood the market in the near future competing for the same wireless spectrum. The IEEE 802.11ah standardization task group is developing a global Wireless LAN (WLAN) standard that will allow wireless access using carrier frequencies below 1 GHz in the ISM (Industrial, Scientific, and Medical) band and will help Wi-Fi-enabled devices to get guaranteed access for short-burst data transmissions, such as meter data. In addition to exploiting the underutilized sub 1 GHz spectrum the improved coverage range allows new applications to emerge such as wide area based sensor networks, sensor backhaul systems and potential Wi-Fi off-loading functions. This paper summarizes the IEEE 802.11ah standardization activities in progress and discusses advantages and challenges in the design of physical layer (PHY) and media access control (MAC) schemes in the sub 1 GHz band.

Radio-over-Fiber based architecture for seamless wireless indoor communication in the 60GHz band

In order to satisfy the increasing demand of wireless broadband multimedia services, much attention has been paid to the 60GHz band where as much as 5GHz of spectrum has been reserved. However, in the indoor environment, the propagation of signals at this millimeter wave band is strongly hindered by walls, people and their movement, furniture, etc. As a result, a mobile user might experience frequent loss of connection as the user moves from one cell to another. In this paper, we propose a flexible and cost-effective Radio-over-Fiber (RoF) based network architecture to support indoor networking at millimeter wave bands. To create sufficient overlap areas between cells and thus to ensure a seamless communication environment for mobile users, the concept of Extended Cell is introduced. We demonstrate the effectiveness of the proposed architecture with a detailed simulation study of an indoor scenario. Furthermore, we analyze the impact of the architecture on the performance of two popular state-of-the-art protocols, namely IEEE 802.11 and IEEE 802.16, to find which Medium Access Control (MAC) protocol is suitable for RoF networks.

Beam switching support to resolve link-blockage problem in 60 GHz WPANs

In this paper, we propose a solution to resolve link blockage problem in 60 GHz WPANs. Line-of-Sight (LOS) link is easily blocked by a moving person, which is concerned as one of the severe problems in 60 GHz systems. Beamforming is a feasible technique to resolve link blockage by switching the beam path from LOS link to a Non-LOS (NLOS) link. We propose and evaluate two kinds of Beam Switching (BS) mechanisms: instant decision based BS and environment learning based BS. We examine these mechanisms in a typical indoor WPAN scenario. Extensive simulations have been carried out, and our results reveal that combining angle-of-arrival with the received signal to noise ratio could make better decision for beam switching. Our work provides valuable observations for beam switching during point-to-point communication using 60 GHz radio.

Performability modelling tools and techniques

Over the last decade considerable effort has been put in the development of techniques to assess the performance and the dependability of computer and communication systems in an integrated way. This so-called performability modelling becomes especially useful when the system under study can operate partially, which is for instance the case for fault-tolerant computer systems and distributed systems. Modelling techniques are a fundamental prerequisite for actually doing performability analysis. A prerequisite of a more practical but not less important nature is the availability of software tools to support the modelling techniques and to allow system designers to incorporate the new techniques in the design process of systems. Since performability modelling requires many aspects of a system to be specified, high requirements should be posed on performability modelling tools. Moreover, these tools should be structured such that the models can be specified at a level that is easy to understand for a system designer, and that the mathematical aspects are hidden as much as possible. The output of the tool should also be such that it can be understood with only limited knowledge of the underlying mathematical model. We have developed a new, fairly general modelling tool framework that can be used as a guide to assess the usability and structure of performability modelling tools. After briefly reviewing the mathematical aspects of performability modelling we discuss this framework. We then discuss 12 recently developed tools (Metaphor, Numas, Metasan, Metfac, Save, Sharpe, SPNP, Tangram, Penpet, UltraSAN, Surf-2, DyQNtool+) that can all be used for some aspects of performability modelling and analysis. We assess among other things their structure, their capabilities in terms of measures that can be obtained, and the used modelling formalism. We also discuss directions for future work in the field of performability modelling tools.

A Survey on Handoffs — Lessons for 60 GHz Based Wireless Systems

Wireless communication is playing an important role in our daily life since it offers flexibility and mobility. New multimedia services demand data-rates of up to hundreds of Mbps and thus higher frequency bands are being explored to support these new high data rate services. However, to support mobility, handoff is a must in many of these networks and systems. In the mean time the 60 GHz band has received much attention due to its 5 GHz of the available spectrum globally. However, the 60 GHz channels face many challenges such as high attenuation and NLOS propagation. The high reduction in signal strength as a function of distance results in a small coverage area, thereby causing frequent handoffs for mobile terminals. In this paper, we discuss and compare handoff algorithms intended for WLAN, GSM, UMTS, etc. We study these algorithms from the point of view of their usability in 60 GHz networks and make recommendations for handoff algorithms in such networks.

Performance analysis of slotted ring protocols in HSLANs

The performance of a number of slotted-ring protocols supporting integration of synchronous and asynchronous traffic in high-speed local area networks (HSLANs) is evaluated. They are the Cambridge fast ring, a variant of the Cambridge fast ring, and Orwell. The performance of their basic access mechanisms is compared and contrasted with that of the multiple-token ring. The effect of a uniframe scheme for supporting synchronous traffic is examined. A delay analysis of the integrated-services slotted-ring protocols is presented. >

Ad hoc networking in future wireless communications

This paper contains an overview of the discussions on future research directions within the subject of ad hoc networking, held at the Wireless World Research Forum meetings during 2001. Ad hoc networking is an emerging research field where ad hoc networks are no longer viewed as stand-alone groups of wireless terminals. On the contrary, ad hoc networks are expected to become fundamental in the future development of infrastructure networks and they will be the basis for enabling ubiquitous communications. Ad hoc networking involves new research issues at all layers.