Peak-to-average power reduction in space division multiplexing based OFDM systems through spatial shifting

A new method to reduce the peak-to-average power ratio (PAPR) in space division multiplexing systems applying orthogonal frequency division multiplexing is proposed. The method applies spatial shifting to partial transmit sequences to achieve a decreased PAPR on all transmit branches.     

Wireless Network Simulation – Your Window on Future Network Performance

The paper describes three relevant perspectives on current wireless simulation practices. In order to obtain the key challenges for future network simulations, the characteristics of “beyond 3G” networks are described, including their impact on simulation.Erik Fledderus (1970) received a PhD in Applied Mathematics in 1997, after which he started working at KPN Research, which merged with TNO in January 2003. He developed the basis for UMTS radio network planning at KPN, and initiated in 2000 a European project proposal, Momentum, in the area of UMTS radio planning and simulation, with 7 partners from Germany and Pottugal. Erik acted as project leader and co-ordinator from 2001-2003. Also at the end of 2000 he initiated together with Eindhoven University of Technology, Agere Systems and Philips Research a research proposal in the area of antenna arrays and MIMO in WLAN and UMTS. One of the results of this project~lies at the basis for the 802.11n-proposal by Agere/Philips.Since March 1st 2003, Erik is part-time professor at Eindhoven University of Technology in the field of Wireless Communication Networks.Within TNO he is senior strategist, program manager of the program Future ICT Architectures, and leading in the knowledge management regarding radio and mobile network technology, and strategist on mobile/wireless technology in general.     

Radio resource allocation in third generation mobile communicationsystems

Code-division multiple access has been widely accepted as the major multiple access scheme in third-generation mobile communication systems. Wide-band CDMA and its hybrid associate time-division CDMA are key elements of the IMT2000 framework of standards. Since the beginning of the 1990s there has been enormous research activity in analysis of the soft (i.e., interference limited) capacity of these CDMA-based systems. Optimal usage of the soft capacity to provide, maintain, and guarantee QoS for different service classes is now becoming a very important issue. Therefore, interest in radio resource allocation has recently. This article presents an overview of RRA schemes (primarily for CDMA-based systems) that are flexible, support traffic services with various QoS requirements, minimize call/session blocking and dropping probabilities, and have acceptable radio resource utilization     

Out of the Shadow: Long Term Cost Development of Intelligent Sensor Networks

The paper addresses intelligent sensor networks (ISNs) as a special version of networked wireless robotics. The success of these networks is partly explained by the technical advances, but as well by cutting down costs of these networks. Using a functional breakdown of intelligent ISNs, the trends of the various functions are discussed. The analysis shows how individual sensor network component prices decline at an almost predictable speed. This is mainly a result of generic developments in technology. These developments sustain because an economy of scale is reached at the level of individual components. This makes the integration of these components the most important barrier to acquire large scale implementation of intelligent ISNs, both with respect to cost and needed R&D breakthroughs. Integration includes the need for standardization and interoperability between different standards. The paper illustrates its generic analysis in two use cases: cooperative driving and smart living.     

Towards Viable Personal Networks and FedNets -- a Value-Web Perspective

The concepts of Personal Networks (PNs) and Federated Networks (FedNets) have been introduced before, but there are no studies published yet about migration strategies towards viable solutions in the market. One of the main reasons is the lack of a clear vision about the different values that various parties involved in achieving PNs and FedNets have to offer to each other and the end user. In fixed broadband communication such value chains and business models are already commonly used for rolling out complex service offering based on fiber-to-the-home and broadband home networks. In this paper we use the knowledge from these business domains to approach the problem of PNs and FedNets.     

The in-vitro biocompatibility of ureido-pyrimidinone compounds and polymer degradation products

Supramolecular biomaterials based on ureido-pyrimidinone (UPy) moieties are versatile polymer materials as their function can be tailored to the application. These UPy-materials can be designed into polymer coatings, self-healing polymers, hydrogels and elastomers. The biocompatibility of UPy-based materials and their degradation products is a long-term success requirement for many regenerative medicine and biomedical applications. Earlier research has shown that UPy-based materials and polymers display no immediate toxic effects, but in-depth in-vitro studies on potential UPy-polymer degradation products have not been executed. Owing to their resemblance to naturally occurring purines and pyrimidines, UPy-compounds and their degradation products could potentially initiate an immune response or be mutagenic. Accordingly, 11 selected UPy-compounds were synthesized, and their effect on cell viability, wound healing, and their immunogenicity and potential mutagenic potential, were studied. We showed that low molecular weight degradation products of UPy-based biomaterials do not affect cell viability, nor do these interfere with several aspects of endothelial function including proliferation, angiogenic sprouting and cellular migration even in levels exceeding plausibly attainable concentrations. Furthermore, the compounds are neither immunogenic nor mutagenic, showing that UPy-biomaterials exhibit good biocompatibility in vitro, and could in principle be used in humans.     

Indoor Radio Propagation and Interference in 2.4 GHz Wireless Sensor Networks: Measurements and Analysis

In wireless sensor networks (WSNs), the performance and lifetime are significantly affected by the indoor propagation and the interference from other technologies using the 2.4 GHz band. Next to an overview of the propagation and coexistence issues in the literature, we present a model for analysing these effects in WSNs. We also present our measurements results on the indoor propagation, the interference of the microwave oven (MWO) and their impact on the performance of the WSN. The propagation measurements reveal significant influence of the multipath: changing a node position with a few centimetres or changing the communication channel can lead up to 30 dB difference in the received power. The power leakage of MWO has been observed around $-$ 20 dBm at 1 m distances to the oven. This leads to extra retries of the 802.15.4 messages which matches our simulation results: the packet success ratio at first try decreases to 30–40 %, which increases the average active time of the sensor, closely located to the MWO. We observe that the ON–OFF pattern of the MWO could be exploited by WSNs to improve the performance.     

Looking for New DNA: The World Around IMT-advanced

Technology, such as IMT-2000 and IMT-A, plays an important role in our society. A number of prominent authors and thinkers have judged the impact of technology as being increasingly radical. This paper connects different visions on technology, thereby bringing different perspectives on innovation into line. An important motivation for this paper has been the predominantly instrumental vision on technology that is present at most European governments. The paper shows that this is an imbalanced vision that neglects the renewing and radical power of technology. On the other hand, the paper focuses on the required skills (‘DNA’) that are needed to help companies bridge the gap from radical innovation to user centred innovation. The paper concludes with an example from personal network technology, illustrating the main concepts and claims.

Polymer‐based Scaffold Designs For In Situ Vascular Tissue Engineering: Controlling Recruitment and Differentiation Behavior of Endothelial Colony Forming Cells

In situ vascular tissue engineering has been proposed as a promising approach to fulfill the need for small‐diameter blood vessel substitutes. The approach comprises the use of a cell‐free instructive scaffold to guide and control cell recruitment, differentiation, and tissue formation at the locus of implantation. Here we review the design parameters for such scaffolds, with special emphasis on differentiation of recruited ECFCs into the different lineages that constitute the vessel wall. Next to defining the target properties of the vessel, we concentrate on the target cell source, the ECFCs, and on the environmental control of the fate of these cells within the scaffold. The prospects of the approach are discussed in the light of current technical and biological hurdles.