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Clustering is a key concept of existing MIMO channel models, such as the COST 2100 model. Parameter based clustering has been studied for a while, but how parameter based clusters relate to the physical environment is not well known yet. A measurement based ray launching tool is developed and used for studying clustering and its relation to physical scatterers. By using estimated angles and delays
The problem of burst losses in OBS networks has an impact on the service quality perceived by end users. In order to guarantee certain level of Service Quality (QoS) in terms of burst losses, wavelength resources have to be dimensioned properly. In this paper, we address the problem of the Virtual Topology (VT) design that concerns the establishment of explicit routing paths and the allocation of
This article presents an architecture of a Digital Front-End Receiver (DFE-Rx) for the next-generation mobile terminals. A main focus is placed in flexibility, scalability and concurrency. The architecture is capable of detecting, synchronizing and reporting carrier-frequency offset, of multiple concurrent radio standards. The proposed receiver is fabricated in a 65nm CMOS low power high-VT cell t
When developing applications for end-user nodes in distributed systems, it is not unusual to find that the business logic part of the solution is relatively inexpensive to develop. The resource intense parts of the solution are more likely to be those of presenting the functionality provided by the node to the end-user, and of connecting the node with the rest of the system. By considering systems
Abstract— Context: Software product lines (SPL) are used in industry to achieve more efficient software development. To test a SPL is complex and costly and often becomes a bottleneck in the product line organization. Objective: This research aims to develop and evaluate strategies for improving system test selection in a SPL. Method: Initially industrial practices and research in both SPL testing
Pervasive middleware systems are important for enabling the configuration and coordination of the services provided by devices in pervasive environments. PalCom is an example of such a system that aims to enable interaction among pervasive services over heterogeneous networks. In this paper we discuss the need for providing networking-media independent messaging among pervasive devices, and identi
Massive MIMO is considered a key technology for the future wireless communication systems. The promising properties in terms of higher spectral and transmit-energy efficiency are brought by the large number of antennas at the base station (BS). As the number of antennas increases, the aperture of the BS antenna array may become much larger, as compared to today's antenna arrays. In this case, mobi
This study is concerned with a specific rerouting strategy in telecommunication networks named Elastic Robust Rerouting (ERR), introduced first in [8]. We recall main points on this strategy, provide mathematical formulation and discuss in details a solution method. The second question studied in this paper is concerned with its distributed version and some related implementation issues. We report
We present a method to compute, quickly and efficiently, the mutual information achieved by an IID (independent identically distributed) complex Gaussian input on a block Rayleigh-faded channel. The method accommodates both scalar and MIMO (multiple-input multiple-output) settings. Operationally, the mutual information thus computed represents the highest spectral efficiency that can be attained u
In this paper we propose a novel trellis based soft-input soft-output MIMO detector with significantly reduced search space. The performance of the detector is measured by evaluating the ultimate communication rate that is achievable for a system employing the novel detector; this limit corresponds to a mutual information that can be determined by standard methods. We also derive an expression tha
The paper is devoted to modeling and optimization of reliable wireless mesh networks that employ directional antennas. We introduce two mixed-integer programming formulations that allow to simultaneously characterize routing patterns and transmission schedules. The first model allows for maximizing the minimal flow in a network. The second model involves reliability constraints and aims at minimiz
Vehicle-to-vehicle (V2V) communications have received increasingattention lately, but there is a lack of reported results regarding important quantities such as path loss. This paper presents parameterized path loss models for V2V communications based on extensive sets of measurement data collected mainly under line-of-sight conditions in four different propagation environments: highway, rural, ur
Context. Development of safety-critical systems is mostly governed by process-heavy paradigms, while increasing demands on flexibility and agility also reach this domain. Objectives. We wanted to explore in more detail the industrial needs and challenges when facing this trend. Method. We launched a qualitative survey, interviewing engineers from four companies in four different industry domains.
[Context & motivation] Growing software companies with increasing product complexity face the issue of how to scale up their Requirements Engineering (RE) practices. In market-driven requirements engineering, release planning and scoping decisions are increasingly challenging as the size and complexity increases. [Problem] This paper presents initial results of an on-going exploratory, qualita
Climate and weather extremes are sporadically recurring events that may have major local or regional impacts on the society and the environment. These events are typically related to unusually high or low temperature, prolonged dry or wet conditions, heavy precipitation, or extreme winds. Extreme events are part of the overall climate and weather alongside average conditions and variability, and t
This paper presents a hardware architecture of pulse shaping filter used in multicarrier systems. The filter can be configured to be used for both transmitter and receiver with limited overhead. Generic implementation complexity analysis for a filter in a multicarrier system with N sub-carriers is presented, while the implemented architecture is for a system with 128 sub-carriers. The pulse shapin
Time-reversal (TR) signal processing has the potential to focus the transmitted signal at a desired receive (Rx) location in both space and time. At lower frequency bands, TR in conjunction with array antennas at transmit (Tx) or Rx has been shown to significantly improve its focusing performance relative to the case of single antennas at both link ends. This work for the first time investigates T
Optimization models related to designing and operating complex systems are mainly focused on some efficiency metrics such as response time, queue length, throughput, and cost. However, in systems which serve many entities there is also a need for respecting fairness: each system entity ought to be provided with an adequate share of the system's services. Still, due to system operations-dependant c
