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An Orthogonal Frequency-Division Multiplexing (OFDM) based multi-user massive Multiple-Input Multiple-Output (MIMO) system is considered. The problem of high Peak-to-Average Ratio (PAR) in OFDM based systems is well known and the large number of antennas (RF-chains) at the Base Station (BS) in massive MIMO systems aggravates this further, since large numbers of these Power Amplifiers (PAs) are use
[Context and motivation] This research preview presents ongoing work on a free software requirements modeling tool called reqT that is developed in an educational context. [Question/problem] The work aims to engage computer science students in Requirements Engineering (RE) through a tool that captures essential RE concepts in executable code. [Principal ideas] Requirements are modeled using an int
Many cryptographic primitives rely on word rotations (R) and xor (X) to provide proper mixing. We give RX-system mixing a very general treatment and deduce some theoretical results on related probability distributions. Pure RX-systems are easy to break, so we show how to apply our theory to a more complex system that uses RX operations in combination with S-boxes. We construct an impractical (key
This book focuses on domain-specific heterogeneous reconfigurable architectures, demonstrating for readers a computing platform which is flexible enough to support multiple standards, multiple modes, and multiple algorithms. The content is multi-disciplinary, covering areas of wireless communication, computing architecture, and circuit design. The platform described provides real-time processing c
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
Heterogeneous parallel systems are becoming mainstream computing platforms nowadays. One of the main challenges the development community is currently facing is how to fully exploit the available computational power when porting existing programs or developing new ones with available techniques. In this direction, several design space exploration methods have been presented and extensively adopted
Sentiment analysis, or opinion mining, is the process of extracting sentiment from documents or sentences, where the expressed sentiment is typically categorized as positive, negative, or neutral. Many different techniques have been proposed. In this paper, we report the reimplementation of nine algorithms and their evaluation across four corpora to assess the sentiment at the sentence level. We e
