1,721,019 research outputs found
Design Criteria for FIR-Based Echo Cancellers
No full textThe most relevant impairment experienced by on-channel repeaters (OCRs) in single frequency networks scenarios is the presence of a coupling-channel between the transmitting and receiving antennas, that generates unwanted echoes. This phenomenon causes a degradation of the repeated signal and, above all, could lead to the instability of OCRs, owing to the positive feedback that could result. For this reason, OCRs are usually equipped with echo canceller units, aimed at removing the coupling contributions. In this paper, we consider a realistic OCR setup and we analytically derive proper design criteria for echo-cancellers, showing the role of system parameters and implementation aspects on their performance. Here, in particular, we investigate the joint effect of the estimation noise and the finite precision arithmetic of digital systems, the system sensitivity to different design parameters and the relation between the echo-cancelling performance and the probability of instability
On Molecular Communications via Diffusion with Multiple Transmitters and Multiple Receivers
No full textThis paper analyzes distributed molecular communications with multiple transmitters and multiple receivers randomly placed in a 3D space. Receivers, whose positions are modeled by a homogeneous Poisson point process, are assumed to be passive and spherical. Since they are not dimensionless, their presence affects the statistics of transmitter points, resulting in a Poisson hole process, instead of the Poisson process usually adopted in previous works on multiple transmitters. Moreover, molecules emissions from different transmitters are considered asynchronous, according to a recently proposed stochastic model. Here, the intensity function of the time point processes modeling molecules emissions is given a further meaning; in particular, it is considered as the propensity function of a chemical reaction. The average amount of received molecules per time unit (receiving rate) is evaluated accordingly for each receiver. When the swarm of receivers is considered as an equivalent, single, spatially distributed receiver, the average amount of received molecules per time and volume units (receiving rate density) is introduced and analytically evaluated
Configuration Issues and Best Effort Performance Investigation of IEEE 802.16e
No full textTh e IEEE 802.16 standard family enables the convergence of fi xed and mobile broadband networks through a common wide area broadband access technology and a flexible network architecture. In this paper we provide an overview of the recent IEEE 802.16e-2005 amendment, aimed at supporting user mobility, and we discuss several issues related to a proper choice of system parameters and strategies to be adopted to fully exploit the technology potential. Moreover, we propose a scheduling strategy aimed at providing a fair service to best effort users. The effectiveness of this proposal is shown via simulation
Smart city pilot project using lora
No full textThis paper presents a smart city pilot project that will be developed in the city of Bologna. Different sensor devices will be deployed in several buildings to measure environmental quantities, such as temperature, humidity, luminosity and CO2. The pilot will use the LoRa low-rate, long-range communication technology to transmit sensed data to the control center. Results of a measurement campaign to characterize the propagation in the Bologna scenario are reported. Such results are then used as input to a simulator that provides both coverage and networklevel performance of the LoRa technology in the considered scenario. The paper shows that a proper parameter setting is needed to cover large urban areas while maintaining the timeon- air sufficiently low to keep packet losses at satisfactory levels
Cooperative and reconfigurable telecommunication systems based on FPGA
No full textThis work has been realized by the author in his PhD course in Electronics, Computer Science and Telecommunication at the University of Bologna, Faculty of Engineering, Italy.
The subject of this thesis regards important channel estimation aspects in wideband wireless communication systems, such as echo cancellation in digital video broadcasting systems and pilot aided channel estimation through an innovative pilot design in Multi-Cell Multi-User
MIMO-OFDM network.
All the documentation here reported is a summary of years of work, under the supervision of Prof. Oreste Andrisano, coordinator of Wireless Communication Laboratory - WiLab, in Bologna.
All the instrumentation that has been used for the characterization of the telecommunication systems belongs to CNR (National Research Council), CNIT (Italian Inter-University Center), and DEIS (Dept. of Electronics,
Computer Science, and Systems).
From November 2009 to May 2010, the author spent his time abroad, working in collaboration with DOCOMO - Communications Laboratories Europe GmbH (DOCOMO Euro-Labs) in Munich, Germany, in the Wireless
Technologies Research Group.
Some important scientific papers, submitted and/or published on IEEE journals and conferences have been produced by the author
Video transmission over wireless channel
No full textThis work has been realized by the author in his PhD course in Electrical, Computer Science and Telecommunication at the University of Bologna, Faculty of Engineering, Italy. All the documentation here reported is a summary of years of work, under the supervision of Prof. Oreste Andrisano, coordinator of Wireless Communication Laboratory - WiLab, in Bologna. The subject of this thesis is the transmission of video in a context of heterogeneous network, and in particular, using a wireless channel.
All the instrumentation that has been used for the characterization of the telecommunication systems belongs to CNR (National Research Council), CNIT (Italian Inter-
University Center), and DEIS (Dept. of Electrical, Computer Science, and Systems).
From November 2009 to July 2010, the author spent his time abroad, working in collaboration with DLR - German Aerospace Center in Munich, Germany, on channel
coding area, developing a general purpose decoder machine to decode a huge family of iterative codes.
A patent concerning Doubly Generalized-Low Density Parity Check codes has been produced by the author as well as some important scientic papers, published on
IEEE journals and conferences
Infomobility Provision through MBMS/UMTS in Realistic Scenarios
No full textNew wireless communication technologies enable new services for infomobility. In this work we explore the feasibility of infomobility applications through multimedia broadcast multicast service (MBMS), a new feature added to the universal mobile telecommunication system (UMTS). We assume to transmit, through MBMS channels, real time traffic information to all vehicles under coverage; such information will be exploited by on board smart navigation systems to update the best route to the destination. Activating this service, part of the base station (BS) power is wasted by MBMS, thus reducing resources available for typical UMTS traffic. In this paper, performance is investigated through simulations, adopting a complete simulation platform that we carefully developed taking into account, by means of an integrated approach, all network protocol layers and realistic road traffic with mobility models. Numerical results are provided by considering as reference scenario the medium-size Italian city of Bologna
Adaptive beaconing for safety enhancement in vehicular networks
No full textFor automotive safety applications, vehicles directly exchange periodic beacons that contain status information such as position, speed, acceleration, etc., and the application layer issues warnings if a hazardous situation is detected. The update rate of these beacons should be high enough to allow the application to swiftly react to prevent accidents and current recommendations provide fixed values for different safety use cases. This approach is sub-optimal since wireless resources might be used when not necessary, e.g., when cars are queuing at a traffic light, and the proposals made for variable beacon periodicity (BP) typically do not take into account the safety aspect or are strictly related to the access technology in use. This paper presents a new algorithm called beaconing adaptation for safety enhancement (BASE) that adapts the BP to minimize the amount of radio resources used by the safety application without breaching safety requirements. BASE is access technology agnostic and focuses on common traffic and traveling conditions (not on particular crossroads, overtaking, etc.), and the results presented in this paper show how it allows for substantial capacity gains in a highway collision-avoidance scenario
Cooperative platforms through heterogeneous communication networks: Perspective and issues
No full textInformation and Communication Technologies (ICT) are becoming more pervasive and central to boost productivity and improve the competitiveness of all businesses and industries, and ICT innovations underpin progress in all other major science fields. This paper addresses the concept of cooperative platform where distributed resources (i.e., instrumentation and circuits, multimedia archives and applications, desktop) interconnected through heterogeneous communication network are remotely accessed and configured by users having Internet connectivity. Perspectives and the experiences made within projects devoted to this topic, are reported in this paper, with the aim to enlighten related issues and present possible solutions. These solutions could provide great benefits in favour of the Small Medium Enterprises (SMEs) for what concern the collaborative design and engineering
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