Search results for "ComputerSystemsOrganization_COMPUTER-COMMUNICATIONNETWORKS"
showing 10 items of 449 documents
A Survey and Taxonomy of Urban Traffic Management: Towards Vehicular Networks
2014
Urban Traffic Management (UTM) topics have been tackled since long time, mainly by civil engineers and by city planners. The introduction of new communication technologies - such as cellular systems, satellite positioning systems and inter-vehicle communications - has significantly changed the way researchers deal with UTM issues. In this survey, we provide a review and a classification of how UTM has been addressed in the literature. We start from the recent achievements of "classical" approaches to urban traffic estimation and optimization, including methods based on the analysis of data collected by fixed sensors (e.g., cameras and radars), as well as methods based on information provide…
Non-convex Optimization for Resource Allocation in Wireless Device-to-Device Communications
2020
Device-to-device (D2D) communication is considered one of the key frameworks to provide suitable solutions for the exponentially increasing data tra c in mobile telecommunications. In this PhD Thesis, we focus on the resource allocation for underlay D2D communications which often results in a non-convex optimization problem that is computationally demanding. We have also reviewed many of the works on D2D underlay communications and identi ed some of the limitations that were not handled previously, which has motivated our works in this Thesis. Our rst works focus on the joint power allocation and channel assignment problem in the D2D underlay communication scenario for a unicast single-inpu…
Automatic construction of test sets: Theoretical approach
2005
We consider the problem of automatic construction of complete test set (CTS) from program text. The completeness criterion adopted is C1, i.e., it is necessary to execute all feasible branches of program at least once on the tests of CTS. A simple programming language is introduced with the property that the values used in conditional statements are not arithmetically deformed. For this language the CTS problem is proved to be algorithmically solvable and CTS construction algorithm is obtained. Some generalizations of this language containing counters, stacks or arrays are considered where the CTS problem remains solvable. In conclusion the applications of the obtained results to CTS constr…
Enhancing HSUPA system level performance with dual carrier capability
2010
The purpose of this paper is to analyze how dual carrier capability can enhance High Speed Uplink Packet Access performance in comparison to using only single carrier. Dual carrier operation gives the User Equipment the possibility to transmit simultaneously using two 5 MHz bands, theoretically doubling the peak data rates and user throughput. The analysis is conducted with a system level simulation tool. This paper first indicates with single carrier simulations that, especially in small cells, terminals have spare power available for dual carrier operation. These observations are verified with dual carrier simulations by showing that the burst throughput can be practically doubled. In the…
Out-of-Band Signaling Scheme for High Speed Wireless LANs
2007
In recent years, the physical layer data rate provided by 802.11 Wireless LANs has dramatically increased thanks to significant advances in the modulation and coding techniques employed. However, previous studies show that the 802.11 MAC operation, namely the distributed coordination function (DCF), represents a limiting factor: the throughput efficiency drops as the channel bit rate increases, and a throughput upper limit does indeed exist when the channel bit rate goes to infinite high. These findings indicate that the performance of the DCF protocol will not be efficiently improved by merely increasing the channel bit rate. This paper shows that the DCF performance may significantly bene…
Outage Probability Analysis of User-Centric SBS-Based HCNets Under Hybrid Rician/Rayleigh Fading
2020
To model dense user equipment (UE) distribution in heterogeneous cellular networks (HCNets), the Poisson cluster process (PCP) has emerged as a promising tool. In user-centric HCNets where UEs are distributed according to a PCP around a small base station (SBS), the network performance has been commonly studied in literature under a Rayleigh fading environment assumption. However, such an assumption may not hold in user-centric HCNets given the possible existence of a strong line-of-sight (LOS) link between UEs and BSs due to a relatively short transmission distance. This letter analyzes the performance of user-centric SBS based HCNets by considering that the desired LOS link experiences Ri…
Correction to: a predictive model for women's assisted fecundity before starting the first IVF/ICSI treatment cycle.
2019
PURPOSE: To introduce a prognostic model for women’s assisted fecundity before starting the first IVF/ICSI treatment cycle. METHODS: In contrast to previous predictive models, we analyze two groups of women at the extremes of prognosis. Specifically, 708 infertile women that had either a live birth (LB) event in the first autologous IVF/ICSI cycle (“high-assisted-fecundity women”, n = 458) or did not succeed in having a LB event after completing three autologous IVF/ICSI cycles (“low-assisted-fecundity women”, n = 250). The initial sample of 708 women was split into two sets in order to develop (n = 531) and internally validate (n = 177) a predictive logistic regression model using a forwar…
A Kalman Filter Approach for Distinguishing Channel and Collision Errors in IEEE 802.11 Networks
2008
In the last years, several strategies for maximizing the throughput performance of IEEE 802.11 networks have been proposed in literature. Specifically, it has been shown that optimizations are possible both at the medium access control (MAC) layer, and at the physical (PHY) layer. In fact, at the MAC layer, it is possible to minimize the channel waste due to collisions and backoff expiration times, by tuning the minimum contention window as a function of the network congestion level. At the PHY layer, it is possible to improve the transmission robustness, by selecting a suitable modulation/coding scheme as a function of the channel quality perceived by the stations. However, the feasibility…
A Restricted-Weakly Connected Dominating Set for Role Assignment in a Multichannel MAC for Wireless Mesh Network
2009
International audience; We propose an efficient way of constructing the wireless mesh structure associated with Molecular MAC, a multichannel access method designed for efficient packet forwarding. We base our role assignment on a restricted Weakly Connected Dominating Set structure. After presenting a formal definition of the role assignment problem, we prove its NP-completeness. Then, we propose a centralized 2-approximation algorithm that maximizes the sum of radio link capacities in the molecular structure. Finally, we extend this protocol so that it can operate in a distributed way still providing the same guarantee. This distributed protocol is self-stabilizing thus robust to topology…
Two new sum-of-sinusoids-based methods for the efficient generation of multiple uncorrelated rayleigh fading waveforms
2009
Article from the journal: IEEE Transactions on Wireless Communications Publisher's version: http://dx.doi.org/10.1109/twc.2009.080769 This paper deals with the design of a set of multiple uncorrelated Rayleigh fading waveforms. The Rayleigh fading waveforms are mutually uncorrelated, but each waveform is correlated in time. The waveforms are generated by using the deterministic sum-of-sinusoids (SOS) channel modeling principle. Two new closed-form solutions are presented for the computation of the model parameters. Analytical and numerical results show that the resulting deterministic SOS-based channel simulator fulfills all main requirements imposed by the reference model with given correl…