1,721,208 research outputs found
Joint Optimization of Uplink Power and Computational Resources in Mobile Edge Computing-Enabled Cell-Free Massive MIMO
Full text linkThe coupling of cell-free massive MIMO (CF-mMIMO) with Mobile Edge Computing
(MEC) is investigated in this paper. A MEC-enabled CF-mMIMO architecture
implementing a distributed user-centric approach both from the radio and the
computational resource allocation perspective is proposed. A multi-objective
optimization problem (MOOP) for the joint allocation of radio and remote
computational resources is formulated, aimed at striking an optimal balance
between total uplink power minimization and sum spectral efficiency
maximization, under resource budget and latency constraints. In order to solve
such a challenging non-convex problem, we convert the MOOP to an equivalent
single-objective optimization problem (SOOP) through the weighted sum method
and propose an iterative algorithm based on alternating optimization and
sequential convex programming, along with an alternative heuristic resource
allocation for distributed networks. Finally, we provide a detailed performance
comparison between the proposed MEC-enabled CF-mMIMO architecture with its
co-located counterpart, and its small-cell implementation. Numerical results
reveal the effectiveness of the proposed resource allocation scheme, under
different access point selection strategies, and the natural suitability of
CF-mMIMO in supporting computation-offloading applications with benefits over
users' transmit power and energy consumption, the effective latency
experienced, and the computation offloading efficiency.Comment: This paper has been published in IEEE Transactions on Communications
on November 23, 2023. {\copyright} 2023 IEEE. Personal use of this material
is permitted. Permission from IEEE must be obtained for all other use
Performance analysis for the improved linear multiuser detectors in BPSK-modulated DS-CDMA systems
No full textRecently, a new class of linear multiuser receivers for direct-sequence code-division multiple-access (CDMA) systems employing binary phase-shift keying modulation has been introduced. Unlike classical decorrelating and minimum mean-square error linear multiuser detectors, the new receivers exploit the information contained in the pseudo-autocorrelation of the observables, and are, thus, capable of achieving much better performance. We present new results on the performance analysis of this class of new receivers. In particular, with reference to a CDMA system with deterministic spreading codes, we show that the new receivers outperform the classical ones in terms of both error probability and near-far resistance. With regard, instead, to CDMA systems with random spreading, we compute the average system near-far resistance, showing that the new receivers can accommodate twice the number of users accommodated by the classical linear multiuser receivers
Widely linear reception strategies for layered space-time wireless communications
No full textA new class of receivers based on widely linear data processing has been recently proposed for data detection in communication systems affected by improper complex noise. In this paper, it is shown that this detection strategy may be applied to wireless communication systems employing multiple transmit and receive antennas and adopting a noncircular modulation. Improved versions of the linear decorrelating and minimum mean square error (mmse) receivers, and of the nonlinear nulling and cancellation (V-BLAST) receiver are, thus, developed and analyzed. In particular, we show that the improved receivers outperform the conventional ones both in terms of the error probability and of the capacity to cope with the power disparities that the fading channel may induce on the data streams transmitted by different antennas. Moreover, the improved receivers exhibit satisfactory performance also in systems with a number of transmit antennas exceeding the number of receive antennas. Finally, we also consider the situation in which the propagation channel is not perfectly known to the receiver, and show that the performance of the improved receivers is less sensitive to the channel estimation errors than the conventional receivers
Blind multiantenna receivers for dispersive DS/CDMA channels with no channel-state information
No full textThe problem of blind multiuser detection for a DS-CDMA system employing multiple transmit and receive antennae over a fading dispersive channel is considered. Relying upon a well known signal representation, we develop a new family of linear receivers adapted to account for MIMO channels. Linear receivers share the key property of substantial immunity to co-channel interference, without requiring any prior knowledge on the signals to be decoded, except for the spreading sequence. The performance assessment, conducted through semianalytical methods - whenever possible - and validated through Monte Carlo counting techniques, shows that the newly proposed receivers perform pretty close to their non-blind counterparts, which rely on prior knowledge of the spreading codes, symbol timings and channel impulse responses for all of the active users
Track-before-detect procedures for early detection of moving target from airborne radars
No full textIn this paper we present a family of track-before-detect (TBD) procedures for early detection of moving targets from airborne radars. Upon a sectorization of the coverage area, the received echoes are jointly processed in the azimuth-range-Doppler domain and in the time domain through a Viterbi-like algorithm that exploits the physically admissible target transitions between successive illuminations, in order to collect all of the energy back-scattered during the time on target (TOT). A reduced-complexity implementation is derived assuming, at the design stage, that the target does not change resolution cell during the TOT in each scan. The constant false alarm rate (CFAR) constraint is also englobed in the proposed procedures as well as the possibility of working with quantized data. Simulation results show that the proposed algorithms have good detection and tracking capabilities even for high target velocities and low quantization rates
Track-before-detect procedures in a multi-target environment
No full textThis paper addresses the problem of early detection of K ges 1 multiple moving targets in radar systems through the use of track-before-detect (TBD) techniques. At first, assuming prior knowledge of K, a binary generalized likelihood ratio test (GLRT) is derived, which shows that the multi-target TBD problem can be regarded as a K-path trellis search. Since optimal implementation of the GLRT has a nonlinear complexity either in the number of targets or in the number of integrated frames, suboptimum algorithms are investigated which allow to trade better estimation and tracking accuracy for a much lower implementation complexity. Next, the TBD problem with K unknown is discussed and a novel multi-hypothesis test strategy is derived as the solution to a constrained optimization problem, which subsumes the conventional binary GLRT as the special case of known K. Finally, numerical examples are provided to assess and compare the performances of the proposed TBD procedures
Silver high-aspect-ratio micro- and nanoimprinting for optical applications
No full textMetal direct nanoimprinting is a fabrication technique based on plastic deformation of ductile metals
such as silver and gold pressed into a structured rigid mold. While this process can be exploited to
manufacture metallic micro- and nanoparts by removing the mold after processing, it can also be
used as a metallization method for producing two-dimensional metallo-dielectric composites. Dense
silver-pillar arrays with diameters down to 140 nm, aspect ratios up to 13, and excellent uniformity
over large areas were fabricated. The sample quality was confirmed by near-infrared optical
reflectances of Si–Ag photonic crystals, which showed strong collective surface plasmon-polarito
Dynamic Mobile Base Stations in 5G Networks - The Moving Network Paradigm
No full text5G is the new generation of the global telecommunication network and is very important for Italy. For these reasons CNIT* decided to organize on December 3-5, 2019, the 5G-Italy event (https://www.5gitaly.eu/), which provides a 360-degree vision about 5G. As a companion initiative, CNIT also edited this book, with the aim of overviewing the status of 5G and of documenting the Italian involvement in 5G research and experimentation. This book will have a first version, printed and presented at the 5G Italy event, but then it will continue to live and grow on the web, updated with contributions coming from the conference. *CNIT (National, Inter-University Consortium for Telecommunications, https://www.cnit.it/) is a non-profit consortium, established in 1995, bringing together 37 public Italian universities to perform research, innovation and education/training activities in the field of Information and Communication Technology (ICT). More than 1,300 professors and researchers, belonging to the member universities, collaborate within CNIT, together with more than 100 CNIT own employees
Green and fast DSL via joint processing of multiple lines and time–frequency packed modulation
Full text linkIn this paper, strategies to enhance the performance, in terms of available data-rate per user, energy efficiency, and spectral efficiency, of current digital subscriber lines (DSL) are proposed. In particular, a system wherein a group of copper wires is jointly processed at both ends of the communication link is considered. For such a scenario, a resource allocation scheme aimed at energy efficiency maximization is proposed, and, moreover, time–frequency packed modulation schemes are investigated for increased spectral efficiency. Results show that a joint processing of even a limited number of wires at both ends of the communication links brings remarkable performance improvements with respect to the case of individual point-to-point DSL connections; moreover, the considered solution does represent a viable means to increase, in the short term, the data-rate of the wired access network, without an intensive (and expensive) deployment of optical links
Timing-Free Blind Multiuser Detection for Multicarrier DS/CDMA Systems with Multiple Antennae
Full text linkThe problem of blind multiuser detection for an asynchronous multicarrier DS-CDMA system employing multiple transmit and receive antennae over a Rayleigh fading channel is considered in this paper. The solutions that we develop require prior knowledge of the spreading code of the user to be decoded only, while no further information either on the user to be decoded or on the other active users is required. Several combining rules for the observables at the output of each receive antenna are proposed and assessed, and the implications of the different options are studied in depth in terms of both detection performance and computational complexity. A closed form expression is also derived for the conditional error probability and a lower bound for the near-far resistance is provided. Results confirm that the proposed blind receivers can cope with both multiple access interference suppression and channel estimation at the price of a limited performance loss as compared to the ideal linear receivers which assume perfect channel state information
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