Separation of digital communication signals through joint space-time decorrelation

In this paper we derive the optimum linear algorithm for the separation by an array of a given number of cyclostationary signals of the type encountered in digital communications. Spatially and temporally uncorrelated noise is considered at the input to each sensor. It is proved that the optimum signal separator can be expressed as a matrix transfer function in the z-domain. It is intended that this algorithm be used as a benchmark to test the performance of adaptive schemes. Therefore, bounds on the noise estimation covariance are obtained assuming perfect knowledge of the number of sources as well as of their timing and DOA.Peer ReviewedPostprint (published version

Average PER performance metrics of iterative successive interference cancellation

© 2019 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes,creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.The average packet error rate (PER) and user-PER profiles of iterative successive interference cancellation (I-SIC) are analyzed for a proof-of-concept scenario where asymptotically many code-division-multiple-access users share the same channel encoder. To characterize the iterative decoding receiver, we propose a novel multivariate PER function evaluated over the consecutive signal-to-interference-plus-noise ratios (SINRs) experienced by each undecoded user. Analytic expressions for the user-energy and user-SINR profiles at every iteration are derived via warping operators on the user ordering that relate the asymptotic distribution of undecoded users at different iterations. Monte Carlo simulations using a chip-level I-SIC implementation assess the accuracy of the proposed user-limit analysis.Peer ReviewedPostprint (author's final draft

Regions de decisió i cota de la unió

Presentació Docent: Regions de Decisió i Cota de la Unió. Assignatura: ICOM - ETSETB (UPC) El document constitueix una còpia per l'estudiant de la presentació de diversos conceptes teòrics relacionats amb la determinació de regions de decisió en el pla IQ per sistemes de comunicacions pas banda. Es presenta de forma gràfica com es determinen les regions de decisió, com es calcula la probabilitat d'error de símbol i com s'estableix una cota superior utilitzant la cota de la unió. Es fa èmfasi en la utilització de raonaments gràficsm utilitzant segons conveniència, propietats bàsiques de teoria de conjunts. El document s'organitza en base a 2 transparències per pàgina.Aquest document presenta de forma gràfica: - La determinació de la regió de decisió R associada a un símbol complexe s = I + jQ . - La determinació de la seva probabilitat d’error i la d’una cot a superior (Cota de la Unió). - Exemples d’aplicació: 8-PSK, QPSK, 3-PSK+0Preprin

Multiantenna GLR detection of a gaussian signal in spatially uncorrelated noise

The exact all-SNR Generalized Log-likelihood Ratio Test (GLRT) of a Gaussian rank-one signal impinging on an - antenna receiver in unknown spatially uncorrelated white noise is derived and compared with some previous low-SNR approximations to this problem. It is confirmed that the coherence matrix used in the mentioned approximations is a sufficient statistic for the GLRT over the complete SNR range. In contrast, this exact, albeit more complex test, requires the unconstrained optimization of a highly nonlinear -variate complex function which can be addressed using classical optimization techniques. A maximum eigenvalue problem combined with a univariate optimization problem serves the purpose of initialization. Results validate the yet unproven close to optimum performance of previous detectors under the rank-one signal model for the tested SNR’s.Peer ReviewedPostprint (published version

Distributed multivariate regression with unknown noise covariance in the presence of outliers: an MDL approach

We consider the problem of estimating the coefficients in a multivariable linear model by means of a wireless sensor network which may be affected by anomalous measurements. The noise covariance matrices at the different sensors are assumed unknown. Treating outlying samples, and their support, as additional nuisance parameters, the Maximum Likelihood estimate is investigated, with the number of outliers being estimated according to the Minimum Description Length principle. A distributed implementation based on iterative consensus techniques is then proposed, and it is shown effective for managing outliers in the data.Peer ReviewedPostprint (author's final draft

Efficient bit-level design of an on-board digital TV demultiplexer

A bit-level description of the signal processing stage of an on-board integrated VLSI multi-carrier demodulator is presented in this paper, along with a description of the optimization procedure that has been developed for the signal processing functions1. The demultiplexer is capable of handling a varying number of carriers in a 36 MHz bandwidth on the satellite up-link. Its architecture has been optimized at bit-level in a way dependent on the known input signal statistics and carrier distributions allowed by the frequency plan.Peer ReviewedPostprint (published version

Estudio del 2,3 - difosfoglicerato intraeritrocetario, con especial referencia a su papel modulador en el transporte de oxígeno en algunas situaciones clínicas

Tesis Univ. Complutense.Fac. de MedicinaTRUEProQuestpu

SINR profile for spectral efficiency optimization of SIC receivers in the many-user regime

© 2015 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes,creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.In dense wireless scenarios, and particularly under high traffic loads, the design of efficient random access protocols is necessary. Some candidate solutions are based on Direct- Sequence Spread Spectrum (DS-SS) combined with a Successive Interference Cancellation (SIC) demodulator, but the perfor- mance of these techniques is highly related to the distribution of the users received power. In that context, this paper presents a theoretical analysis to calculate the optimum user SINR profile at the decoder maximizing the spectral efficiency in bps/Hz for a specific modulation and practical Forward Error Correction (FEC) code. This solution is achieved by means of Variational Calculus operating in the asymptotic large-user case. Although a constant SINR function has been typically assumed in the literature (the one maximizing capacity), the theoretical results evidence that the optimum SINR profile must be an increasing function of the users received power. Its performance is compared with that of the uniform profile for two representative scenarios with different channel codes in a slightly overloaded system. The numerical results show that the optimum solution regulates the network load preventing the aggregate throughput from collapsing when the system is overloaded. In scenarios with a large number of transmitters, this optimum solution can be implemented in an uncoordinated manner with the knowledge of a few public system parameters.Peer ReviewedPostprint (published version

Energy and rate allocation for massive multiple access with interference cancelation

This article addresses the problem of energy and code allocation to many users accessing, under spreading-based nonorthogonal multiple access, a wireless node set up with a successive interference cancellation architecture aided by redundancy-check error control. As an application, we consider the asynchronous access of a delay-tolerant satellite system, where users employ finite-length channel codes and are subject to a known power unbalance induced by the known distribution of the channel’s attenuation. The article develops, as a mathematically tractable approximation to massively populated systems, a unified framework to compute the best energy and code allocation rules that maximize the spectral efficiency of a network that handles asymptotically many users. Concretely, the presented approach circumvents the exponential complexity in the number of users when modeling the propagation of packet decoding failures through the receiver’s decoding scheme. It also enables a deterministic analysis of the more complex features affecting the receiver, making the related performance optimization problem amenable to systematic tools from differential and variational calculus. The derived expressions evidence the most favorable three-way unbalance between energy, rate, and reliability for receiver performance. Low-level system simulations are carried out for validation.This work was supported in part by the Spanish Ministry of Science and Innovation through project RODIN (PID2019-105717RB-C22/AEI/10.13039/501100011033) and in part by Grant 2017 SGR 578.Peer ReviewedPostprint (published version

Optimal power control law for equal-rate DS-CDMA networks governed by a successive soft interference cancellation scheme

©2018 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.This paper studies the throughput maximization of a dense multiple access network of low-rate subscribers that share the same practical Forward Error Correction (FEC) code and modulation scheme, and transmit to a central node that implements a Successive Soft Interference Cancellation (soft SIC) strategy in order to mitigate Multiple Access Interference (MAI). In the user-asymptotic case, we make use of Variational Calculus (VC) tools to derive, in terms of the Packet Error Rate (PER) of the shared encoder and the Residual Energy (RE) from imperfect cancellation, the optimum energy profile that maximizes the network spectral efficiency, when a sum power constraint at the SIC input is enforced. Comparative performance analyses using a representative encoder are carried out. Simulation results show the benefit of the adopted soft SIC scheme in front of other SIC strategies, obtaining relevant throughput gains under high traffic loads.Peer ReviewedPostprint (author's final draft