Results
- Showing results for:
- Reset all filters
Search results
-
Journal articleLooney D, Goverdovsky V, Rosenzweig I, et al., 2016,
A Wearable In-Ear Encephalography Sensor for Monitoring Sleep: Preliminary Observations from Nap Studies
, Annals of the American Thoracic Society, Vol: 13, Pages: 2229-2233, ISSN: 2329-6933RATIONALE: To date the only quantifiable measure of neural changes that define sleep is electroencephalography (EEG). Although widely used for clinical testing, scalp-electrode EEG is costly and poorly tolerated by sleeping patients. OBJECTIVES: This is a pilot study to assess the agreement between EEG recordings obtained from a new ear-EEG sensor and those obtained simultaneously from standard scalp electrodes. METHODS: Participants were 4 healthy men, ages 25 to 36 years. During naps, EEG tracings were recorded simultaneously from the ear sensor and standard scalp electrodes. A clinical expert, blinded to the data collection, analyzed 30-second epochs of recordings from both devices using standardized criteria. The agreement between scalp- and ear-recordings was assessed. MEASUREMENTS AND MAIN RESULTS: We scored 360 epochs (scalp-EEG and ear-EEG) of which 254 (70.6%) were scored as non-rapid-eye movement (NREM) sleep using scalp-EEG. The ear-EEG sensor had a sensitivity of 0.88 (95% CI 0.82 to 0.92) and specificity of 0.78 (95% CI 0.70 to 0.84) in detecting N2/N3 sleep. The kappa coefficient, between the scalp- and ear-EEG, was 0.65 (95% CI 0.58 to 0.73). As a sleep monitor (all NREM sleep stages versus wake), the in-ear sensor had a sensitivity of 0.91 (95% CI 0.87 to 0.94) and specificity of 0.66 (95% CI 0.56 to 0.75). The kappa coefficient was 0.60 (95% CI 0.50 to 0.69). CONCLUSIONS: Substantial agreement was observed between recordings derived from a new ear-EEG sensor and conventional scalp electrodes on 4 healthy volunteers during daytime naps.
-
Conference paperLawson M, Brookes M, Dragotti PL, 2016,
Capturing the plenoptic function in a swipe
, Conference on Applications of Digital Image Processing XXXIX, Publisher: Society of Photo-optical Instrumentation Engineers, ISSN: 0277-786X -
Journal articleMoore AH, Evers C, Naylor PA, 2016,
Direction of Arrival Estimation in the Spherical Harmonic Domain using Subspace Pseudo-Intensity Vectors
, IEEE/ACM Transactions on Audio, Speech, and Language Processing, Vol: 25, Pages: 178-192, ISSN: 2329-9290Direction of Arrival (DOA) estimation is a fundamental problem in acoustic signal processing. It is used in a diverse range of applications, including spatial filtering, speech dereverberation, source separation and diarization. Intensity vector-based DOA estimation is attractive, especially for spherical sensor arrays, because it is computationally efficient. Two such methods are presented which operate on a spherical harmonic decomposition of a sound field observed using a spherical microphone array. The first uses Pseudo-Intensity Vectors (PIVs) and works well in acoustic environments where only one sound source is active at any time. The second uses Subspace Pseudo-Intensity Vectors (SSPIVs) and is targeted at environments where multiple simultaneous sources and significant levels of reverberation make the problem more challenging. Analytical models are used to quantify the effects of an interfering source, diffuse noise and sensor noise on PIVs and SSPIVs. The accuracy of DOA estimation using PIVs and SSPIVs is compared against the state-of-the-art in simulations including realistic reverberation and noise for single and multiple, stationary and moving sources. Finally, robust performance of the proposed methods is demonstrated using speech recordings in real acoustic environments.
-
Conference paperLiu L, Ling C, 2016,
Polar codes and polar lattices for independent fading channels
, IEEE International Symposium on Information Theory (ISIT), Publisher: Institute of Electrical and Electronics Engineers (IEEE), Pages: 4923-4935, ISSN: 1558-0857In this paper, we design polar codes and polar lattices for independent identically distributed fading channels when the channel state information is only available to the receiver. For the binary input case, we propose a new design of polar codes through single-stage polarization to achieve the ergodic capacity. For the non-binary input case, polar codes are further extended to polar lattices to achieve the ergodic Poltyrev capacity, i.e., the capacity without power limit. When the power constraint is taken into consideration, we show that polar lattices with lattice Gaussian shaping achieve the ergodic capacity of fading channels. The coding and shaping are both explicit, and the overall complexity of encoding and decoding is O(N log2 N).
-
Journal articleLiu WILIIAM, Ling C, 2016,
Efficient Integer Coefficient Search forCompute-and-Forward
, IEEE Transactions on Wireless Communications, Vol: 15, Pages: 8039-8050, ISSN: 1558-2248Integer coefficient selection is an important decodingstep in the implementation of compute-and-forward (C-F)relaying scheme. Choosing the optimal integer coefficients in CFhas been shown to be a shortest vector problem (SVP) whichis known to be NP hard in its general form. Exhaustive searchof the integer coefficients is only feasible in complexity for smallnumber of users while approximation algorithms such as LenstraLenstra-Lovasz(LLL) lattice reduction algorithm only find avector within an exponential factor of the shortest vector. Anoptimal deterministic algorithm was proposed for C-F by Sahraeiand Gastpar specifically for the real valued channel case. In thispaper, we adapt their idea to the complex valued channel andpropose an efficient search algorithm to find the optimal integercoefficient vectors over the ring of Gaussian integers and the ringof Eisenstein integers. A second algorithm is then proposed thatgeneralises our search algorithm to the Integer-Forcing MIMO CFreceiver. Performance and efficiency of the proposed algorithmsare evaluated through simulations and theoretical analysis.
-
Conference paperManikas A, Sridhar V, Kamil Y, 2016,
Array of sensors: A spatiotemporal-state-space model for target trajectory tracking (Invited Paper)
, 2016 IEEE Sensor Array and Multichannel Signal Processing Workshop (SAM), Publisher: IEEE, ISSN: 2151-870XIn this paper, with the objective of tracking the trajectoryof multiple mobile targets, a novel spatiotemporal-state-space modelis introduced for an array of sensors distributed in space. Underthe wideband assumption, the proposed model incorporates the arraygeometry in conjunction with crucial target parameters namely (i) ranges,(ii) directions, (iii) velocities and (iv) associated Doppler effects. Computersimulation studies show some representative examples where the proposedmodel is utilised to track the locations of sources in space with a veryhigh accuracy.
-
Journal articleSong C, Park J, Clerckx B, et al., 2016,
Generalized Precoder Designs Based on Weighted MMSE Criterion for Energy Harvesting Constrained MIMO and Multi-User MIMO Channels
, IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS, Vol: 15, Pages: 7941-7954, ISSN: 1536-1276 -
Conference paperNazemi S, Leung KK, Swami A, 2016,
Optimization framework with reduced complexity for sensor networks with in-network processing.
, IEEE Wireless Communications and Networking Conference (WCNC), Publisher: IEEE, ISSN: 1525-3511We propose a framework for optimizing in-network processing (INP) in wireless sensor networks. INP provides a platform for processing (e.g., fusing, aggregating or compressing) the data along the transmission routes in the sensor network. This can reduce the volume of transmitted data, therefore optimizing the utilization of energy and bandwidth. However, such data processing must ensure that the end result can meet given QoI requirements. We formulate the QoI-aware INP problem as a non-linear optimization problem to identify the optimal degree of data compression at each sensor node subject to satisfying a QoI requirement for the end-user. The formulation arranges all involved sensor nodes in a tree where data is transfered and processed from nodes to their parent nodes toward the root node of the tree. Under the assumption of uniform parameter setting, we show that the processing tree can be collapsed into a linear graph where the number of nodes represents the node levels of the original processing tree. This represents a significant reduction in complexity of the problem. Numerical example are provided to illustrate the performance of the proposed approach.
-
Journal articleXu D, Gao H, Mandic DP, 2016,
A new proof of the generalized Hamiltonian-Real calculus
, Royal Society Open Science, Vol: 3, ISSN: 2054-5703The recently introduced generalized Hamiltonian–Real (GHR)calculus comprises, for the first time, the product and chainrules that makes it a powerful tool for quaternion-basedoptimization and adaptive signal processing. In this paper,we introduce novel dual relationships between the GHRcalculus and multivariate real calculus, in order to provide anew, simpler proof of the GHR derivative rules. This furtherreinforces the theoretical foundation of the GHR calculus andprovides a convenient methodology for generic extensions ofreal- and complex-valued learning algorithms to the quaterniondomain.
-
Conference paperMoore AH, Naylor P, 2016,
Linear prediction based dereverberation for spherical microphone arrays
, 15th International Workshop on Acoustic Signal Enhancement (IWAENC), Publisher: IEEEDereverberation is an important preprocessing step in manyspeech systems, both for human and machine listening. Inmany situations, including robot audition, the sound sourcesof interest can be incident from any direction. In such circumstances,a spherical microphone array allows direction of arrivalestimation which is free of spatial aliasing and directionindependentbeam patterns can be formed. This contributionformulates the Weighted Prediction Error algorithm in thespherical harmonic domain and compares the performance toa space domain implementation. Simulation results demonstratethat performing dereverberation in the spherical harmonicdomain allows many more microphones to be usedwithout increasing the computational cost. The benefit ofusing many microphones is particularly apparent at low signalto noise ratios, where for the conditions tested up to 71%improvement in speech-to-reverberation modulation ratio wasachieved.
-
Journal articleKim Y, Ryu J, Kim KK, et al., 2016,
Motor Imagery Classification Using Mu and Beta Rhythms of EEG with Strong Uncorrelating Transform Based Complex Common Spatial Patterns
, Computational Intelligence and Neuroscience, Vol: 2016, ISSN: 1687-5265Recent studies have demonstrated the disassociation between the mu and beta rhythms of electroencephalogram (EEG) during motor imagery tasks. The proposed algorithm in this paper uses a fully data-driven multivariate empirical mode decomposition (MEMD) in order to obtain the mu and beta rhythms from the nonlinear EEG signals. Then, the strong uncorrelating transform complex common spatial patterns (SUTCCSP) algorithm is applied to the rhythms so that the complex data, constructed with the mu and beta rhythms, becomes uncorrelated and its pseudocovariance provides supplementary power difference information between the two rhythms. The extracted features using SUTCCSP that maximize the interclass variances are classified using various classification algorithms for the separation of the left- and right-hand motor imagery EEG acquired from the Physionet database. This paper shows that the supplementary information of the power difference between mu and beta rhythms obtained using SUTCCSP provides an important feature for the classification of the left- and right-hand motor imagery tasks. In addition, MEMD is proved to be a preferred preprocessing method for the nonlinear and nonstationary EEG signals compared to the conventional IIR filtering. Finally, the random forest classifier yielded a high performance for the classification of the motor imagery tasks.
-
Journal articleAkansu AN, Malioutov D, Palomar DP, et al., 2016,
Introduction to the Issue on Financial Signal Processing and Machin Learning for Electronic Trading
, IEEE Journal of Selected Topics in Signal Processing, Vol: 10, Pages: 979-981, ISSN: 1932-4553The twelve papers in this special issue presents relevant research contributions from the disciplines of finance, mathematics, data science and engineering to facilitate scientific cross-fertilization. It will also serve the signal processing community to be exposed to the state of the art in mathematical finance, financial engineering, financial signal processing an electronic trading, and to foster future research in this emerging area. The main themes of this special issue include using tools from machine learning and signal processing that help to address some of the main problems arising in quantitative finance: modeling risk and correlations of financial instruments and their baskets, returns and liquidity, and problems involving risk-aware resource allocation -namely portfolio optimization. These problems involve tools from convex and discrete optimization, non-parametric statistics, time-series modeling,graph theory and high-dimensional covariance estimation.
-
Journal articleNaylor PA, Zahedi A, Jensen S, et al., 2016,
Source Coding in Networks with Covariance Distortion Constraints
, IEEE Transactions on Signal Processing, Vol: 64, Pages: 5943-5958, ISSN: 1053-587XWe consider a source coding problem with a networkscenario in mind, and formulate it as a remote vectorGaussian Wyner-Ziv problem under covariance matrix distortions.We define a notion of minimum for two positive-definitematrices based on which we derive an explicit formula for therate-distortion function (RDF). We then study the special casesand applications of this result. We show that two well-studiedsource coding problems, i.e. remote vector Gaussian Wyner-Ziv problems with mean-squared error and mutual informationconstraints are in fact special cases of our results. Finally,we apply our results to a joint source coding and denoisingproblem. We consider a network with a centralized topology anda given weighted sum-rate constraint, where the received signalsat the center are to be fused to maximize the output SNR whileenforcing no linear distortion. We show that one can design thedistortion matrices at the nodes in order to maximize the outputSNR at the fusion center. We thereby bridge between denoisingand source coding within this setup.
-
Conference paperXue W, Brookes M, Naylor PA, 2016,
Cross-Correlation Based Under-Modelled Multichannel Blind Acoustic System Identification with Sparsity Regularization
, 24th European Signal Processing Conference (EUSIPCO), Publisher: IEEE, Pages: 718-722, ISSN: 2076-1465 -
Journal articleCui Y, Wu Y, Jiang D, et al., 2016,
User-centric interference nulling in downlinkmulti-antenna heterogeneous networks
, IEEE Transactions on Wireless Communications, Vol: 15, Pages: 7484-7500, ISSN: 1558-2248In heterogeneous networks (HetNets), strong interference due to spectrum reuse affects each user's signal-to-interference ratio (SIR), and hence is one limiting factor of network performance. In this paper, we propose a user-centric interference nulling (IN) scheme in a downlink large-scale HetNet to improve coverage/outage probability by improving each user's SIR. This IN scheme utilizes at most maximum IN degree of freedom (DoF) at each macro-base station to avoid interference to uniformly selected macro (pico) users with signal-to-individual-interference ratio below a macro (pico) IN threshold, where the maximum IN DoF and the two IN thresholds are three design parameters. Using tools from stochastic geometry, we first obtain a tractable expression of the coverage (equivalently outage) probability. Then, we obtain the asymptotic expressions of the coverage/outage probability in the low and high SIR threshold regimes. The analytical results indicate that the maximum IN DoF can affect the order gain of the outage probability in the low SIR threshold regime, but cannot affect the order gain of the coverage probability in the high SIR threshold regime. Moreover, we characterize the optimal maximum IN DoF, which optimizes the asymptotic coverage/outage probability. Finally, numerical results show that the proposed scheme can achieve good gains in coverage/outage probability over some baseline schemes.
-
Journal articleRehman NU, Abbas SZ, Asif A, et al., 2016,
Translation invariant multi-scale signal denoising based on goodness-of-fit tests
, SIGNAL PROCESSING, Vol: 131, Pages: 220-234, ISSN: 0165-1684 -
Journal articleGao G, Liu CH, Chen M, et al., 2016,
Cloud-Based Actor Identification With Batch-Orthogonal Local-Sensitive Hashing and Sparse Representation
, IEEE Transactions on Multimedia, Vol: 18, Pages: 1749-1761, ISSN: 1941-0077Recognizing and retrieving multimedia content withmovie/TV series actors, especially querying actor-specific videosin large scale video datasets, has attracted much attention inboth the video processing and computer vision research field.However, many existing methods have low efficiency both intraining and testing processes and also a less than satisfactoryperformance. Considering these challenges, in this paper, wepropose an efficient cloud-based actor identification approach withbatch-orthogonal local-sensitive hashing (BOLSH) and multi-taskjoint sparse representation classification. Our approach is featuredby the following: 1) videos from movie/TV series are segmented intoshots with the cloud-based shot boundary detection; 2) while facesin each shot are detected and tracked, the cloud-based BOLSHis then implemented on these faces for feature description; 3)the sparse representation is then adopted for actor identificationin each shot; and 4) finally, a simple application, actor-specificshots retrieval is realized to verify our approach. We conductextensive experiments and empirical evaluations on a large scaledataset, to demonstrate the satisfying performance of our approachconsidering both accuracy and efficiency.
-
Conference paperLuzzi L, Ling C, Vehkalahti R, 2016,
Almost universal codes for fading wiretap channels
, 2016 IEEE International Symposium on Information Theory (ISIT), Publisher: IEEE, ISSN: 2157-8117We consider a fading wiretap channel model where the transmitter has only statistical channel state information, and the legitimate receiver and eavesdropper have perfect channel state information. We propose a sequence of non-random lattice codes which achieve strong secrecy and semantic security over ergodic fading channels. The construction is almost universal in the sense that it achieves the same constant gap to secrecy capacity over Gaussian and ergodic fading models.
-
Conference paperLiu L, Ling C, 2016,
Polar codes and polar lattices for independent fading channels
, ISIT 2016, Publisher: IEEE, Pages: 978-982, ISSN: 2157-8117In this paper, we design polar codes and polar lattices for i.i.d. fading channels when the channel state information is only available to the receiver. For the binary input case, we propose a new design of polar codes through single-stage polarization to achieve the ergodic capacity. For the non-binary input case, polar codes are further extended to polar lattices to achieve the egodic Poltyrev capacity, i.e., the capacity without power limit. When the power constraint is taken into consideration, we show that polar lattices with lattice Gaussian shaping achieve the egodic capacity of fading channels. The coding and shaping are both explicit, and the overall complexity of encoding and decoding is O(N log2 N).
-
Conference paperWang Z, Ling C, 2016,
Further results on independent Metropolis-Hastings-Klein sampling
, ISIT 2016, Publisher: IEEE, ISSN: 2157-8117Sampling from a lattice Gaussian distribution is emerging as an important problem in coding and cryptography. This paper gives a further analysis of the independent Metropolis-Hastings-Klein (MHK) algorithm we presented at ISIT 2015. We derive the exact spectral gap of the induced Markov chain, which dictates the convergence rate of the independent MHK algorithm. Then, we apply the independent MHK algorithm to lattice decoding and obtained the decoding complexity for solving the CVP as Õ(e∥Bx-c∥2 / mini ∥b̂i∥2). Finally, the tradeoff between decoding radius and complexity is also established.
-
Conference paperJoudeh H, Clerckx B, 2016,
A Rate-Splitting Strategy for Max-Min Fair Multigroup Multicasting
, IEEE 17th International Workshop on Signal Processing Advances in Wireless Communications (SPAWC), Pages: 1-5We consider the problem of transmit beamforming to multiple cochannel multicast groups. The conventional approach is to beamform a designated data stream to each group, while treating potential inter-group interference as noise at the receivers. In overloaded systems where the number of transmit antennas is insufficient to perform interference nulling, we show that inter-group interference dominates at high SNRs, leading to a saturating max-min fair performance. We propose a rather unconventional approach to cope with this issue based on the concept of Rate-Splitting (RS). In particular, part of the interference is broadcasted to all groups such that it is decoded and canceled before the designated beams are decoded. We show that the RS strategy achieves significant performance gains over the conventional multigroup multicast beamforming strategy.
-
Conference paperCampello A, Ling C, Belfiore JC, 2016,
Algebraic lattice Codes achieve the capacity of the compound block-fading channel
, ISIT 2016, Publisher: IEEE, ISSN: 2157-8117We propose a lattice coding scheme that achieves the capacity of the compound block-fading channel. Our lattice construction exploits the multiplicative structure of number fields and their group of units to absorb ill-conditioned channel realizations. To shape the constellation, a discrete Gaussian distribution over the lattice points is applied. A by-product of our results is a refined analysis of the probability of error of the lattice Gaussian distribution in the AWGN channel.
-
Journal articleDragotti P, Wei X, 2016,
FRESH – FRI-based single-image super-resolution algorithm
, IEEE Transactions on Image Processing, Vol: 25, Pages: 3723-3735, ISSN: 1057-7149In this paper, we consider the problem of single image super-resolution and propose a novel algorithm that outperforms state-of-the-art methods without the need of learning patches pairs from external data sets. We achieve this by modeling images and, more precisely, lines of images as piecewise smooth functions and propose a resolution enhancement method for this type of functions. The method makes use of the theory of sampling signals with finite rate of innovation (FRI) and combines it with traditional linear reconstruction methods. We combine the two reconstructions by leveraging from the multi-resolution analysis in wavelet theory and show how an FRI reconstruction and a linear reconstruction can be fused using filter banks. We then apply this method along vertical, horizontal, and diagonal directions in an image to obtain a single-image super-resolution algorithm. We also propose a further improvement of the method based on learning from the errors of our super-resolution result at lower resolution levels. Simulation results show that our method outperforms state-of-the-art algorithms under different blurring kernels.
-
Conference paperHe T, Gkelias A, Ma L, et al., 2016,
Robust monitor placement for network tomography in dynamic networks
, 35th IEEE Annual International Conference on Computer Communications (IEEE INFOCOM), Publisher: IEEE, ISSN: 1063-6692We consider the problem of placing the minimumnumber of monitors in a dynamic network to identify additivelink metrics from path metrics measured along cycle-free pathsbetween monitors. Our goal is robust monitor placement, i.e.,the same set of monitors can maintain network identifiabilityunder topology changes. Our main contribution is a set of moni-tor placement algorithms with different performance-complexitytradeoffs that can simultaneously identify multiple topologiesoccurring during the network lifetime. In particular, we show thatthe optimal monitor placement is the solution to a generalizedhitting set problem, for which we provide a polynomial-timealgo-rithm to construct the input and a greedy algorithm to selectthemonitors with logarithmic approximation. Although the optimalplacement is NP-hard in general, we identify non-trivial specialcases that can be solved efficiently. Our secondary contributionis a dynamic triconnected decomposition algorithm to computethe input needed by the monitor placement algorithms, whichis the first such algorithm that can handle edge deletions. Ourevaluations on mobility-induced dynamic topologies verify theefficiency and the robustness of the proposed algorithms.
-
Journal articleMa L, He T, Swami A, et al., 2016,
Network capability in localizing node failures via end-to-end path measurements
, IEEE/ACM Transactions on Networking, Vol: 25, Pages: 434-450, ISSN: 1063-6692We investigate the capability of localizing node failures in communication networks from binary states (normal/failed) of end-to-end paths. Given a set of nodes of interest, uniquely localizing failures within this set requires that different observable path states associate with different node failure events. However, this condition is difficult to test on large networks due to the need to enumerate all possible node failures. Our first contribution is a set of sufficient/necessary conditions for identifying a bounded number of failures within an arbitrary node set that can be tested in polynomial time. In addition to network topology and locations of monitors, our conditions also incorporate constraints imposed by the probing mechanism used. We consider three probing mechanisms that differ according to whether measurement paths are: (i) arbitrarily controllable; (ii) controllable but cycle-free; or (iii) uncontrollable (determined by the default routing protocol). Our second contribution is to quantify the capability of failure localization through: 1) the maximum number of failures (anywhere in the network) such that failures within a given node set can be uniquely localized and 2) the largest node set within which failures can be uniquely localized under a given bound on the total number of failures. Both measures in 1) and 2) can be converted into the functions of a per-node property, which can be computed efficiently based on the above sufficient/necessary conditions. We demonstrate how measures 1) and 2) proposed for quantifying failure localization capability can be used to evaluate the impact of various parameters, including topology, number of monitors, and probing mechanisms.
-
Journal articleJoudeh H, Clerckx B, 2016,
Robust Transmission in Downlink Multiuser MISO Systems: A Rate-Splitting Approach
, IEEE Transactions on Signal Processing, Vol: 64, Pages: 6227-6242, ISSN: 1053-587XWe consider a downlink multiuser MISO systemwith bounded errors in the Channel State Information at theTransmitter (CSIT). We first look at the robust design problemof achieving max-min fairness amongst users (in the worstcasesense). Contrary to the conventional approach adopted inliterature, we propose a rather unorthodox design based on aRate-Splitting (RS) strategy. Each user’s message is split intotwo parts, a common part and a private part. All commonparts are packed into one super common message encodedusing a public codebook, while private parts are independentlyencoded. The resulting symbol streams are linearly precodedand simultaneously transmitted, and each receiver retrieves itsintended message by decoding both the common stream andits corresponding private stream. For CSIT uncertainty regionsthat scale with SNR (e.g. by scaling the number of feedbackbits), we prove that a RS-based design achieves higher max-min(symmetric) Degrees of Freedom (DoF) compared to conventionaldesigns (NoRS). For the special case of non-scaling CSIT (e.g.fixed number of feedback bits), and contrary to NoRS, RS canachieve a non-saturating max-min rate. We propose a robustalgorithm based on the cutting-set method coupled with theWeighted Minimum Mean Square Error (WMMSE) approach,and we demonstrate its performance gains over state-of-the artdesigns. Finally, we extend the RS strategy to address the Qualityof Service (QoS) constrained power minimization problem, andwe demonstrate significant gains over NoRS-based designs.
-
Journal articleWu X, Yan Z, Ling C, et al., 2016,
Artificial-noise-aided physical layer phase challenge-response authentication for practical OFDM transmission
, IEEE Transactions on Wireless Communications, Vol: 15, Pages: 6611-6625, ISSN: 1558-2248In this paper, we propose a novel Artificial-Noise- Aided PHYsical layer Phase Challenge-Response Authentication Scheme (ANA-PHY-PCRAS) for practical orthogonal frequency division multiplexing (OFDM) transmission. In this new scheme, Tikhonov-distributed artificial noise is introduced to interfere with the phase-modulated key for resisting potential key-recovery attacks. Then, we address various practical issues for ANAPHY- PCRAS with OFDM transmission, including correlation among subchannels, imperfect carrier and timing recoveries. Among them, we show that the effect of sampling offset is significant and a search procedure in the frequency domain should be incorporated for verification. With practical OFDM transmission, the number of uncorrelated subchannels is often insufficient. Hence, we employ a time-separated approach for allocating enough subchannels and a modified ANA-PHY-PCRAS is proposed to alleviate the discontinuity of channel phase at far-separated time slots. Finally, the key equivocation is derived for the worst case scenario. We conclude that the enhanced security of ANA-PHY-PCRAS comes from the uncertainties of both the wireless channel and introduced artificial noise, compared to the traditional challenge-response authentication scheme implemented at the upper layer.
-
Journal articleHao C, Clerckx B, 2016,
Achievable sum DoF of the K-user MIMO interference channel with delayed CSIT
, IEEE Transactions on Communications, Vol: 64, Pages: 4165-4180, ISSN: 1558-0857This paper considers a K-user multiple-inputmultiple-output(MIMO) interference channel (IC) where 1) thechannel state information obtained by the transmitters (CSIT) iscompletely outdated, and 2) the number of transmit antennasat each transmitter, i.e., M, is greater than the number ofreceive antennas at each user, i.e., N. The usefulness of thedelayed CSIT was firstly identified in a K-phase RetrospectiveInterference Alignment (RIA) scheme proposed by Maddah-Aliet al for the Multiple-Input-Single-Output Broadcast Channel,but the extension to the MIMO IC is a non-trivial step as eachtransmitter only has the message intended for the correspondinguser. Recently, Abdoli et al focused on a Single-Input-SingleOutputIC and solved such bottleneck by inventing a K-phaseRIA with distributed overheard interference retransmission. Inthis paper, we propose two K-phase RIA schemes suitable forthe MIMO IC by generalizing and integrating some key featuresof both Abdoli’s and Maddah-Ali’s works. The two schemesjointly yield the best known sum Degrees-of-Freedom (DoF)performance so far. For the case MN ≥K, the achieved sum DoFis asymptotically given by 6415N when K→∞.
-
Journal articleZhang Y, Dragotti P-L, 2016,
Sampling streams of pulses with unknown shapes
, IEEE Transactions on Signal Processing, Vol: 64, Pages: 5450-5465, ISSN: 1053-587XThis paper extends the class of continuous-time signals that can be perfectly reconstructed by developing a theory for the sampling and exact reconstruction of streams of short pulses with unknown shapes. The single pulse is modelled as the delayed version of a wavelet-sparse signal, which is normally not band limited. As the delay can be an arbitrary real number, it is hard to develop an exact sampling result for this type of signals. We achieve the exact reconstruction of the pulses by using only the knowledge of the Fourier transform of the signal at specific frequencies. We further introduce a multi-channel acquisition system which uses a new family of compact-support sampling kernels for extracting the Fourier information from the samples. The shape of the kernel is independent of the wavelet basis in which the pulse is sparse and hence the same acquisition system can be used with pulses which are sparse on different wavelet bases. By exploiting the fact that pulses have short duration and that the sampling kernels have compact support, we finally propose a local and sequential algorithm to reconstruct streaming pulses from the samples.
-
Conference paperReynolds S, Copeland CS, Schultz SR, et al., 2016,
An extension of the FRI framework for calcium transient detection
, IEEE 13th International Symposium on Biomedical Imaging (ISBI), Publisher: IEEE, Pages: 676-679, ISSN: 1945-7928Two-photon calcium imaging of the brain allows the spatiotemporal activity of neuronal networks to be monitored at cellular resolution. In order to analyse this activity it must first be possible to detect, with high temporal resolution, spikes from the time series corresponding to single neurons. Previous work has shown that finite rate of innovation (FRI) theory can be used to reconstruct spike trains from noisy calcium imaging data. In this paper we extend the FRI framework for spike detection from calcium imaging data to encompass data generated by a larger class of calcium indicators, including the genetically encoded indicator GCaMP6s. Furthermore, we implement least squares model-order estimation and perform a noise reduction procedure ('pre-whitening') in order to increase the robustness of the algorithm. We demonstrate high spike detection performance on real data generated by GCaMP6s, detecting 90% of electrophysiologically-validated spikes.
This data is extracted from the Web of Science and reproduced under a licence from Thomson Reuters. You may not copy or re-distribute this data in whole or in part without the written consent of the Science business of Thomson Reuters.
