H. Leib

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• Ph.D., M.Sc, B.Sc.
• Professor at McGill University

Relaying with network coding forms a basis for a variety of collaborative communication systems. A linear block coding framework for multi-way relaying using network codes introduced in the literature shows great promise for understanding, analyzing, and designing such systems. So far, this technique has been used with low-density parity check (LDP...

This work considers the notion of random tensors and reviews some fundamental concepts in statistics when applied to a tensor based data or signal. In several engineering fields such as Communications, Signal Processing, Machine learning, and Control systems, the concepts of linear algebra combined with random variables have been indispensable tool...

This work considers the notion of random tensors and reviews some fundamental concepts in statistics when applied to a tensor based data or signal. In several engineering fields such as Communications, Signal Processing, Machine Learning, and Control Systems, the concepts of linear algebra combined with random variables have been indispensable tool...

In past few decades, tensor algebra also known as multi-linear algebra has been developed and customized as a tool to be used for various engineering applications. In particular, with the help of a special form of tensor contracted product, known as the Einstein Product and its properties, many of the known concepts from Linear Algebra could be ext...

Modern communication systems employ multi-domain modulation and coding techniques for effectively exploiting all available resources. Hence in such systems the transmit and receive signals have an inherent multi-domain structure which can be represented using tensors. This work considers the capacity of higher order tensor channels associated with...

In this work, we consider a selective Detect-and-Forward (a symbol based decode-and-forward) (DetF) multi-relay two-way network employing differential MPSK with regularized Weighted Decision Feedback Differential Coherent (WDFDC) receivers. Regularized WDFDC receivers based on a regularized linear predictor (RLP) were proposed for one-way relay net...

Most modern communication systems invariably employ multiple domains, such as space, time, frequency, users, propagation delay, and code sequences, for transmission and reception. Such multi-domain communication systems can be modelled using tensors, which are multi-way arrays and can be considered as an extension of vectors and matrices to higher...

Tensors are multi-way arrays which can be used to model systems spanning many domains. This work proposes to use tensors for characterizing, analyzing, and designing multi-domain communication systems. Most modern day communication systems make use of coding and modulation across different domains such as space, frequency, time. Hence a unified mat...

Most modern communication systems, such as those intended for deployment in IoT applications or 5G and beyond networks, utilize multiple domains for transmission and reception at the physical layer. Depending on the application, these domains can include space, time, frequency, users, code sequences, and transmission media, to name a few. As such,...

Tensors are higher order generalization of vectors and matrices which can be used to describe signals indexed by more than two indices. This paper introduces a tensor framework for minimum mean square error (MMSE) estimation for multi-domain signals and data using the Einstein Product. The framework addresses both proper and improper complex tensor...

Tensors are multi-way arrays which are natural generalization of vectors and matrices to higher orders, and can be used to represent data and signals depending on a multitude of indices. Hence they are heavily used in various disciplines including signal processing, multi-domain communications, machine learning and Big Data. This paper introduces a...

The Ensemble Kalman filter (EnKF) was introduced for highly dimensional systems, but it has poor performance in the presence of strong nonlinearities. The Cubature Kalman filter (CKF) has outstanding performance in strongly nonlinear systems, however, it is limited by high dimensionality. In this work, we provide a comparison between the EnKF and t...

This paper introduces a network linear block coding framework for multi-way relaying with differential MPSK modulation. We consider a system with K user terminals and L relays employing a selective detect-and-forward protocol. We show that such a system can be represented as a systematic (K + L,K) linear block code. This framework allows the use of...

The demand for mobile data is likely to grow at a pace more than envisaged in the coming years. Further, as applications such as the internet of things (IoT) come to fruition, there will be increased diversity in the types of devices demanding internet connectivity and their requirements. Significant increase in data rate requirements is also expec...

This paper considers regularized Weighted Decision Feedback Differential Coherent(WDFDC) receivers for selective Detect-and-Forward multi-relaying systems, operating over fast fading channels. Non-regularized WDFDC receivers have been employed in such One-Way Relay Network (OWRN) with DQPSK modulation, and shown to provide significant performance g...

Working with the abstract concepts of signals in time and frequency domains without a concrete tool to understand the very nature of these fundamental concepts has been a major impediment for undergraduate engineering students attending a course on Signals and Systems or Communications. Classroom teaching in such courses has been traditionally conf...

Large-scale multiple-input multiple-output (LS-MIMO) technology constitutes a foundation for next generation wireless communication systems. Detection techniques are a key issue for practical applications of LS-MIMO. Selection based list detection is an attractive approach for LS-MIMO systems because of its massively parallelizable nature. In this...

This paper considers coded multichannel cooperative spectrum sensing (MC-CSS) employing local Neyman–Pearson testing at each sensor and channel decoding integrated with fusion-based decision. A joint multichannel decoding and decision fusion (JMCDDF) algorithm for performing a likelihood ratio test at the fusion center is derived based on the belie...

Orthogonal Frequency Division Multiplexing (OFDM) is a technique for wideband transmission that is commonly used in modern wireless communication systems because of its good performance over frequency selective channels. However OFDM systems are sensitive to channel time variations resulting in Inter-Carrier Interference (ICI), that without suitabl...

The use of random point processes as models for neural spike trains allows the derivation of powerful statistical estimation techniques for time varying firing rates. Frequently, however, such estimators are based on the assumption that spike sequences follow a Poisson point process. Because of the biophysical properties of neuronal action potentia...

Large MIMO constitutes a principal technology for next generation wireless communication systems. Detection algorithms for large MIMO schemes tend to require long simulation times on conventional computer systems. In order to improve simulation efficiency of decoders in large MIMO systems, we propose to use General Purpose Graphic Processing Units...

This paper considers the integration of channel decoding with fusion based decision, for coded collaborative spectrum sensing (CSS) employing local Neyman-Pearson (NP) testing at each sensor. We derive a belief-propagation (BP) algorithm for joint channel decoding and decision fusion (JCDDF), based on a factor graph model for coded CSS schemes. Usi...

This paper considers a detect-and-forward multirelay wireless system employing differential MPSK modulation with decision-feedback differential coherent (DFDC) receivers. The DFDC receivers overcome the limitation of conventional differential detectors when used over time-varying fading channels and provide performance gains. Using a selective appr...

Cognitive Radio (CR) is a paradigm for a more flexible and efficient usage of radio spectrum, where spectrum sensing is a vital function. When spectrum sensing is performed by several sensors in cooperation to overcome multipath fading and shadowing, a proper media access control (MAC) protocol is needed to coordinate the information exchange betwe...

This work considers a simple bit level combining technique, aided by robust bit reliability information, for uplink collaborating multiple-input multiple-output (MIMO) base-stations (also known as macrodiversity MIMO), operating over composite Rayleigh-lognormal fading channels. Bit reliability weights based on a robust modification of the logarith...

Multiple-input multiple-output (MIMO) transmission techniques constitute an important technology in modern wireless communication. Hence, performance analysis methods for such systems are of considerable interest. This paper considers first the average pairwise error probability for uncoded MIMO systems employing maximum likelihood detection over a...

The fifteen papers in this special issue are devoted to the topic of spectrum and energy efficiency of wireless and mobile communications networks.

Common neuron firing rate estimators have been criticized because of their Poisson assumption, not accounting for the refractory period of action potentials that induces history dependency in spike sequences. Hence rate estimators that can account for such dependency, although seemingly more difficult to formulate, could provide more accurate resul...

Orthogonal Frequency Division Multiplexing (OFDM) is a promising technology for high data rate transmission, that is widely used in modern wireless communication systems because of its suitability for frequency selective channels. However channel time variations destroy the orthogonality between sub-carriers resulting in Inter-Carrier Interference...

The high complexity of optimal detection for spatial multplexing multiple-input multiple-output systems motivates the need for more practical alternatives. Among many suboptimal schemes reported in the literature, very few can be proven to provide close to optimal performance with low fixed complexity. The recently introduced Selection based Minimu...

This work considers the application of Newton's iterative method of matrix inversion for reducing the complexity of calculating the unconstrained solution in Sphere Decoding (SD) for Multiple-Input Multiple-Output (MIMO) wireless communication systems. This paper also proposes a simpler initialization procedure for Newton's method. It is shown that...

Accurately recovering stimulus information from measured neural responses is a common task in the analysis and modeling of the central nervous system. Notable variability in action potential timing invoked by similar stimuli suggests stochastic modeling is appropriate. This work presents a Maximum Likelihood estimator for a parametrized rate functi...

While being a major broadband wireless access technology, OFDM transmission over fast fading channels poses a significant challenge. Time variations in an OFDM channel destroy the subcarriers orthogonality and complicate the problem of symbol detection. This paper considers a Sphere Decoding (SD) algorithm for OFDM over such channels. This SD algor...

Discretization of the received continuous time signal is an essential stage in any receiver for a digital communication system. Over fast fading channels, inappropriate discretization of the received signal can result in SNR performance losses and high error floors. This paper presents a new framework for discrete representation of continuous time...

Using a framework that lies at the intersection of communications, estimation and control, this work considers feedback communication over noisy Gaussian feedforward as well as unconstrained feedback Time Dispersive Channels (TDCs), and presents a linear scheme that reduces transmission delay for a fixed encoder dimension. The approach is based on...

This chapter considers pilot symbol assisted linear mean square error channel estimation in the joint space-time-frequency (STF) domains, for multiple-input multiple-output orthogonal frequency division multiplexing (MIMO-OFDM) systems. Through the use of properly designed and placed pilot sequences, and three dimensional processing, the proposed S...

MIMO communication is a core technology for wireless systems. This work presents a fixed complexity scheme based on simplified channel partition and efficient tree based precancellation employing the MMSE criterion. This algorithm is then extended to a variable complexity tree search scheme that provides lower average complexity. The resulting algo...

This paper considers multiple-antenna broadcast channels (BCs) with multi-dimensional space-time modulation schemes, created by various allocations of signal dimensions to transmit antennas. The signal dimensions are divided into disjoint subsets, where one is shared between all users, and each of the others are assigned to different users. This mo...

MIMO communication is a core technology for wireless systems. This work presents an improved fixed complexity detection technique for underdetermined and overdetermined MIMO systems, based on a low complexity, diversity optimal, incremental channel partition. This new algorithm also employs a new efficient tree search implementation of the precance...

This work considers a joint channel estimation and data detection technique for Multiple Space-Time Trellis Codes (MSTTCs) operating over unknown time-varying channels with large Doppler spread. We propose an algorithm, called Doppler Adaptive Smoothed Data Detection and Kalman Estimation (DA-SDD-KE), that jointly detects data and estimates the cha...

Phase ambiguities affect any joint decoding and channel estimation algorithm over fading channels, making codes that mitigate this problem of considerable interest. This work presents a design that transforms a Space-Time Trellis Code (STTC), prone to carrier phase ambiguities, into a Phase Ambiguity Diminishing STTC (PAD-STTC) that is robust to su...

In this work, we consider a multi-antenna channel with orthogonally multiplexed non-cooperative users, and present its achievable information rate regions with and without channel knowledge at the transmitter. With an informed transmitter, we maximize the rate for each user. With an uninformed transmitter, we consider the optimal power allocation t...

Multiple-input multiple-output (MIMO) systems achieve very high bandwidth efficiencies through spatial multiplexing. However, the complexity of optimal detection in such systems motivates the need for more practical alternatives. Recently, a suboptimal lower complexity detection scheme called ¿generalized parallel interference cancellation¿ (GPIC...

This paper considers the design of soft decision distributed detection schemes for achieving macrodiversity in uplink cellular communication systems with and without channel knowledge at the fusion center. Distributed detection macrodiversity (DDM) techniques are proposed where the quatizer thresholds of local detectors at base stations (radio acce...

This work presents a joint channel estimation and data detection algorithm over high Doppler fading channels, for space-time trellis codes (STTCs) having more than one code vector per trellis branch. Such codes are referred to as multiple STTCs (MSTTCs). This algorithm belongs to the per-survivor processing (PSP) family, where a survivor sequence a...

This paper considers achievable information rates for space--time modulation schemes created by various allocations of signal dimensions to transmit antennas, and various transmit power allocations. We employ a deterministic space and time dispersive channel model following the 3rd Generation Partnership Project (3GPP) standards. With informed tran...

This work presents a field programmable gate array (FPGA) implementation of the min-sum iterative decoding algorithm for the (8,4) extended Hamming code using a reconfigurable computing system. The Mitrion-C high level language (HLL) is used to program the FPGAs, since it provides flexible tools for FPGA-based prototyping and functional verificatio...

This paper investigates the application of Zipper orthogonal frequency-division multiplexing (OFDM), which is a frequency-domain duplexing technique based on interleaving subcarriers, to multiple-antenna cellular communications. By studying the Cramer-Rao lower bound as well as the performance of a minimum-mean-square-error-based interpolator, we s...

This paper considers the newly introduced fountain codes for fixed-rate error control coding, with emphasis on Raptor codes. The performance of Raptor codes of low-to-moderate rates with iterative decoding is evaluated over memoryless, as well as correlated, fading channels. A global decoding algorithm, incorporating feedback between the component...

This work generalizes the "MAP-PSP" algorithm for joint channel estimation and data detection to space-time trellis codes (STTCs) having more than one code vector per trellis branch. The latter codes are referred to as multiple STTCs (MSTTCs). We consider fast fading multiple transmit antenna channels, and investigate the effect of spatial correlat...

This paper considers intelligent transmit antenna selection (TAS) combined with power allocation (PA) for closed-loop multiple-input-multiple-output (MIMO) wireless communications. We present two novel TAS techniques for Vertical Bell Laboratories Layered Space-Time (V-BLAST) systems combined with PA that improve the uncoded error rate performance...

This paper considers a new class of full-diversity space-time (ST) codes for multiple-transmit-antenna wireless systems. These codes, relying on partitioning the transmit antennas into groups, consist of a combination of delay transmit diversity with orthogonal ST block codes and specially designed symbol mappings of information bits into channel s...

The concept of next generation (xG) networks is a novel paradigm that attempts to mitigate spectrum overcrowding and inefficiencies. This objective is envisaged to be accomplished by allowing unlicensed users to utilize licensed parts of the spectrum opportunistically, without disrupting the quality of service (QoS) for licensed users. The cornerst...

This work considers fixed-rate Raptor coded transmission over fading channels with memory following the Jakes' model. The effect of the normalized fade rate on the performance of low-to-moderate rate Raptor codes, when decoded with an improved soft-decision decoding algorithm, is investigated. Results show that, over slow fading channels, the perfo...

This paper compares the performance and computational complexity of two joint channel estimation and data detection algorithms for space-time trellis codes (STTCs) over time-varying flat fading channels. The first algorithm, the maximum a posteriori probability-per survivor processing (MAP-PSP), employs an improved survivor branch decision techniqu...

This work considers joint channel estimation and data detection of space-time trellis codes (STTCs) over time-varying flat fading channels with unknown normalized Doppler shift, f _dT. An algorithm based on an improved per survivor processing (PSP) technique, where the survivor branch decision is formulated in the symbol by symbol maximum...

The problem of the relay channel with confidentiality was first formulated by Oohama in 2001, at which time an inner bound for the capacity region was stated. However, a proof of this inner bound remained unavailable in the literature, a fact that has hindered the development of further results involving more complex cooperative diversity channels....

First Page of the Article

This paper introduces a low-complexity full-rate full-diversity space-time (ST) code for wireless communication systems with four transmit antennas. This novel code is designed by combining delay-diversity transmission with Alamouti's orthogonal ST block code. Analytical and computer simulation results show that this code yields significant frame-e...

Multi-dimensional space-time modulation schemes can be classified by the manner in which signal dimensions are shared among transmit antennas. In aggregate transmit antenna (ATA) systems, a generalization of Tarokh, Seshadri, Calderbank's (TSC) approach, there is total sharing of dimensions. In orthogonal transmit antenna (OTA) systems, a generaliz...

The paper considers channel estimation, in the context of space-time coding. Kalman filtering (KF), in its prediction form, is employed to track the fading channel in a multiple-antenna system, using orthogonal space-time codes and three different decoders. The system's performance is evaluated through computer simulations. The effect of the Dopple...

This paper considers the Shannon capacity region of a space and time dispersive multiple-input multiple-output (MIMO) broadcast channel with multi-dimensional space-time modulation. We assume no inter-user cooperation and consider a non-fading environment with orthogonally multiplexed users. With the single user capacity being achieved by water-fil...

This paper considers the performance analysis of space-time trellis codes over quasistatic Rayleigh fading channels. We present three methods to calculate the frame error rate (FER) of such codes. The first is based on the union bound using the exact pair wise error probability (PEP). The second method is a generalization of the PEP-based union bou...

This paper considers detection techniques for unresolved Ricean/Rayleigh fading multipath channels. It is well known that the optimal receiver has an estimator-correlator form, with a minimum mean-square error (MMSE) estimate. With known multipath delays and unknown specular phases, the Ricean non-coherent multipath channel is a case where the rece...

Multiple antennas play an important role in improving radio communications. In view of this role, the area of multiple antenna communication systems is in the forefront of wireless research. This article reviews two key related aspects of multiple antenna communication systems: multiple access interference mitigation at the receiver via multi-user...

This paper considers a chip-locked space-time (CLST) filtering technique for direct-sequence code-division multiple access (DS-CDMA) systems. CLST filtering exploits the knowledge of the multiple access interference (MAI) chip delays, as well as the fact that the MAI spectrum is colored in the time and space domains. Chip delays of interferers from...

This work considers space-time channel coding for systems with multiple-transmit and a single-receive antenna, over space uncorrelated block-fading (quasi-static) channels. Analysis of the outage probability over such channels reveals the existence of a threshold phenomenon. The outage probability can be made arbitrary small by increasing the numbe...

This paper considers the information transfer capacity of a space dispersive multipath channel with multiple antenna at the transmitter and receiver. The Shannon capacity is evaluated for such multiple-input multiple-output (MIMO) channels with multi-dimensional space-time modulation. Assuming a non-fading environment and a known channel at the tra...

This paper considers specular coherent and noncoherent optimal detection for unresolved multipath Ricean fading channels with known delays. The focus is on receiver structures and performance. Specular coherent detection employs the carrier phase of the Ricean specular component, while noncoherent detection does not. Therefore, a specular coherent...

In this work, the idea of combined shaping and coding of a signal constellation over a multitone channel is introduced. In selecting such a constellation, we are faced with the problems of distributing the rate and the energy axnong the subchannels. Assuming continuous approximation, these factors can be selected independently. However, in the disc...

This paper considers an improved single-user detection technique for asynchronous direct-sequence code-division multiple-access (DS-CDMA) systems using long sequence spreading (random-CDMA) Most of the known detection schemes for DS-CDMA suffer from either poor performance under power-imbalance (near-far like) conditions, excessive complexity, or i...

This letter considers the decoding of the IS-95(A) uplink code in an effort to assess its best achievable performance. Union bounds on the bit error probability for the IS-95(A) indicate that the interleaver affects significantly system performance. Computer simulation results for iterative decoding show that performance gains in the order of 0.6 d...

Space-time (ST) coding is an efficient technique for combatting short-term fading in telecommunication systems with multiple transmit antennas. This paper presents a multi-dimensional framework for such a system that contrasts two approaches for assigning signal dimensions to antennas. With aggregate transmit antennas (ATA), a dimension is employed...

This paper considers specular coherent and non-coherent optimal, as well as sub-optimal detection structures for unresolved multipath Ricean fading channels with known delays. Specular coherent receiver structures require carrier phase estimation of the Ricean specular component. Non-coherent structures, on the other hand, do not make use of the sp...

This paper considers truncated type-II hybrid automatic repeat-request (ARQ) schemes with noisy feedback over block fading channels. With these ARQ techniques, the number of retransmissions is limited, and, similar to forward error correction (FEC), error-free delivery of data packets cannot be guaranteed. Bounds on the average number of transmissi...

Direct sequence code division multiple access (DS-CDMA) is a core technology for wireless access that is proposed for future generation (3G) mobile and personal communication systems. The use of a base-station antenna array is strongly endorsed in these systems, because of its capabilities of filtering out the interference in the space domain. This...

This correspondence presents several corrections and an addendum to the original article by Feng-Wen Sun and H. Leib (see ibid., vol.43, no.4, p.1205-17, July 1997)

This paper considers a technique for very low rate channel coding. The main application for such codes is in spread-spectrum systems where significant bandwidth spreading is possible. New, very low rate binary channel codes based on a combination of a trellis code with a first-order Reed-Muller block code (trellis/Reed-Muller (TRM) codes) are prese...

This correspondence considers union upper bound techniques for error control codes with limited interleaving over block fading Rician channels. A modified bounding technique is presented that relies on limiting the conditional union bound before averaging over the fading process. This technique, although analytically not very attractive, provides t...

This paper considers coded diversity schemes over block-fading Rician channels using random coding techniques. Two random coding upper bounds on the error probability of block codes are derived: a new bound and a simpler but looser bound assuming binary input distribution. Also, a new lower bound for any block code is derived using the strong conve...

Driven by our increasingly mobile society's ever growing demand for communications, today's providers of wireless telecommunication services must ensure reliable radio coverage “everywhere”. Computer based techniques that reduce the need for expensive experimental measurements are invaluable tools for achieving this objective. Various computational...

In this paper we consider noncoherent detection structures for multipath Ricean/Rayleigh fading channels. The multipath components are assumed to be unresolved, with known delays. These delays could have been estimated, for example, by using super-resolution techniques or sounding the channel with a wide-band pulse. We show that the Rayleigh channe...

We consider the construction and analysis of linear block codes for M-ary phase-shift keying that can be decoded without carrier phase synchronization. Under these circumstances, the function that has a significant impact on performance is the noncoherent distance, analogous to the Euclidean distance for the coherent case. The major difficulty in c...

This paper considers receiver structures and performance for unresolved mixed mode Ricean/Rayleigh multipath channels. A fading channel is said to be mixed mode if the first path gain is Ricean distributed and the other path gains are Rayleigh. The optimal receiver for this case consists of a decorrelation stage combined with a quadratic form, as w...

This paper considers coded diversity schemes on block fading Rayleigh channels. Based on random coding techniques we analyze the performance of binary block codes on such channels. New upper and lower bounds to the error probability are derived. The new upper bound, that is tighter than previously known results, reveals that the maximum diversity o...

This paper considers type-II hybrid ARQ schemes with convolutional codes over block fading Rayleigh channels with limited interleaving. Examples of systems that our results can be used for are GSM (or PCS1900) and TDMA based proposals for UMTS. These systems employ slow frequency hopping TDMA, and typically operate over fading channels. Analytical...

Signature sequences with good even even and odd (or polyphase) correlations are crucial for asynchronous code-division multiple access (CDMA). When the data sequence is random, the even and odd (or polyphase) correlations are equally important. However, for most known signature sequences, only their even correlations were analyzed. It appears that...

Hamamoto (see ibid., vol.44, no. 8, p.959-66, 1996) presented a detection technique for differential phase-shift keying (DPSK) with improved performance over conventional differential coherent detection. Leib (see ibid., vol.43, no.2/3/4, p.722-25, 1995) comments that this technique had been introduced much earlier. As correctly stated by Hamamoto...

Rate 1/n convolutional codes with interleaving depth of n are analysed in a frequency non-selective block fading Rician channel. The channel is assumed to be constant during the transmission of a block and independent from block to block. A generalised transfer function, T(D ₁,…,D_n,N), is used for calculation of union transfer...