Predrag Spasojevic

Predrag Spasojevic
Rutgers, The State University of New Jersey | Rutgers · Department of Electrical and Computer Engineering

PhD

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205
Publications
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Publications

Publications (205)
Article
Full-text available
Autonomous teams of unmanned ground and air vehicles rely on networking and distributed processing to collaborate as they jointly localize, explore, map, and learn in sometimes difficult and adverse conditions. Co-designed intelligent wireless networks are needed for these autonomous mobile agents for applications including disaster response, logis...
Article
In this paper, we investigate covert communication in intelligent reflecting surface (IRS) assisted networks with a friendly jammer where the jammer radiates random power jamming signals to confuse Willie in detecting the existence of the communication between Alice and Bob. We propose a novel technique that jointly optimizes the transmission proba...
Article
The vehicle-to-vehicle (V2V) distance ranging system is a critical component of transportation automation, including the railroad industry. Although the mainline rail traffic is strictly regulated by sophisticated train control and dispatching systems, self-propelled rail vehicles, such as maintenance-of-way equipment and light rail vehicles, still...
Article
This letter investigates reduction in the degree of cyclostationarity (DCS) of digital communication signals in the presence of polarization diversity. Reduction in DCS decreases the probability of detection of an intruder that searches for periodic patterns in the transmitted signal. We propose a DCS reducing scheme that exploits dual-polarization...
Article
Easily and flexibly deployable ad-hoc communication networks emerging in tactical military or even civilian contexts, frequently suffer from poor synchronization due to lack of coordinating infrastructure. In addition to synchronization issues, and especially in military settings, security from the aspect of detectability is also of crucial importa...
Article
This letter investigates covert communication in an intelligent reflecting surface (IRS)-assisted system. We propose a novel algorithm that jointly optimizes the transmission probability, transmit power at a transmitter, and the reflection matrix of an IRS with the goal of maximizing the achievable rate at a receiver while ensuring the covertness o...
Article
Since statistical channel models fail to reproduce the intra-cluster parameters due to the site-specific nature of the millimeter-wave (mmWave) channel, in this paper, we propose a ray tracing intra-cluster model (RT-ICM) for mmWave channels. The model considers only the first-order reflection; thereby reducing the computation load while capturing...
Preprint
Full-text available
Beamforming is the primary technology to overcome the high path loss in millimeter-wave (mmWave) channels. Hence, performance improvement needs knowledge and control of the spatial domain. In particular, antenna structure and radiation parameters affect the beamforming performance in mmWave communications systems. In order to address the impairment...
Data
As we claim in the paper, narrow beams can degrade the spectral efficiency for non-stationary channels. Using the technique we detailed in the paper, we can widen the beams without changing the transceiver structure. In this figure, we show that the widened beams using the proposed technique can result in better spectral efficiency performance when...
Preprint
Full-text available
Beamforming for mmWave communications is well-studied in the PHY based on the channel parameters to develop optimum receiver processing techniques. However, even before signal processing, antenna structure and radiation parameters affect the beamforming performance primarily. For example, in contrast to common belief, narrow beamwidth (bmW) may res...
Conference Paper
Full-text available
Due to the sparsity and site-specific nature of the mmWave channels, statistical channel models can easily deviate from a specific real scenario. On the other hand, to overcome the high path loss, high gain beams steered to the clusters are exploited. To increase the spatial filtering efficiency due to beamforming, in our previous work, we model th...
Preprint
A significant portion of the 5th generation of wireless networks will operate in the mm-wave bands. One of the several challenges associated with mm-wave propagation is to overcome shadowing due to signal blockage caused by environmental objects. Particularly susceptible are nodes in a device-to-device network that typically operate at low power an...
Conference Paper
Availability of large array usage in millimeter wave communications gives the opportunity to create narrow beams that yield to high antenna gains. However, in some cases, wider beams are of interest in order to increase the coverage area or reduce the outages caused by the channel variations. To address this need, beam broadening approaches with no...
Preprint
Full-text available
In millimeter-wave (mmWave) channels, to overcome the high path loss, beamforming is required. Hence, the spatial representation of the channel is essential. Further, for accurate beam alignment and minimizing the outages, inter-beam interferences, etc., cluster-level spatial modeling is also necessary. Since, statistical channel models fail to rep...
Article
A Boolean generator for a large number of standard complementary QAM sequences of length 2k is proposed. This Boolean generator is derived from the authors’ earlier paraunitary generator, which is based on matrix multiplications. Both generators are based on unitary matrices. In contrast to previous Boolean QAM algorithms which represent complement...
Article
Full-text available
We propose strategies to achieve a high-throughput FPGA architecture for quasi-cyclic low-density parity-check codes based on circulant-1 identity matrix construction. By splitting the node processing operation in the min-sum approximation algorithm, we achieve pipelining in the layered decoding schedule without utilizing additional hardware resour...
Conference Paper
Single Input Multiple Output (SIMO) Blind Channel Identification (BCI) using Subspace-based Methods, notably the Cross-Relations (CR) and Noise-Subspace (SS) Methods, are sensitive to selection of the channel order. Previous work on model order selection shows that at low SNR, accurate selection is not always possible, and in some cases, there is d...
Conference Paper
If Alice must communicate with Bob over a channel shared with the adversarial Eve, then Bob must be able to validate the authenticity of the message. In particular we consider the model where Alice and Eve share a discrete memoryless multiple access channel with Bob, thus allowing simultaneous transmissions from Alice and Eve. By traditional random...
Conference Paper
We consider a model where a single sensor observes a bandwidth of spectrum occupied by several non-orthogonal in both time and frequency signals. The sensor constructs a tensor based on the trispectrum and which can be modeled as a block partitioned tensor (BPT). By decomposing this tensor we can estimate signal activity in both time and frequency....
Article
Full-text available
The increasing data rates expected to be of the order of Gb/s for future wireless systems directly impact the throughput requirements of the modulation and coding subsystems of the physical layer. In an effort to design a suitable channel coding solution for 5G wireless systems, in this brief we present a massively-parallel 2.48Gb/s Quasi-Cyclic Lo...
Article
We consider a scenario where a single sensor is observing a bandwidth of the radio spectrum occupied by several signals which are non-orthogonal in both time and frequency. We form a tensor using anti-diagonal slices of the trispectrum and show that it can be modeled by a block-partitioned tensor (BPT) structure. Current BPT decomposition algorithm...
Article
In this paper, we present families of rate compatible (RC) structured irregular repeat-accumulate (SIRA) and structured generalized irregular repeat-accumulate (SG-IRA) codes, which are particularly attractive for 5G wireless systems due to their linear-time encoding property. The family of codes is generated using a technique called row-splitting,...
Article
Full-text available
We present an efficient and scalable high-throughput FPGA-based architecture for the Min-Sum Algorithm (MSA) based decoder for Quasi-Cyclic Low-Density Parity-Check (QC-LDPC) codes. We present a compact representation of the parity-check matrix (PCM) which allows for a significant improvement in throughput (3x in our case study) compared to convent...
Article
Recent changes in policy regarding the opportunistic use of licensed radio spectrum have paved the way for new innovative technologies like cognitive radio (CR). This technology puts tight demands on systems built to sense spectrum occupancy. Any strategy employed for opportunistic spectrum usage has to consider the tradeoffs between time spent sea...
Article
We consider reception of non-persistently excitated radio signals that overlap in time and frequency from a group of transmitters to a single receiver. The signals can be categorized as using a linear modulation or a non-linear modulation that can be approximated as a finite sum of linearly modulated signals. An analysis of a particular slice of th...
Article
Full-text available
A unique decomposition of arbitrary pairs of complementary sequences (including standard binary, polyphase and QAM sequences as well as non-standard sequences and kernels) based on paraunitary matrices is presented. This decomposition allows us to describe the internal structure of any sequence pair of length L using basic paraunitary matrices defi...
Conference Paper
Full-text available
We present a general algorithm for generating arbitrary standard complementary pairs of sequences (including binary, polyphase, M-PSK and QAM) of length íµí¿ íµí±µ using Boolean functions. The algorithm follows our earlier paraunitary algorithm, but does not require matrix multiplications. The algorithm can be easily and efficiently implemented in...
Conference Paper
Full-text available
We present a general algorithm for generating arbitrary standard complementary pairs of sequences (including binary, polyphase, M-PSK and QAM) of length 2N using Boolean functions. The algorithm follows our earlier paraunitary algorithm, but does not require matrix multiplications. The algorithm can be easily and efficiently implemented in hardware...
Article
As we are surrounded by an ever-larger variety of post-PC devices, the traditional methods for identifying and authenticating users have become cumbersome and time consuming. In this paper, we present a capacitive communication method through which a device can recognize who is interacting with it. This method exploits the capacitive touchscreens,...
Data
function X=booleanCS(P,C,S,r,s); % P(k) is a permutation of k=1...N % C(k), S(k) complex values for k=1...N+1 % Depending on r, s that can have values: 0 ili 1 % X is one of the sequences: a, b, a rev./conj. and b rev./conj./inv.
Article
Full-text available
We present a general algorithm for generating arbitrary standard complementary pairs of sequences (including binary, polyphase, M-PSK and QAM) of length 2^N using Boolean functions. The algorithm follows our earlier paraunitary algorithm, but does not require matrix multiplications. The algorithm can be easily and efficiently implemented in hardwar...
Article
Full-text available
We propose an efficient application layer coding scheme suitable for time-limited wireless broadcast framework of the MBMS standards. The scheme, referred to as doped broadcast, is based on Fountain codes, and uses feedback to implement and control the tradeoff between the reconstruction delay, broadcast overhead, and decoding time/complexity. As t...
Article
Full-text available
Iterative receivers with minimum mean square error turbo equalization are computationally involved, as they require some form of matrix inversion. In this article, we propose a low complexity iterative receiver that implements successive interference cancelation-based MAP decoding (SIC-MAP) in doubly dispersive channels for orthogonal frequency div...
Conference Paper
Full-text available
A unique decomposition of arbitrary pairs of complementary sequences (including binary, polyphase and QAM) based on paraunitary matrices is presented. This decomposition allows us to describe the internal structure of any sequence pair of length N using basic paraunitary matrices defined by N complex coefficients named omega vector. When the omega...
Article
Full-text available
Turbo equalization schemes based on minimum mean square error criteria available in the literature for multiple-input multiple-output (MIMO) systems are computationally expensive, as they require a relatively large matrix inversion. In this article, we propose a suboptimal, successive interference cancelation (SIC)-based maximum a posteriori (MAP)...
Article
Full-text available
Based on the erasure channel FEC model as defined in multimedia wireless broadcast standards, we illustrate how doping mechanisms included in the design of erasure coding and decoding may improve the scalability of the packet throughput, decrease overall latency and potentially differentiate among classes of multimedia subscribers regardless of the...
Article
Full-text available
As we are surrounded by an ever-larger variety of post-PC devices, the traditional methods for identifying and authenticating users have become cumbersome and time-consuming. In this paper, we present a capacitive communication method through which a device can recognize who is interacting with it. This method exploits the capacitive touchscreens,...
Article
Full-text available
Today's identification and authentication mechanisms for touchscreen-enabled devices are cumbersome and do not support brief usage and device sharing. To address this challenge, this work explores a novel form of "wireless" communication that exploits the capacitive touchscreens which are now used in laptops, phones, and tablets, as a signal receiv...
Article
We study and compare three coded schemes for single-server wireless broadcast of multiple description coded content to heterogeneous users. The users (sink nodes) demand different number of descriptions over links with different packet loss rates. The three coded schemes are based on the LT codes, growth codes, and randomized chunked codes. The sch...
Article
In Cognitive Radio, the key to overcome the spectrum scarcity is reliable spectrum sensing, which will allow efficient opportunistic spectral reuse with minimum interference to licensed users. We consider energy detection based sensing that requires efficient noise power estimation technique in order to reliably detect the primary transmissions. We...
Article
Even though in many network scenarios erasure-impaired sources represent a more appropriate data model than frequently used Gaussian and binary sources, they only recently entered the scene of compression coding through introduction of binary erasure quantization over sparse graphs. Binary erasure quantization (BEQ) considers ternary sources (zeros...
Conference Paper
Full-text available
This paper studies source location anonymity in a large monitoring wireless sensor network with a single data collector, and under a global attack. The qualifier "global" indi- cates the capability of the eavesdropper (attacker) to capture all network transmissions, and to discern their time and location. We propose a scheme for generating fake net...
Conference Paper
CDMA (Code Division Multiple Access) allows distinct users to communicate simultaneously on the same frequency band using binary sequences uniquely allocated to each user. For a given sequence length, we are confronted with a trade off between large set size (maximizing user capacity) and low maximum absolute inner product (minimizing instantaneous...
Conference Paper
Vehicular networking has significant potential to enable diverse range of applications, including safety and conve- nience. As the number of vehicles and applications using wireless spectrum grow, one can expect to see a shortage of either spatially or temporally available spectrum. In this paper, we advocate that dynamic spectrum access for vehicl...
Conference Paper
,..., , , ) ( ) ( ) ( ) ( − = + = ) ) ,..., , , ,.... , , , , , − = − = = + = ⎥ ⎥ ⎢ ⎢ ,... , , ,...., , , , , ) ( , ) ( , ) ( , ) ( , ) ( − = − = = + = = ) ( , ∑ − = − = = , * , , * , , − = ,..., , , , * , , * , , * , , − = − − = + + − − . , * , , * , , − − − − − − = ( , , , + − ≈ ≈ ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛ + + = ∑ − = , , , . ,... , ) ( ) ( ' , ) ( ' , ) (...
Article
Full-text available
Constant amplitude zero autocorrelation (CAZAC) sequences are increasingly used in new communication systems (e.g. LTE, WiMax). The (unique) Björck sequence whose length P is an odd prime is a less known CAZAC sequence. By modifying the Björck sequence through CAZAC transformations, a Björck set of P orthog-onal sequences is introduced. The maximum...
Article
Full-text available
A secret-key generation scheme based on a layered broadcasting strategy is introduced for slow-fading channels. In the model considered, Alice wants to share a key with Bob while keeping the key secret from Eve, who is a passive eavesdropper. Both Alice-Bob and Alice-Eve channels are assumed to undergo slow fading, and perfect channel state informa...
Conference Paper
Turbo equalization schemes based on minimum mean square error (MMSE) criteria available in the literature for multiple-input multiple-output (MIMO) systems are compu- tationally expensive, as they require a relatively large matrix inversion. In this paper, we propose a low complexity turbo equal- ization (TE) scheme with successive interference can...
Article
Turbo equalization schemes based on minimum mean square error (MMSE) criteria available in the literature for multiple-input multiple-output (MIMO) systems are computationally expensive as they require a relatively large matrix inversion. In this paper, we propose a low complexity turbo-equalization scheme with successive interference cancellation...
Conference Paper
Turbo equalization schemes based on minimum mean square error (MMSE) criteria available in the literature are computationally involved as they require some form of matrix inversion. In this paper, we propose a low complexity turbo-equalization scheme with successive interference cancellation (TE-SIC) for the equalization of doubly dispersive channe...
Conference Paper
We consider spectrum sensing and Non-Contiguous OFDM) with interference avoidance to facilitate opportunistic secondary transmission. In this application protecting an incumbent primary user of the spectrum from secondary emissions is a key design requirement. We present an adaptive sense-and-carefully-transmit system which integrates a spectrum s...
Article
Full-text available
In the problem of location anonymity of the events exposed to a global eavesdropper, we highlight and analyze some aspects that are missing in the prior work, which is especially relevant for the quality of secure sensing in delay-intolerant applications monitoring rare and spatially sparse events, and deployed as large wireless sensor networks wit...
Article
Full-text available
We propose an efficient scheme for generating fake network traffic to disguise the real event notification in the presence of a global eavesdropper, which is especially relevant for the quality of service in delay-intolerant applications monitoring rare and spatially sparse events, and deployed as large wireless sensor networks with single data col...
Article
Full-text available
To reduce computational complexity and delay in randomized network coded content distribution, and for some other practical reasons, coding is not performed simultaneously over all content blocks, but over much smaller, possibly overlapping subsets of these blocks, known as generations. A penalty of this strategy is throughput reduction. To analyze...
Article
We propose a programmable heterogeneous multi-processor system-on-chip (MPSoC) platform architecture for flexible radio processing that aims at striking a balance between performance (as provided by ASICs) and flexibility (as provided by SDR). Based on a novel hardware-oriented Virtual Flow Pipelining (VFP) framework, the key highlights of this sol...
Article
We consider the problem of RF signal analysis where one sensing node observes a frequency band possibly used by multiple packet based radio transmitters producing signals with non-persistent excitation. Since each combination of active transmitted signals results in a composite signal with its distinct statistical properties, the received signal at...
Conference Paper
The Multi-Protocol Multi-Band (MPMB) Software Defined Radio (SDR) devices require flexible as well as efficient physical layer (PHY) processing. We address an efficient implementation of flexible PHY for Interleaving and De-Interleaving operation through Application Specific Instruction Set Processors (ASIPs). We propose a multi-standard (802.11a,...
Conference Paper
Full-text available
Coding over subsets (known as generations) rather than over all content blocks in P2P distribution networks and other applications is necessary for a number of practical reasons such as computational complexity. A penalty for coding only within generations is an overall throughput reduction. It has been previously shown that allowing contiguous gen...
Conference Paper
Full-text available
Wireless communication standards are developed at an ever-increasing rate of pace, and significant amounts of effort is put into research for new communication methods and concepts. On the physical layer, such topics include MIMO, cooperative communication, and error control coding, whereas research on the medium access layer includes link control,...
Conference Paper
Full-text available
To reduce computational complexity and delay in randomized network coded content distribution (and for some other practical reasons), coding is not performed simultaneously over all content blocks but over much smaller subsets known as generations. A penalty is throughput reduction. We model coding over generations as the coupon collector's brother...
Conference Paper
An irregular LDGM-LDPC code is studied as a sub-code of an LDPC code with some randomly punctured output-bits. It is shown that the LDGM-LDPC codes achieve rates arbitrarily close to the channel-capacity of the binary-input symmetric-output memoryless (BISOM) channel with bounded complexity. The measure of complexity is the average-degree (per info...