Department Publications

Low-resolution analog-to-digital converters (ADCs) are a promising way to cut power consumption in future 6G receivers. However, they break many assumptions behind traditional communication system design. Instead of optimizing each block separately, this work uses an end-to-end autoencoder (AE) to jointly learn and optimize the transmitter and receiver for systems with phase quantization. Two key obstacles arise: (1) phase quantization is non-differentiable, which blocks gradientbased training back to the transmitter, and (2) standard crossentropy loss leads to poor block error rate (BLER) performance. To overcome these issues, we introduce a differentiable approximation of phase quantization and a new loss function that adds a distance-based regularization term to improve symbol separability. Simulations show that the proposed AE achieves near-optimal BLER for uncoded -ary phase shift keying …

Low-resolution digital-to-analog converters (DACs) and analog-to-digital converters (ADCs) are important enablers of energy-efficient wideband uplinks, but they introduce nonlinear distortions whose impact depends on the operating point and, in multi-user systems, on the time- and frequency-resource split. This paper studies quantization-aware uplink resource allocation for multi-user orthogonal multiple access (OMA), focusing on frequency division multiple access (FDMA) and time division multiple access (TDMA) with finite-resolution quantization at both the user transmitters and the base station receiver. Using Bussgang-style decompositions for power-preserving DAC quantization and mid-point ADC quantization, we derive a closed-form, conservative lower bound on the per-user achievable rate in terms of the allocation variables, channel gains, noise level, and quantization distortion factors. Under this …

Noncoherent phase shift keying receivers with coarse phase quantization require one additional bit of phase resolution than their coherent counterparts to achieve full diversity. In this letter, we propose a differential encoding scheme that applies a fixed, resolution-dependent phase shift to the transmitted symbols to remove this identified one-bit performance penalty. The impact of phase quantization on the error performance is characterized under the proposed differential encoding strategy. We show that the proposed differential encoding enables an -bit phase-quantized noncoherent receiver to match the error performance of a conventional -bit phase-quantized noncoherent receiver. Ultimately, our results demonstrate that the one-bit performance penalty previously observed in phase-quantized noncoherent receivers is not a fundamental limitation due to the lack of receiver channel state information, but …

This paper proposes a support vector machine (SVM)-based framework for signal detection in low-resolution single-input multiple-output (SIMO) systems, operating without channel state information (CSI). We consider n-bit phase quantization under M-PSK modulation and develop a CSI-free, model-free detector that directly maps quantized observations to symbol estimates. For QPSK modulation, the proposed method achieves symbol error probability (SEP) performance within 15% of the coherent maximum likelihood detector (MLD). We further extend the framework to higher-order M-PSK modulations, providing the first model-free, CSI-free SEP performance characterization for low-resolution, phase-quantized SIMO systems; addressing a regime where no general MLD solution is available.

This manuscript introduces NeuroDetect, a model-free deep learning-based signal detection framework tailored for phase-modulated wireless systems with low-resolution analog-to-digital converters (ADCs). The proposed framework eliminates the need for explicit channel state information, which is typically difficult to acquire under coarse quantization. NeuroDetect utilizes a neural network architecture to learn the nonlinear relationship between quantized received signals and transmitted symbols directly from data. It achieves near-optimum performance, within a worst-case 12% margin of the maximum likelihood detector that assumes perfect channel knowledge. We rigorously investigate the interplay between ADC resolution and detection accuracy, introducing novel penalty metrics that quantify the effects of both quantization and learning errors. Our results shed light on the design trade-offs between ADC resolution and detection accuracy, providing future directions for developing energy-efficient high-speed and wideband wireless systems.

This paper investigates an intelligent reflective surface (IRS) assisted secure multi-user two-way communication system. The aim of this paper is to enhance the physical layer security by optimizing the minimum secrecy-rate among all user-pairs in the presence of a malicious user. The optimization problem is converted into an alternating optimization problem consisting of two sub-problems. Transmit power optimization is handled using a fractional programming method, whereas IRS phase shift optimization is handled with semi-definite programming. The convergence of the proposed algorithm is investigated numerically. The performance gain in minimum secrecy-rate is quantified for four different user configurations in comparison to the baseline scheme. Results indicate a 3.6-fold gain in minimum secrecy rate over the baseline scheme when the IRS is positioned near a legitimate user, even when the malicious …

Future wireless systems are expected to rely on large antenna arrays at the base station (BS) to meet growing demands for data rates. However, the power consumption and hardware complexity of high-resolution analog-to-digital converters (ADCs) pose significant challenges to the practical deployment of such arrays. Low-resolution ADCs offer a power- and cost-effective alternative, motivating a deeper understanding of information-theoretic limits with low-resolution quantization. This letter establishes capacity scaling laws for both single-input single-output (SISO) and multi-antenna systems with low-resolution quantization. We show that, unlike the classical capacity growth in unquantized systems, the capacity of low-resolution systems approaches n at a rate for SISO and multiple-input single-output (MISO) systems, where n is the number of quantization bits and is the signal-to-noise ratio. For …

The imminent emergence of quantum computers poses unprecedented challenges to the current cryptographic standards that secure vital digital communications and data worldwide. This paper addresses the vulnerabilities of existing cryptographic systems susceptible to quantum-based attacks and emphasizes a dedicated transition plan to post-quantum cryptography (PQC). We first examine the current state of cryptographic practices, highlight the quantum threat, and present the framework and need for PQC. In addition, a comprehensive strategy is presented that encompasses the identification, protection, detection, response, and recovery phases and integrates PQC into existing security infrastructures, specifically the Cybersecurity Framework Version 2.0 of the National Institute of Standards and Technology (NIST). Methods and technologies discussed include the development of robust PQC algorithms, tools …

This paper proposes a novel approach that utilizes differential encoding to overcome the channel estimation problem in communication systems with low-resolution quantization receivers. For differentially encoded data, we derive the maximum likelihood detection rule for the canonical block-2 detectors, employing just two consecutive quantized observations at the channel output and without any receiver-side channel state information. We establish the optimality of this maximum likelihood detection rule within the class of block- detectors, where , under the condition that , with and denoting the number of quantization bits and input alphabet size, respectively. The derived detector has a simple and easily implementable structure, comparing the quantization region indices of consecutive observations to determine the transmitted message index. By leveraging the structure of the derived optimum …

This paper derives the optimum detection rule for communication systems with n-bit phase quantization when data is differentially encoded at the transmitter. The proposed approach avoids the channel estimation problem at the receiver. First, a maximum likelihood detection rule for block-2 detectors utilizing only two consecutive quantized observations at the channel output is obtained. Second, it is shown that the derived maximum likelihood detection rule continues to be optimum for the class of block-L detectors for L ≥ 3 when n = log 2 M, where M is the input alphabet size. Finally, utilizing the structure of the derived optimum detector, a message error probability expression is obtained for Rayleigh fading wireless channels. A simulation study is performed to illustrate the performance of the optimum detectors as well as the performance loss due to the lack of channel knowledge at the receiver. The proposed …

This letter investigates the exploitation of an intelligent reflecting surface (IRS) to communicate securely in a two-way network consisting of an untrusted user. In particular, the transmit powers and the phase shift at each element of the IRS are optimized to maximize the sum-secrecy rate, such that the IRS-reflected and non-IRS-reflected signals are added destructively at the untrusted user. The proposed iterative algorithm converges rapidly to a feasible solution of high accuracy with a few iterations. Numerical results demonstrate sum-secrecy rate gains up to 120% compared to naive or partially optimized schemes.

This paper investigates the communication reliability for single-input-multiple-output wireless systems with low-resolution phase quantizers. First, the maximum-likelihood detector with -bit phase quantization is derived when there are antennas at the receiver. Then, three low-complexity antenna selection strategies for data detection are proposed and their symbol error probability performance is characterized. It is shown that having 3 or more bits is sufficient to attain the full diversity order , achievable with infinite-bit quantizers, for quadrature phase shift keying modulation under Rayleigh fading. In particular, it is established that the proposed low-complexity max-distance and max-norm antenna selection strategies perform the same as the maximum-likelihood detector in terms of the asymptotic system reliability for . On the other hand, the diversity order decreases dramatically from to when is …

In this paper, we investigate antenna selection strategies for multi-antenna wireless communication systems with low-resolution quantizers. We propose three sub-optimum but low-complexity antenna selection strategies and characterize their symbol error probability performance. We show that the strategy that selects the diversity branch with channel rotated constellation points being furthest away from the decision boundary is the best strategy in terms of symbol error probability. Using numerical analysis, we provide evidence to suggest that this selection strategy achieves the same diversity order as the optimum maximum likelihood (ML) detector under the same operating conditions. An extensive simulation study is performed to illustrate the accuracy of the derived results.

In this letter, we propose a physical-layer security (PLS) scheme for millimeter-wave systems. Our scheme employs analog beamforming with random frequency variation (RFV) for transmitted symbols. We derive the exact closed-form expression of the secrecy rate of our RFV scheme. Furthermore, we verify the superior performance of RFV scheme compared to previously proposed PLS schemes. In particular, the RFV scheme provides higher secrecy rate for more than 70% of the angular range, when the bandwidth is 10% of the carrier frequency. Furthermore, there is no array gain loss at the legitimate user, compared to previously proposed PLS schemes.

Physical unclonable functions (PUFs) are widely considered in secret key generation for resource constrained devices. However, PUFs require additional hardware overhead. In this letter, we focus on developing a PUF-efficient, robust, and secure key generation scheme. First, a novel method for extracting quaternary PUF responses is proposed to increase the entropy of a PUF response, in which a 2-bit response is extracted from evaluating a single PUF cell multiple times. The probability masses of the responses can be adjusted by setting parameters appropriately. Then, a chosen secret model based fuzzy extractor (FE) is designed to extract secret keys from the quaternary PUF responses. To improve the security of this FE, it is modeled as a wiretap channel system, and wiretap polar coding is adopted to reduce secrecy leakage. An upper bound of secrecy leakage is also given in this letter, and it suggests that …

This paper studies optimum detectors and error rate analysis for wireless systems with low-resolution quantizers in the presence of fading and noise. A universal lower bound on the average symbol error probability (SEP), correct for all M-ary modulation schemes, is obtained when the number of quantization bits is not enough to resolve M signal points. In the special case of M-ary phase shift keying (M-PSK), the maximum likelihood detector is derived. Utilizing the structure of the derived detector, a general average SEP expression for M-PSK modulation with n-bit quantization is obtained when the wireless channel is subject to fading with a circularly-symmetric distribution. For the Nakagami-m fading, it is shown that a transceiver architecture with n-bit quantization is asymptotically optimum in terms of communication reliability if n ≥ log 2 M + 1. That is, the decay exponent for the average SEP is the same and equal …

The paper considers physical layer security (PLS) of an untrusted unmanned aerial vehicle (UAV) network, where a multitude of UAVs communicate in full-duplex (FD) mode. A source-based jamming (SBJ) scheme is exploited for secure communication without utilizing any external jammers. Firstly, the optimal power allocation between the confidential signal and the jamming signal is derived to maximize the secrecy rate of each link between the source and the destination. Then, the best UAV selection scheme is proposed to maximize the overall secrecy rate of the network. The corresponding secrecy outage probability (SOP) and the average secrecy rate (ASR) of the network are analyzed based on the proposed UAV selection and the optimal power allocation schemes. Asymptotic results are also obtained to derive the achievable diversity order. Results are validated through numerical evaluations while …

This paper considers a low-resolution wireless communication system in which transmitted signals are corrupted by fading and additive noise. First, a universal lower bound on the average symbol error probability (SEP), correct for all M-ary modulation schemes, is obtained when the number of quantization bits is not enough to resolve M signal points. Second, in the special case of M-ary phase shift keying (M-PSK), the optimum maximum likelihood detector for equi-probable signal points is derived. Third, utilizing the structure of the derived optimum receiver, a general average SEP expression for the M-PSK modulation with n-bit quantization is obtained when the wireless channel is subject to fading with a circularly-symmetric distribution. Finally, an extensive simulation study of the derived analytical results is presented for general Nakagami-m fading channels. It is observed that a transceiver architecture with n-bit …

We consider a single-input-single-output (SISO) system with quadrature phase shift keying (QPSK) modulation and derive an easy-to-evaluate expression for the symbol error probability (SEP) when a general n-bit phase quantization is used at the receiver. We further evaluate the expressions asymptotically to characterize the diversity order and the quantization penalty at high signal-to-noise ratios (SNRs). We observe that the system with n-bit phase quantization achieves full diversity order of one when n > 2. Numerical examples are used to verify the analysis.

The aim of this study is to design a Home Automation system by interfacing Power Line Communication (PLC) with GSM communication which would enable the user to control appliances by sending commands via SMS. A communication model based on Star Topology is utilized in this home automation system which can be scaled at a low cost. The communication system facilitates secured communication by using BlumGoldwasser cryptosystem. The communication system employs a master Central Control System placed at the switch board and slave receiver nodes in household appliances. This system was planned from the outset to make as simpler and cost effective as possible so that it would be affordable to more households in low income countries. The system was tested in a lab environment at a maximum distance of 20 m and the operation was verified. Subsequently, Signal levels were obtained at …

This paper describes a demand management system based on narrow band Power line communication and GSM technologies which can be used by the electricity provider to reduce electrical load by turning off nonessential equipment in establishments during high demand periods where enough electricity cannot be supplied. This solution is thought to have less impact on the lives of the public. The system uses Blum-Goldwasser cryptosystem for secure power line communication and to mitigate rogue devices. The system does not require internet connectivity. Therefore, ideal for countries with less internet coverage.

This paper introduces a model to study both single tier and multitier wireless communication systems consisting of a multitude of wireless access points (AP), and operating according to the classical opportunistic beamforming framework. The AP locations in the proposed network model are determined by using planar Poisson point processes. The extreme value distribution of signal-to-interference-plus-noise-ratio (SINR) on a beam is of fundamental importance for obtaining performance bounds for such an opportunistic communication system. Two tight distribution approximation results are provided for the distribution of maximum SINR on a beam, which is hard to obtain due to correlation structure of the underlying inter-AP interference field, using key tools from stochastic geometry. These approximations hold for general path loss models that satisfy some mild conditions. Simulations and numerical evaluations …

The achievable average rate of a full-duplex (FD) multiple-input-single-output interference channel with linear transceiver structures is analyzed. The impact of transmit front-end noise is included in the analysis. Both cooperative and non-cooperative strategies for the FD interference channel are considered and the closed-form expressions are derived for the achievable average rate of each strategy.