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Channel Coding at Low Capacity [article]

Mohammad Fereydounian, Hamed Hassani, Mohammad Vahid Jamali, Hessam Mahdavifar
2020 arXiv   pre-print
Low-capacity scenarios have become increasingly important in the technology of the Internet of Things (IoT) and the next generation of mobile networks. Such scenarios require efficient and reliable transmission of information over channels with an extremely small capacity. Within these constraints, the performance of state-of-the-art coding techniques is far from optimal in terms of either rate or complexity. Moreover, the current non-asymptotic laws of optimal channel coding provide inaccurate
more » ... predictions for coding in the low-capacity regime. In this paper, we provide the first comprehensive study of channel coding in the low-capacity regime. We will investigate the fundamental non-asymptotic limits for channel coding as well as challenges that must be overcome for efficient code design in low-capacity scenarios.
arXiv:1811.04322v2 fatcat:wbaant4tjbbkjd5zcgyy67inne

Covert Millimeter-Wave Communication via a Dual-Beam Transmitter [article]

Mohammad Vahid Jamali, Hessam Mahdavifar
2019 arXiv   pre-print
In this paper, we investigate covert communication over millimeter-wave (mmWave) frequencies. In particular, a dual-beam mmWave transmitter, comprised of two independent antenna arrays, attempts to reliably communicate to a receiver Bob when hiding the existence of transmission from a warden Willie. In this regard, operating over mmWave bands not only increases the covertness thanks to directional beams, but also increases the transmission data rates given much more available bandwidths and
more » ... les ultra-low form factor transceivers due to the lower wavelengths used compared to the conventional radio frequency (RF) counterpart. We assume that the transmitter Alice employs one of its antenna arrays to form a directive beam for transmission to Bob. The other antenna array is used by Alice to generate another beam toward Willie as a jamming signal with its transmit power changing independently from a transmission block to another block. We characterize Willie's detection performance with the optimal detector and the closed-form of its expected value from Alice's perspective. We further derive the closed-form expression for the outage probability of the Alice-Bob link, which enables characterizing the optimal covert rate that can be achieved using the proposed setup. Our results demonstrate the superiority of mmWave covert communication, in terms of covertness and rate, compared to the RF counterpart.
arXiv:1908.07591v1 fatcat:7zuzz6uud5ajrf7a6n7d7vqqde

Femtosecond CDMA Using Dielectric Metasurfaces: Design Procedure and Challenges [article]

Taha Rajabzadeh, Mohammad Hosein Mousavi, Sajjad Abdollahramezani, Mohammad Vahid Jamali, Jawad A. Salehi
2017 arXiv   pre-print
Inspired by the ever-increasing demand for higher data transmission rates and the tremendous attention toward all-optical signal processing based on miniaturized nanophotonics, in this paper, for the first time, we investigate the integrable design of coherent ultrashort light pulse code-division multiple-access (CDMA) technique, also known as femtosecond CDMA, using all-dielectric metasurfaces (MSs). In this technique, the data bits are firstly modulated using ultrashort femtosecond optical
more » ... ses generated by mode-locked lasers, and then by employing a unique phase metamask for each data stream, in order to provide the multiple access capability, the optical signals are spectrally encoded. This procedure spreads the optical signal in the temporal domain and generates low-intensity pseudo-noise bursts through random phase coding leading to minimized multiple access interference. This paper comprehensively presents the principles and design approach to realize fundamental components of a typical femtosecond CDMA encoder, including the grating, lens, and phase mask, by employing high-contrast CMOS-compatible MSs. By controlling the interference between the provided Mie and Fabry-Perot resonance modes, we tailor the spectral and spatial responses of the impinging light locally and independently. Accordingly, we design a MS-based grating with the highest possible refracted angle and, in the meantime, the maximized efficiency which results in a reasonable diameter for the subsequent lens. Moreover, to design our MS-based lens commensurate with the spot size and distance requirements of the pursuant phase mask, we leverage a new optimization method which splits the lens structure into central and peripheral parts, and then design the peripheral part using a collection of gratings converging the impinging at the subsequent phase mask.
arXiv:1712.00834v1 fatcat:76ji2doqtngbpbp3ytkeezvmtq

Outage Probability Analysis of Uplink NOMA over Ultra-High-Speed FSO-Backhauled Systems [article]

Mohammad Vahid Jamali, Seyed Mohammad Azimi-Abarghouyi, Hessam Mahdavifar
2018 arXiv   pre-print
In this paper, we consider a relay-assisted uplink non-orthogonal multiple access (NOMA) system where two radio frequency (RF) users are grouped for simultaneous transmission, over each resource block, to an intermediate relay which forwards the amplified version of the users' aggregated signals in the presence of multiuser interference to a relatively far destination. In order to cope with the users' ever-increasing desire for higher data rates, a high-throughput free-space optics (FSO) link
more » ... employed as the relay-destination backhaul link. Dynamic-order decoding is employed at the destination to determine the priority of the users based on their instantaneous channel state information (CSI). Closed-form expressions for the individual- and sum-rate outage probability formulas are derived in the case of independent Rayleigh fading for the users-relay access links when the FSO backhaul link is subject to Gamma-Gamma turbulence with pointing error. This work can be regarded as an initial attempt to incorporate power-domain NOMA over ultra-high-speed FSO-backhauled systems, known as mixed RF-FSO systems.
arXiv:1809.02893v1 fatcat:dzusgjtzhjdhxht7k5v3zxmrfu

A Low-Complexity Recursive Approach Toward Code-Domain NOMA for Massive Communications [article]

Mohammad Vahid Jamali, Hessam Mahdavifar
2018 arXiv   pre-print
Nonorthogonal multiple access (NOMA) is a promising technology to meet the demands of the next generation wireless networks on massive connectivity, high throughput and reliability, improved fairness, and low latency. In this context, code-domain NOMA which attempts to serve K users in M≤ K orthogonal resource blocks, using a pattern matrix, is of utmost interest. However, extending the pattern matrix dimensions severely increases the detection complexity and hampers on the significant
more » ... s that can be achieved using large pattern matrices. In this paper, we propose a novel approach toward code-domain NOMA which factorizes the pattern matrix as the Kronecker product of some other factor matrices each with a smaller dimension. Therefore, both the pattern matrix design at the transmitter side and the mixed symbols' detection at the receiver side can be performed over much smaller dimensions and with a remarkably reduced complexity and latency. As a consequence, the system can significantly be overloaded to effectively support the requirements of the next generation wireless networks without any considerable increase on the system complexity.
arXiv:1804.05242v1 fatcat:u7ym24eppnc43iu66nfvdap7iq

Designing A Dimmable OPPM-Based VLC System Under Channel Constraints [article]

Ata Chizari, Mohammad Vahid Jamali, Jawad A. Salehi, Akbar Dargahi
2016 arXiv   pre-print
In this paper, we design a dimming compatible visible light communication (VLC) system in a standard office room according to illumination standards under channel constraints. We use overlapping pulse position modulation (OPPM) to support dimming control by changing the code weights. The system parameters such as a valid interval for dimming together with an upper bound for bit rate according to the channel delay spread are investigated. Moreover, considering the dispersive VLC channel and
more » ... Monte Carlo (MC) simulations, a method is proposed to determine the minimum code length in different dimming levels in order to achieve a valid bit error rate (BER). Finally, trellis coded modulation (TCM) is suggested to be applied to OPPM in order to take advantage of consequent coding gain which could be up to 3 dB.
arXiv:1602.08765v1 fatcat:dobpkcojrfci3hmijlefq5yqni

Low-Complexity Decoding of a Class of Reed-Muller Subcodes for Low-Capacity Channels [article]

Mohammad Vahid Jamali, Mohammad Fereydounian, Hessam Mahdavifar, Hamed Hassani
2022 arXiv   pre-print
We present a low-complexity and low-latency decoding algorithm for a class of Reed-Muller (RM) subcodes that are defined based on the product of smaller RM codes. More specifically, the input sequence is shaped as a multi-dimensional array, and the encoding over each dimension is done separately via a smaller RM encoder. Similarly, the decoding is performed over each dimension via a low-complexity decoder for smaller RM codes. The proposed construction is of particular interest to low-capacity
more » ... hannels that are relevant to emerging low-rate communication scenarios. We present an efficient soft-input soft-output (SISO) iterative decoding algorithm for the product of RM codes and demonstrate its superiority compared to hard decoding over RM code components. The proposed coding scheme has decoding (as well as encoding) complexity of 𝒪(nlog n) and latency of 𝒪(log n) for blocklength n. This research renders a general framework toward efficient decoding of RM codes.
arXiv:2202.03654v1 fatcat:bvwsmlbq4fapdilvls7he7ajdi

Deterministic Identification for Molecular Communications over the Poisson Channel [article]

Mohammad Javad Salariseddigh, Uzi Pereg, Holger Boche, Christian Deppe, Vahid Jamali, Robert Schober
2022 arXiv   pre-print
Jamali was supported by the DFG under Grant JA 3104/1-1. Schober was supported by MAMOKO under Grant 16KIS0913.  ... 
arXiv:2203.02784v1 fatcat:x62lpthbuna27bhfzaev6i63jm

ProductAE: Towards Training Larger Channel Codes based on Neural Product Codes [article]

Mohammad Vahid Jamali, Hamid Saber, Homayoon Hatami, Jung Hyun Bae
2021 arXiv   pre-print
There have been significant research activities in recent years to automate the design of channel encoders and decoders via deep learning. Due the dimensionality challenge in channel coding, it is prohibitively complex to design and train relatively large neural channel codes via deep learning techniques. Consequently, most of the results in the literature are limited to relatively short codes having less than 100 information bits. In this paper, we construct ProductAEs, a computationally
more » ... ent family of deep-learning driven (encoder, decoder) pairs, that aim at enabling the training of relatively large channel codes (both encoders and decoders) with a manageable training complexity. We build upon the ideas from classical product codes, and propose constructing large neural codes using smaller code components. More specifically, instead of directly training the encoder and decoder for a large neural code of dimension k and blocklength n, we provide a framework that requires training neural encoders and decoders for the code parameters (k_1,n_1) and (k_2,n_2) such that k_1 k_2=k and n_1 n_2=n. Our training results show significant gains, over all ranges of signal-to-noise ratio (SNR), for a code of parameters (100,225) and a moderate-length code of parameters (196,441), over polar codes under successive cancellation (SC) decoder. Moreover, our results demonstrate meaningful gains over Turbo Autoencoder (TurboAE) and state-of-the-art classical codes. This is the first work to design product autoencoders and a pioneering work on training large channel codes.
arXiv:2110.04466v1 fatcat:smdlcptcezhepblmu6jhe7qtya

Covert Millimeter-Wave Communication: Design Strategies and Performance Analysis [article]

Mohammad Vahid Jamali, Hessam Mahdavifar
2021 arXiv   pre-print
In this paper, we investigate covert communication over millimeter-wave (mmWave) frequencies. In particular, a mmWave transmitter, referred to as Alice, attempts to reliably communicate to a receiver, referred to as Bob, while hiding the existence of communication from a warden, referred to as Willie. In this regard, operating over the mmWave bands not only increases the covertness thanks to directional beams, but also increases the transmission data rates given much more available bandwidths
more » ... d enables ultra-low form factor transceivers due to the lower wavelengths used compared to the conventional radio frequency (RF) counterpart. We first assume that the transmitter Alice employs two independent antenna arrays in which one of the arrays is to form a directive beam for data transmission to Bob. The other antenna array is used by Alice to generate another beam toward Willie as a jamming signal while changing the transmit power independently across the transmission blocks in order to achieve the desired covertness. For this dual-beam setup, we characterize Willie's detection error rate with the optimal detector and the closed-form of its expected value from Alice's perspective. We then derive the closed-form expression for the outage probability of the Alice-Bob link, which enables characterizing the optimal covert rate that can be achieved using the proposed setup. We further obtain tractable forms for the ergodic capacity of the Alice-Bob link involving only one-dimensional integrals that can be computed in closed forms for most ranges of the channel parameters. Finally, we highlight how the results can be extended to more practical scenarios, particularly to the cases where perfect information about the location of the passive warden is not available.
arXiv:2007.13571v2 fatcat:nlo423vivndj7erbib4qeljvey

Uplink Non-Orthogonal Multiple Access over Mixed RF-FSO Systems [article]

Mohammad Vahid Jamali, Hessam Mahdavifar
2020 arXiv   pre-print
In this paper, we consider a relay-assisted uplink non-orthogonal multiple access (NOMA) system. In this system, two radio frequency (RF) users are grouped for simultaneous transmissions, over each resource block, to an intermediate relay. The relay then forwards the amplified version of the users' aggregated signals, in the presence of multiuser interference, to a relatively far destination. In order to cope with the users' ever-increasing desire for higher data rates, a high-throughput
more » ... ace optics (FSO) link is employed as the relay-destination backhaul link. It is assumed that the FSO backhaul link is subject to Gamma-Gamma turbulence with pointing error. Also, a Rayleigh fading model is considered for the user-relay access links. Under these assumptions, we derive closed-form expressions for the outage probability and tractable forms, involving only one-dimensional integrals, for the ergodic capacity. Moreover, the outage probability and ergodic capacity analysis are extended to the conventional RF-backhauled systems in the presence of multiuser interference to both relay and destination nodes, and Rician fading for the relay-destination RF link. Our results reveal the superiority of FSO backhauling for high-throughput and high-reliability NOMA systems compared to RF backhauling. This work can be considered as a general analysis of dual-hop uplink NOMA systems as well as the first attempt to incorporate power-domain NOMA in mixed RF-FSO systems.
arXiv:1903.00326v2 fatcat:eohp4d74abcffehsijvxxusww4

Reed-Muller Subcodes: Machine Learning-Aided Design of Efficient Soft Recursive Decoding [article]

Mohammad Vahid Jamali, Xiyang Liu, Ashok Vardhan Makkuva, Hessam Mahdavifar, Sewoong Oh, Pramod Viswanath
2021 arXiv   pre-print
Reed-Muller (RM) codes are conjectured to achieve the capacity of any binary-input memoryless symmetric (BMS) channel, and are observed to have a comparable performance to that of random codes in terms of scaling laws. On the negative side, RM codes lack efficient decoders with performance close to that of a maximum likelihood decoder for general parameters. Also, they only admit certain discrete sets of rates. In this paper, we focus on subcodes of RM codes with flexible rates that can take
more » ... code dimension from 1 to n, where n is the blocklength. We first extend the recursive projection-aggregation (RPA) algorithm proposed recently by Ye and Abbe for decoding RM codes. To lower the complexity of our decoding algorithm, referred to as subRPA in this paper, we investigate different ways for pruning the projections. We then derive the soft-decision based version of our algorithm, called soft-subRPA, that is shown to improve upon the performance of subRPA. Furthermore, it enables training a machine learning (ML) model to search for good sets of projections in the sense of minimizing the decoding error rate. Training our ML model enables achieving very close to the performance of full-projection decoding with a significantly reduced number of projections. For instance, our simulation results on a (64,14) RM subcode show almost identical performance for full-projection decoding and pruned-projection decoding with 15 projections picked via training our ML model. This is equivalent to lowering the complexity by a factor of more than 4 without sacrificing the decoding performance.
arXiv:2102.01671v1 fatcat:7ycflgbs4feahgfn6g5hlypyya

Cellular Underwater Wireless Optical CDMA Network: Potentials and Challenges

Farhad Akhoundi, Mohammad Vahid Jamali, Navid Bani Hassan, Hamzeh Beyranvand, Amir Minoofar, Jawad A. Salehi
2016 IEEE Access  
Underwater wireless optical communications are an emerging solution to the expanding demand for broadband links in oceans and seas. In this paper, a cellular underwater wireless optical code division multiple-access network is proposed to provide broadband links for commercial and military applications. The optical orthogonal codes are employed as signature codes of underwater mobile users. Fundamental key aspects of the network, such as its backhaul architecture, its potential applications,
more » ... its design challenges, are presented. In particular, a promising underwater localization and positioning scheme based on this cellular network is presented. Furthermore, the proposed network is used as infrastructure of centralized, decentralized and relay-assisted underwater sensor networks for high-speed real-time monitoring. Finally, probable design challenges, such as cell edge coverage, blockage avoidance, power control, and network capacity, are addressed. INDEX TERMS Underwater wireless optical communications, optical CDMA networks, underwater sensor networks, relay-assisted transmission, undersea localization and positioning, power control. I. INTRODUCTION Rapidly growing commercial and military applications for underwater communication demands for a reliable, flexible and practical multi-access network. Recent studies have shown that there are two major solutions to this demand: acoustic and optical transmission. Due to the limited bandwidth of acoustic systems, their maximum achievable rates are restricted to 10∼100 kbps. Furthermore, the low speed of acoustic waves in undersea media (≈1500 m/s) which results in a high latency in long range communications causes problems for synchronization and multiple access techniques. Alternatively, in comparison with the traditional acoustic approach, wireless optical communication has three main advantages: higher bandwidth, higher security and lower time latency [1], [2] . Despite their promising advantages, limited attainable communication range of underwater wireless optical communication (UWOC) systems, i.e., less than 100 meters with realistic average transmit powers, hampers their widespread usage. The general reason is that optical beam propagation through water suffers from three main disturbing effects: absorption, scattering and turbulence. In recent years, various studies have been carried out in order to investigate how these three impairing effects can be modeled for different water types and also some intelligent techniques have been proposed to mitigate these effects and hence to improve the performance of UWOC systems and extend their viable communication range. In [3] , Mobley has accomplished an in-depth study of light interaction in water to characterize absorption and scattering effects of different water types based on theoretical analysis and experimental evidence reported in [4] . Consequently, variety of worthwhile researches have been carried out to better model the UWOC channel behavior with respect to the absorption and scattering effects. For example, in [5] Jaruwatanadilok presented mathematical modeling of an UWOC channel and its performance evaluation using radiative transfer theory. Moreover, Dong et al. succeeded to present a closed-form expression of double Gamma function to model the channel impulse response in the presence of absorption and scattering effects [6] . They also proposed a weighted Gamma function polynomial to model the 4254 2169-3536
doi:10.1109/access.2016.2593398 fatcat:6wocpv5r5bgfjntweztbccxtyu

KO codes: Inventing Nonlinear Encoding and Decoding for Reliable Wireless Communication via Deep-learning [article]

Ashok Vardhan Makkuva, Xiyang Liu, Mohammad Vahid Jamali, Hessam Mahdavifar, Sewoong Oh, Pramod Viswanath
2021 arXiv   pre-print
In order to overcome this issue, we obtain the soft-decision version of the MAP decoder, referred to as Soft-MAP decoder, to come up with differentiable decoding at the leaves (Jamali et al., 2021) .  ... 
arXiv:2108.12920v1 fatcat:rmv2iefpfjacxctqscacxvxaza

Mining DNA Sequences Based on Spatially Coded Technique Using Spatial Light Modulator [article]

Masoome Fazelian, Sajjad AbdollahRamezani, Sima Bahrani, Ata Chizari, Mohammad Vahid Jamali, Pirazh Khorramshahi, Arvin Tashakori, Shadi Shahsavari, Jawad A. Salehi
2016 arXiv   pre-print
In this paper, we present an optical computing method for string data alignment applicable to genome information analysis. By applying moire technique to spatial encoding patterns of deoxyribonucleic acid (DNA) sequences, association information of the genome and the expressed phenotypes could more effectively be extracted. Such moire fringes reveal occurrence of matching, deletion and insertion between DNA sequences providing useful visualized information for prediction of gene function and
more » ... ssification of species. Furthermore, by applying a cylindrical lens, a new technique is proposed to map two-dimensional (2D) association information to a one-dimensional (1D) column of pixels, where each pixel in the column is representative of superposition of all bright and dark pixels in the corresponding row. By such a time-consuming preprocessing, local similarities between two intended patterns can readily be found by just using a 1D array of photodetectors and postprocessing could be performed on specified parts in the initial 2D pattern. We also evaluate our proposed circular encoding adapted for poor data alignment condition. Our simulation results together with experimental implementation verify the effectiveness of our dynamic proposed methods which significantly improve system parameters such as processing gain and signal to noise ratio (SNR).
arXiv:1603.08106v1 fatcat:kb4mseauqfflvo3ghqeqr7qeoq
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