Saeed Abdallah

• Doctor of Philosophy
• University of Sharjah

This paper investigates the performance of a multi-reconfigurable intelligent surface (RIS)-assisted fluid antenna system (FAS). In this system, a single-antenna transmitter communicates with a receiver equipped with a planar FAS through multiple RISs in the absence of a direct link. To enhance the system performance, we propose two novel selection...

Integrated sensing and communications (ISAC) has emerged as a promising solution for addressing spectrum congestion in sixth-generation communication systems. In this work, we consider the deployment of ISAC in a full-duplex cell-free (FD-CF) multi-input multi-output (MIMO) system that is aided by a reconfigurable intelligent surface (RIS). To over...

Ambient backscatter communication (AmBC) has attracted significant attention as a viable paradigm for energy efficient communication in the next generation of Internet-of-Things (IoT). Channel estimation, a vital task in AmBC receiver design, becomes more challenging when accounting for more practical scenarios such as frequency selective fading an...

Ambient backscatter communication (AmBC) has attracted attention as an enabling technology for green device-to-device (D2D) communication for the next generation of Internet-of-Things (IoT) networks. Most existing works assume that the signals of the source and the backscattering device (BD) are perfectly synchronized at the reader. Perfect synchro...

Incorporating rate splitting multiple access (RSMA) into integrated sensing and communication (ISAC) presents a significant security challenge, particularly in scenarios where the location of a potential eavesdropper (Eve) is unidentified. Splitting users' messages into common and private streams exposes them to eavesdropping, with the common strea...

Massive multiple-input multiple-output (MIMO) is one of the essential technologies in beyond fifth generation (B5G) communication systems due to its impact in attaining high power efficiency and spectrum efficiency. The design of low-complexity detectors for massive MIMO continues to attract significant research and industry attention due to the cr...

Motivated by advances in energy harvesting and Internet-of-Things (IoT) technologies, this paper addresses the joint spectrum-efficient routing and power allocation problem in wireless networks of passive tags that communicate over multihop tag-to-tag paths by backscattering signals from an ambient radio frequency (RF) source. Our objective is to f...

Ambient backscatter communication (AmBC) is a highly promising technology that enables the ubiquitous deployment of low-cost, low-power devices to support the next generation of Internet-of-Things (IoT) applications. This paper addresses channel estimation for full-duplex multi-antenna AmBC systems. This is highly challenging due to the large numbe...

6G networks have the burden to provide not only higher performance compared to 5G, but also to enable new service domains as well as to open the door over a new paradigm of mobile communication. This paper presents an overview on the role and key challenges of signal processing (SP) in future 6G systems and networks from the conditioning of the sig...

The carrier-to-noise density measured by global positioning system (GPS) receivers can be used as an indicator of signal quality and to predict the receivers' performance. It is the ratio of the carrier power to the noise power per unit bandwidth, expressed in decibel-Hertz (dB-Hz). The traditional method of estimating the carrier-to-noise density...

Recognition of the modulation scheme is the intermediate step between signal detection and demodulation of the received signal in communication networks. Automatic modulation recognition (AMR) plays a central role in many applications, especially in the military and security sectors. In general, several properties of the received signal are extract...

With the advent of fifth generation (5G) systems and the Internet‐of‐Things (IoT), the number of interconnected wireless devices is increasing significantly. Protocols that allow these deceives to interconnect peer‐to‐peer through wireless links are becoming of interest. The major challenge is the inevitable interference among the simultaneously ac...

In this work, we consider amplify-and-forward two-way relay networks operating under the imperfect conditions of in-phase and quadrature-phase (I/Q) imbalance. We propose novel, efficient solutions for the problem of joint channel and I/Q imbalance estimation and the related problem of optimal pilot design. Three different estimation algorithms are...

Multiple-input multiple-output (MIMO) molecular communication (MC) systems can provide significantly better data rates than single-input single-output (SISO) systems. A major challenge in MIMO MC systems is the presence of inter-link interference, in addition to inter-symbol interference. Accurate estimation of all the channel information is thus e...

This paper explores the problem of energy-efficient shortest path planning on off-road, natural, real-life terrain for unmanned ground vehicles (UGVs). We present a greedy path planning algorithm based on a composite metric routing approach that combines the energy consumption and distance of the path. In our work, we consider the Terramechanics be...

Ambient backscatter communication systems (ABCSs) have been gaining popularity as a green alternative to conventional communication systems. To deploy such systems, it is important to acquire the channel state information (CSI) and to account for hardware imperfections such as carrier-frequency offsets (CFOs) and inphase/quadrature (I/Q) imbalance....

Abstract This paper considers the problem of joint timing‐offset and channel estimation for physical‐layer network coding systems operating in frequency‐selective environments. Three different algorithms are investigated for the joint estimation of the channel coefficients and the fractional timing offset. The first algorithm is based on the maximu...

In this work, we propose a low-overhead channel estimator for diffusive molecular communication systems. Since diffusive molecular communication systems rely on the random propagation of molecules as a means of communication, they may potentially suffer from inter-symbol-interference in addition to the noise introduced by the channel and external s...

The problem of finding the route with maximum end-to-end spectral efficiency in a multihop wireless network has been subject to considerable interest in the recent literature. It has been established that the problem is polynomially solvable in networks that employ time division multiple access (TDMA) or frequency division multiple access (FDMA). T...

The cloud radio access network (C-RAN) aims at migrating the traditional base station functionality to a cloud-based centralized base band unit (BBU) pool, thereby providing a promising paradigm for fifth-generation (5G) wireless systems. This results in a novel wireless architecture in which mobile users communicate with the cloud via distributed...

In this letter, we consider the problem of channel estimation for diffusive molecular communication (MC) systems. The presence of memory in diffusive MC channels, along with channel noise caused by various sources, necessitate the development of accurate channel estimators to acquire the channel impulse response (CIR). Previous works proposed pilot...

n this paper, we consider the problem of joint timing-offset and channel estimation for amplify-and-forward (AF) two-way relay networks (TWRNs). This problem is solved for generic pulse-shaping filters, taking into account the filter truncation in practical communication and considering both pilot-based and semi-blind estimation strategies. Beginni...

Heterogeneous networks that consist of densely deployed base stations of different (macro and small-cell) tiers are envisioned to be among the key technologies for providing the high data rates required in 5G systems. Moreover, interconnecting small-cell base stations via millimeter-wave (mm-wave) backhaul links is a flexible and cost-effective alt...

This work considers the problem of joint channel and carrier frequency offset (CFO) estimation for asynchronous amplify-and-forward (AF) two-way relay networks (TWRNs). This problem has not been solved to the best of our knowledge, and the presence of timing offsets between the two terminals, in addition to the frequency offsets, makes it necessary...

In this paper, we consider the problem of channel estimation for asynchronous amplify-and-forward (AF) two-way relay networks. We propose a novel, semi-blind channel estimation algorithm for this problem based on the expectation maximization (EM) framework. The proposed EM algorithm has low complexity and only a small number of EM iterations is nee...

In an uplink massive multiple-input-multiple-output (MIMO) deployment with distributed single-antenna users and a large base-station array, we investigate the performance of low complexity Vertical Bell Laboratories Layered Space Time (C-V-BLAST) and zero forcing (ZF) receivers. Unlike previous work which assumes that the channel is perfectly known...

Rate adaptation which adjusts the transmission rate based on channel quality, plays a key role in the performance of 802.11 networks and is critical for achieving high throughput. Traditional statistics-based methods for rate adaptation are unsuited for mobility scenarios because of the delay involved in statistics gathering. Methods based on chann...

We consider the problem of channel estimation for OFDM-based amplify-and-forward (AF) two-way relay networks (TWRNs). While previous works have adopted a pilot-based approach, we propose a semi-blind approach that exploits both the transmitted pilots as well as the received data samples to improve the estimation performance. Our proposed semi-blind...

In this letter, we propose an expectation maximization (EM)-based algorithm for semi-blind channel estimation of reciprocal channels in amplify-and-forward (AF) two-way relay networks (TWRNs). By utilizing data samples as well as pilots, the proposed algorithm provides substantially higher estimation accuracy than the conventional training-based le...

We propose an expectation maximization (EM)-based algorithm for semi-blind channel estimation of reciprocal channels in amplify-and-forward (AF) two-way relay networks (TWRNs). By incorporating both data samples and pilots into the estimation, the proposed algorithm provides substantially higher accuracy than the conventional training-based approac...

In this paper, we derive for the first time the exact Cramer-Rao bounds (CRBs) on semi-blind channel estimation for amplify-and-forward two-way relay networks. The bounds cover a wide range of modulation schemes that satisfy a certain symmetry condition. In particular, the important classes of PSK and square QAM are covered. For the case square QAM...

We consider the problem of channel estimation for amplify-and-forward two-way relays assuming channel reciprocity and M-PSK modulation. In an earlier work, a partially-blind maximum-likelihood estimator was derived by treating the data as deterministic unknowns. We prove that this estimator approaches the true channel with high probability at high...

We analyze the mean-squared error (MSE) performance of widely linear (WL) and conventional subspace-based channel estimation for single-input multiple-output (SIMO) flat-fading channels employing binary phase-shift-keying (BPSK) modulation when the covariance matrix is estimated using a finite number of samples. The conventional estimator suffers f...

We analyze the mean-squared error (MSE) performance of widely linear (WL) and conventional subspace-based channel estimation for single-input multiple-output (SIMO) flat-fading channels employing binary phase-shift-keying (BPSK) modulation when the covariance matrix is estimated using a finite number of samples. The conventional estimator suffers f...

We consider the problem of channel estimation for amplify-andforward (AF) two-way relay networks (TWRNs). The majority of works on this problem develop pilot-based algorithms that allocate significant resources for training. We will show in this work that such overhead is not necessary when the terminals employ M -ary phase-shift keying (M -PSK). U...

We consider the problem of channel estimation for amplify-and-forward (AF) two-way relay networks (TWRNs). Most works on this problem focus on pilot-based approaches which impose a significant training overhead that reduces the spectral efficiency of the system. To avoid such losses, this work proposes blind channel estimation algorithms for AF TWR...

We present two channel estimation algorithms for amplify-and-forward two-way relay networks that employ constant-modulus constellations. The proposed algorithms do not assume complete knowledge of the transmitted symbols: they only require the transmission of a very short training sequence in order to resolve the inevitable phase ambiguity in the c...

We propose a novel widely linear (WL) minimum variance (MV) channel estimation algorithm for multicarrier code-division multiple access (MC-CDMA) systems. The presented algorithm outperforms the regular MV channel estimation algorithms when the modulation scheme is real-valued (such as BPSK). We build on the results of [1] to find a highly accurate...