Giuseppe Caire

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Verified

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• PhD
• Professor (Full) at Technische Universität Berlin

Space-fed large antenna arrays offer superior efficiency , simplicity, and reductions in size, weight, power, and cost (SWaP-C) compared to constrained-feed systems. Historically, horn antennas have been used for space feeding, but they suffer from limitations such as bulky designs, low aperture efficiency (≈ 50%), and restricted degrees of freedom...

Space-fed large antenna arrays offer superior efficiency, simplicity, and reductions in size, weight, power, and cost (SWaP-C) compared to constrained-feed systems. Historically, horn antennas have been used for space feeding, but they suffer from limitations such as bulky designs, low aperture efficiency ($\approx 50\%$), and restricted degrees of...

Flat-top beam designs are essential for uniform power distribution over a wide angular sector for applications such as 5G/6G networks, satellite communications, radar systems, etc. Low sidelobe levels with steep transitions allow negligible cross sector illumination. Active array designs requiring amplitude taper suffer from poor power amplifier ut...

Coded caching leverages the differences in user cache memories to achieve gains that scale with the total cache size, alleviating network congestion due to high-quality content requests. Additionally, distributing transmitters over a wide area can mitigate the adverse effects of path loss. In this work, we consider a partially connected network whe...

We consider unsourced random access (uRA) in a cell-free (CF) user-centric wireless network, where a large number of potential users compete for a random access slot, while only a finite subset is active. The random access users transmit codewords of length L symbols from a shared codebook, which are received by B geographically distributed radio u...

Next-generation wireless networks are expected to provide the capability of robust environmental sensing in addition to reliable communications to meet intelligence requirements. A promising solution is the integrated sensing and communication (ISAC) technology, which performs both functionalities using the same spectrum and hardware resources. Mos...

This paper investigates the achievable region of a K -user discrete memoryless (DM) multiple access wiretap (MAC-WT) channel, where each user transmits both secret and open (i.e., non-confidential) messages. All these messages are intended for the legitimate receiver (Bob), while the eavesdropper (Eve) is only interested in the secret messages. I...

A transceiver device, in particular for wireless communication is disclosed. The transceiver device comprises a multi-antenna feeder array, comprising a plurality of active antennas configured to transmit electromagnetic radiation based on a data stream precoded with a precoder for beamforming the electromagnetic radiation. Moreover, the transceive...

This paper considers the secure aggregation problem for federated learning under an information theoretic cryptographic formulation, where distributed training nodes (referred to as users) train models based on their own local data and a curious-but-honest server aggregates the trained models without retrieving other information about users’ local...

We consider scalable cell-free massive multiple-input multiple-output networks under an open radio access network paradigm comprising user equipments (UEs), radio units (RUs), and decentralized processing units (DUs). UEs are served by dynamically allocated user-centric clusters of RUs. The corresponding cluster processors (implementing the phy...

In this paper, we investigate the performance of the cross-domain iterative detection (CDID) framework with orthogonal time frequency space (OTFS) modulation, where two distinct CDID algorithms are presented. The proposed schemes estimate/detect the information symbols iteratively across the frequency domain and the delay-Doppler (DD) domain via pa...

We present numerical results with a focus on power transfer between two standard linear antenna arrays placed in the near field, where a much smaller active multi-antenna feeder (AMAF) space feeds a far larger passive array referred to as a reflective intelligent surface (RIS). The interest is in the regime of focal length to diameter ratio (F/D) l...

We propose a power- and hardware-efficient, pragmatic, modular, multiuser/multibeam array-fed RIS architecture particularly suited to operate in very high frequency bands (high mmWave and sub-THz), where channels are typically sparse in the beamspace and line-of-sight (LOS) is required to achieve an acceptable received signal level. The key modu...

This work proposes a maximum likelihood-based parameter estimation framework for a multistatic millimeter wave integrated sensing and communication system using energy-efficient hybrid digital-analog arrays. Due to the typically large arrays used in the higher frequency bands to mitigate isotropic path loss, such arrays may operate in the near-fiel...

We consider a user-centric cell-free massive MIMO wireless network with L remote radio units, each with M antennas, serving K single-antenna user devices (UEs). Most of the current literature considers the regime LM - K , where the K UEs are active on each time-frequency slot, and evaluates the system performance in terms of ergodic ra...

Secure aggregation, which is a core component of federated learning, aggregates locally trained models from distributed users at a central server. The “secure” nature of such aggregation consists of the fact that no information about the local users’ data must be leaked to the server except the aggregated local models. In order to guarantee securit...

Multiple access is the cornerstone technology for each generation of wireless cellular networks, which fundamentally determines the method of radio resource sharing and significantly influences both the system performance and transceiver complexity. Meanwhile, resource allocation (RA) design plays a crucial role in multiple access, as it can manage...

The evolution of wireless networks is set to undergo a significant transformation, moving beyond the enhancements introduced with 5G towards a revolutionary new paradigm. This shift is not just an upgrade of existing communication technologies but a fundamental reimagining of how wireless networks operate, driven by the integration of sensing capab...

This work proposes a maximum likelihood (ML)-based parameter estimation framework for a millimeter wave (mmWave) integrated sensing and communication (ISAC) system in a multistatic configuration using energy-efficient hybrid digital-analog (HDA) arrays. Due to the typically large arrays deployed in the higher frequency bands to mitigate isotropic p...

We consider unsourced random access (uRA) in user-centric cell-free (CF) wireless networks, where random access users send codewords from a common codebook during specifically dedicated random access channel (RACH) slots. The system is conceptually similar to the so-called 2-step RACH currently discussed in 3GPP standardization. In order to cope wi...

p>We propose a power-and hardware-efficient, pragmatic , modular, multiuser/multibeam array-fed RIS architecture particularly suited to operate in very high frequency bands (high mmWave and sub-THz), where channels are typically sparse in the beamspace and line-of-sight (LOS) is required to achieve an acceptable received signal level. The key modul...

Federated learning (FL) has recently gained significant momentum due to its potential to leverage large-scale distributed user data while preserving user privacy. However, the typical paradigm of FL faces challenges of both privacy and robustness: the transmitted model updates can potentially leak sensitive user information, and the lack of central...

This paper aims to answer a fundamental question in the area of Integrated Sensing and Communications (ISAC): What is the optimal communication-centric ISAC waveform for ranging? Towards that end, we first established a generic framework to analyze the sensing performance of communication-centric ISAC waveforms built upon orthonormal signaling base...

Multiple access is the cornerstone technology for each generation of wireless cellular networks and resource allocation design plays a crucial role in multiple access. In this paper, we present a comprehensive tutorial overview for junior researchers in this field, aiming to offer a foundational guide for resource allocation design in the context o...

This paper investigates radar-assisted user acquisition for downlink multi-user multiple-input multiple-output (MIMO) transmission using Orthogonal Frequency Division Multiplexing (OFDM) signals. Specifically, we formulate a concise mathematical model for the user acquisition problem, where each user is characterized by its delay and beamspace resp...

For planar array-fed arrays, the center feed outperforms an end feed due to its inherent geometric symmetry, the compelling low-sidelobe beamshape of the principal eigenmode (maximum power transfer between the two arrays), and a smaller optimum focal length. Also, it is fascinating to see yet another physical manifestation of singular value decompo...

The array design of multiple-input multiple-output (MIMO) systems in a line-of-sight (LoS) environment is investigated. Properly designed uniform array configurations at the transmitter (Tx) and receiver (Rx) can extract maximum spatial multiplexing gain only for a fixed transmit distance between the Tx and Rx arrays and for a fixed orientation of...

p>We present numerical results with a focus on power transfer between two standard linear antenna arrays placed in the near field, where a much smaller active multi-antenna feeder (AMAF) space feeds a far larger passive array referred to as a reflective intelligent surface (RIS). The interest is in the regime of focal length to diameter ratio (F/D)...

By trading coverage and hardware complexity for abundance of spectrum, sub-THz mobile access networks are expected to operate under highly directive and relatively spectrally inefficient transmission regimes, while still offering enormous capacity gains over current sub-6 GHz alternatives. Building on this assumption, and supported by extensive ind...

Sensing and communications (S&C) were historically developed in parallel. In the last decade, they have been evolving from separation to integration, giving rise to the integrated sensing and communication (ISAC) paradigm, that has been recognized as one of 6G key usage scenarios. Despite the plethora of research works dedicated to ISAC signal proc...

Pathloss quantifies the reduction in power density of a signal radiated from a transmitter. The attenuation is due to large-scale effects such as free-space propagation loss and interactions (e.g., penetration, reflection, and diffraction) of the signal with objects such as buildings, vehicles, trees, and pedestrians in the propagation environment....

Coded Caching is a technology that promises to reduce cacheable traffic by turning stored content at the users to multicast opportunities. In wireless channels, though, users experience different rates causing each message to be communicated with the group’s worst-user’s rate, which in turn impacts significantly the achieved performance. In this wo...

p>This paper presents a novel, power- and hardware-efficient, multiuser, multibeam RIS (Reflective Intelligent Surface) architecture for multiuser MIMO, especially suited to operate in very high frequency bands (e.g., high mmWave and sub-THz), where channels are typically sparse in the beamspace and line-of-sight (LOS) is the dominant component. Th...

p>This paper presents a novel, power- and hardware-efficient, multiuser, multibeam RIS (Reflective Intelligent Surface) architecture for multiuser MIMO, especially suited to operate in very high frequency bands (e.g., high mmWave and sub-THz), where channels are typically sparse in the beamspace and line-of-sight (LOS) is the dominant component. Th...

p>This paper presents a novel, power- and hardware-efficient, multiuser, multibeam RIS (Reflective Intelligent Surface) architecture for multiuser MIMO, especially suited to operate in very high frequency bands (e.g., high mmWave and sub-THz), where channels are typically sparse in the beamspace and line-of-sight (LOS) is the dominant component. Th...

Global Navigation Satellite Systems typically perform poorly in urban environments, where the likelihood of line-of-sight conditions between devices and satellites is low. Therefore, alternative location methods are required to achieve good accuracy. We present LocUNet: A convolutional, end-to-end trained neural network (NN) for the localization ta...

Caching prefetches some library content at users’ memories during the off-peak times (i.e., placement phase ), such that the number of transmissions during the peak-traffic times (i.e., delivery phase ) are reduced. A coded caching strategy was originally proposed by Maddah-Ali and Niesen (MN) leading to a multicasting gain compared to the conv...

p>This paper presents a novel, power- & hardware-efficient, multiuser, multibeam RIS (Reflective Intelligent Surface) architecture for multiuser MIMO, especially for very high frequency bands (e.g., high mmWave and sub-THz), where channels are typically sparse in the beamspace and LOS is the dominant component. The key module is formed by an active...

Only 0.3W (beamforming array) for 5Gbps at 100m. Conference: one6G Summit 2023, Munich

Sensing and communications (S&C) have been historically developed in parallel. In recent decade, they have been evolving from separation to integration, giving rise to the integrated sensing and communications (ISAC) paradigm, that has been recognized as one of the six key 6G usage scenarios. Despite the plethora of research works dedicated to ISAC...

Motivated by automotive applications, we consider joint radar sensing and data communication for a system operating at millimeter wave (mmWave) frequency bands, where a Base Station (BS) is equipped with a co-located radar receiver and sends data using the Orthogonal Time Frequency Space (OTFS) modulation format. We consider two distinct modes of o...

This paper studies the fundamental limits of the shared-link coded caching problem with correlated files, where a server with a library of ${\mathsf N}$ files communicates with ${\mathsf K}$ users who can locally cache ${\mathsf M}$ files. Given an integer ${\mathsf r}\in [{\mathsf N}]$ , correlation is modelled as follows: each ${\mathsf...

This work proposes a maximum likelihood (ML)-based parameter estimation framework for a millimeter wave (mmWave) integrated sensing and communication (ISAC) system in a multi-static configuration using energy-efficient hybrid digital-analog arrays. Due to the typically large arrays deployed in the higher frequency bands to mitigate isotropic path l...

p>This letter presents numerical results with a focus on power transfer between two antenna arrays placed in the near field, where a much smaller active multi-antenna feeder (AMAF) center feeds a far larger passive array referred to as a reflective intelligent surface (RIS). The AMAF is configured along the principal eigenmode of the AMAF-RIS propa...

We study the problem of providing channel state information (CSI) at the transmitter in multi-user “massive” MIMO systems operating in frequency division duplexing (FDD). The wideband MIMO channel is a vector-valued random process correlated in time, space (antennas), and frequency (subcarriers). The base station (BS) broadcasts periodically β <sub...

We investigate radar parameter estimation and beam tracking with a hybrid digital-analog (HDA) architecture in a multi-block measurement framework using an extended target model. In the considered setup, the backscattered data signal is utilized to predict the user position in the next time slots. Specifically, a simplified maximum likelihood frame...

We consider the cache-aided multiple-input single-output (MISO) broadcast channel, which consists of a server with $L$ antennas and $K$ single-antenna users, where the server contains $N$ files of equal length and each user is equipped with a local cache of size $M$ files. Each user requests an arbitrary file from library. The objective is...

p>This letter presents numerical results with a focus on power transfer between two antenna arrays placed in the near field, where a much smaller active multi-antenna feeder (AMAF) center feeds a far larger passive array referred to as a reflective intelligent surface (RIS). The AMAF is configured along the principal eigenmode of the AMAF-RIS propa...

p>This letter presents numerical results with a focus on power transfer between two antenna arrays placed in the near field, where a much smaller active multi-antenna feeder (AMAF) center feeds a far larger passive array referred to as a reflective intelligent surface (RIS). The AMAF is configured along the principal eigenmode of the AMAF-RIS propa...

The integrated sensing and communication (ISAC) paradigm, where sensing and communication functions are synergistically implemented by possibly sharing the same frequency band and hardware, has emerged as one of key technologies in future wireless systems. While substantial efforts have been devoted to investigate various techniques under different...

In this chapter, we will focus on the ISAC design by using orthogonal time frequency space (OTFS) waveforms. OTFS is a recently proposed two-dimensional modulation scheme, whose core is the delay-Doppler (DD) domain signal processing. As the success of radar sensing is built upon the accuracy of delay and Doppler estimation, the DD domain signal pr...

In this work, we propose a waveform based on Modulation on Conjugate-reciprocal Zeros (MOCZ) originally proposed for short-packet communications in [1], as a new Integrated Sensing and Communication (ISAC) waveform. Having previously established the key advantages of MOCZ for noncoherent and sporadic communication, here we leverage the optimal auto...

In this paper, a reduced-complexity cross-domain iterative detection for orthogonal time frequency space (OTFS) modulation is proposed, which exploits channel properties in both time and delay-Doppler domains. Specifically, we first show that in the time domain effective channel, the path delay only introduces interference among samples in adjacent...

We consider a user-centric cell-free massive MIMO wireless network with $L$ remote radio units, each with $M$ antennas, serving $K_{\rm tot}$ user equipments (UEs). Most of the literature considers the regime $LM \gg K_{\rm tot}$, where the $K$ UEs are active on each time-frequency slot, and evaluates the system performance in terms of ergodic rate...

In this paper, we study the pulse shaping for delay-Doppler (DD) communications. We start with constructing a basis function in the DD domain following the properties of the Zak transform. Particularly, we show that the constructed basis functions are globally quasi-periodic while locally twisted-shifted, and their significance in time and frequenc...

We consider a $4 \times 4$ line-of-sight multiple-input multiple-output (LoS MIMO) system with uniform circular arrays (UCAs) at the transmitter (Tx) and receiver (Rx). First, we show that the optimum design of non-tilted UCAs of four antennas can be generalized to the design of optimum elliptical arrays (EAs). Afterwards, we investigate the effe...

Integrated Sensing and Communication (ISAC) is recognized as a promising technology for the next-generation wireless networks, which provides significant performance gains over individual sensing and communications (S&C) systems via the shared use of wireless resources. The characterization of the S&C performance tradeoff is at the core of the theo...

We introduce a hardware-efficient space-fed antenna system that utilizes the eigenmodes of the over-the-air propagation matrix. Featuring a small active multi-antenna feeder (AMAF) and a large reflective intelligent surface (RIS), both configured as linear arrays in near-field proximity, this system offers remarkable flexibility. It can generate di...

We consider fairness scheduling in a user-centric cell-free massive MIMO network, where $L$ remote radio units, each with $M$ antennas, serve $K_{\rm tot} \approx LM$ user equipments (UEs). Recent results show that the maximum network sum throughput is achieved where $K_{\rm act} \approx \frac{LM}{2}$ UEs are simultaneously active in any given time...

Channel splicing is a rather new and very promising concept. It allows to realize a wideband channel sounder by combining multiple narrow-band measurements. Among others, channel splicing is a sparse sensing techniques suggested for use in joint communication and sensing (JCAS), channel measurements and prediction using cheap hardware that cannot m...