In this letter, we consider the problem of channel estimation for large intelligent metasurface (LIM) assisted massive multiple-input multiple-output (MIMO) systems. The main challenge is that LIM integrated with a number low-cost metamaterial antennas can only passively reflect incident signals by certain phase shifts, and does not have any signal processing capability. To deal this, introduce general framework transmitter-LIM LIM-receiver cascaded channel, propose two-stage algorithm...

Thanks to the line-of-sight (LoS) transmission and flexibility, unmanned aerial vehicles (UAVs) effectively improve throughput of wireless networks. Nevertheless, LoS links are prone severe deterioration by complex propagation environments, especially in urban areas. Reconfigurable intelligent surfaces (RISs), as a promising technique, can significantly environment enhance communication quality intelligently reflecting received signals. Motivated this, joint UAV trajectory RIS's passive...

Millimeter wave (MmWave) communications is capable of supporting multi-gigabit wireless access thanks to its abundant spectrum resource. However, severe path loss and high directivity make it vulnerable blockage events, which can be frequent in indoor dense urban environments. To address this issue, paper, we introduce intelligent reflecting surface (IRS) as a new technology provide effective reflected paths enhance the coverage mmWave signals. In framework, study joint active passive...

Reconfigurable intelligent surface (RIS) is envisioned to be an essential component of the paradigm for beyond 5G networks as it can potentially provide similar or higher array gains with much lower hardware cost and energy consumption compared massive multiple-input multiple-output (MIMO) technology. In this paper, we focus on one fundamental challenges, namely channel acquisition, in RIS-assisted multiuser MIMO system. The state-of-the-art acquisition approach such a system fully passive...

Reconfigurable intelligent surfaces (RISs) are regarded as a promising emerging hardware technology to improve the spectrum and energy efficiency of wireless networks by artificially reconfiguring propagation environment electromagnetic waves. Due unique advantages in enhancing channel capacity, RISs have recently become hot research topic. In this article, we focus on three fundamental physical-layer challenges for incorporation into networks, namely, state information acquisition, passive...

This paper investigates the passive beamforming and information transfer (PBIT) technique for multiuser multiple-input multiple-output (Mu-MIMO) systems with aid of reconfigurable intelligent surfaces (RISs), where RISs enhance primary communication via (P-BF) at same time deliver additional by on-off reflecting modulation (in which RIS is carried on/off state each element). For P-BF design, we propose to maximize achievable user sum rate RIS-aided Mu-MIMO channel formulate problem as a...

Large intelligent surface (LIS) has emerged as a promising new solution to improve the energy and spectrum efficiency of wireless networks. A LIS, composed large number low-cost nearly-passive reconfigurable reflecting elements, enhances communications by impinging electromagnetic waves. In this letter, we propose novel passive beamforming information transfer (PBIT) technique adopting spatial modulation on index LIS in which simultaneously primary communication (by beamforming) sends its...

This paper investigates a novel unmanned aerial vehicles (UAVs) secure communication system with the assistance of reconfigurable intelligent surfaces (RISs), where UAV and ground user communicate each other, while an eavesdropper tends to wiretap their information. Due limited capacity UAVs, RIS is applied further improve quality communication. The time division multiple access (TDMA) protocol for communications between user, namely, downlink (DL) uplink (UL) communications. In particular,...

To exploit massive amounts of data generated at mobile edge networks, <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">federated learning</i> (FL) has been proposed as an attractive substitute for centralized machine learning (ML). By collaboratively training a shared model devices, FL avoids direct transmission and thus overcomes high communication latency privacy issues compared to ML. improve the efficiency in aggregation,...

To exploit the potential of reconfigurable intelligent surface (RIS) in supporting integrated sensing and communication (ISAC), this paper proposes a novel joint active passive beamforming design for RIS-enabled ISAC system consideration target size. First, detection probability is derived closed-form based on illumination power an approximated scattering area target, new concept ultimate resolution (UDR) defined first time to measure capability. Then, optimization problem formulated...

In this letter, we propose a turbo compressed sensing algorithm with partial discrete Fourier transform (DFT) matrices. Interestingly, the state evolution of proposed is shown to be consistent that derived using replica method. Numerical results demonstrate outperforms well-known approximate message passing (AMP) when DFT matrix involved.

Ambient backscatter communication (AmBC) is a promising solution to energy-efficient and spectrum-efficient Internet of Things with stringent power cost constraints. In an AmBC system, recovering the tag information at reader, however, challenging task due difficulty in acquiring relevant channel-state (CSI). To eliminate need estimate CSI, this paper, we propose label-assisted transmission framework, which two known labels are transmitted from before data transmission. By exploring received...

A low power 60-GHz on-off-keying (OOK) receiver has been implemented in a commercial 90 nm RF CMOS process. By employing novel on-chip antenna together with architecture optimization, the achieves sensitivity of -47 dBm at bit-error rate (BER) less than 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-3</sup> . Using transmitter transmit 1.5 dBm, transmission distance 5 cm can be achieved 1.2 Gbps data rate. In this design, minimizes...

In this work, we study the multiuser detection (MUD) problem for a grant-free massive-device multiple access (MaDMA) system, where large number of single-antenna user devices transmit sporadic data to multi-antenna base station (BS). Specifically, put forth two MUD schemes, termed random sparsity learning (RSL-MUD) and structured (SSL-MUD) time-slotted non-time-slotted MaDMA systems, respectively. RSL-MUD scheme, active users generate packets with sparsity. SSL-MUD introduce...

In practical massive MIMO systems, a substantial portion of system resources are consumed to acquire channel state information (CSI), leading drastically lower capacity compared with the ideal case, where perfect CSI is available. this paper, we show that overhead for acquisition can be largely compensated by potential gain due sparsity in certain transformed domain. To end, propose novel blind detection scheme simultaneously estimates and data factorizing received signal matrix. We...

This paper proposes a new full-duplex (FD) secrecy communication scheme for the unmanned aerial vehicle (UAV) and investigates its optimal design to achieve maximum energy efficiency (EE) of UAV. Specifically, UAV receives confidential information from ground source meanwhile sends jamming signals interfere with potential eavesdropper. As has limited on-board in practice, we aim maximize EE communication, by jointly optimizing trajectory source/UAV transmit/jamming powers over finite flight...

In this letter, the joint power control of D2D users and passive beamforming reconfigurable intelligent surfaces (RIS) for a RIS-aided device-to-device (D2D) communication network is investigated to maximize energy efficiency.This non-convex optimization problem divided into two subproblems, which are control.The subproblems optimized alternately.We first decouple at RIS based on Lagrangian dual transform.This solved by using fractional programming.Then we optimize Dinkelbach method.By...

For massive machine-type communications, centralized control may incur a prohibitively high overhead. Grant-free non-orthogonal multiple access (NOMA) provides possible solutions, yet poses new challenges for efficient receiver design. In this paper, we develop joint user identification, channel estimation, and signal detection (JUICESD) algorithm. We divide the scheme into two modules: slot-wise multi-user (SMD) combined estimation (CSCE). SMD is designed to decouple transmissions of...

Unmanned aerial vehicle (UAV) and reconfigurable intelligent surface (RIS) have been recently applied in the field of mobile edge computing (MEC) to improve data exchange environment by proactively changing wireless channels through maneuverable location deployment signals reflection, respectively. Nevertheless, they may suffer from inherent limitations, e.g., UAV's low endurance RIS's finite coverage, which limit their wider applications. UAV-mounted RIS (U-RIS), as a promising integrated...

Accurate channel estimation with small pilot overhead is vital to improve the capacity and reliability of massive MIMO systems. Recently, compressed sensing has been applied reduce in such systems by exploiting underlying structured sparsity. In this paper, we propose a turbo (Turbo-CS) framework for design analysis sparse algorithms. framework, Markov prior used model sparsity channels. Then extend Turbo-CS algorithm independent identically distributed priors solve resulting problem chain...

We investigate efficient communication over multiple-input multiple-output (MIMO) two-way relay channels (TWRCs), where two multi-antenna users exchange information via a relay. propose new MIMO physical-layer network coding (PNC) scheme that includes novel eigen-direction alignment (EDA) precoding. The proposed EDA precoding efficiently aligns the two-user's eigen-modes into same set of orthogonal directions, and multiple independent PNC streams are implemented aligned eigen-modes. derive...

Featured by centralized processing and cloud based infrastructure, Cloud Radio Access Network (C-RAN) is a promising solution to achieving an unprecedented system capacity in future wireless cellular networks. The huge gain mainly comes from the coordinated signal at server. However, full-scale coordination large-scale C-RAN requires of very large channel matrices, leading high computational complexity estimation overhead. To tackle this challenge, we establish unified theoretical framework...

This paper investigates the anti-jamming three-dimensional (3D) trajectory design to safeguard legitimate communications of unmanned aerial vehicle (UAV)-enabled wireless sensor networks (WSNs). Specifically, a UAV is dispatched collect data over multiple ground sensors (GSs) in presence malicious jammer. Under practical probabilistic line-of-sight (LoS) channel model, we aim maximize minimum (average) expected rate among GSs finite flight period, by jointly optimizing GS transmission...

By reconfiguring the propagation environment of electromagnetic waves artificially, reconfigurable intelligent surfaces (RISs) have been regarded as a promising and revolutionary hardware technology to improve energy spectrum efficiency wireless networks. In this paper, we study RIS aided multiuser multiple-input multiple-output (MIMO) power transfer (WPT) system, where transmitter is equipped with constant-envelope analog beamformer. First, maximize total received users by jointly...

In this paper, we consider a reconfigurable intelligent surface (RIS)-assisted two-way relay network, in which two users exchange information through the base station (BS) with help of an RIS. By jointly designing phase shifts at RIS and beamforming matrix BS, our objective is to maximize minimum signal-to-noise ratio (SNR) users, under transmit power constraint BS. We first single-antenna BS case, propose algorithms design amplification parameter, namely SNR-upper-bound-maximization (SUM)...