In the fifth generation (5G) of wireless communication systems, hitherto unprecedented requirements are expected to be satisfied. As one promising techniques addressing these challenges, non-orthogonal multiple access (NOMA) has been actively investigated in recent years. contrast family conventional orthogonal (OMA) schemes, key distinguishing feature NOMA is support a higher number users than resource slots with aid allocation. This may realized by sophisticated inter-user interference...

In fifth generation wireless networks, the escalating teletraffic and energy consumption has necessitated development of green communication techniques in order to further enhance both system's spectral efficiency efficiency. past few years, novel index modulation (IM) emerged as a promising technology that is widely employed communications. this paper, we present survey on IM provide readers with better understanding its principles, advantages, potential applications. We start comprehensive...

For uplink large-scale multiple-input-multiple-output (MIMO) systems, the minimum mean square error (MMSE) algorithm is near optimal but involves matrix inversion with high complexity. In this paper, we propose to exploit Gauss-Seidel (GS) method iteratively realize MMSE without complicated inversion. To further accelerate convergence rate and reduce complexity, a diagonal-approximate initial solution GS method, which much closer final than traditional zero-vector solution. We also an...

The low-resolution analog-to-digital convertor (ADC) is a promising solution to significantly reduce the power consumption of radio frequency circuits in massive multiple-input multiple-output (MIMO) systems. In this letter, we investigate uplink spectral efficiency (SE) MIMO systems with ADCs over Rician fading channels, where both perfect and imperfect channel state information are considered. By modeling quantization noise as an additive noise, derive tractable exact approximation...

Large-scale orthogonal frequency division multiplexing (OFDM) multiple-input multiple-output (MIMO) is a promising candidate to achieve the spectral efficiency up several tens of bps/Hz for future wireless communications. One key challenge realize practical large-scale OFDM MIMO systems high-dimensional channel estimation in mobile multipath channels. In this paper, we propose time-frequency training (TFT-OFDM) transmission scheme systems, where each TFT-OFDM symbol without cyclic prefix...

In the last two decades, digital television terrestrial broadcasting (DTTB) systems have been deployed worldwide. With approval of fourth DTTB standard called Digital Television/ Terrestrial Multimedia Broadcasting (DTMB) by International Telecommunications Union (ITU) in December 2011, research on first-generation standards is coming to an end. Recently, with rapid progress advanced signal processing technologies, nextgeneration like Video Broadcasting-Terrestrial-Second Generation (DVB-T2)...

The users at cell edge of a massive multiple-input-multiple-output (MIMO) system suffer from severe pilot contamination (PC), which leads to poor quality service (QoS). To enhance the QoS for these users, soft reuse (SPR) combined with multicell block diagonalization (MBD) precoding is proposed. Specifically, are divided into two groups according their large-scale fading coefficients, referred as center who only modest PC, and PC. Based on this distinction, SPR scheme proposed improving...

The mixed radio frequency (RF)/free-space optical (FSO) relaying is a promising technology for coverage improvement, while there lacks unified expressions to describe its performance. In this paper, performance analysis framework of dual-hop relay system over asymmetric RF/FSO links presented. More specifically, we consider the RF link follows generalized $\kappa$-$\mu$ or $\eta$-$\mu$ distributions, FSO experiences gamma-gamma distribution, respectively. Novel analytical probability density...

At the time of this writing, there is substantial research interest in subject visible light communications (VLC) owing to its ability offer significant traffic offloading potential highly crowded radio frequency (RF) scenarios. We introduce user-centric design VLC for heterogeneous networks (HetNet), where three key aspects are identified and elaborated on: signal coverage quality, system control, service provision aspects. More explicitly, concepts amorphous cell formation as well...

Reconfigurable intelligent surfaces (RISs), consisting of many low-cost elements that reflect the incident waves by an adjustable phase shift, have attracted sudden attention for their potential reconfiguring signal propagation environment and enhancing performance wireless networks. The passive nature RISs is indeed beneficial, but lack radio frequency (RF) chains at RIS has made channel estimation extremely challenging. We face this challenge proposing a joint transmit precoding framework...

Large‐scale multiple‐input multiple‐output (MIMO) with high spectrum and energy efficiency is a very promising key technology for future 5G wireless communications. For large‐scale MIMO systems, accurate channel state information (CSI) acquisition challenging problem, especially when each user has to distinguish estimate numerous channels coming from large number of transmit antennas in the downlink. Unlike conventional orthogonal pilots whose pilot overhead prohibitively increases antennas,...

Huge overhead of beam training imposes a significant challenge in millimeter-wave (mmWave) wireless communications. To address this issue, paper, we propose wide based approach to calibrate the narrow direction according channel power leakage. handle complex nonlinear properties leakage, deep learning is utilized predict optimal directly. Specifically, three assisted calibrated schemes are proposed. The first scheme adopts convolution neural network implement prediction on instantaneous...

Wideband extremely large-scale multiple-input-multiple-output (XL-MIMO) plays an important role in boosting the data rate for 6G networks. Because of huge bandwidth and large number antennas, wideband XL-MIMO introduces a significant near-field beam split effect, where beams at different frequencies are focused on locations. This effect results severe array gain loss, existing works mainly consider to compensate this loss by utilizing time-delay (TD) beamforming. paper demonstrates that...

Two key impediments to reconfigurable intelligent surface (RIS)-aided vehicular communications are, respectively, the double fading experienced by signal on RIS-aided cascaded links and high-mobility-induced intractability of acquiring channel state information (CSI). To overcome these challenges, a novel kind RIS is presented in this paper, namely active omni-surface (RIOS), each element which supported loads, that concurrently transmits reflects incident amplified rather than just...

Next-generation communication systems aim for providing pervasive services, including the high-mobility scenarios routinely encountered in mission-critical applications. Hence we harness recently-developed reconfigurable intelligent surfaces (RIS) to assist cell-edge users. However, face of high Doppler frequencies, existing RIS channel estimation techniques that assume block fading generally result irreducible error floors. In order mitigate this problem, propose a new technique, which is...

Leveraging the concept of electromagnetic signal and information theory, holographic multiple-input multiple-output (MIMO) technology opens door to an intelligent endogenously holography-capable wireless propagation environment, with their unparalleled capabilities for achieving high spectral energy efficiency. Less examined are important issues such as acquisition accurate channel by accounting MIMO's peculiarities. To fill this knowledge gap, paper investigates estimation MIMO systems...

For millimeter-wave (mmWave) massive multiple-input-multiple-output (MIMO) systems, codebook-based analog beamforming (including transmit precoding and receive combining) is usually used to compensate the severe attenuation of mmWave signals. However, conventional schemes involve complicated search among predefined codebooks find out optimal pair precoder combiner. To solve this problem, by exploring idea turbo equalizer together with tabu (TS) algorithm, we propose a Turbo-like scheme based...

As a complementary technology for conventional radio frequency communication, visible light communication (VLC) is potential form of the optical wireless which can provide both and illumination simultaneously. Since load balancing power control interference management are key challenges in network deployment, we consider joint user association allocation scheme cell-free VLC to improve system performance. It mathematically formulated as non-convex utility maximization problem consideration...

The convergence of radar sensing and communication applications in the millimeter-wave (mmWave) low terahertz (THz) bands has been envisioned as a promising technology, since it incorporates high-rate data transmission hundreds gigabits per second (Gbps) mm-level spectrum- cost-efficient manner, by sharing both frequency hardware resources. However, joint (JRC) system faces considerable challenges mmWave low-THz scale, due to peculiarities propagation channel radio-frequency (RF) front ends....

Since the optical wireless channel in visible light communication (VLC) systems is subject to non-negativity of signal and average power, classic Shannon capacity formula not applicable VLC systems. To derive a simple closed-form upper bound on capacity, sphere packing argument method has been applied previously. However, there an obvious gap between existing sphere-packing bounds lower at high signal-to-noise-ratios (OSNRs), which mainly caused by inaccurate mathematical approximation...

In visible light communication (VLC) systems, white emitting diodes (LEDs) are used as illumination sources and transmitters simultaneously. Compared to the phosphor-converted LEDs, multi-chip LEDs have higher modulation bandwidth. Consequently, based VLC systems great potential for high data rate transmission. Since each chip of can be modulated independently, parallel channels viable information this paper, in order maximize multi-user sum-rate multi-input single-output an electrical...

Beam tracking is an effective way to maintain high-quality links in mobile millimeter wave MIMO systems, which achieved by accurately estimating angle-of-departure (AoD) and angle-of-arrival (AoA) of the desired path. Considering slow variations angular velocity for time-varying AoD AoA, a second-order AoD/AoA variation model proposed extended Kalman filter (EKF) based beam tracking. By utilizing two well configured pairs, unknown path gain removed from EKF's measurement optimal estimation...

Vehicular ad-hoc network (VANET) is a promising technology to realize communications among vehicles in intelligent transportation systems. Conventional VANET utilizes radio frequency (RF) for vehicle communications. However, as the density increases, RF-based suffers from limited bandwidth and unavoidable interference. Visible light communication (VLC) emerging complement candidate, which possesses advantages of wide spectrum, high power efficiency low interference, but also has drawback...

UAVs are envisioned to be an important part of the device-centric IoT. These bespoke Unmanned Aircraft Systems (UASs) that support significantly differ from traditional terrestrial and aeronautical networks, both which evolving toward their next-generation forms. The major challenges UAS include augmented interference due strong LoS, dynamic shadowing effects owing 3-D aerial maneuvering, excessive Doppler shift high UAV mobility, SWAP constraints. Against this background, we propose invoke...

The radio frequency (RF) impairments of analog devices have been regarded as an important factor degrading the performance Terahertz (THz) communications, where in-phase/quadrature (IQ) imbalance and phase noise (PN) are two typical RF at THz transceiver. In this paper, we investigate channel estimation (CE) equalization for receiver in presence wideband IQ PN, single-carrier frequency-domain is used. Since PN inserted between impulse response (CIR) receiver, CIR cannot be treated together...