Jianhua Zhang

Beijing University of Posts and Telecommunications | BUPT · Department of Communication Engineering

Holographic Multiple-Input and Multiple-Output (MIMO) is envisioned as a promising technology to realize unprecedented spectral efficiency by integrating a large number of antennas into a compact space. Most research on holographic MIMO is based on isotropic scattering environments, and the antenna gain is assumed to be unlimited by deployment spac...

Technology research and standardization work of sixth generation (6G) has been carried out worldwide. Channel research is the prerequisite of 6G technology evaluation and optimization. This paper presents a survey and tutorial on channel measurement, modeling, and simulation for 6G. We first highlight the challenges of channel for 6G systems, inclu...

Terahertz (THz) communication is envisioned as the possible technology for the sixth-generation (6G) communication system. THz channel propagation characteristics are the basis of designing and evaluating for THz communication system. In this paper, THz channel measurements at 100 GHz and 132 GHz are conducted in an indoor office scenario and an ur...

We consider an intelligent reflecting surface (IRS)-aided wireless-powered non-orthogonal multiple access (NOMA) network, in which double IRSs are adopted to boost the communication between the transmitter and receiver. We split the overall process into two phases: i) downlink wireless energy transmission (WET) in the first phase and ii) uplink wir...

To reduce the downlink beam sweep overhead of mmWave systems, we propose a deep reinforcement learning based dynamic beam selection (DRL-DBS) method. A new learning motivation is presented by analyzing the dynamic change laws of high- and low-frequency channels in the spatial domain: to learn the index offset between the optimal beam of mmWave and...

Joint communication and sensing (JCAS) has been recognized as a promising technology in the sixth generation (6G) communication. A realistic channel model is a prerequisite for designing JCAS systems. Most existing channel models independently generate the communication and sensing channels under the same framework. However, due to the multiplexing...

Massive MIMO is envisioned as a promising technology in 5G and beyond 5G communication. Channel models are of great importance for the development and performance assessment of massive MIMO systems. Since massive MIMO systems are equipped with large-aperture antenna arrays, antenna elements at different spatial positions would observe different cha...

Recently, whether the channel prediction can be achieved in diverse communication scenarios by directly utilizing the environment information gained lots of attention due to the environment impacting the propagation characteristics of the wireless channel. This paper presents an environment information-based channel prediction (EICP) method for con...

To meet the demands for spectral efficiency (SE) and massive connectivity for the future wireless networks, we propose an unmanned aerial vehicle (UAV)-enabled massive multiple-input multiple-out (MIMO) non-orthogonal multiple access (NOMA) two-way relay (TWR) system, where multiple pairs of ground users (GUs) aim to exchange their information via...

Conventionally statistical path loss models are high-dimensional data-based without utilizing specific environment features. In this letter, a novel environment features-based model (EFBM) for path loss prediction is presented. We connect the propagation environment and channel by representing the environment with low-dimensional features: distance...

Visual information, captured for example by cameras, can effectively reflect the sizes and locations of the environmental scattering objects, and thereby can be used to infer communications parameters like propagation directions, receiver powers, as well as the blockage status. In this paper, we propose a novel beam alignment framework that leverag...

Terahertz (THz) channel propagation characteristics are vital for the design, evaluation, and optimization for THz communication systems. Moreover, reflection plays a significant role in channel propagation. In this letter, the reflection coefficient of the THz channel is researched based on extensive measurement campaigns. Firstly, we set up the T...

In this paper, a time-varying channel prediction method based on conditional generative adversarial network (CPcGAN) is proposed for time division duplexing/frequency division duplexing (TDD/FDD) systems. CPcGAN utilizes a discriminator to calculate the divergence between the predicted downlink channel state information (CSI) and the real sample di...

In order to support the future digital society, sixth generation (6G) network faces the challenge to work efficiently and flexibly in a wider range of scenarios. The traditional way of system design is to sequentially get the electromagnetic wave propagation model of typical scenarios firstly and then do the network design by simulation offline, wh...

Blockage prediction is significant to support mobility for millimeter wave (mmWave) communications, while the prediction range is limited to centimeters in current work. This letter proposes a long-range blockage prediction scheme leveraging the frequency-dependent diffraction fringe characteristics. Firstly, Fresnel-Kirchhoff diffraction is introd...

In this paper, a time-varying channel prediction method based on conditional generative adversarial network (CPcGAN) is proposed for time division duplexing/frequency division duplexing (TDD/FDD) systems. CPcGAN utilizes a discriminator to calculate the divergence between the predicted downlink channel state information (CSI) and the real sample di...

With the research of the upcoming sixth generation (6G) systems, new technologies will require wider bandwidth, larger scale antenna arrays and more diverse wireless communication scenarios on the future channel modeling. Considering channel model is prerequisite for system design and performance evaluation of 6G technologies, we face a challenging...

We consider an intelligent reflecting surface (IRS)-aided wireless powered non-orthogonal multiple access (NOMA) network, in which double IRSs are adopted to boost the communication between transmitter and receiver. We split the overall process into two phases: downlink wireless energy transmission (WET) in the first phase, and followed by the upli...

Millimeter-wave (mmWave) communications and visible light communications (VLC) are proposed to form hybrid mmWave/VLC systems. Furthermore, channel modeling is the foundation of system design and optimization. In this paper, we compare the propagation characteristics, including path loss, root mean square (RMS) delay spread (DS), K-factor, and clus...

Reconfigurable intelligent surface (RIS) is an electromagnetic surface, and has abundant low-power reflecting elements which can dynamically tune the wireless propagation environment by changing their phase shifts. Non-orthogonal multiple access (NOMA) technology would be capable of greatly improving the spectral efficiency of communication via dif...

Sixth Generation (6G) wireless communication network has been expected to provide global coverage, enhanced spectral efficiency, and AI(Artificial Intelligence)-native intelligence, etc. To meet these requirements, the computational concept of Decision-Making of cognition intelligence, its implementation framework adapting to foreseen innovations o...

With the large-scale commercialization of 5th generation (5G) network globally, 5G together with artificial intelligence (AI), cloud and big data is accelerating the digitalization of the world, which push the society move towards a "digital twin" world composed of the physical world and its digital mirror. The digital twin world will enable us to...

Intelligent reflecting surface (IRS) is an electromagnetic surface, and has abundant low-power reflecting elements which can dynamically tune the wireless propagation environment by changing their phase shifts. Non-orthogonal multiple access (NOMA) technology would be capable of greatly improving the spectral efficiency of communication via differe...

The upcoming sixth generation (6G) wireless communication networks will face the great challenges of extremely low power demand, high transmission reliability and massive connectivities. To meet these requirements, we propose a novel non-orthogonal multiple access (NOMA) assisted two-way ambient backscatter communication (TW-AmBC) system. Specifica...

We consider an intelligent reflecting surface (IRS) wireless-powered NOMA internet-of-things (IoT) network, where multiple NOMA IoT devices can communicate with access point (AP) with the aid of IRS. Specifically, IoT devices can harvest energy from a nearby appropriative power station (PS) during the wireless energy transfer (WET) phase through th...

Visual information, captured for example by cameras, can effectively reflect the sizes and locations of the environmental scattering objects, and thereby can be used to infer communications parameters like propagation directions, receiver powers, as well as the blockage status. In this paper, we propose a novel beam alignment framework that leverag...

Channel covariance matrix (CCM) is one critical parameter for designing the communications systems. In this paper, a novel framework of the deep learning (DL) based CCM estimation is proposed that exploits the perception of the transmission environment without any channel sample or the pilot signals. Specifically, as CCM is affected by the user’s m...

The tripolarized MIMO system can provide one more degree of freedom and have a more compacted size over a dual-polarized MIMO system, which is attractive for high-capacity wireless communication systems. In this paper, we analyze and model channel properties for tripolarized MIMO systems based on experimental channel measurements in typical indoor...

Terahertz (THz) communication has been envisioned as a key enabling technology for sixth-generation (6G). In this paper, we present an extensive THz channel measurement campaign for 6G wireless communications from 220 GHz to 330 GHz. Furthermore, the path loss is analyzed and modeled by using two single-frequency path loss models and a multiple-fre...

This paper presents an empirical study of the uplink and downlink azimuth angle of arrival (AoA) in an urban micro (UMi) scenario at 28 GHz. At present, most UMi measurements are conducted in the downlink and then the uplink situation is inferred assuming channel reciprocity. Although the channel correlation coefficient of the uplink and downlink c...

Channel covariance matrix (CCM) is one critical parameter for designing the communications systems. In this paper, a novel framework of the deep learning (DL) based CCM estimation is proposed that exploits the perception of the transmission environment without any channel sample or the pilot signals. Specifically, as CCM is affected by the user's m...

Industrial internet of things (IIoT) is an emerging area that fifth-generation (5G) mobile communication system penetrates industrial manufacturing applications. The indoor factory has larger space and there are a lot of metal machine tools distributed in it, which makes its radio propagation characteristics and corresponding channel models signifi...

By reviewing the evolution law and ubiquity of mobile communication, this review investigates Sixth Generation (6G) Mobile Communication System. To support the new object, "genie" which represents knowledge and consciousness, a Ubiquitous-X network is proposed. The proposed network is a 6G information exchange hub network that enables cooperation a...

With the commercialization of fifth generation networks worldwide, research into sixth generation (6G) networks has been launched to meet the demands for high data rates and low latency for future services. A wireless propagation channel is the transmission medium to transfer information between the transmitter and the receiver. Moreover, channel p...

The bands 3.5 and 28 GHz are both very important for the fifth-generation (5G) wireless communication system. To model their propagation characteristics and study their channel properties, we conduct measurements at these two frequencies in indoor and outdoor scenarios. The measured bandwidths at 3.5 and 28 GHz are 100 and 400 MHz, respectively. To...

In this paper, the Gaussian mixture model (GMM) is introduced to the channel multipath clustering. In the GMM field, the expectation-maximization (EM) algorithm is usually utilized to estimate the model parameters. However, the EM widely converges into local optimization. To address this issue, a hybrid differential evolution (DE) and EM (DE-EM) al...

Wireless channel models are the prerequisites of the development of any communication system. They are indispensable and widely used in many aspects, such as radio technique research, equipment development, communication system design, performance evaluation, and network optimization. With the approach of commercial deployment of the fifth‐generati...

This paper investigates the physical layer security issue in unmanned aerial vehicle (UAV) communication networks. Specifically, two UAVs transmit confidential messages to their specified ground destinations by sharing the same spectrum, while a ground eavesdropper attempts to wiretap the confidential messages. In the considered scenario, although...

Accurate channel state information (CSI) is important for the coherent detection of multiple-input-multiple-output (MIMO) system. Especially in a high-speed scenario, fast time-varying CSI gotten by the conventional channel estimation schemes tend to be out of date, thus tracking and predicting CSI are more attractive and indispensable. Motivated b...

Three dimensional (3D) Multiple Input and Multiple Output (MIMO) is one of the most promising techniques for the 5th generation (5G) mobile communication system. To support its research, the property of elevation angle in 3D channel model should be accurately modeled. Conventionally, 3D channel is modeled with an assumption that the mean elevation...

Traditional link prediction indices focus on the degree of the common neighbor and consider that the common neighbor with large degree contributes less to the similarity of two unconnected endpoints. Therefore, some of the local information-based methods only restrain the common neighbor with large degree for avoiding the influence dissipation. We...

The broadcast nature of air-to-ground line-of-sight (LoS) wireless channel imposes a great challenge in secure unmanned aerial vehicle (UAV) communications. To address this issue, this paper investigates UAV-ground communications from the physical layer security perspective. Specifically, the investigated scenario includes a UAV serving as the base...

Cluster-based channel model is the main stream of fifth generation mobile communications, thus the accuracy of clustering algorithm is important. Traditional Gaussian mixture model (GMM) does not consider the power information which is important for the channel multipath clustering. In this paper, a normalized power weighted GMM (PGMM) is introduce...

Based on outdoor microcellular measurements at 26 and 32 GHz, the path loss models are modified by a proposed dynamic rain model to see the difference of the path loss models between clear and rainy air with respect to rainfall intensities and transceiver distances. Moreover, a dynamic rain cell model for a multiuser system is developed to investig...

In this letter, a novel angular sampling method–random offset sampling (ROS) is proposed for the simulation of ray-based physical reference channel models. This new method employs an asymmetrical random angular offset to the equal power sampling method, which makes the simulated channel match the spatial-temporal characteristics of the reference ch...