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This paper considers a frequency-division-duplexing (FDD) massive multiple-input multiple-output (MIMO) system that operates with two-stage beamforming based on user grouping. In this system, we propose a first stage beamformer and a user grouping method for the two-stage beamforming. The proposed first stage beamformer maximizes an approximate sum rate calculated from the second-order statistic of...
Interference alignment (IA) is a prospective method to manage interference between users in multi-user networks. On the other hand, jamming can be an effective way to combat adversarial eavesdropping for legitimate networks. In this paper, a beneficial jamming scheme is proposed for interference alignment networks. In the scheme, the jammer utilizes its precoding vector to constrain the jamming signal...
Hybrid precoding provides a compromise between the system performance and the implementation complexity in millimeter wave (mmWave) systems, while cloud radio access network (C-RAN) is a green network composed of central baseband unit (BBU), distributed low-cost remote radio heads (RRHs) and low-latency fronthaul links connecting BBU and RRHs. This paper jointly optimizes the user scheduling and hybrid...
Due to the openness of the physical layer, the physical layer security has been widely discussed. It is considered as an effective way to improve the secrecy rate that we add artificial noise to D2D communications underlaying cellular networks. Compared to previous studies, in this paper we not only think of the situation where artificial noise is added to the original communication signal between...
In this paper, we propose hybrid beamforming scheme for multi-user transmission in millimeter wave (mmWave) communications. The sum rate maximization problem considering limited feedback is formulated and solved by the joint scheduling and hybrid beamforming algorithm with two-stage channel state information (CSI) feedback framework. In the proposed scheme, the base station (BS) first narrows down...
In order to satisfy rate requirement in the enhanced mobile broadband (eMBB) application group, wireless technologies as Air Interfaces (AI) are widely studied, including non-orthogonal multiple access (NOMA) and massive multiple-input multiple-output (mMIMO). In this paper, we propose a Minorization-Maximization (MM) based hybrid precoding scheme in NOMA-mMIMO system. Firstly, we introduce a user...
This paper considers the use of massive multiple input, multiple output (MIMO) combined with single-carrier with frequency-domain equalization (SC-FDE) modulations using a precoding approach. Although millimeter wave (mm-Wave) communications are expected to be a key part of 5G, these frequencies present considerable challenges due to high propagation free-space path losses and implementation difficulties...
In this work, we present the design of a novel large load-controlled multiple-active multiple-passive (LC-MAMP) antenna array that operates at 19.25 GHz. In addition, we describe a method that enables us to perform robust, low-complexity, arbitrary channel-dependent precoding with such arrays as well as a communication protocol that limits the computational complexity associated with beam tracking...
This paper investigates scheduling and precoding techniques via hybrid analog-digital transmitters in mm-wave frequency bands. As in spectrum sharing sub-6GHz scenarios, the presence of non-intended receivers limits the overall achievable rates. In order to circumvent this problem, we propose a scheduling and precoding algorithm able to maximize the sum-rate while keeping the interference to the external...
Mobile traffic in cellular based networks is increasing exponentially, mainly due to the use of data intensive services like video. Network operators are urged to explore new technologies in order to enhance the capacity, data rates and maximizing the utilization of available spectrum resources. One effective way to cope with these demands is to reduce the cell-size by deploying small-cells along...
The emerging 5G mobile communication standard aims to increase the throughput and, in the same time, to considerably increase the number of users serviced concurrently (Internet of Things). The key direction for achieving these requirements is to heavily extend the use of the spatial degrees of freedom, especially in the multi-user scenarios. Multi-User Massive MIMO (MU-MIMO) is one of the key technologies...
5G network is visualized to simplify the burden on current cellular infrastructure by offering significantly higher data rates through increased channel bandwidth. 5G communication system is expected toexploit spectrum band at millimeter wave (mmWave)frequencies. But the mobile communication at these mmWave spectrum band is far more complex than the current frequencies that are being used around the...
In this work, a novel symbol-level precoding scheme is proposed, for managing the multi-user interference in the forward downlink channel of a multi-beam satellite system. Besides exploiting the constructive interference effect, the proposed scheme aims at improving the robustness of the transmitted signals to the non-linear distortions of practical satellite systems. This is done by reducing the...
In a conventional cellular wireless networks, single cell processing (SCP) is usually considered where inter-cell interference is treated as noise. As we know, interference can cause severe information leakage for secret communication, the paper studies the secrecy performance with coordination beamforming (CBf) scheme in the downlink of a two-cell multi-user MIMO (MU-MIMO) cellular network. For CBf,...
Sparse code multiple access system with multiple antennas offers unprecedented massive connectivity and capacity. To reduce the interference in a downlink multiple user SCMA (MU-SCMA) system, we propose a layer-aware interference mitigation scheme (L-AIMS). Firstly, preprocess the codewords of paired users to mitigate the intra-layer interference. Secondly, adopt the generalized singular value decomposition...
Polarization division multiple access (PDMA) is a method to simultaneously transmit two independent signals by using vertical and horizontal polarization in the same frequency band. In PDMA systems, the received signal can experience significant interference from cross-polarized signals if the transmit and receive antennas are misaligned in terms of polarization state. In this paper, a precoding technique...
This paper studies confidential message transmission in a relay aided IoT system in the presence of cellular interference. Here the IoT devices share the same spectrum resources as the cellular users (CU) and an eavesdropper attempts to extract the confidential messages from these devices. For this system, the expressions for the mean square errors (MSE) at the legitimate and eavesdropping users have...
Regular zero-forcing (RZF) precoding algorithm is well- known as its low complexity and high performance in massive MIMO systems. However, when the number of transmitting antennas increases, the matrix inversion in RZF leads to high algorithmic complexity. In this paper, we propose an improved Newton iteration to estimate the matrix inversion in RZF precoding. Compared with the traditional Newton...
Interference alignment (IA) networks seem secure, due to the fact that signals from the legitimate network may act as interference to disrupt the external eavesdropping. However, when some users inside the network are cooperating to eavesdrop one certain user, it will not be secure any longer. Thus, we concentrate on the eavesdropping attacks in this paper, and propose a novel collusive eavesdropping...
Capacity-coverage tradeoff balancing is a classical but critical problem for practical wireless multi- cell network optimization. Increasing the average capacity is often at the expense of decreasing the cell coverage and vice versa. It becomes more complex in massive multiple-input/multiple-output (MIMO) networks to balance the above two performance indicators since capacity is much highly improved...
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