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The following paper discusses a conducted synthesis and assessment of the effectiveness of control algorithms for null formation in the radiation pattern of a flat phased antenna array according to two coordinates; the procedure is performed by adjusting the amplitude distribution in rows and columns.
The performance of millimeter wave (mmWave) networks is limited by severe blocking effects. Mobile relaying exploiting possible two-hop line-of-sight connections is a strong candidate for coverage extension and consistent user experience in mmWave networks. Here, relaying based on opportunistic analog beamforming is investigated, and sets of fixed beams are used for cell discovery, relay discovery...
Multicasting has become a particularly important technique in the context of cache-enabled cloud radio access networks proposed for 5G systems, where it can be used to transmit common information to multiple users to improve both spectral and energy efficiency. For the efficient spectrum utilization, the future communications are based on aggressive frequency reuse, where the required data rates can...
In this paper we consider a centralized radio access network (C-RAN) architecture with a fully analog fronthaul link between remote antenna units (RAUs) and baseband units (BBUs) based on the radio over fiber (RoF) paradigm. Beamforming to separate uplink signals received from a pool of users is splitted between RAU and BBU. Optical beamforming is performed at the RAU site with the aim of reducing...
Interference management (IM) is essential to wireless communication networks, but interference suppression, a key component of IM, is known to degrade users' achievable spectral efficiency (SE). It is thus important to select an appropriate IM method with optimal operating parameters according to diverse network deployments, transmit power differences of various communication equipments, and dynamically...
Multi-User Multiple Input Multiple Output (MU-MIMO) enables a multi-antenna access point (AP) to serve multiple users simultaneously, and has been adopted as the IEEE 802.11ac standard. While several PHY-MAC designs have recently been proposed to improve the throughput performance of a MU-MIMO WLAN, they, however, usually assume that all the concurrent streams are of roughly equal length. In reality,...
Large-scale MU-MIMO is a promising technology to scale network capacity and the capacity gain grows linearly with the numbers of antennas and users in theory. However, its practical deployment faces three critical challenges in the state-of-the-art WLANs: i) the demand of a large number of expensive RF chains; ii) the linear growth of feedback overheads with the number of antennas; iii) the lack of...
In this paper we formulate a general link packing problem for mmWave networks. Each link is a 4-tuple determined by the choice of receiving user, transmitting access point, transmit beamforming vector and receive beamforming vector. The problem seeks to optimize the weighted sum over active links, where each link is allowed to have any arbitrarily chosen weight or priority and an active link must...
In this paper, the application of non-orthogonal multiple access (NOMA) to millimeter-wave (mmWave) communications is considered, where random beamforming is used in order to reduce the system overhead. Stochastic geometry is used to characterize the performance of the proposed mmWave-NOMA transmission scheme, by using the key features of mmWave systems, e.g., mmWave transmission is highly directional...
This paper investigates how to achieve secure information transmission in multi-cell multi-user networks, where artificial noise (AN) aided multi-cell coordinated beamforming (MCBF) is designed to guarantee the authorized users' QoS requirements while avoiding the information being intercepted by unauthorized users. To realize the green communication target, we formulate an optimization problem to...
The Interfering Broadcast Channel (IBC) applies to the downlink of (cellular and/or heterogeneous) multi-cell networks, which are limited by multi-user (MU) interference. The interference alignment (IA) concept has shown that interference does not need to be inevitable. In particular spatial IA in the MIMO IBC allows for low latency transmission. However, IA requires perfect and typically global Channel...
Non-Orthogonal Multiple Access (NOMA) is a key multiple access technique for 5th generation (5G) mobile communication systems. In this paper, we propose a capacity-based user selection (NOMA-CUS) algorithm for multiuser multiple input single output (MISO) downlink NOMA system with zero-forcing beamforming. NOMA-CUS algorithm improves the sum rate of the NOMA system by selecting the users in each cluster...
This paper studies user-centric cluster scheme in cloud radio access network (Cloud-RAN), where distributed Radio Remote Heads (RRHs) are connected to a centralized Based Band Units (BBUs) pool and all baseband processing is performed via high-bandwidth low-latency backhaul network. In user-centric cluster scheme, BBU schedules multiple RRHs for each user to form the serving cluster, and then BBU...
Wireless backhauling is a promising technology for Ultra-Dense Networks (UDN). Resource management for access and backhaul is a key issue. Different from conventional resource allocation approaches, we partition radio resources for access and backhaul, taking into account the impacts of cooperative transmission modes. This problem is formulated to maximize the area throughput of UDN to obtain the...
Prior results on performance analysis for cognitive relay networks mainly involve perfect channel state information (CSI), which is not readily available. Thus, the effects of outdated CSI on the performance of a multi-antenna multi-relay cognitive radio system are investigated in this work. To exploit the benefits of multiple antennas, collaborative zero-forcing beamforming at the secondary source...
Multi-group multicast beamforming in wireless systems with large antenna arrays and massive audience is investigated in this paper. Multicast beamforming design is a well-known non-convex quadratically constrained quadratic programming (QCQP) problem. A recent attempt is to apply convex-concave procedure (CCP) to find a stationary solution, whose complexity, however, increases dramatically as the...
In this paper, we study the robust design of downlink multicast Cloud Radio Access Network (C-RAN), equipped with wireless backhaul. Due to feedback delays, channel estimation or quantization errors, etc., only impaired Channel State Information (CSI) might be available at the Central Processor (CP). In order to achieve a power-efficient system, we aim to minimize the network power cost while guarantee...
This work deals with beamforming for the MaMISO Interfering Broadcast Channel (IBC), i.e. the Massive Multi-Input Single-Output (MaMISO) Multi-User Multi-Cell downlink (DL). The novel beamformers are here optimized for the Expected Weighted Sum Rate (EWSR) for the case of Partial Channel State Information at the Transmitters (CSIT). Gaussian partial CSIT can optimally combine channel estimate and...
This paper proposes an approach for receiving small uplink data transmissions from a massive amount of machine type communication (MTC) devices in ultra-dense networks (UDNs). In particular, we propose using a beamforming based solution for distributing (broadcasting) uplink grants for small data transmissions. Receive beamforming is also employed in order to receive the subsequent uplink small data...
This paper considers the downlink transmission of cloud-radio access networks with limited fronthaul capacity constraint. Unlike the existing approaches where power of fronthaul is a quadratic or linear function of respective variables, we consider a more practical model where the power consumed by fronthaul depends on the rate served by the corresponding remote radio head (RRH). Then, we formulate...
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