The Infona portal uses cookies, i.e. strings of text saved by a browser on the user's device. The portal can access those files and use them to remember the user's data, such as their chosen settings (screen view, interface language, etc.), or their login data. By using the Infona portal the user accepts automatic saving and using this information for portal operation purposes. More information on the subject can be found in the Privacy Policy and Terms of Service. By closing this window the user confirms that they have read the information on cookie usage, and they accept the privacy policy and the way cookies are used by the portal. You can change the cookie settings in your browser.
Our efforts are being made to realize a high speed and high frequency utilization efficiency millimeter-wave band backhaul system for the purpose of applying it to the 5th generation (5G) mobile networks. We propose a fixed wireless access (FWA) system of full duplex radio communication (called the Directional Division Duplex (DDD) system) capable of simultaneous bi-directional communication of the...
Massive Multiple-Input Multiple-Output (MIMO) antenna arrays are being studied for 5G due to their ability to focus energy towards desired receiver, reducing interference to other users, giving rise to higher spectral and energy efficiencies. Conventional analysis assumes that the large scale fading component of the channel model is constant across the entire Massive MIMO antenna array. However, when...
Directional antennas shape transmission patterns to provide greater coverage distance and reduced coverage angle. When used in an ad-hoc network, this reduces interference among transmitting nodes and thereby increases throughput. A problem that has not been addressed is how to compute individual beam patterns that maximize some measure of global network performance. Historically, the focus has been...
The paper investigates an array of two reconfigurable circularly-polarized antennas with omnidirectional radiation pattern. The results are based on a previously reported antenna, which offers a steerable dipole-like radiation pattern. Its capabilities allow reception of a signal from practically any direction with steering realized by rotation of the pattern around a single axis. In this paper we...
This work proposes a systematic algorithm to build up a spacing-constrained non-uniform linear array (NLA) configuration. Obtainable DoF due to the proposed algorithm can have much better performance than existing NLA configurations. By further applying spatial smoothing and array interpolation techniques, performance indices, such as number of incident signal (NIS) detection and direction of arrival...
This paper describes smart antenna array beamforming using hybrid Taguchi-Genetic evolution algorithm. The electromagnetic interference is reduced by controlling sidelobe levels and placing nulls in the undesired directions. Based on the concept of the orthogonal array, Taguchi method effectively reduces the number of tests required in an optimization process. This method effectively obtains the optimum...
This paper addresses the problem of initial synchronization of users in an indoor mm-Wave scenario. With the use of a massive number of antenna elements at access nodes, the resulting beams have narrow beam width. However, the transmission of individual narrow beams may cause poor coverage in some areas as the energy is concentrated over the direction of their main lobes. To cope with that, a beam...
Large in the number of transmit elements, multi-antenna arrays with per-element limitations are in the focus of the present work. In this context, physical layer multigroup multicasting under per-antenna power constrains, is investigated herein. To address this complex optimization problem low-complexity alternatives to semi-definite relaxation are proposed. The goal is to optimize the per-antenna...
How would a cellular network designed for high energy efficiency look like? To answer this fundamental question, we model cellular networks using stochastic geometry and optimize the energy efficiency with respect to the density of base stations, the number of antennas and users per cell, the transmit power levels, and the pilot reuse. The highest efficiency is neither achieved by a pure small-cell...
Increasing the spectral efficiency was always the motivation behind the evolution of wireless communication systems. Also, due to the widespread usage of wireless systems, securing the transmitted data rises as a main concern nowadays. Hereby, we introduce a scheme that increases the capacity of wireless systems by transmitting multiple independent data streams, while using the space domain as a source...
A modification to the well-known Applebaum adaptive beamformer is proposed employing a low complexity space-time network-resonant IIR beamfiler. The network-resonant filter is a multiple input multiple output (MIMO) linear multidimensional recursive discrete system. It is applied as a pre-filter to an Applebaum adaptive beamformer in order to perform highly directional receive mode beamforming with...
This study describes a high throughput constant envelope (CE) pre-coder for Massive MIMO systems. A large number of antennas (M), in the order of 100s, serve a relatively small number of users (K) simultaneously. The stringent amplitude constraint (only phase changes) in the CE scheme is motivated by the use of highly power-efficient non-linear RF power amplifiers. We propose a scheme that computes...
The problem of estimating the time-of-arrival (TOA) of a known signal in the presence of interferences and multipath propagation is addressed. This problem, is essential in high precision receivers of the Global Navigation Satellite Systems. This paper presents the maximum likelihood TOA estimator when an antenna array is used in the receiver. The desired signal impinges the array with a known direction-of-arrival...
By using multiple receiving antennas and modeling co-channel interference (CCI) together with the noise as additive temporally white Gaussian noise with some spatial color, CCI may be suppressed. This paper proposes spatio-temporal interference rejection combining by modeling the CCI and noise as an autoregressive Gaussian process. In this way, the joint spatial-temporal properties of the CCI may...
Full duplex (FD) communications have been brought into the center of the research activity as an effective way to increase spectral efficiency. This study introduces a novel antenna cancellation technique with the use of a parasitic antenna array at the FD transceiver. Elaborate Multiple-Input-Multiple-Output (MIMO) techniques that use parasitic arrays, such as Beamspace MIMO, have been recently proposed...
This paper analyzes the performance of a large-scale multiuser multiple-input multiple-output (MU-MIMO) system with amplify-and-forward (AF) relaying in the presence of co-channel interference. Each user terminal (UT) has a single antenna while the relay is equipped with very large antenna arrays. To evaluate the impact of large number of relay antennas on the performance of the considered system,...
When antenna arrays are introduced in a cellular system, one critical aspect is the design of beamformers for downlink transmission. We extend a recently proposed strategy for optimal downlink beamforming to give increased robustness to channel uncertainties and to incorporate constraints on the dynamic range. The solution can be efficiently calculated using semidefinite optimization. In a few cases,...
In this paper, practical CSI acquisition methods for massive MIMO systems are investigated. The implementation issues of channel reciprocity based feedback in TDD are discussed, and a two-dimension feedback mechanism for FDD is proposed where the horizontal and vertical domain channels are reported separately. System level evaluation results demonstrate that massive MIMO with the two-dimensional feedback...
This work exploits the benefits of adaptive downtilt and vertical sectorization schemes for Long Term Evolution Advanced (LTE-A) networks equipped with active antenna systems (AAS). We highlight how the additional control in the elevation domain (via AAS) enables use of adaptive downtilt and vertical sectorization techniques, thereby improving system spectrum efficiency. Our results, based on a full...
When a signal is subject to interference from co-channel users, a multiple element antenna array is used and sensors outputs are combined, the so-called beamforming, in such a way to achieve an optimal Signal-to-Noise-and-Interference-Ratio (SINR). The achieved SINR, however, is not necessarily high. This depends on the interfering scenario, namely, positions and powers of the interfering sources...
Set the date range to filter the displayed results. You can set a starting date, ending date or both. You can enter the dates manually or choose them from the calendar.