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High mobility may destroy the orthogonality of subcarriers in OFDM systems, resulting in inter-carrier interference (ICI), which may greatly reduce the service quantity of high speed railway (HSR) wireless communications. This paper focuses on ICI mitigation in the HSR downlinks with distributed transmit antennas. In such a system, its key feature is that the ICIs are caused by multiple carrier frequency...
A minimum dispersion based beamformer is developed for multiple-input multiple-output (MIMO) radar. In statistics, dispersion is defined as the expectation of the pth power of the modulus of a random variable, which can be considered as a generalization of variance with p = 2. By noticing that the linear combination of the transmitted waveforms at the target location exhibits non-Gaussian property,...
The synthesis method of a beam pattern with nulls in specified directions is presented. A solution of the system of equations is used in the synthesis of the beam pattern. The expression for calculating of the beamformer complex weights is derived.
We propose a pilot decontamination method for noncooperative cellular massive MIMO systems using pilot and data alignment in the time-frequency plane. In this method, pilot and data channels are assigned such that the terminals in any two adjacent cells operate over non-overlapping pilot channels but the terminals may share data channels. The former condition is imposed to circumvent pilot contamination...
Direction-Of-Arrival (DOA) estimation is one of the most important field in array signal processing. This paper presents a compact Reactance based Uniform Circular Array (RB-UCA) antenna system and a technique to steer nulls using optimized reactances as well as to estimate DOAs. A comparison between optimized and random reactances is presented by finding the array pattern when two interfering signals...
Abstract-In November 2015 the latest world radio conference took place and as a result the below 6 GHz RF bands have become more important for 5G in the foreseeable future. In the 5GPPP project Fantastic5G options for higher spectral efficiency based on massive MIMO, joint transmission cooperative multi point and interference mitigation are being investigated. Most of these concepts have been already...
As microwave spectrum becomes increasingly scarce, millimeter wave communication has gained wide attention for its sufficient bandwidth, which is also considered as one of the key technologies in the Fifth Generation (5G) communication networks. Different from microwave, millimeter communication is easy to suffer from the blockages. In order to take advantage of the wide spectrum and avoid the big...
We consider Hybrid Automatic Repeat \& reQuest with Chase-combining (HARQ-CC) for uplink spectral efficiency enhancement in a multicell system with base- stations (BSs) using large antenna arrays. Each BS uses a zero-forcing receiver and knows only the channel gains of users in its own cell. We first derive the outage probability and long-term average transmission rate (LATR) of the proposed HARQ-CC...
GPS receiver operation can be interrupted by intentional/unintentional jammers even with low power levels. As the jammers become more abundant, protection of critical systems gains importance. In this work, it is aimed to suppress the GPS L1 band jammers using spatial filtering with antenna arrays. After experimental studies, it is achieved to suppress the jammers and to recover the GPS operation...
Calculation of profiled optical element is described in the paper. This element is a part of fiber optic device intended to be used in Radio-over-Fiber systems. Calculation is based on Manakov equation system for forward and backward inter-group interference rays. Numerical integration of second order wave equation is used only for 50 microns element length. For 200 microns element length this calculation...
In this paper, we study the downlink performance of two important 5G network architectures, i.e. massive multiple-input multiple-output (M-MIMO) and small-cell densification. We propose a comparative modeling for the two systems, where the user and antenna/base station (BS) locations are distributed according to Poisson point processes (PPPs). We then study the SIR distribution and the outage rate...
A general framework for the analysis of expected per-user signal-to-interference-plus-noise-ratio (SINR) of a multiuser multiple-input-multiple-output system is presented. Our analysis assumes spatially correlated Rayleigh fading channels with regularized zero-forcing precoding on the downlink. Unlike previous works, our analytical expressions are averaged over the eigenvalue densities of the complex...
In this paper, CoMP (Coordinated Multi-Point Transmission and Reception) technique is studied to mitigate interference effects in cellular networks in which distributed antenna systems (DAS) are utilized. Power control and resource allocation problem is jointly optimized in a multi-user, multi-carrier downlink scenario where backhaul between base station and remote radio heads (antenna) are assumed...
Massive multiple input multiple output (MIMO) enables the improvement on the transmission rate without increasing the burden on the signal processing by employing a large number of antennas at a base station. It was reported an effect of applying a massive MIMO to small cell at the 2-GHz band. However, main target of the massive MIMO will be the small cells at the high-frequency band, because the...
Indoor localization has been actively researched in recent years due to the increasing demand for location-awareness services. However, to balance localization accuracy and system cost is always a challenge for indoor localization systems. Radio frequency identification (RFID) is a promising technology to achieve both goals, because of its reasonable cost and reliability. In this paper, we propose...
Improving antenna arrays characteristics such as power consumption, cost and complexity has gained wide attention in the context of cognitive radio networks. One antenna array configuration that offers great potential is the electronically-steerable parasitic array radiator (ESPAR) antenna. In this paper, we propose a transmitter patch ESPAR antenna system for underlay spectrum sharing in cognitive...
Millimeter wave (mmWave) communications has been considered as a promising technology for 5G cellular networks. Exploiting directional beamforming using antenna arrays to combat path loss is one of the defining features in mmWave cellular networks. However, previous works on mmWave network analysis usually adopt simplified antenna patterns for tractability. In this paper, we show that there are huge...
A concept of full-dimension MIMO (FD-MIMO) adopting 2-dimensional (2D) antenna array has been proposed with intent to cope with practical challenges of massive MIMO systems. In this paper, we investigate an FD-MIMO operation that can be transparently applied with current 3GPP LTE specifications, and propose a novel method that facilitates an accurate estimation of channel quality indicator (CQI) at...
This paper provides performance analysis of multiuser multiple input multiple output (MIMO) downlink system based on zero forcing (ZF) assuming communication with moving targets. Under different conditions of antenna number, Doppler frequency, and channel estimation interval, performance of several simple methods which attempt to extend the ZF area based on channel prediction using linear extrapolation...
This paper present further validations of a Method of Moment (MoM) based technique dedicated to fast simulation of SKA-low arrays. In particular, the embedded element patterns and array patterns are studied. The patterns obtained using this technique are compared with those using the commercial software CST. The comparison shows the importance of the mutual coupling in modeling these patterns. Further...
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