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Massive MIMO systems, where base stations are equipped with hundreds of antennas, are an attractive way to handle the rapid growth of data traffic. As the number of users increases, the initial access and handover in contemporary networks will be flooded by user collisions. In this work, we propose a random access procedure that resolves collisions and also performs timing, channel, and power estimation...
New waveform candidates are being investigated for the fifth generation wireless systems. Among the promising candidates, generalized frequency division multiplexing (GFDM) offers the flexibility to address a wide range of requirements (e.g. low latency, coarse synchronization, etc.). Due to the non- orthogonality of GFDM, the transmit signal subjects to inter-symbol and inter-carrier interference...
In this paper, we propose a new frequency synchronization scheme for multiuser orthogonal frequency division multiplexing (OFDM) uplink with a large-scale uniform linear array (ULA) at base station (BS). Considering that the incident signal at BS from each user can be restricted within a narrow angular spread, the proposed scheme performs carrier frequency offset (CFO) estimation for each user individually...
This paper presents sparse Bayesian learning (SBL)-based estimation schemes for an approximately sparse wireless multipath channel impulse response (MCIR) in a space-time trellis coded (STTC) multiple-input multiple-output (MIMO) orthogonal frequency division multiplexing (OFDM) system. The proposed schemes consider space-time trellis encoding over consecutive OFDM symbols and employ the multiple...
The two major sources of disturbances for an efficient and reliable data transmission through power lines, known as power line communication (PLC), are impulsive noise (IN) and narrow band interference (NBI). In this paper, we propose an algorithm to cancel the IN and NBI simultaneously for an OFDM based PLC system. The proposed method exploits the duality of the problem, where the IN is sparse in...
In this paper a high performance least square solver is presented which use recursive Cholesky decomposition. Wireless communication systems require solving least square equations in order to obtain taps weights of the FIR filter. It is thus about to develop a fast and efficient algorithm for computation pseudo-inverse matrices. This paper also presents the recursive way to calculate the correlation...
There has been growing interest in millimeter wave (mmWave) multiple-input multiple-output (MIMO) systems, which would likely employ hybrid analog-digital precoding with large-scale analog arrays deployed at wide bandwidths. Primary challenges here are how to efficiently estimate the large-dimensional frequency-selective channels and customize the wideband hybrid analog-digital precoders and combiners...
This paper deals with carrier frequency offset (CFO) estimation for interleaved orthogonal frequency division multiple access (OFDMA) uplink systems. Firstly, gravitational search algorithm (GSA) with center-symmetric trimmed correlation matrix and multiple signal classification criterion is presented for the purpose of efficient estimation. It has been shown that the estimate accuracy of the searching-based...
The inter-carrier interference (ICI) caused by Doppler spread in mobile channels affects the OFDM orthogonality. This paper presents a comparative study of the performance of different low complexity methods to estimate the ICI power present in mobile reception. In addition, a new method based on experimental results is proposed. Several computer simulations based on OFDM systems with Log-likelihood...
In this paper we propose a compressive channel estimation for fast fading channel in orthogonal frequency division multiplexing (OFDM) systems. We formulate the sparse compressive sensing (CS) problem by exploiting the delay-Doppler sparse structure of the doubly dispersive channel. To combat the severe inter-carrier interference (ICI) caused by the Doppler shift, this estimator is based on the banded...
In this paper, we present the simulation results of FFO(fractional frequency offset) influences on PLC preamble correlation based PLC synchronization in DOCSIS 3.1 Downstream. FFO makes inter-carrier interferences and breaks orthogonality in OFDM based transmission system. It degrades the performance of OFDM by reducing SNR(signal to noise ratio). The performance of PLC synchronization is influenced...
The combination of MIMO techniques with OFDM, MIMO-OFDM, is a promising way of achieving high spectral efficiency in wireless communication systems. However, the performance of MIMO-ODFM systems is highly degraded by RF impairments such as phase noise. Similar to the SISO case, phase noise in MIMO-OFDM systems results in a common phase error (CPE) and inter carrier interference (ICI). In this paper...
In this paper, we propose a phase noise cancellation algorithm in MIMO-OFDM systems where each transmit (TX) and receive (RX) antenna is equipped with independent oscillator. Most of previous works have considered phase noise model only in SISO-OFDM or simplified phase noise model in MIMO systems assuming that each TX and RX end shares one local oscillator. Recently, however, the local oscillator...
The paper introduces a novel method for distance estimation based on an OFDM signal combined with the Zadoff-Chu sequences. By exploiting the properties of these sequences, it is possible to evaluate the distance between two active nodes with a very good precision and accuracy. The technique effectiveness is demonstrated by measuring the distance between a single transmitter and a synchronized receiver...
This paper is concerned with the joint estimation of phase noise and time-varying channel responses in full-duplex multiple-input multiple-output (MEMO) orthogonal frequency division multiplexing (OFDM) systems. The time-variation of phase noise and multipath MIMO channel responses gives rise to the identiflability problem of estimating a large number of unknowns which is much greater than the number...
Mobile Communication systems are affected apparently by the Doppler Frequency and Doppler Rate. In multicarrier systems, because of sensitiveness to frequency offset, estimation and compensation are of great importance, which determine system performance directly. In this paper, we consider this problem in FBMC-OQAM system, and based on the property of it, a proper structure of preamble sequence,...
Although the Filter bank multicarrier with offset quadrature amplitude modulation (FBMC-OQAM) systems are robust against double selective fading channels, it unfortunately is still sensitive to timing offset and carrier frequency offset (CFO) errors. To solve this synchronization problem, in this paper, we propose a new data-aided timing and CFO synchronization scheme, that exploits the conjugate-symmetry...
In this paper, we propose an integer frequency offset estimation and compensation method based on PLC preamble correlation in DOCSIS 3.1 Downstream system. The proposed method finds out the PLC preamble subcarrier location recovered from PLC data and the one obtained from PLC preamble correlation. We showed the performance of PLC preamble detection in the received signal through the maximum value...
In this paper, we propose a comparison method of training symbol (or preamble) and Cyclic Prefix (CP) to improved the frequency synchronization in orthogonal frequency division multiplexing (OFDM). The problems that arise in OFDM system is the time-shift and frequency mismatch between the oscillators in the transmitter and the receiver. It is known as a Carrier Frequency Offset (CFO) problem. By exploring...
Modern wireless systems and standards increasingly rely on OFDM for high-throughput communications. However, these systems are often highly vulnerable to selective jamming attacks, particularly when a jammer targets (part of) the known frame preamble. In this paper, we consider one of the most disruptive jamming attacks against the preamble-based frequency offset (FO) estimation in IEEE 802.11a/n/ac/ax...
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