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The implementation of channel estimation procedures in modern wireless networks exposes them to the risk of pilot contamination attacks. To protect the system from such types of malicious intervention, a recently proposed method, based on legitimate pilots from shifted constellations, can be applied. In this paper, the detection capability of this method is studied in both the presence and absence...
Recently, a switch-based hybrid massive MIMO structure that aims to reduce the hardware complexity and power consumption has been proposed as a potential candidate for millimeter wave (mmWave) communications. In this paper, we investigate a matrix completion (MC)-based low-complexity channel estimator for such systems, which is compatible with the switch-based hybrid structure. We conduct a thorough...
Conventional correlation-based frame synchronization techniques can suffer significant performance degradation over multi-path frequency-selective channels. As a remedy, in this paper we consider joint frame synchronization and channel estimation. This, however, increases the length of the resulting combined channel and its estimation becomes more challenging. On the other hand, since the combined...
The performance of massive multiple-input multiple-output (MIMO) systems is heavily affected by pilot contamination. This paper considers the problem of pilot contamination in massive MIMO systems, and investigates the normalized mean square error (NMSE) of the minimum mean square error (MMSE) channel estimation algorithm in the presence of pilot contamination. An effective uplink training strategy...
A key focus of wireless communications research is on solutions that catalyze broadband access everywhere at anytime. Relaying has been introduced as a solution to enable communication between users who suffer from poor channel conditions. Distributed relay networks are a special case where spatial diversity is obtained by using a relay consisting of many geographically dispersed nodes. Due to bandwidth...
Generalized frequency division multiplexing (GFDM) with the flexible structure is one of the promising candidates for the fifth generation wireless communication system. This paper focuses on training sequence design that is used in the estimation of in-phase(I) and quadrature(Q) imbalance parameters on GFDM receivers as well as frequency selective channel. Combining with the structure of low complexity...
Multichannel receivers are usually employed in high-rate underwater acoustic communication to achieve spatial diversity. Passive time reversal combined with a single-channel adaptive decision feedback equalization (PTR-DFE) is a low-complexity solution to achieve both spatial and temporal focusing. Block-based PTR-DFE (BB-PTR-DFE) extends PTR-DFE to time-varying channels. Multichannel DFE (M-DFE)...
In consideration of the harsh environment of underwater acoustic channel and the high reliability transmission requirement, a carrier interleaved underwater acoustic MC-CDMA communication system using complete complementary sequence (MIC-CDMA/CCS) is proposed in this paper. We use OFDM modulation to reduce the complexity of the system, obtain the diversity gain by frequency domain spread spectrum,...
Underwater acoustic channel is a time varying, strong multipath, serious Doppler frequency shift, and high noise interference channel. Aiming at the requirements of strong stability and high reliability to support reliable transmission over long distance, a direct sequence spread spectrum based on single carrier underwater acoustic communication system using dual spread spectrum code (SC-CDMA/DSSC)...
In this paper, we propose a novel Superimposed Training (ST) technique for Orthogonal Frequency Division Multiplexing (OFDM) systems, where data and training signals are divided in orthogonal code domains in order to mitigate the interference between them. The data signal is partitioned into disjoint bins, which are spread using orthogonal codes and multiplexed in code domain. Then, the new data signal...
This paper describes a novel way to use the existing communication infrastructure of LTE (Long Term Evolution) to monitor the change in the environment along with its feasibility analysis. This system is named LTE-CommSense by the authors and can be used in many environment sensing objectives namely monitoring of crop growth over a period of time, disaster monitoring, sea state monitoring, snow avalanche...
Spectral efficiency and capacity of Land Mobile Satellite (LMS) systems can be enhanced by using MIMO (Multiple Input Multiple Output). Polarization diversity is an efficient technique to realize MIMO in LMS communications. Polarization diversity employs different polarization to realize multiple independent propagation paths. Dual polarized antennas offer a space and cost effective alternative compared...
In most Multiple-Input Multiple-Output Orthogonal Frequency Division Multiplexing (MIMO-OFDM) systems, channel estimation is required for equalization and symbol detection. It often exploits the specified pilot symbols consuming not only a large part of the throughput but also significant power resources. This paper quantifies the theoretical maximum power reduction of the transmitted pilots when...
In this paper, we study the channel estimation problem for a cyclic prefix OFDM (CP-OFDM) based millimeter wave (mmWave) hybrid analog-digital MIMO system, where the analog processing is achieved using only phase shift networks. A three-dimensional (3-D) Standard ESPRIT in discrete Fourier transform (DFT) beamspace approach is developed to estimate the unknown frequency-selective channel. The required...
In this work, the problem of channel estimation in multicarrier communications with the Type-I even discrete cosine transform (DCT1e) is addressed. A novel scheme, based on using the DCT1e, both at the transmitter and the receiver, is introduced. The proposed approach does not require adding any redundancy or knowing the exact length of the channel's impulse response. By constructing a symmetric training...
The conventional algorithm of channel estimation based on IEEE802.11ac is Least Square (LS) algorithm, which uses the Very High Throughput-Long Training Field (VHTLTF) of frame header as training sequence. While the conventional algorithm does not take into account the effects of noise and the varying characteristics of channel in time domain. In order to describe the slow change of channel in time...
The performance of full-duplex (FD) decode-and-forward (DF) relaying systems for point-to-point multi-antenna transmission is considered. Three different relaying schemes are investigated: co-located, distributed cooperative and distributed non-cooperative. To mitigate the effects of loop interference (LI) caused by FD operation at the relay, a digital cancellation scheme based on pilot-aided channel...
Pilot contamination attack is an important kind of active eavesdropping activity conducted by a malicious user during channel training phase. In this paper, motivated by the fact that frequency asynchronism could introduce divergence of the transmitted pilot signals between intended user and attacker, we propose a new uncoordinated frequency shift (UFS) scheme for detection of pilot contamination...
In this paper, we propose a new approach to estimate the gain and the noise figure of EDFAs. This is an important tool for solving the adaptive control of operating point (ACOP) problem in optical amplifiers. The proposal uses an artificial neural network to enable a quick estimation of both amplifiers features requiring a small amount of memory. Results show that the neural network estimator is 80...
In this paper, the problem of blind adaptive equalization of HF channel is considered using a state space approach. HF channel is multipath propagation channel due to multiple reflections on ionospheric layers, which causing intersymbol interference (ISI) at the receiver output. The problem of ISI suppression is referred to as deconvolution or channel equalization. At present, a family of methods...
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