Serwis Infona wykorzystuje pliki cookies (ciasteczka). Są to wartości tekstowe, zapamiętywane przez przeglądarkę na urządzeniu użytkownika. Nasz serwis ma dostęp do tych wartości oraz wykorzystuje je do zapamiętania danych dotyczących użytkownika, takich jak np. ustawienia (typu widok ekranu, wybór języka interfejsu), zapamiętanie zalogowania. Korzystanie z serwisu Infona oznacza zgodę na zapis informacji i ich wykorzystanie dla celów korzytania z serwisu. Więcej informacji można znaleźć w Polityce prywatności oraz Regulaminie serwisu. Zamknięcie tego okienka potwierdza zapoznanie się z informacją o plikach cookies, akceptację polityki prywatności i regulaminu oraz sposobu wykorzystywania plików cookies w serwisie. Możesz zmienić ustawienia obsługi cookies w swojej przeglądarce.
The existed preamble structure for orthogonal frequency division multiplex/offset QAM (OFDM/OQAM) system requires two zero-value guard symbols to guarantee ISI and ICI avoidance (equivalent to 3/2 complex value symbols in OFDM with cyclic prefix system), which leads to OFDM/OQAM system with low spectrum efficiency. In this paper, we shorten the preamble with 1 zero-value guard symbol to improve the...
In this paper we study the impact of the overlapping between neighboring MPCs (multipath component) on the performance of channel estimation. We consider IR-UWB (impulse radio) signals, and the IEEE802.15.3a and IEEE802.15.4a UWB channel models. We show that for a pulse width (PW) sufficiently smaller than the average MPC rate of arrival (ROA) the probability to have more than three overlapping MPCs...
In this paper, we consider the problem of estimating the physical parameters that describe a multipath MIMO communication channel model characterized by specular reflections due to remote scatterers. Using the impulse response channel coefficients, we introduce a channel model based on a 3rd-order tensor structure that admits a Parafac decomposition with rank equal to the number of propagation paths...
We combine the characteristics of the Super Exponential (SE) method with Logic Strings and Second Order Statistics (SOS) to blindly estimate a multipath channel. The estimator benefits from the good quality of estimation inherent of SOS methods to estimate the magnitude of a channel's transfer function allied to the fact that the SE can estimate the channel phase response, and that Logic String estimator...
Multi-radio wireless mesh networks (MR-WMNs) are being increasingly deployed to provide affordable Internet access on large residential areas. MR-WMNs allow the supported mesh clients (MCs) to access the Internet gateway by multi-hop packet forwarding over the mesh routers (MRs), which can be equipped with multiple radio interfaces. In such a scenario, the routing protocol should (i) decide the address...
This paper proposes a pilot-aided joint channel estimation and synchronization scheme for burst-mode orthogonal frequency division multiplexing (OFDM) systems over time- and frequency-selective (doubly selective) channels. Based on the basis expansion model (BEM) for representing doubly-selective channels, a least-square (LS) cost function of carrier frequency offset (CFO) and BEM coefficients is...
In this paper, a novel demodulation structure in high-frequency (HF) channel is introduced and studied. Frequency-offset estimation, fractionally spaced adaptive equalization and carrier recovery techniques are involved. Frequency-offset correction is carried out based on channel impulse response estimation. Fractionally spaced adaptive equalization and carrier recovery are combined with non-linear...
A fine time tracking system is presented for orthogonal frequency division multiplexing (OFDM) systems working in multipath fading channels. Due to the channel variability, coarse timing is the most common sampling synchronization level performed in these environments. However, in case of slow time variant channels, fine time tracking can help in some way to the channel equalization, improving the...
A method for estimating the Doppler spread in mobile orthogonal frequency division multiplexing (OFDM) systems is described. The estimation is based on phase message of time domain channel estimation over several OFDM symbols. In OFDM systems, channel estimation is popularly performed in frequency domain. Channel frequency response estimates are affected by noise and inter-carrier interference (ICI)...
Transmission schemes based on orthogonal frequency division multiplexing (OFDM) are promising for underwater acoustic (UWA) communications, thanks to their robustness to large multipath spreads. On the other hand, due to the significant time variations in the UWA channels, the effectiveness of the standard OFDM receivers is impaired by intercarrier interference (ICI). In this paper, we propose two...
The combination of multi-input multi-output (MIMO) with orthogonal frequency division multiplexing (OFDM) is regarded as a promising technique for the future wireless communications. However, the performance of MIMO OFDM systems is very sensitive to carrier frequency offset (CFO) which introduces inter-carrier-interference (ICI). Consequently, CFO estimation plays a key role in MIMO OFDM systems....
Coherent modulation is more appropriate than differential modulation for orthogonal frequency division multiplexing (OFDM) systems requiring high data rate and spectral efficiency. Channel estimation is therefore required as an integral part of the receiver design. An iterative maximum likelihood-based channel estimation algorithm for an OFDM system in dispersive time-varying channels is proposed...
In this paper, a new array signal processing technique, which make use of the particle swarm optimization (PSO), is proposed. Using cross ambiguity function (CAF) calculation an optimization criteria is defined and PSO is used to find the global minimum point of the obtained cost function. Developed particle swarm optimization - direction finding technique (PSO-DF) estimates time delay, Doppler shift,...
The exact time-of-arrival (TOA) information of the multi-path signals is crucial for optimal channel estimation in vehicular OFDM systems. Super-resolution algorithms such as ESPRIT (Estimation of Signal Parameters via Rotational Invariance Technique) have been applied to retrieve this information from embedded pilots in the received OFDM symbols. These algorithms have high applicability for vehicular...
In this paper, we propose an efficient estimation technique for time-varying multipath channels by exploiting two dimensional delay-time nature in pilot inserted orthogonal frequency division multiplexing (OFDM) systems. The proposed technique consists of multipath snapshot estimation at periodic channel observation instances over an OFDM block and the linear interpolation of two consecutive multipath...
We present two new noise variance estimation methods for OFDMA signals transmitted through an unknown multipath fading channel. We focus on blind estimation as it does not require any pilot sequences and is therefore applicable to contexts, such as cognitive radio for instance, where little prior signal knowledge is available. The two estimators are respectively based on the time-frequency sparsity...
In SC-FDE (single carrier with frequency domain equalization) systems, timing offset brings ISI (inter-symbol interference). In order to obtain better timing precision in multi-path, a new timing offset estimation method applied to SC-FDE systems is proposed based on the analysis of Schmidl & Coxpsilas and Minnpsilas algorithms. By designing new training symbols and introducing corresponding calculation...
The paper proposes a novel approach for time delay and channel gain estimation for multipath fading Code Division Multiple Access (CDMA) signals using the unscented Kalman filter (UKF). Given the nonlinear dependency of the channel parameters on the received signals in multiuser/multipath scenarios, we show that the UKF achieves better performance than its linear counterparts. The UKF, which is a...
This paper presents a method to estimate Time of arrival (TOA) of impulse radio ultra wideband (IR-UWB) in a multipath communication channel. Matrix Pencil (MP) is used to recover these delays from the channel frequency response. This algorithm has some key advantages over traditional super-resolution techniques such as multiple signal classification (MUSIC) method. Most importantly, Matrix Pencil...
In this paper we propose a new speed estimation technique, applicable to both mobile and base stations, based on the characteristics in the power spectrum of mobile fading channels. Our analytic performance analysis, verified by Monte Carlo simulations, shows that our low-complexity estimator is not only robust to both Gaussian and non-Gaussian noises, but also insensitive to nonisotropic scattering...
Podaj zakres dat dla filtrowania wyświetlonych wyników. Możesz podać datę początkową, końcową lub obie daty. Daty możesz wpisać ręcznie lub wybrać za pomocą kalendarza.