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.
Time varying channel breaks the orthogonality between the subcarriers of Orthogonal Frequency Domain Multiplexing (OFDM). This introduces Intercarrier Interference (ICI). One of the ways to mitigate ICI is to first estimate the channel and then equalize it. In this paper we propose to estimate the channel using Discrete Proplate Spheroidal Sequences (DPS) using pilot carriers interleaved with data...
In the MIMO-OFDM system channel estimation based on the superimposed pilot is one of most potential and powerful techniques for broad-band wireless communications. In most traditional algorithms, the channel parameters are estimated by calculating the first-order statistical properties of receiving information. However, there are some limitations in such methods. These methods require the first-order...
This paper proposes a superimposed training strategy to estimate the individual frequency and channel parameters in an amplify-and-forward (AF) two-way relay network (TWRN). Two efficient suboptimal estimation algorithms and an iterative process to further improve the performance are proposed. The estimation Cramér-Rao Bound (CRB) on the proposed estimation strategy is also derived. The simulations...
This paper proposed a new Modified algorithm under the Vectoring Mode CORDIC algorithm called MVM-CORDIC algorithm, which is used to calculate the angle of frequency offset estimation in the communications system. From the simulation result, we can see that under the certain accuracy the MVM-CORDIC algorithm can reduce the iteration number by contrasting to the conventional CORDIC algorithm, meanwhile...
We present an improved estimator of the phase noise θ(t) in OFDM systems, based on the approximation of the time-varying phasor exp(jθ(t)) by a discrete-cosine transform (DCT) basis expansion, containing only a few terms. Using pilot symbols, an initial least-squares estimate of the phase noise is obtained. The initial estimate is iteratively improved by also exploiting the soft decisions from the...
We propose a dual diagonal linear-minimum-mean-square-error (DD-LMMSE) channel estimation algorithm for orthogonal frequency division multiplexing (OFDM) systems involving joint channel estimation and signal detection. Computational complexity and mean-square-error (MSE) analysis are presented to evaluate the efficiency of the proposed algorithm. Compared with the optimal LMMSE method, the proposed...
In this paper, an OFDM-based high resolution, channel sounding (CS) method is proposed under T/2-spaced sampling. The proposed CS method consists of three iterative steps. In each iteration, it attempts to catch a new path with accurate fractional delay. Besides, it is equipped with EDC criterion for path order determination. The CFR-MSE performance can be greatly improved over the conventional LS...
We propose two practical schemes for the cancellation of nonlinear distortions caused by the power amplifiers (PA) in Orthogonal Frequency Division Multiplexing (OFDM) systems. The algorithms are iterative and located at the receiver. They utilize a soft channel decoder to improve the capabilities of the distortion estimation and relay all the computational complexity to the receiver. Simulation results...
A novel, reduced complexity iterative channel estimation algorithm for OFDM systems using superimposed pilots is proposed. It utilizes past channel estimations of double correlated channel as a side information to reduce number of iterations. Since pilots are available at all positions of the time-frequency OFDM grid in superimposed technique, the performance of the channel estimation does not degrade...
We propose an iterative Inter-Carrier Interference (ICI) estimation and cancellation technique for OFDM systems based on simultaneously estimating entries of each off-diagonal vector of the channel frequency response matrix (CFRM) of a double-selective fading channel. We show by theoretical analysis that the ICI gains in each off-diagonal vector of the CFRM share the same statistical characteristics...
Carrier frequency synchronization is the critical technique in orthogonal frequency division multiplexing (OFDM) systems. In this paper, an improved carrier frequency offset (CFO) estimation method is proposed, which divides the Schmidl's CFO estimation into coarse and fine estimation by using PN sequence iteration, the new method has higher estimation accuracy and larger estimation range than that...
In this paper, we propose a new channel estimation algorithm for orthogonal frequency division multiplexing (OFDM) systems. For fast fading environment, we introduce a new method which is extended to the Alamouti Coded OFDM case. At the first stage of this algorithm, the channel response is estimated for pilot sub-carriers and then, the channel response for data sub-carriers are interpolated by Gaussian...
When high power amplifiers are in OFDM transmitters employed in the area of their nonlinear characteristics, the transmitters became more energy efficient and their consumption decreases. However, transmitted signal is nonlinearly amplified and therefore subject to nonlinear distortion. When assuming perfect channel state information present at the receiver, only data symbols are nonlinearly distorted,...
To mitigate the asynchronous ICI (inter-cell interference), the CFR (channel frequency response) and SCM (spatial covariance matrix) should be accurately estimated. Therefore, the enhanced asynchronous ICI mitigation scheme which can effectively reduce the estimation error of both CFR and SCM, and improve performance for MIMO (multiple-input multiple-output)-OFDMA (orthogonal frequency division multiple...
This is a recent research on Space-Division-Multiple-Access-Orthogonal frequency Division Multiplexing (SDMA-OFDM) for channel estimation based on iterative joint channel estimation and a new Genetic Algorithm (GA). Assisted iterative joint channel estimation and Multi-User Detection (MUD) is the most recent approach for MTMO SDMA-OFDM systems and GA-aided MUD techniques for providing the best capacity...
The classical channel estimation method in TDS-OFDM is carried out based on the PN sequence in the GI which suffers from the intersymbol interference of the previous OFDM data symbols. This paper presents a novel data-aided channel estimation method to refine the initial channel estimation obtained from PN sequence. The data symbols are rebuilt based on the log-likelihood ratio (LLR) from the output...
A modified deterministic structure based carrier frequency offset (CFO) estimation algorithm is presented for the interleaved orthogonal frequency division multiple access (OFDMA) uplink transmission. The presented algorithm combines the conventional deterministic structure algorithm with multiple access interference (MAI) cancellation method so that the estimation performance can be significantly...
Multiple antenna systems have been shown to provide significant performance improvements for network nodes; however, the vast majority of nodes in military networks will be limited to single channel devices due to mobility (size and power) and ease of use considerations. In this paper we apply a new joint synchronization-pilot sequence (JSPS) optimization design technique to multiple transmitter OFDM...
The aeronautical wireless channel is a time-frequency double-selective channel, which will destroy the orthogonality of the OFDM sub-carriers remarkably, inducing a severe intercarrier interference (ICI). The aeronautic channel is also a sparse channel. So we could utilize the property of sparseness to design an appropriate channel estimation method. In this paper, a novel channel estimation scheme...
To estimate carrier frequency offset, a polynomial-rooting-and-evaluation algorithm is proposed for symbols with constant modulus in OFDM systems. This algorithm makes use of the orthogonal subspace of the squared spectrum vector of the channel. The algorithm improves an existing non-iterative method.
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.