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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...
A minimum mean square error estimation (MMSE) using a virtual pilot channel estimation scheme was proposed by our researchers for improving the error performance of the IEEE 802.11p. However, compared to the STA channel estimation scheme, the MMSE scheme cannot provide an acceptable error performance in a low SNR region. To alleviate this, we propose an adaptive channel estimation scheme, which selectively...
We propose computationally efficient carrier frequency offset estimators for multicarrier underwater acoustic communication using identical pilot tones equi-spaced in the frequency domain. The first estimator uses the phase of the maximal eigenvector of a channel-dependent correlation matrix. Next, the phase of the minimal eigenvector of a channel-independent correlation matrix is combined with the...
Impulsive noise in power lines usually bears higher power spectral density than the background noise. Even a sample of such noise, if not mitigated, destroys symbols in all the subcarriers affecting channel estimation and information detection. In this paper, we study two maximum-likelihood approaches to estimate the channel in the presence of impulsive noise for an OFDM based PLC system. In both...
Multicast plays an important role in wireless networks to delivery a common message to multiple users simultaneously. Multicast beamforming can further boost the system performance by utilizing channel state information (CSI) at the base station (BS) equipped with multiple antennas. This paper provides a validation of multicast beamforming over actual channels measured in the Shanghai Jiao Tong University...
High-speed broadband power line communications (BB-PLC) have become a good option for all residential subscribers. Today regulations imply the use of multi-carrier (MC) systems, like orthogonal frequency-division multiplexing (OFDM) or, as an alternative, the use of single-carrier (SC) technologies as main modulation scheme. In this work, it is proposed a complementary sequences (CS) based frequency...
We study the impact of differential modal delay (DMD) on inter-symbol frequency domain averaging (ISFA) based coherent optical OFDM channel estimation. We find the maximum ISFA window for a 78 ns DMD channel is 6 MHz.
This paper considers power allocation between data and pilot symbols for an orthogonal frequency division multiplexing (OFDM) system in a high-speed train (HST) environment. The channel gains are very quickly time-varying within an OFDM symbol so both their estimation and symbol detection must be simultaneously implemented with unavoidable inter-carrier interferences. The average channel complex gains...
In this paper, the frequency-domain pilot-multiplexing techniques (FDPMTs) for the channel estimation in single-carrier frequency-domain equalization (SC-FDE) systems are investigated. An innovative, simple, but effective pilot-position detection technique (PDT) is proposed. This novel PDT is based on Lilliefors test and Monte Carlo simulation results demonstrate that our proposed new scheme is more...
In the Release (Rel.) 11 Long Term Evolution (LTE)-Advanced radio interface, the Enhanced Physical Downlink Control Channel (EPDCCH) is specified, which transmits downlink control information (DCI) signals. The EPDCCH is frequency-domain-multiplexed with data symbols and is used to transmit more DCI signals than the Physical Downlink Control Channel (PDCCH) for Rel. 8 LTE due to the application of...
This paper presents an adaptive scheme in overcoming signal distortion, caused by I/Q imbalance and multipath propagation, in an OFDM receiver. Estimation of I/Q imbalance and channel parameters is performed in the frequency domain with the aid of pilot tones. These estimated values are then used to adjust the gain and phase to reduce the distortion caused by I/Q imbalance. The resulting less distorted...
Channel impairments degrade the performance of accurate data signal detection and decoding. The said problem becomes further severe in low SNR environment. As a result it reduces the performance of channel estimation. To alleviate this problem we develop a pilot based Pre FFT (time domain) channel estimation technique in the presence of Rayleigh fading channel. A novel time domain channel estimation...
In this paper, we investigate the pilot position selection (PPS) problem in the frequency domain pilot multiplexing technique (FDPMT) for channel estimation of single-carrier block transmission with frequency domain equalization (SC-FDE). Unlike the widely accepted point of view that the conventional PPS technique is the optimal one, this paper for the first time questions this viewpoint and demonstrates...
The location method based on TOA estimation is a research hotspot in the field of wireless location. In this paper, an new TOA estimation algorithm is proposed for providing a better estimation performance. The cross correlation matrix is employed to process channel estimation in frequency domain, which is benefit to the noise suppression. Channel estimation based on the optimal threshold is employed...
In order to solve channel estimation's pilot interference problem, this paper researched OFDM system channel estimation model, analyzed the OFDM symbol's pilot pattern, proposed a new octagon guide frequency pattern design method, and combined with low signal to noise space of virtual pilot technology, used the interpolation method to eliminate interference, further improved the OFDM system channel...
This paper describes the performance of singular value decomposition (SVD) estimation techniques for multiband orthogonal frequency-division multiplexing (OFDM) of ultra-wideband (UWB) system in Saleh-Valenzuela channel modelling. The performance of SVD estimation is compared against LS and MMSE methods corresponding to zero-padded of a UWB system. The crucial limitation in UWB system is strictly...
In this paper, we describe the guideline for pilot design with the common pilot scheme and the user-specific pilot scheme. Here, channels for estimation with the common pilot scheme are non-precoded channels and channels with the user-specific pilot scheme are precoded channels in multiple input multiple output (MIMO) systems. Both two pilot schemes are included in the standards because two pilot...
We study the effects of channel estimation errors on bit error rate (BER) performance of a DFT-precoded OFDM system with frequency domain linear minimum mean square error (MMSE) equalizer, by analytically studying the effects of channel estimation errors on the mean square error (MSE) of the equalizer output, which can be related to the BER performance using a Gaussian approximation. We first obtain...
A semi-blind equalization method is proposed for precoding single carrier system with frequency domain equalization(SC-FDE). The method is modified according to Bussgang algorithm and the implementation is easy because it does not need complex computation. Simulations are used to demonstrate the proposed method.
By using frequency-domain oversampling at the receiver, we propose a novel blind channel estimation scheme for multiple-input multiple-output (MIMO) orthogonal frequency division multiplexing (OFDM) systems. Specifically, a subspace blind channel estimation approach is developed, based only on second-order statistics of the received signal. The estimated MIMO channel is nicely determined by Nt minimum...
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